View Full Version : Car actively trying to swap ends on track?
cbaclawski
05-12-2019, 10:25 AM
For background, I have a 1990 ZR-1 with the Lingenfelter 368 package that has been outfitted for road course duty.
After a bad first outing involving a failing master cylinder and a tire wall, I replaced the Master, all 4 calipers, front rotors, installed the DRM bias spring, and am running Hawk DTC-70 race pads/Motul 660 fluid/Sumitomo staggered 160tw tires.
Finally got the car back on track a couple days ago, and working brakes are nice to have (though I'd still only call them "adequate" not great by any means).
Now that I've been able to run a few laps, I can honestly say that this car feels like it is actively trying to spin in every corner! The line between power oversteer and lift off oversteer is virtually non-existent. It is an absolute handful just to get it around the course, let alone post a decent laptime.
You guys think this is:
1-something specific to my car?
2-a C4 thing, go find a dragstrip?
3-poor driving by me? (have 50+ days, many with professional instruction at this track driving everything from a Mazda rx-8 to a v12 vantage S - Though I make no claims on being a great driver, I'd say I'm at least experienced, and average)
What would you do to address the handling? A big wing in the back? Coilover's?(rides kinda high in the back) Slicks? Learn to drive? Something else?
Love the car, and it's a blast on the straights, but it's overall not really fun at the track getting lapped by cars with <1/3 the power. (I'm even about 4 sec/lap faster in my rx-8 with 140 lb/ft at the crank on a good day)
HELP!
RussMcB
05-12-2019, 10:52 AM
It's definitely not a C4 thing.
My first thought is the rear toe has toe out, either static or dynamic (something is loose and allowing the toe to go "out").
You didn't mention an alignment. Hopefully you have a good one. If not, get one. If yes, tell us the settings. I grabbed something off the web a while back, with three good, general settings for street, high spirited driving, and race track. I'll find them and post here later.
My guess is your driving would not need to be radically different than the RX-8. In other words, if you're driving the RX-8 well, you should be able to drive the ZR-1 well, too.
rush91
05-12-2019, 10:53 AM
I've never tracked my Z, so take my opinion as you will....but I was running Sumitomos for about 3 years. I just got a new set of Nitto 555 G2s, and it changed the car. Besides Haibeck chip I'm 100% stock. The car no longer flips the *** end out, just hooks and goes....Sumi's are a great tire if you have a daily driver. They ride smooth, are quiet and inexpensive to replace. But for track duty I just think there are way, way better tires.
lfalzarano
05-12-2019, 10:53 AM
Not a fan of Sumitoma for the street or track. It’s a good value tire, but not really a track tire. If you need a combo street/track tire, Michelin and Goodyear are your best tire. If you are serious about track performance, racing slicks are your ticket. This is just a starting point of improving your times.
Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)
cbaclawski
05-12-2019, 12:27 PM
It's definitely not a C4 thing.
My first thought is the rear toe has toe out, either static or dynamic (something is loose and allowing the toe to go "out").
You didn't mention an alignment. Hopefully you have a good one. If not, get one. If yes, tell us the settings. I grabbed something off the web a while back, with three good, general settings for street, high spirited driving, and race track. I'll find them and post here later.
My guess is your driving would not need to be radically different than the RX-8. In other words, if you're driving the RX-8 well, you should be able to drive the ZR-1 well, too.
You know, now that you mention it, I just kinda assumed the Race shop I use did a track alignment when they did all the other work. It's certainly possible that this was overlooked. Even if it was done, my previous "incident" with the tire wall could certainly have knocked it out. Please do post the settings you have and I will start there. Thanks for waking me up!
I've never tracked my Z, so take my opinion as you will....but I was running Sumitomos for about 3 years. I just got a new set of Nitto 555 G2s, and it changed the car. Besides Haibeck chip I'm 100% stock. The car no longer flips the *** end out, just hooks and goes....Sumi's are a great tire if you have a daily driver. They ride smooth, are quiet and inexpensive to replace. But for track duty I just think there are way, way better tires.
Not a fan of Sumitoma for the street or track. It’s a good value tire, but not really a track tire. If you need a combo street/track tire, Michelin and Goodyear are your best tire. If you are serious about track performance, racing slicks are your ticket. This is just a starting point of improving your times.
Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)
I went with the Sumitomo's for a couple reasons:
1- the track I frequent in a known tire eater - generally lucky to get 2 weekends out of a set. So price was definitely a factor.
2- The sumi's are UTQG treadwear 160, while the goodyear's are ~340 if I remember correctly, and there aren't too many options in our size. I know treadwear ratings aren't the definitive answer regarding tire performance and "stickiness", but in my experience lower/softer tires have tended to grip better than higher/harder(and also wear more evenly). Though reading the comments on this board regarding the sumi's, they don't seem to be highly regarded.
3-I have previously preferred to run on aggressive street tires, not true race tires as they tend to be more communicative of mistakes and give more warning before completely disappearing.
I think I'll definitely go in a different direction next time - these will be corded soon enough...
XfireZ51
05-12-2019, 01:58 PM
Think I would rather stay out of a wall than worry about a few extra bucks for tires.
cbaclawski
05-12-2019, 02:10 PM
Think I would rather stay out of a wall than worry about a few extra bucks for tires.
Clearly I didn't anticipate that. And frankly while not the best tire in the world, the Sumitomo's aren't that bad, especially brand new. I highly doubt it's a tire issue. If anything with a staggered setup I'd have expected some understeer if the tires were the culprit. Plenty of grip in the front.
MarkSS
05-12-2019, 04:29 PM
Three thoughts... #1 alignment as mentioned above.
#2 tires as mentioned as well
#3 what tire pressure are you running. A couple psi can make a huge difference in the feel.
My experience with ZR1s is they tend to understeer on entry and can be made to oversteer on exit with too quick an application of the throttle. Good alignment, tires, and correct tire pressure can help a lot. It sounds like something isn't right with your car beyond just the tire brand.
conesare2seconds
05-12-2019, 04:35 PM
Check the ladder (c-beam) bolts for tightness. Assuming you don’t have beam plates: There’s just enough room on the fronts to hold the top with a box wrench laid along the ladder while tightening from below with a socket. If they are loose you may experience step out in the rear when transitioning from power on to power off and vice versa. Beam plates are a few bucks well spent on a car that sees track use.
cbaclawski
05-12-2019, 05:18 PM
Three thoughts... #1 alignment as mentioned above.
#2 tires as mentioned as well
#3 what tire pressure are you running. A couple psi can make a huge difference in the feel.
