50 4Ever

DO NOT SET THEM TO MAX. When I am on the track I see speeds over 150. Tire pressure is very important at high speeds. A friend of mine, with GY Runflats, set his pressure in the morning and never checked it, until he slid off the track at a high rate of speed. With the GY's you do not want to see in escess of 36 psi, or the tires lose grip. I check my tires before each session, when they are hot,, and decrease the pressure to 32 front and 33 rear.

30 psi cold is a guideline, not a rule. You drive on hot tires, not cold, and I have found that a pressure for street driving that workd is 35 psi after the tires warm up. So in the summer I run 30 psi cold, and winter I run 32 psi cold. They always warn up to around 35 psi year around.

Good luck

hydrasport

My 08 w/Z51 also gets a little "loose" at higher speeds and watching this conversation has raised a few questions for me. The PFADT alignment does not state whether it's for a Z06, Z51 or base model. I have the sheet printed out and I'm going to get an alignment using the "street" settings this week. Do the PFADT settings change based on model for mostly street use?
Has any one watched the rear wheels toe in and out while the car is up on jackstands? (as in checking transmission fluid level)With the engine idling, letting the wheels roll in forward or reverse and stopping the wheels quickly, you can watch the toe setting move at least a half inch inward or outward, depending on which direction the tires are rolling when you stop them. You can imagine what the tires do at high speed.
Those thinking that higher tire pressures will cause an unstable feeling at hiway speeds, have you read the handbook? Have you been to a HPD school? They always want the pressures increased from the recommended settings on the tire pressure label.

LowRyter

so you recommend track hot pressure and 32 and 35 hot for the street (which about 31 cold)?

I'll keep that in mind when I go on the track.

mvvette97

Hey guys I finally got the alignment spec sheet from the dealer. Here it is. does it look ok or possibly be the issue I am having?

extrapilot

I would think that your toe would favor being in the negative range, then what's listed here.
Here's what PFADT recommends for various driving conditions.

extrapilot

You mention that the steering seems light, I know mine feels a lot heavier while at highway speeds.
I believe that the steering should feel tighter with speed. I wondering if there's a problem in the steering rack, or signal to the rack to change the effect. Something to consider.

Grand Sport Jim

I had the same issues you mention with my original F1 Supercar's. I was following every damn rut in the road, no matter how minuscule. The alignment was set to factory specs which was just not suitable. I printed off PFADT's specs and went to my Corvette pro shop, http://www.corvettecenter-ct.com, and my problem was cured. I now run Michelin Pilot Super Sport's to the PFADT specs and they are perfect. I've doubled the speed limit (plus) with zero issues.

extrapilot

Proof positive here.
It seems he needs to run more negative camber and more toe, looking at PFADT's specs, which will improve the handling all around.

franman69

Yeah.. lose the Goodyears if you want the car to handle at speed. Yes, could be pressure, yes could be shocks, but I'm betting on the rock hard tires with rigid side walls. My 07 Z51 car is a track monster, stable as a rock and putting on the track tires actually makes it squirley on the highway (over lane seems and expansion joints) but sticks like glue on a track. With my Nito INVO on the street she's a dream. Quiet smooth and great street grip. Tires and alignment make ALL the difference.

mvvette97

What spec did you use? Performance street?

HOXXOH

So you mean the cops didn't catch you doing 31 MPH in that 15 MPH school zone?

redzone

The ZR1 has 140 lbs of lift @150 MPH. I've never seen/read anything about a base coupe, but it would certainly be somewhat more.

jwrichter

Again, GET RID OF THE TIRES. Run the Michelin SS and you won't have any issues. Put on the tires and then get it aligned.

thehaggis

Alignment was my issue with instability, but all the above are equally important.

mvvette97

I talked to a guy at a local shop that he said he can check out the alignment. I told him about the pfadt specs and he said no problem. Should he do the performance street spec or the performance street with track use with street tires?

extrapilot

IMO... Just the street version, but both are going to show inside tire wear, unless your going to drive aggressively to even out the outside also.
I'm thinking that the toe in your case has more to do with the issues your experiencing. You should compare the two before specs to check if they fall in line with each other.
Also keep in mind that the alignment equipment needs to be in calibration and it's possible your car was last setup with a machine not in cal. Just another variably....

7.0Ltrs of Love

any updates??? im facing this on my ZR1.... bought it back over the winter so didnt have much time to play with the OEM run flats but i know i got on it and it was definitely stable on those tires... switched to MT DRs in the rear and now im all over the road under WOT... hooks great though! some are blaming it on "softer sidewall" but i will not go by that as ive owned MANY and still do other cars like camaros all with even more side wall and the same tires and those "lower class" cars felt wayyy more stable at speed! matter of fact i feel way safer in my 2002 camaro on the same DRs but 18" version going 160+....car is glued and goes straight! my world class handling ZR1 feels like a death wish under WOT!

mvvette97

It's alot better than it was. I has the PFADT alignment done and it helped. first did the Performance street spec and it was alot better so then had him bump it up to the Performance street-track setting. That helped even more than the first setting. it will probably cause some more tire wear in the inside of the tires but I only drive the car maybe 1000 miles a year. that said it still tends to wobble around at speeds over 130 but not near as bad. I just don't really think it's a tire issue because I have these cheap Riken Raptors on my bmw 530i and have had it up to 150 on the same road and it was very planted with no wobble at all. It just strikes me funny that a 4 door euro car with cheap tires and almost a 100k on it feels safer than my corvette with 20k on it. I almost wonder if it has something to do with the wide tires on the vette possibly catching ruts and dips in the highway.

Itshakes

This is exactly your problem. Replaced the tires on our '13 GS....put on Bridgestone RE050A........like night and day difference.....these tires like high speeds!!

TxLefty

The wider tires will tramline more. It appeared that on alignment spec that you showed us that front and rear were toed out. I would think that would make the car feel unstable. I was trying to remember the toe specs on the formula cars we were running and it I think we ran toe out on the front and toe in on the rear. The caster looks ok and I don't think that camber is going to make much if any difference for this problem. My 2011 GS has the Goodyears on it and at 160 and about 34 lbs (hot)it felt fine.