Alignment settings & tires for racing

[jrtoffroad]

Hey guys,

I've been autocrossing my Z recently (details and vid's here: http://www.zr1.net/forum/showthread.php?p=111592#post111592 ) and am just about ready to pull the trigger on a new set of Nitto NT01's. Any experience with these? I plan to run them in the stock size on my extra rims and use them only for racing. I'd love to know how the hold up, is the grip comparable to other r compound tires, and what pressures work well as a baseline for our cars.

I'd also like to step up to some more aggressive alignment settings. From what I've read I'm thinking:
Front: 1.5-2 deg negative camber, no toe in, and caster at stock specs
Rear: ~1 deg neg camber, 1/16" toe in

Thoughts? I do drive this on the street, and plan to use it for road course work as well as autocross and drag racing. I've read mixed opinions on caster but, from what I understand, to achieve significant negative camber on a C4 I'll likely have to remove all the shims and have no caster adjustment (my car is lowered, not sure if this still holds).

THANKS!
Jordan

[tccrab]

Here's a link to Dynomites solutions pages that address alignment:
http://www.zr1.net/forum/showpost.php?p=100559&postcount=2

Depends on what kind of racing you do:
http://i71.photobucket.com/albums/i159/tccrab/4x4vette2.jpg
:-D:dancing

TomC
'Crabs

[PhillipsLT5]

http://www.vbandp.com/Tech-Info/

[batchman]

Hey Jordan welcome to autoxing the Z. I run in BSP up in New England, the Evos have me pwned except on a small lot/1st gear course (the car is an absolute RIOT on one of those!).

I run (huge) a6's, can't comment on the Nittos other than I have used 555R2s before on another car, a good dual use tire but not competitive with full slicks. I gather the nt01's answer the same description. Probably a good choice for event day if you're not chasing FTD, and should work in some wet and some cold better than the true slicks (v710/a6/r6) and will last longer too.

I have my front as you describe, but rear at -2.5deg and about 1/4" toe in. I only got about -1.5 in front and need more, so it's offset bushings for me. Street manners are fine except for rut-worn roads will pull you around a bit. I found the rear bar was too big even with the wild alignment. Of course I've doubled the spring rates (and need to do it again LOL).

I found the slow rack to be an obstacle so I campaigned for an SCCA rules change and got it, now I run a quick rack from a z51 This gave me trouble with power steering pump and cooling, if you have issues get the Turn One ZR-1 "stock replacement for autocrossing" and you'll be good. I went through a whole lot to discover that ;).

I'd start with low 30s for tire pressure, start same all around and re-check them before each run as they will increase and heat-soak. Get yourself one of those cheapie IR pryometers and use it to check tire temps inside, middle, and outside - adjust pressures (and alignment) until you're as uniform across the tire as you can get. Decrease pressure at the end that loses grip first, try a couple pounds at a time. Don't go below 28 or so trying to fix the too-big sway bar though!

One other tip, these cars understeer under braking so get your braking done in a straight line! And make sure your brake fluid is fresh since once you find the right pedal you'll want the middle one soon after!

Best,
- Jeff

[lbszr]

Hey guys,

I've been autocrossing my Z recently (details and vid's here: http://www.zr1.net/forum/showthread.php?p=111592#post111592 ) and am just about ready to pull the trigger on a new set of Nitto NT01's. Any experience with these? I plan to run them in the stock size on my extra rims and use them only for racing. I'd love to know how the hold up, is the grip comparable to other r compound tires, and what pressures work well as a baseline for our cars.

I'd also like to step up to some more aggressive alignment settings. From what I've read I'm thinking:
Front: 1.5-2 deg negative camber, no toe in, and caster at stock specs
Rear: ~1 deg neg camber, 1/16" toe in

Thoughts? I do drive this on the street, and plan to use it for road course work as well as autocross and drag racing. I've read mixed opinions on caster but, from what I understand, to achieve significant negative camber on a C4 I'll likely have to remove all the shims and have no caster adjustment (my car is lowered, not sure if this still holds).

THANKS!
Jordan

It's good for the road track. The 01 has good longevity, but I'm running 2.5 up front and still have to flip the tires on the wheels to get all their life. Rear is 1.6 camber and they wear pretty even on the track. Cold 26 psi seems to give me the best traction when they get up to temp, with less camber, they need more pressure though (at least if your going for maximum tire wear). I don't think their the stickiest, but a good price. For competition, I see Hoosier and Kumho 710 used a lot. I don't know how the 01 would do for autocross, it might not get up to temp fast enough. Nitto might have some good suggestions, their nt05 might be good for autocross and the road track. If your driving to the track, the r compounds are not good.