My experience with ZR1s is they tend to understeer on entry and can be made to oversteer on exit with too quick an application of the throttle. Good alignment, tires, and correct tire pressure can help a lot. It sounds like something isn't right with your car beyond just the tire brand.
I had virtually no understeer on entry, but I was definitely overbraking prior to turn in knowing I had to walk a tightrope to keep the back end in. On exit anything more than maintenance throttle until almost full track out and, you guessed it, the back end broke loose.
This Thread has got me thinking, though it was very unstable everywhere, it was more pronounced in right handers... hmm...
Was aiming for 39psi hot. I started them at 31, and had to bleed a little off after the first session. That's the basic "sweet spot" in my other track cars, above that they get a bit squirmy. What would you recommend for the Z?
Check the ladder (c-beam) bolts for tightness. Assuming you don’t have beam plates: There’s just enough room on the fronts to hold the top with a box wrench laid along the ladder while tightening from below with a socket. If they are loose you may experience step out in the rear when transitioning from power on to power off and vice versa. Beam plates are a few bucks well spent on a car that sees track use.
I'll definitely look at this. (Though I'll have to google Ladder Bolts to figure out what they look like and where they are) Sounds like an easy enough thing to check, I have a lift in the garage...
Thanks All!
d15b7
05-12-2019, 09:16 PM
hey there. I own a (totally stock except for the sumitomo tires) 1990 ZR-1. and I hold road racing licences with SCCA and NASA and VRG and others, plus I'm a certified instructor for Porsche and BMW CCA and NASA and others. my ZR-1 predominantly understeers unless you are rolling on the power too quickly and then it transitions to very easily correctible oversteer. the car is a pussycat to drive, especially compared to my two race cars (Lotus Super Seven vintage racer and my fast car, a Honda Civic with a K24 engine swap and a big turbo (around 550 whp, and less than 2400 lbs with me in it) stripped and caged with fully adjustable suspension/coilovers/double adjustable shocks.
so -- I'd most definitely say that there is something very amiss with your car. most likely as others have stated the suspension is really off; have a good race shop do a good 'track ready' 4 wheel alignment. have them check to make sure that none of the bushings/ball joints are bad or binding. your car should be fun to drive on track and not a white knuckle ride!
PS if you want better braking performance out of the stock calipers try getting some Raybestos ST43 pads for it; I know they are expensive but they are fantastic and basically will not fade. ever. my Honda runs 15" wheels which limit me to 11" front rotors and the ST43s are the only pads that will last over a 25 min session stopping from 160+ mph at VIR raceway. I've tried all the others (hawk, porterfield, carbotech and others). the ST43s are simply amazing.
cbaclawski
05-12-2019, 10:05 PM
hey there. I own a (totally stock except for the sumitomo tires) 1990 ZR-1. and I hold road racing licences with SCCA and NASA and VRG and others, plus I'm a certified instructor for Porsche and BMW CCA and NASA and others. my ZR-1 predominantly understeers unless you are rolling on the power too quickly and then it transitions to very easily correctible oversteer. the car is a pussycat to drive, especially compared to my two race cars (Lotus Super Seven vintage racer and my fast car, a Honda Civic with a K24 engine swap and a big turbo (around 550 whp, and less than 2400 lbs with me in it) stripped and caged with fully adjustable suspension/coilovers/double adjustable shocks.
so -- I'd most definitely say that there is something very amiss with your car. most likely as others have stated the suspension is really off; have a good race shop do a good 'track ready' 4 wheel alignment. have them check to make sure that none of the bushings/ball joints are bad or binding. your car should be fun to drive on track and not a white knuckle ride!
PS if you want better braking performance out of the stock calipers try getting some Raybestos ST43 pads for it; I know they are expensive but they are fantastic and basically will not fade. ever. my Honda runs 15" wheels which limit me to 11" front rotors and the ST43s are the only pads that will last over a 25 min session stopping from 160+ mph at VIR raceway. I've tried all the others (hawk, porterfield, carbotech and others). the ST43s are simply amazing.
That's great to hear! I've run with all those groups! I don't have any competition licenses, but do have a couple TT licenses and have run A group with BMWCCA (e46 330i prepped to be a D-Modified/Nasa ST/TT-5).
To be honest my experience in this car has really made me insecure about my skill level. It is anything BUT a pussycat to drive. I know I wasn't rolling on the power too quickly, as just breathing on it past maintenance would kick out the back, and ANY lift would have the same effect. I swear it was like balancing a bowling ball on a needle, and slow to boot.
I'll start with the alignment, and have the suspension(stock) gone over to look for binding/looseness. The before/after charts should tell the story... hopefully...
Regarding the pads, I'll definitely give those a shot once the DTC-70's need to be replaced (they aren't what I'd call cheap either...) but it might be a while, I don't get a chance to take this one out that often... (too many track cars, not enough track days! - sounds like you have the same issue, lol)
550hp 2400lb civic eh? ~4lb:hp on a FWD car? I can't even imagine what that must be like! I'm scared just thinking about the boost kicking in...
Thanks again
MarkSS
05-13-2019, 10:18 AM
ZR1s are not perfectly balanced, so a couple psi less in the rears compared to fronts may help. If you have a pyrometer, dailing in the tire pressure is easier.
It seems like you may have something worn out though. I have seen the trailing arms wear out, you may want to check that as well.
Another
RussMcB
05-13-2019, 11:14 AM
... Please do post the settings you have and I will start there. I forget where I found this on the web. Maybe from "VBP Racing"?
http://zr1.net/forum/picture.php?albumid=453&pictureid=3972
d15b7
05-13-2019, 11:52 AM
550hp 2400lb civic eh? ~4lb:hp on a FWD car? I can't even imagine what that must be like! I'm scared just thinking about the boost kicking in...
ya it takes a smoooth driving style and a very careful right foot application!
here's a short clip of me in the Honda from last fall; I was at NJMP Thunderbolt instructing for the PCA and decided to take the Civic and burn off some of my old obsolete tires from years ago (I used to run it in Limited FWD class before the big EFR7163 turbo. in Limited I ran Nitto NT01 225-45-15 tires). these were 8 yrs old (!) and I was gonna throw them out but figured 'why not use them one last time?'. I run the car in Unlimited now and use a Hoosier A7 295-35-15 up front (massive MASSIVE difference in available traction!)
so in this short clip I was running at only 15 psi (around 450 whp or so maybe a touch less) with the old old beat tires. have to be reallyyyyy cautious applying the throttle (and often I short shift because it'll just light up the fronts coming off the corners). and I only use 4th 5th 6th once I'm out of the pits. even so this clip is from the Red group (Instructors and Racers) and as you can see my old Civic was reeling them in and eating them up haha.
https://1drv.ms/v/s!AmUHWCpbUJmAq34ysK_Q7oEOmnf-
(the 295-35-15 Hoosier A7s plus turning the boost up equates to about 5-6 secs a lap faster).
cbaclawski
05-13-2019, 01:47 PM
ZR1s are not perfectly balanced, so a couple psi less in the rears compared to fronts may help. If you have a pyrometer, dailing in the tire pressure is easier.
