Car actively trying to swap ends on track?

[cbaclawski]

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]

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]

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]

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

[cbaclawski]

Originally Posted by RussMcB

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!

Originally Posted by rush91

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.

Originally Posted by lfalzarano

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

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]

Think I would rather stay out of a wall than worry about a few extra bucks for tires.

[cbaclawski]

Originally Posted by XfireZ51

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]

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]

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]

Originally Posted by MarkSS

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?

Originally Posted by conesare2seconds

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!