With stock control arm bushings, 1.5, 2 is probably the maximum you'll get, maybe even less. Just match the other side to the side that has the least. I think 1.3 was all I could get from the drivers side on mine with stock bushings, the conical washers were even machined down as thin as possible, I forget what caster ended up at, I matched that to the other side also. The rear with the 1/16 toe in will make it handle really good.

I've only put about 3000 a year on mine, but I can't really say the camber is causing bad tire wear on the street, and if it did I would keep flipping the tire on the wheel. 0.0 toe on the front.

Hope some of this helps:cheers:

[jrtoffroad]

Thanks for the advice!

Vette brakes advice seems to jive with what I was thinking. Interesting to see how little neg camber they recommend up front in a C5, wonder why....


Batchman,
Glad you weighed in, I've followed your autocross thread. I planning to stick with stock sizes front and rear (you're running 315's up front right?!), but still find the car to be a little tail happy. Although fun, wondering if it'd help to slap a 30mm bar up front.

Haven't had any real complaints with the steering ratio yet, but that probably means I'm just not fast enough :o.

I was running ~37 up front and ~36 in the rear with my street tires, but found a little better traction after lowering that to about 35 & 33. The pyro gauge is a great idea, afraid I'm not getting much out of reading the side wall.

lbszr,
Thanks for the input. I really like the price of the NT01...but have also been looking at the Hoosier, Kumho, and BFG slicks.

Guess I'll see how far I can go with stock control arm bushings, then figure out which tires are in the budget.

[lbszr]

Just had to put this eye candy on here in case you wanted to be able to dial in almost anything, from Guldstrand.http://i188.photobucket.com/albums/z41/myphotos123456/G92749-G92750.jpg

I did offset bushings. But after pricing, it wouldn't cost that much more to do these control arms instead. I'm not adding in new upper ball joints though, which might be needed.

I think the C5's run less camber in "theory" because the frames flex less. But I rode in a C5 Z06 with -3 camber up front with R6 Hoosiers, starting at 20 psi cold. His front tires were wearing even and that thing stuck to the track like glue, on a road course.

[lbszr]

Thought these specs were interesting from the General Motors ZR-1 dirvers manual.

http://i188.photobucket.com/albums/z41/myphotos123456/File01212.jpg

[jrtoffroad]

Wow, those control arms are hot. Shouldn't tempt me with things like that :-D

Thanks for putting up the pics of the drivers manual...I need to get one of those! Did those come with the car from the factory? Could you verify what it says for toe-in? It's a little hard to read.

-Jordan

[lbszr]

Wow, those control arms are hot. Shouldn't tempt me with things like that :-D

Thanks for putting up the pics of the drivers manual...I need to get one of those! Did those come with the car from the factory? Could you verify what it says for toe-in? It's a little hard to read.

-Jordan

The manual came from the zrnetregistry. I don't think they have them now. I'm not sure, but I think they did come with the car when they were new.

The manual lists 10' for the front toe in, and 25' for the rear toe in. Actually, I'm not sure what that means? If 25' means .25 inch, that seems like a lot to me.

http://i188.photobucket.com/albums/z41/myphotos123456/Project1.jpg

[VetteMed]

25' probably = 25 minutes, or 0.25 degree?

[lbszr]

25' probably = 25 minutes, or 0.25 degree?

You got it, I forgot I had a calculator to that, it comes out to .41666667 degrees, and .1666666667 degrees on the front. Now we need somebody to figure that out to inches.:eek:

I don't have tools to measure toe in angle.

[jrtoffroad]

Thanks for the math Dynomite.

You're assuming it's 10' & 25' between the tire and the vehicles centerline. I thought it would be the angle between the two wheels, thus giving you 1/2 your calculation or a total toe-in of ~ 1/32 and 1/16 when measuring tire to tire.

Thoughts?

[lbszr]

[QUOTE=Dynomite;111767]Excellent point..I made some assumptions :D
That I am not sure about......normal Toe In is comparing distance between Front of tires (right and left tire) to distance between Rear of tires (right and left tire) on same axle.

It appears however since angles are used it is for the individual tire angle around vertical (Toe In) and the individual tire angle around longitudinal (Camber).