It seems like you may have something worn out though. I have seen the trailing arms wear out, you may want to check that as well.
Another
Adding that to the list of things to check, thanks!
I forget where I found this on the web. Maybe from "VBP Racing"?
http://zr1.net/forum/picture.php?albumid=453&pictureid=3972
Perfect, exactly what i was looking for, Thanks!!
ya it takes a smoooth driving style and a very careful right foot application!
here's a short clip of me in the Honda from last fall; I was at NJMP Thunderbolt instructing for the PCA and decided to take the Civic and burn off some of my old obsolete tires from years ago (I used to run it in Limited FWD class before the big EFR7163 turbo. in Limited I ran Nitto NT01 225-45-15 tires). these were 8 yrs old (!) and I was gonna throw them out but figured 'why not use them one last time?'. I run the car in Unlimited now and use a Hoosier A7 295-35-15 up front (massive MASSIVE difference in available traction!)
so in this short clip I was running at only 15 psi (around 450 whp or so maybe a touch less) with the old old beat tires. have to be reallyyyyy cautious applying the throttle (and often I short shift because it'll just light up the fronts coming off the corners). and I only use 4th 5th 6th once I'm out of the pits. even so this clip is from the Red group (Instructors and Racers) and as you can see my old Civic was reeling them in and eating them up haha.
https://1drv.ms/v/s!AmUHWCpbUJmAq34ysK_Q7oEOmnf-
(the 295-35-15 Hoosier A7s plus turning the boost up equates to about 5-6 secs a lap faster).
Awesome video!
It's always fun to get a point by from a modern Porshe in an old "beater" that has no business doing so (stock anyway)...
lfalzarano
05-13-2019, 04:09 PM
Found these baseline specs on Corvette Central tech site. :cheers:
https://tech.corvettecentral.com/2011/07/wheel-alignment-specs/
The rear Toe-in is slightly different, than that mentioned above.
It was also recommended to check your steering linkage for wear.
Vette Guy
05-14-2019, 03:48 AM
First, please explain "has been outfitted for road course duty".
Installing a 30mm solid front sway bar w/o upgrading the rear.... this would provide the oversteer you experience.
Second, you are on brakes hard into turns... maybe your rear is not settled proior to turn-in. Are you running DT-70s on the rear? May try DT-60s to reduce bias if rear is getting too squirrely. I'm a believer in the stock calipers with the right pads.... especially on Sumis.
Third, bad shocks would also provide an unplanted rear end, possibly exacerbated by a lowered front if bump steer is not corrected.
Russ provided good alignment settings - recommend -1.5 front/rear camber. As said, you can use a pryometer to dial your alignment in, but that's a whole different level doing alignments at the track in a C4.
Coil-overs do not work better than stock springs. They have 2 advantages - Easily adjusted ride-height and quick change springs at the track. Save your money.
A stock C4 is very predictable and easily correctable, particularly with street tires. I think you will really enjoy your track time once you find the "Ah-ha" problem.
Keep us posted!
Regards,
Mark
cbaclawski
05-14-2019, 10:41 AM
First, please explain "has been outfitted for road course duty".
Installing a 30mm solid front sway bar w/o upgrading the rear.... this would provide the oversteer you experience.
Second, you are on brakes hard into turns... maybe your rear is not settled proior to turn-in. Are you running DT-70s on the rear? May try DT-60s to reduce bias if rear is getting too squirrely. I'm a believer in the stock calipers with the right pads.... especially on Sumis.
Third, bad shocks would also provide an unplanted rear end, possibly exacerbated by a lowered front if bump steer is not corrected.
Russ provided good alignment settings - recommend -1.5 front/rear camber. As said, you can use a pryometer to dial your alignment in, but that's a whole different level doing alignments at the track in a C4.
Coil-overs do not work better than stock springs. They have 2 advantages - Easily adjusted ride-height and quick change springs at the track. Save your money.
A stock C4 is very predictable and easily correctable, particularly with street tires. I think you will really enjoy your track time once you find the "Ah-ha" problem.
Keep us posted!
Regards,
Mark
1: - racetech seats and harnesses, Ron Davis Radiator, new master with drm bias spring, high temp brake fluid, all 4 calipers replaced, dtc-70 pads on all 4 corners, car shipped to Chicago and thoroughly gone through mechanically, including new tune and removal of secondaries. Suspension components were inspected, but are stock, no aftermarket sways.
2- not really hard on the brakes into turns, even where I'd usually trail brake a bit I over slowed the car and was completely off the brakes and definitely settled at turn in. The problem persisted even in long sweepers, long after turn in. Any hint of throttle until almost full track out would bring it out (I was absolutely not mashing the gas...)
3- The shocks were inspected by Marc Haibeck, he didn't think they required anything, but they are original to the car - Front end stock height.
Thanks much!
Vette Guy
05-14-2019, 11:01 AM
Puzzling, but we’ll get there! Does the car roll in corners or does it remain fairly stiff? Do you get any sensation of weight transfer as you add power through turns? Or can you not add enough power? By chance, does your shifter jump up in the console?
Wondering if C-Beam is flexing at attachment points, binding in control arms or issue with sway bar mismatch/end link issue.
Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)
RussMcB
05-14-2019, 12:15 PM
Here's a quick, free thing you can do. Are you familiar with checking toe alignment using strings? It is often done by using four jack stands to create a rectangle around the car. The two side strings should be parallel with the car's centerline. Then you can measure the distances between the string and the front and rear of the rims. By comparing the gaps you should be able to tell if a rear wheel is excessively toed in or out.
This method is very good at identifying a single rear wheel that is out of alignment.
An easier, quicker (and much less accurate) method I often do is to tie a string end to something on the rear of the car, like a tail pipe, then pull it around to the side of the car, touching the rear tire's rear sidewall and the rear tire's front sidewall, then seeing where it is relative to, say, the "ZR-1" badge on the front fender. If it is a foot away from the car, that rear tire has a ton of toe out. If the string hits the middle of the door, that rear tire has a lot of toe in.
Hope that makes sense. maybe I could make a drawing or find something on the web to better describe it. Maybe Google "sting alignment".
https://www.hotrod.com/articles/ctrp-1204-determining-wheel-alignment-string-your-car/
d15b7
05-14-2019, 12:15 PM
hi again! Mark is asking really good questions. I'm leaning more and more towards 'broken or failing suspension component combined with alignment way out of wack'.
on a previous racecar I had a lower control arm bushing disintegrate during a race and the toe would radically change during braking and acceleration and the car became almost totally undrivable near the end of the race. I wrestled/limped it to the checkered flag but the last 3 laps were hair raising. visually looking at the car after the race revealed nothing, but once I got it home and up on stands and prying on the suspension and control arms revealed a totally failed lower control arm bushing which allowed tons of movement of the wheel during braking and acceleration allowing that wheel to toe in and out radically.
look carefully with the car up on a rack and pull/push/pry very hard on all components. and of course check the alignment too. good luck man!
cbaclawski
05-14-2019, 02:30 PM
Puzzling, but we’ll get there! Does the car roll in corners or does it remain fairly stiff? Do you get any sensation of weight transfer as you add power through turns? Or can you not add enough power? By chance, does your shifter jump up in the console?
Wondering if C-Beam is flexing at attachment points, binding in control arms or issue with sway bar mismatch/end link issue.
Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)
Very little roll, better there than I expected, and can definitely feel the weight transfer, though it's slight due to light throttle...
The shifter feels great, Best feeling shifter I have...
cbaclawski
05-14-2019, 02:38 PM
Here's a quick, free thing you can do. Are you familiar with checking toe alignment using strings? It is often done by using four jack stands to create a rectangle around the car. The two side strings should be parallel with the car's centerline. Then you can measure the distances between the string and the front and rear of the rims. By comparing the gaps you should be able to tell if a rear wheel is excessively toed in or out.
This method is very good at identifying a single rear wheel that is out of alignment.
An easier, quicker (and much less accurate) method I often do is to tie a string end to something on the rear of the car, like a tail pipe, then pull it around to the side of the car, touching the rear tire's rear sidewall and the rear tire's front sidewall, then seeing where it is relative to, say, the "ZR-1" badge on the front fender. If it is a foot away from the car, that rear tire has a ton of toe out. If the string hits the middle of the door, that rear tire has a lot of toe in.
Hope that makes sense. maybe I could make a drawing or find something on the web to better describe it. Maybe Google "sting alignment".
https://www.hotrod.com/articles/ctrp-1204-determining-wheel-alignment-string-your-car/
I'm somewhat familiar with the string alignment, and I might just do that just to see if there is an obvious issue. I have to get a new front tire mounted anyway, so was planning to have a professional alignment done at the same time, using the spec chart you posted...
hi again! Mark is asking really good questions. I'm leaning more and more towards 'broken or failing suspension component combined with alignment way out of wack'.
on a previous racecar I had a lower control arm bushing disintegrate during a race and the toe would radically change during braking and acceleration and the car became almost totally undrivable near the end of the race. I wrestled/limped it to the checkered flag but the last 3 laps were hair raising. visually looking at the car after the race revealed nothing, but once I got it home and up on stands and prying on the suspension and control arms revealed a totally failed lower control arm bushing which allowed tons of movement of the wheel during braking and acceleration allowing that wheel to toe in and out radically.
look carefully with the car up on a rack and pull/push/pry very hard on all components. and of course check the alignment too. good luck man!
"almost undriveable" sounds about right. I thoroughly teched the car and pulled by hand on the components, but just to check for obvious looseness, I didn't really "pry" or pull that hard...
I have a set of quickjacks so it'll be relatively easy to go over it more thoroughly...
Thanks to all, I really want to enjoy this car on track, and have invested a lot to do so. It is much appreciated
cbaclawski
05-20-2019, 03:50 PM
So I had to get a tire replaced anyway, and while it was there I had them do an alignment. Not a race shop, so all they could do is try to get back to factory specs, but at least I could get a read on what it was.
Before:
Left Front +.01deg camber +7.0 caster -.04deg toe
right front +.01 camber +6.7 caster -.04deg toe
left rear 0.0 camber -0.37deg toe
right rear -0.7 camber +0.12deg toe
rear total toe/thrust angle -0.25deg
after:
LF +0.1 camber +5.9 caster -0.03 toe
RF +0.2 camber +5.7 caster -0.05 toe
LR +0.2 camber +0.07deg toe
RR +0.0 camber +0.06deg toe
rear total toe 0.12deg thrust angle 0.01deg
Not an alignment guru by any means, and clearly the "after" is not the ideal track alignment, but are the "before" #'s bad enough to account for my handling issues??
RussMcB
05-20-2019, 05:45 PM
I notice you had some toe out on one rear tire. That's not good, but maybe not enough to cause bad handling. It will (or did) mean your car was "crabbing" slightly down the road. Probably not enough to notice.
I wonder if they were able to check for looseness that wouldn't show up in a simple, static alignment. For instance, (as mentioned by folks earlier), the problem could be bad bushings or C Beam allowing the rear alignment to go out of whack when power is applied, and when the suspension gets loaded when you start to turn in.
Do you have a suction cup Go-Pro mount you can put your camera facing a rear wheel and see if it does something crazy? Can you make it happen in an isolated parking lot or road?
I notice you have slight positive camber. That seems odd. But, if they are putting it to specs, I guess that's within range.
RussMcB
05-20-2019, 05:55 PM
Do you have a suction cup Go-Pro mount you can put your camera facing a rear wheel and see if it does something crazy? Can you make it happen in an isolated parking lot or road?This suggestion came from my thought process whenever I have a problem I'm trying to figure out:
1. Can I reproduce the problem, predictably?
2. Can I gather some kind of data when it's happening to give me clues about the cause?
Maybe that will spark some thoughts.
It's often a challenge when you have a problem at the race track and need to diagnose it at home (or on public roads).
cbaclawski
05-20-2019, 06:03 PM
I notice you had some toe out on one rear tire. That's not good, but maybe not enough to cause bad handling. It will (or did) mean your car was "crabbing" slightly down the road. Probably not enough to notice.
I wonder if they were able to check for looseness that wouldn't show up in a simple, static alignment. For instance, (as mentioned by folks earlier), the problem could be bad bushings or C Beam allowing the rear alignment to go out of whack when power is applied, and when the suspension gets loaded when you start to turn in.
Do you have a suction cup Go-Pro mount you can put your camera facing a rear wheel and see if it does something crazy? Can you make it happen in an isolated parking lot or road?
I notice you have slight positive camber. That seems odd. But, if they are putting it to specs, I guess that's within range.
Yeah don't like the positive camber. On the rear toe, had toe out on one side(driver) and toe in on the other, which I interpret to mean that the wheels were pointed, albeit slightly, to the driver side. Considering that the majority of the loose back manifested in right handers, with the back coming out towards the driver's side, It kinda makes sense, I just don't know if it was enough to matter that much. Next step is to get it up in the air at home to check the bushings/beams...