If you are correct (you prolly are) we end up with a Toe In Rear of 1/8 inch and Toe in Front of 1/16 inch (called a Racetrack Setup) ;)
http://www.guldstrand.com/alignment.asp

lbszr did you buy these adjustable control arms and install them on a ZR1? It appears to me these would fit on my 91' ZR1 as well as my 91' Corvette with L98 ;)
http://www.guldstrand.com/scripts/prodList.asp?idCategory=42

/QUOTE]

Thanks for figuring all that out, that makes my brain hurt.

I have not bought those control arms, just wish I would of when I had the front end apart. -2.5 Camber is all I can get, even with the offset bushings on the lower control arm. I believe the control arms would fit on both your 91's. It looks like any C4 88-96 would use the same one.

That confuses things with VBP measureing wheel to wheel, and GM's track specs measureing from the wheel to the centerline of the car for base settings. It looks like they both agree on the same measurement for the rear toe in, which is where I have mine set. The front toe in might give it a sluggish feeling on the turn in's, but make it stable on the straights. At 0.0 front toe in, mine is still good on the straights.

[VetteMed]

Those of you who are doing your own alignments, what equipment are you using to do so?

[batchman]

Just a note as it took many tries to get my wife's 88 Z51 car to behave. We wound up rear at -3 deg camber and 1/4" total toe-in on the rear end, a recipe passed down from a couple nat champ c4 autoxers. The car looks broken but the thing finally hooks - no more oversteer. It has to do with bump steer ie when the outside is under compression the toe changes dyamically. The 1/4" total toe-in sets it up to be correct for the max load in the corner, which in autox is an awful lot of your lap.

I backed away some from those settings due to much wider tire - 335 vs 295, ironically I've wound up using the same spring as her car but lighter sway bar. I still need to dial this in a little further but it's looking like -2.6 or so and maybe 3/16ths total toe in for rear traction in corner slightly prioritized over launch.

HTH,
- Jeff

[jrtoffroad]

Those of you who are doing your own alignments, what equipment are you using to do so?

I'd also be curious to hear what everyone is using. I did see this article on completing an autocross alignment for a C4 corvette:

http://www.flintcorvetteclub.com/images/Autocrossing/Alignment%20%28Web%29.pdf

[lbszr]

Those of you who are doing your own alignments, what equipment are you using to do so?

I've seen brackets online for under 200$.

Or you can do a set up like this, http://wiki.seloc.org/a/Geo_Alignment_Rig_(Home_Made) (I don't know how to fix it, but add a parenthesis to the end of the address) I use pvc pipes with fishing string and bungee cord it to the tail pipes and lower front spoiler. Laser level for toe, and no calculations since I set it to 0.0. Harbor Freight digital angle measure was 20 or 30$, and it's been checked to +-.15 degree. I put it on four wheel dollys for easy settling, or it could be rolled, or grease plates. Setting up the strings takes the longest. Probably 12 hours to get it the first time. About 3 hours now. The castor can be checked with string also, but wasn't easy.

[lbszr]

I'd also be curious to hear what everyone is using. I did see this article on completing an autocross alignment for a C4 corvette:

http://www.flintcorvetteclub.com/images/Autocrossing/Alignment%20%28Web%29.pdf

Looks like a good article. If the string setup is not secured to the car though. It would not be centered anymore when the car is moved or needs jacked up and resettled to adjust the rear toe, and double check after tightening toe rods.

[jrtoffroad]

Alright, got the car aligned yesterday:

FRONT
Camber: -1.5 -1.6
Caster: 5.5 5.6
Toe in: 0 0


REAR
Camber: -1.2 -1.2
Toe in: 1/8 total (1/16 per wheel)

We noticed a fair difference with me in or out of the car, so these settings were achieved with me in the car. Not as much front camber as I was hoping for, but I may try grinding down the spacers, should get me pretty close to 2 deg.

Another Autocross this weekend, can't wait to see how it feels!

QUESTION:
I played around with the rear bolts to level the rear. My car does NOT have a noticeable lean, but I was trying to get it perfect and now have 1 bolt set maybe 1 inch shorter than the other (really didn't make much of a difference in the suspension height). Is there any issue with this? Is this the proper way to dial in the rear suspension, or should I just set both bolts the same?