Thanks,
Curt
cbaclawski
05-20-2019, 07:08 PM
This suggestion came from my thought process whenever I have a problem I'm trying to figure out:
1. Can I reproduce the problem, predictably?
2. Can I gather some kind of data when it's happening to give me clues about the cause?
Maybe that will spark some thoughts.
It's often a challenge when you have a problem at the race track and need to diagnose it at home (or on public roads).
I do have a camera I can attach if it comes to that, but there is really no data I can think of as it happens pretty much anytime the car is turning, more exaggerated in right hand turns (which is most of them when running clockwise)
You are totally right about being hard to diagnose track issues at home or on the roads. There really isn't anywhere I can simulate track conditions safely on the road, at least around here. I'd love to go test out the changed alignment and see if that helped, and if so, fine tune it some more. Short of a track day I just cant. Also, I have a TT event this coming weekend in the e46, so I'm spending most of my time teching/readying that car. Next event I have is June 23 weekend, and wasn't planning on bringing the Z, so it might be 2 months before I can even see if I'm on the right track.
Thanks again,
Curt
Vette Guy
05-21-2019, 12:50 AM
Agree with Russ, as I don’t think it was enough to cause bad handling. That said, prior to running C-Beam plates (run them on all my cars) the back end would kick out to one side (I just can’t recall which side) when I spun tires. Again, doubt this is the cause, but could contribute to it.
A ‘96 GS ended touring laps at the Gathering this past weekend after encountering the same problem... he was running Sumis. Add the possibility of tires to the list, particularly as they were 315 rears. Doubt he had the track experience you have though.
The puzzle continues....
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cbaclawski
05-21-2019, 01:11 AM
Anybody got a pic of the c-beam?
I can at least get under the car and check that the existing bolts are tight if I know what I'm looking for...
Searching on google confused me more than I already was...
Vette Guy
05-21-2019, 01:22 AM
9606
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cbaclawski
05-21-2019, 01:27 AM
9606
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Thanks, Hopefully I can get under there tomorrow...
spork2367
05-21-2019, 09:00 AM
...and there aren't too many options in our size.
Rear tires available in 315/35R17
Hoosier A7
Hoosier R7
Mickey Thompson ET Street S/S
Mickey Thompson ET Street R
Toyo Proxes R888R
Toyo Proxes TQ
BFG G-Force R1
BFG G-Force R/S
Goodyear Eagle F1 GS-D3
Nitto NT555
Nitto NT555 G2
Nitto NT555R
Nitto NT05
Nitto NT05R
Nitto NT01
Nitto Motivo
Kumho Victoracer V700 (available but discontinued)
335/35R17
Michelin Pilot Sport PS2
Pirelli P Zero System
cbaclawski
05-21-2019, 06:11 PM
Rear tires available in 315/35R17
Hoosier A7
Hoosier R7
Mickey Thompson ET Street S/S
Mickey Thompson ET Street R
Toyo Proxes R888R
Toyo Proxes TQ
BFG G-Force R1
BFG G-Force R/S
Goodyear Eagle F1 GS-D3
Nitto NT555
Nitto NT555 G2
Nitto NT555R
Nitto NT05
Nitto NT05R
Nitto NT01
Nitto Motivo
Kumho Victoracer V700 (available but discontinued)
335/35R17
Michelin Pilot Sport PS2
Pirelli P Zero System
This is a great list, thank you. I'm going to keep chasing suspension issues for now, but if that fails I'll def try another tire. If I do get it sorted, I'll need new tires even sooner than later anyway!
Thanks again
ZWILD1
05-22-2019, 07:08 PM
I installed the Michelin PS2's so my son could do the HPDI at BG. Glad I spent the money. I rode with him on the touring laps which got pretty spirited. The car was stuck to the track really well. Not one twitch from the rear and the car has the power to kick it out. He really had me gripping as we went through the turns at BG. I was impressed with how well the car actually did staying planted. I was on top watching from the observation area when the 96 GS owner came up saying he was all over the place running on the Sumitomo tires. I think he was the only C4 that was not staying planted at the HPDI.
Vette Guy
05-22-2019, 07:56 PM
Maybe a bad run of 315 Sumis? That did cross my mind...
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cbaclawski
05-22-2019, 09:02 PM
I installed the Michelin PS2's so my son could do the HPDI at BG. Glad I spent the money. I rode with him on the touring laps which got pretty spirited. The car was stuck to the track really well. Not one twitch from the rear and the car has the power to kick it out. He really had me gripping as we went through the turns at BG. I was impressed with how well the car actually did staying planted. I was on top watching from the observation area when the 96 GS owner came up saying he was all over the place running on the Sumitomo tires. I think he was the only C4 that was not staying planted at the HPDI.
Maybe a bad run of 315 Sumis? That did cross my mind...
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Certainly could be. I haven't had a chance to get in to the suspension or the c-beam yet. Planning on thoroughly going over both and tweaking the new alignment a touch, then giving it one more shot with these tires. If that doesn't fix it, tires are the next logical step.
My track events are pretty booked up already until July(though I may be able to squeeze it in one day of a 2 day event in June). Once I get done going over it I'll post here if I find a smoking gun. Otherwise it might be a month or 2 before I get a chance to test it... Unless there is one of those SCCA "track night in America" events in the meantime (but not at Charlotte motor speedway - definitely not the place to test it!)
Hib Halverson
05-27-2019, 01:19 PM
I'll be honest, because of time constraints this morning...I have a long list of honey-dos to address...I skimmed this thread.
In reading it fast, apparently the OP has been over the car or had a service shop go over the car and the suspension and brakes are in excellent working order, with the exception of checking the torque beam bolts at the trans and axle. As others have suggested, installing torque beam plates at the time you check those bolts is a good idea.
If any of my assumptions are incorrect, then the suspension, brakes, torque beam bolts and powertrain mounts need to be inspected in their entirety and serviced/replaced as necessary.
Ok, now a few comments...
On suspension condition...if you're going to regularly going to track the car, the suspension needs to be better than just "good" condition. All suspension and chassis parts need to be in excellent condition or new. Ball joints, front tie rod ends, bushings, stab. bar links, trailing arms, rear tie rods and etc need to be at least in "very good" condition if not new.
Ditch the Sumitomo tires. They are crap. I don't care what anyone else, here, says. For track use Sumitomos are at the bottom of the list of tires I'd consider for tracking. You need some tires suitable for track activities. The tires need to be predictable at the limit, ie: their breakaway is such that the driver has some good feedback as he/she approaches the tire's limit, they need to have excellent grip and they need to have good steering feel. Someone else posted a list of tires. I'd be looking at some of the brands on that list.
The alignment you have, now, is not inappropriate for track use. The car is going to be way tight and you'll burn though a set of front tires in no time. Ah, well, considering the Sumitomos, maybe that's not so bad. A good street track alignment is half a degree negative camber all the way around, as much front caster as you can get with that negative camber, zero toe up front and a 16th to a 32nd toe-in per side in the rear. A track-only alignment needs to be more aggressive in negative camber both front and rear.
All ZR-1s suffer from drop- or trail-throttle oversteer to some extent, so you need to be like a Porsche guy: don't lift abruptly at corner entrance or that sucker is going to rotate faster than you can say "in the fence". That said, in this case, it sounds like the car's normal trail-throttle oversteer is being amplified by some aspect of the car's set-up or condition of suspension parts. Again, inspect everything and service/replace as necessary and give the Sumitomos to someone who you don't like.
If you're really serious about tracking, you may want to update SRC to the 92-95 config with the late shocks and the late controller because the late system can change bypass valve position much faster. Even better would be a set of late SRC shocks with Bilstein "Moraca" valving, if you can find a set. That valving included some changes to address the ZR-1s tendency towards trail-throttle oversteer. The idea is to better control the car's weight transfer during the transition from accel to dccel.
You said this car has been prepared by someone else for "road course duty". Can you post the spring codes and the stabilizer bar sizes? Also, what kind of stabilizer bar links does the car have? Lastly, does it have base or Z51 lower front control arms?
Coilovers are likely not the solution in this instance. While they do offer a lot of adjustment and can enable a lower ride height, the downside is, in a track environment, you have to know how to use all that adjustment and the whole set-up needs to be more stiff because of the ride travel you loose when you go from composite leaf springs to coil overs. What I'd do is try to get the car sorted with the production-based suspension and then, later, once you can lap the car competitively with the plastic springs, then covert to coilovers if you feel the need. I would not look at a coilover conversion as a quick fix.
Hope you get the car sorted so it's quicker on the track.
cbaclawski
05-28-2019, 08:34 PM
I'll be honest, because of time constraints this morning...I have a long list of honey-dos to address...I skimmed this thread.
In reading it fast, apparently the OP has been over the car or had a service shop go over the car and the suspension and brakes are in excellent working order, with the exception of checking the torque beam bolts at the trans and axle. As others have suggested, installing torque beam plates at the time you check those bolts is a good idea.
If any of my assumptions are incorrect, then the suspension, brakes, torque beam bolts and powertrain mounts need to be inspected in their entirety and serviced/replaced as necessary.
Ok, now a few comments...
On suspension condition...if you're going to regularly going to track the car, the suspension needs to be better than just "good" condition. All suspension and chassis parts need to be in excellent condition or new. Ball joints, front tie rod ends, bushings, stab. bar links, trailing arms, rear tie rods and etc need to be at least in "very good" condition if not new.
Ditch the Sumitomo tires. They are crap. I don't care what anyone else, here, says. For track use Sumitomos are at the bottom of the list of tires I'd consider for tracking. You need some tires suitable for track activities. The tires need to be predictable at the limit, ie: their breakaway is such that the driver has some good feedback as he/she approaches the tire's limit, they need to have excellent grip and they need to have good steering feel. Someone else posted a list of tires. I'd be looking at some of the brands on that list.
The alignment you have, now, is not inappropriate for track use. The car is going to be way tight and you'll burn though a set of front tires in no time. Ah, well, considering the Sumitomos, maybe that's not so bad. A good street track alignment is half a degree negative camber all the way around, as much front caster as you can get with that negative camber, zero toe up front and a 16th to a 32nd toe-in per side in the rear. A track-only alignment needs to be more aggressive in negative camber both front and rear.
All ZR-1s suffer from drop- or trail-throttle oversteer to some extent, so you need to be like a Porsche guy: don't lift abruptly at corner entrance or that sucker is going to rotate faster than you can say "in the fence". That said, in this case, it sounds like the car's normal trail-throttle oversteer is being amplified by some aspect of the car's set-up or condition of suspension parts. Again, inspect everything and service/replace as necessary and give the Sumitomos to someone who you don't like.
If you're really serious about tracking, you may want to update SRC to the 92-95 config with the late shocks and the late controller because the late system can change bypass valve position much faster. Even better would be a set of late SRC shocks with Bilstein "Moraca" valving, if you can find a set. That valving included some changes to address the ZR-1s tendency towards trail-throttle oversteer. The idea is to better control the car's weight transfer during the transition from accel to dccel.
You said this car has been prepared by someone else for "road course duty". Can you post the spring codes and the stabilizer bar sizes? Also, what kind of stabilizer bar links does the car have? Lastly, does it have base or Z51 lower front control arms?
Coilovers are likely not the solution in this instance. While they do offer a lot of adjustment and can enable a lower ride height, the downside is, in a track environment, you have to know how to use all that adjustment and the whole set-up needs to be more stiff because of the ride travel you loose when you go from composite leaf springs to coil overs. What I'd do is try to get the car sorted with the production-based suspension and then, later, once you can lap the car competitively with the plastic springs, then covert to coilovers if you feel the need. I would not look at a coilover conversion as a quick fix.
Hope you get the car sorted so it's quicker on the track.
Wow, Thank you!
I tried to give alignment specs to the quickie lube shop where the car was, but they didn't have the equipment to do anything other than "factory" I figured since it was there getting a tire replaced anyway, just let them do it. Even if for no other reason than to see the before #'s and potentially rule that in or out as the issue. I'll have it done correctly soon, but haven't had time yet.
I don't know the spring codes or stabilizer bar sizes, but I'd assume they are whatever came stock in 1990. Being a ZR1 I'd expect it to have the z51 lower front control arms. Again though, I'm not 100% sure. Was this an option on ZR1's or did they all come with the z51?
The car has been inspected by my local race shop (which is admittedly more of a BMW racing shop), and also shipped to Marc Haibeck for a thorough once over. Both were told of my intentions with the car and gave the suspension a clean bill of health. The beam bolts may well have been checked, but seem easy enough for me to double check just in case.
My plan is, time permitting, go over everything you mentioned myself just to be sure. I have both a 4 post lift and a set of quickjacks, so access shouldn't be a problem.
Hopefully I can get the car controllable on the sumi's, wear them out quickly, then go to a better tire. If I can get it decent on the existing tires, it'd probably be great on better tires.
If after everything is done, and it's still uncontrollable, I'll swap the tires proactively. If that doesn't work, I'll just put street pads back on it and reinstall the factory seats and enjoy it for what it is on the road...(I really hope it doesn't come to that)
Thanks again for your interest and help!