Thanks!
Jordan

[lbszr]

Alright, got the car aligned yesterday:

FRONT
Camber: -1.5 -1.6
Caster: 5.5 5.6
Toe in: 0 0


REAR
Camber: -1.2 -1.2
Toe in: 1/8 total (1/16 per wheel)

We noticed a fair difference with me in or out of the car, so these settings were achieved with me in the car. Not as much front camber as I was hoping for, but I may try grinding down the spacers, should get me pretty close to 2 deg.

Another Autocross this weekend, can't wait to see how it feels!

QUESTION:
I played around with the rear bolts to level the rear. My car does NOT have a noticeable lean, but I was trying to get it perfect and now have 1 bolt set maybe 1 inch shorter than the other (really didn't make much of a difference in the suspension height). Is there any issue with this? Is this the proper way to dial in the rear suspension, or should I just set both bolts the same?

Thanks!
Jordan

Looks like a good alignment for the track, if you mark the tierods, you could give it a little toe out at the track for comparison. Your doing better than mine. About 1.7 I think was max camber with the spacers ground down on mine.

I've been thinking about a way to corner balance without the scales.....The sway bars need to be disconnected to adjust the springs or the sway bar will hold it level even if the springs are out of wack. After the springs are set, the sway bar either needs shimmed or adjustable links so the bolts slide in with no binding.

Without scales.....My theory was to jack up the front in the middle so it can "balance", to get the front suspension out of the picture, and adjust the rear with sway bar disconnected, then jack up the rear in the middle and do the front, but the front spring is not easy to adjust, so eventually I want to get the adjustable springs from VBP.

With that test, mine is level on the rear spring and has a little lean on the front spring, but the sway bar is trying to hold it level with binding on the bolt. I need to get that fixed........

[jrtoffroad]

Thanks for the advice, maybe I'll toe out the alignment a little for my afternoon runs and see how I like it.

Really wish I had access to some scales.

I'm wondering if I'd be better off disconnecting my swaybars and measuring the ride height (on a level surface) at all corners then adding the diagonals and comparing (LF + RR compared to RF + LR)...as you would when corner balancing with the corner weights. It would be far from perfect, but seems more valuable than worrying about left to right levelness of the rear of the car. From what I've read, it sounds like balancing the RR & LR is only valuable in drag racing and does not help keep the car consistent in left and right hand corners.

How do you adjust the front? I wonder if there is enough adjustment in just the rear to achieve a 'well balanced' car.

-Jordan

[lbszr]

Thanks for the advice, maybe I'll toe out the alignment a little for my afternoon runs and see how I like it.

Really wish I had access to some scales.

I'm wondering if I'd be better off disconnecting my swaybars and measuring the ride height (on a level surface) at all corners then adding the diagonals and comparing (LF + RR compared to RF + LR)...as you would when corner balancing with the corner weights. It would be far from perfect, but seems more valuable than worrying about left to right levelness of the rear of the car. From what I've read, it sounds like balancing the RR & LR is only valuable in drag racing and does not help keep the car consistent in left and right hand corners.

How do you adjust the front? I wonder if there is enough adjustment in just the rear to achieve a 'well balanced' car.

-Jordan

1/4 turn is about 1/16"

The front spring can be shimmed but I have never done it.

I believe the rear spring could be adjusted to match the front, but if it doesn't match, the corner balance would be worse.

[jrtoffroad]

Thought I might as well post an update to this thread.

I'm now running a set of NT-01's in stock sizes on my original 91' rims. They're simply amazing compared to my old GY's (which I'm now running as street tires only on 5 spokes). It's a completely different car, I'm having to re-learn how to drive it. I've run them in 3 events now and get faster every run. For pressures I've worked my way down to 33 front and 29 rear (hot).

I realize these are NOT drag slicks, but I'll have to take them to the track. They've made a word of difference in the way the car launches.

I also further tweaked my alignment. I was getting some outside wear on my passenger tires. When I originally setup my alignment, I did it with no weight in the passenger seat. I think this was a mistake, since I have a passenger 95% of the time. So, with weight in the driver & passenger seats I now have the following alignment specs:

FRONT
Camber: -1.9 -2.0
Caster: 5.5 5.5 (need to re-check my print out, but this is close)
Toe in: 0 0

REAR
Camber: -1.3 -1.3
Toe in: 1/8 total (1/16 per wheel)

Car feels very neutral and predictable here. Can't wait until the next event!

[lbszr]

Sounds like your having fun. I've been running 01's and thought they handled a lot better than street tires also. I've been wanting to try Hoosiers, but they're not cheap and don't seem to last as long.