WARP TEN
05-29-2019, 10:49 AM
Maybe a bad run of 315 Sumis? That did cross my mind....
.......Ditch the Sumitomo tires. They are crap. I don't care what anyone else, here, says. For track use Sumitomos are at the bottom of the list of tires I'd consider for tracking.............
Have to concur with both. Not sure there has ever been a good run of Sumis. I had a couple of sets of Sumis, one I bought because they were cheap ('93) and one because they were on the car when I bought it ('95). They got hard fast, seemed to have little traction and on my '95 I had a wheel vibration that I could not eliminate by balancing until I finally got to a great tire place in Bowling Green (S&R Tire on Lover's Lane) with an excellent tech and a Hunter Road Force machine in 2014. He had to spin all the tires on the wheel rims to get them even close and one tire he said he could not balance properly because it was so far out of manufacturer's specification. He eliminated about 95% of the vibration though which was a help. I switched to Michelin Pilot Sports shortly thereafter. Great tires even if a little bit wider in the rear. --Bob
cbaclawski
05-30-2019, 07:21 PM
Ok, While I still haven't had a chance to inspect the suspension/c-beam (real life, other projects...) It seems pretty clear that the Sumitomo's, even if not the main problem, certainly aren't helping anything.
So here is my dumb question:
Since the car really only struggles for rear grip and the front seems great, how bad of an idea would it be to replace only the rears? One of the fronts is 100% brand new, and the other is 90%(they'll even out after 2 track sessions, the driver side wears much faster)
Maybe I'm just being cheap, but I run 4 track cars, and the expenses really add up. If possible, I'd like to spend as little as I can replacing essentially new tires on a car that only gets 2-3 track days a year....
Curt
RussMcB
05-30-2019, 07:47 PM
Wait until you've had a chance to find the real culprit, then go back to the track with your four Sumitomo's and see if you found and fixed the problem.
I'm thinking (without really knowing) that the Sumitomo's may be lousy tires, but they are unlikely to be the real problem, and you should still be able to have some fun with them before replacing them. I mean, they can't be so bad and unpredictable that they try to kill you every corner, right? :-)
I'm a low budget racer, too, so I certainly understand using up what you have before spending money to replace it.
cbaclawski
05-30-2019, 08:43 PM
Wait until you've had a chance to find the real culprit, then go back to the track with your four Sumitomo's and see if you found and fixed the problem.
I'm thinking (without really knowing) that the Sumitomo's may be lousy tires, but they are unlikely to be the real problem, and you should still be able to have some fun with them before replacing them. I mean, they can't be so bad and unpredictable that they try to kill you every corner, right? :-)
I'm a low budget racer, too, so I certainly understand using up what you have before spending money to replace it.
That was kind of my plan, get the car running straight, burn out these tires(which only takes a couple days @ CMP), then replace the tires and start pushing it. With all the negativity towards the sumitomo's, and the possibility that they could be a real part of the problem, I was starting to waver...
Thanks
cbaclawski
05-30-2019, 11:08 PM
I finally got the back wheels off and inspected every suspension joint and lubed the bushings. Everything seemed in order. It felt really good on the street, but it's hard to simulate track conditions on the street, in the dark.
I'm still planning on getting it up on the 4 post to tweak the alignment and inspect the c-beam, but feel like maybe between the somewhat better alignment and the lubricated joints, I'm making progress.
I'll be thrilled if I can get this right. There was a guy at the SCCA Time trial I attended last weekend in a heavily modified non-zr1 c4(don't know year, but def. pre '91) turning some really fast laps. I didn't get a chance to talk to him so I don't know exactly what his set up was, but I'd put money on it that properly configured my car has more potential than whatever he was running. (though for all I know I suppose it could have had a pro-charged lsx, giant brakes, etc... but I doubt it)
32valvesftw
05-31-2019, 09:04 AM
You need to try different tires and see what happens. The single biggest improvement to the handling of my car was getting rid of the BFG tires on and going with Nittos, now that the Nittos have a few years on them they are getting less grippy. How old are the Sumis did you check the date code? Maybe squirt some tire compound in them for a few laps and see what happens.
cbaclawski
05-31-2019, 09:12 AM
You need to try different tires and see what happens. The single biggest improvement to the handling of my car was getting rid of the BFG tires on and going with Nittos, now that the Nittos have a few years on them they are getting less grippy. How old are the Sumis did you check the date code? Maybe squirt some tire compound in them for a few laps and see what happens.
I haven't checked the date code(which I will do), but they were purchased new from Tire rack < 1yr ago.
Tire Compound? That sounds interesting, what is it and what does it do?
When I had the tires off last night, I inspected them and they didn't feel hardened, though I'm not sure how much you can tell just by feeling them cold...
32valvesftw
05-31-2019, 07:52 PM
Tire compound is a chemical used to soften tires and improve their grip.
A couple of examples below. The kart racing guys use this as do some stock cars (but not legally)
https://www.speedwaymotors.com/Track-Claw-2995-Tire-Strengthener-Softener-1-Gallon,2162.html?sku=91044150&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=Cj0KCQjwocPnBRDFARIsAJJcf96qeouZ2KZ_x7wnw1cq rxj8ad9fuQ6CEsGg4KFkE4u3gM_MTqjlVWoaAg3qEALw_wcB
https://www.ombwarehouse.com/9863-fts-black-bite-must-ship-ups-ground/?gclid=Cj0KCQjwocPnBRDFARIsAJJcf96Qri_sIUe4OpUEP-gdby6RzhWMxlJUWmcuu4ni9B1Q8s7xV4s07j4aAmEzEALw_wcB
cbaclawski
05-31-2019, 08:24 PM
Tire compound is a chemical used to soften tires and improve their grip.
A couple of examples below. The kart racing guys use this as do some stock cars (but not legally)
https://www.speedwaymotors.com/Track-Claw-2995-Tire-Strengthener-Softener-1-Gallon,2162.html?sku=91044150&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=Cj0KCQjwocPnBRDFARIsAJJcf96qeouZ2KZ_x7wnw1cq rxj8ad9fuQ6CEsGg4KFkE4u3gM_MTqjlVWoaAg3qEALw_wcB
https://www.ombwarehouse.com/9863-fts-black-bite-must-ship-ups-ground/?gclid=Cj0KCQjwocPnBRDFARIsAJJcf96Qri_sIUe4OpUEP-gdby6RzhWMxlJUWmcuu4ni9B1Q8s7xV4s07j4aAmEzEALw_wcB
Any experience with it? How long does it last? I'm intrigued!
cbaclawski
06-01-2019, 01:47 AM
C-Beam bolts are good and tight...
I gave them all everything I've got with a long torque wrench, could only budge one of them, and even then less than 1/4 turn. I'm not a small dude either (6'2" 275lb who once benched 225lb 32 times on a burnout set)
Tomorrow I'm going to tweak the alignment a bit to give it some rear toe in and a touch of negative camber.
Then I need to get it back on track, I think there is a SCCA Track night coming up in between events I've already committed to in other cars... Fingers Crossed!
RussMcB
06-01-2019, 08:12 AM
Any experience with it? How long does it last? I'm intrigued!I've used it in the past, when I've had race tires more than a year old, they're hard, not grippy, and you want to get some more mileage out of them. The one I've used the most is "Formula V", but there are probably other good ones, too. You might want to buy it from a road racing parts store rather than drag racing or karting. https://www.jegs.com/i/Formula-V/398/FORMULA+V/10002/-1
C-Beam bolts are good and tight...That's too bad. I was hoping that was the problem. Oh, well, at least you now have peace of mind regarding them.I think there is a SCCA Track Night coming up ... Charlotte next weekend? I'm planning to go.
Want me to bring my ZR-1 race tires/wheels? :-)
cbaclawski
06-01-2019, 11:21 AM
I've used it in the past, when I've had race tires more than a year old, they're hard, not grippy, and you want to get some more mileage out of them. The one I've used the most is "Formula V", but there are probably other good ones, too. You might want to buy it from a road racing parts store rather than drag racing or karting. https://www.jegs.com/i/Formula-V/398/FORMULA+V/10002/-1
That's too bad. I was hoping that was the problem. Oh, well, at least you now have peace of mind regarding them.Charlotte next weekend? I'm planning to go.
Want me to bring my ZR-1 race tires/wheels? :-)
I wasn't planning on running the roval, I've done it before and it was a blast, but in my Low Hp cars the oval part is kinda boring after a while, and I don't have the cajones to take a powerful car out there. I'm definitely not taking the Z out there until I'm 100% sure it is handling properly... It's one thing to go off @ 80 into a sand pit, an entirely different animal when there's a wall and you are going 160. If I get it sorted, I'll probably hit that track next year with it.
I was thinking the June 27th TNIA at CMP in SC, but I'll already be there the 22-23 for 2 full day track days, so I don't know if I'll have the energy to make that one. That's my opportunity to test the Z, so I might try...
All that said, I live in south Charlotte and CMS is not that far, I'd definitely come out just to watch if you were bringing your Z, and even if you are bringing a different car, maybe I'll drive my Z up there so you can peek at it, and run the touring laps.
Which brings us to the wheels/tires we've discussed on and off for what seems like a couple years ;) . Given my current issues with the car, I may finally be interested in them, and the Charlotte event next weekend would make for an easy transaction. I'm mostly interested in the tires, remind me what's on the wheels? How old are they? I'll PM you my email.
RussMcB
06-01-2019, 12:22 PM
I'm mostly interested in the tires, remind me what's on the wheels? How old are they? I'll PM you my email.Nitto NT05 tires. I guess they are three years old now. They've been stored in my garage all this time. Most of the details are here:
http://zr1.net/forum/showthread.php?t=26298
I was pretty happy with them. The car was easy to drive at the the limit. Never spun out with them. :-)
on edit: I just reread that post more closely, and (at that time) I was planning to keep four mounted wheels and tires for my own use, and selling the 'extras' in case someone was interested in them. However, now (since I have a full time race car), I actually have (almost) two full sets of race tires/wheels available.
This is a busy weekend for me, but I will try to pull them all out enough to take some current pictures. Got your PM with email. I'll touch base with you there, later. Thanks for the interest.
cbaclawski
06-01-2019, 02:16 PM
Nitto NT05 tires. I guess they are three years old now. They've been stored in my garage all this time. Most of the details are here:
http://zr1.net/forum/showthread.php?t=26298
I was pretty happy with them. The car was easy to drive at the the limit. Never spun out with them. :-)
on edit: I just reread that post more closely, and (at that time) I was planning to keep four mounted wheels and tires for my own use, and selling the 'extras' in case someone was interested in them. However, now (since I have a full time race car), I actually have (almost) two full sets of race tires/wheels available.
This is a busy weekend for me, but I will try to pull them all out enough to take some current pictures. Got your PM with email. I'll touch base with you there, later. Thanks for the interest.
Sounds good, still a few days till the even, so no hurry. Are you going june 6 or 7? Looks like there is an event both days. I'll tentatively plan on going whatever day you are regardless of whether we figure out a wheel/tire package...
RussMcB
06-01-2019, 09:02 PM
I'll get there Friday afternoon. I'm doing the SARRC races. Saturday is a qualifying session, then a short race Saturday afternoon. Saturday evening there will be some racing under the lights (different class than mine). Sunday is a longer (40 minute) race. I'm in group 7. Here's the event schedule (PDF download):
https://ucarecdn.com/8fe626da-c9e1-44fa-82b7-26a3e62020f6/
If you remind me I can put you on my crew list so you can get in for free. I promise not to make you work. :-)
Hib Halverson
06-05-2019, 12:22 AM
Ok, While I still haven't had a chance to inspect the suspension/c-beam (real life, other projects...) It seems pretty clear that the Sumitomo's, even if not the main problem, certainly aren't helping anything.
So here is my dumb question:
Since the car really only struggles for rear grip and the front seems great, how bad of an idea would it be to replace only the rears? One of the fronts is 100% brand new, and the other is 90%(they'll even out after 2 track sessions, the driver side wears much faster)
Maybe I'm just being cheap, but I run 4 track cars, and the expenses really add up. If possible, I'd like to spend as little as I can replacing essentially new tires on a car that only gets 2-3 track days a year....
Curt
Why risk putting it in the fence with tires which are clearly not working for you?
Invest some money is some good tires that will work well on the track and you'll go a lot quicker and in a more safe manner.
cbaclawski
06-05-2019, 03:32 PM
Why risk putting it in the fence with tires which are clearly not working for you?
Invest some money is some good tires that will work well on the track and you'll go a lot quicker and in a more safe manner.
Obviously there is no rational argument against anything you just said.
However, I never claimed to be bright! Also, if it isn't the tires, I don't want to mask an underlying issue(whether car or driving ability) that better tires might hide.
Probably going to buy some rear scuffs from Russ, and if it pushes I'll feel confident enough to replace all 4 with a better, or at least matched set.
I will say that post alignment, even though it's not a "Track" alignment, it does feel much better on the street. Rear "Thrust angle" was off quite a bit...
Curt
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