JRS 94

Guess I missed where it said replaced with new MPSS solved the problem. Great if that's the case.

JoesC5

I have also run my Z06 to speeds above 150 in Mexico and over 160 on the track, with the tire pressure set to 30 psi(cold), with the running (hot) pressure around 34-35 psi.

In the 2015 owners manual(cars are fitted with OE Michelin Super sport tires),it says the following on tire pressures.......

"The tires require inflation pressure adjustment when driving the vehicle at speeds of 160km/h (100mph) or higher, where it is legal. Set the cold inflation pressure to the maximum inflation pressure shown on the tire sidewall, or 265kPa (38 psi), whichever is lower. See the example following. Return the tires to the recommended cold tire inflation pressure when high-speed driving has ended."

Yet the owners manual contradicts itself when it says(for track use of the car)...

"Z51 Only: Limit vehicle load to the driver only, with no other cargo. Inflate tires to 180 kPa (26 psi) and drive at a maximum speed of 280 km/h (174 mph).
Z06 Only: Limit vehicle load to the driver only, with no other cargo. Inflate tires to 180 kPa (26 psi) and drive at a maximum speed of 296 km/h (184 mph)."

So, which is it for high speed driving? 38 psi or 26 psi?

Also GM says to limit the top speed to 174 MPH(Z51) and 184 MPH(Z06). Yet both the Z51 and the Z06 are fitted with (y) rated tires that are good for 186+ MPH speeds.

AzDave47

To some degree it will depend on what M PSS tires you run. The PSS ZP's in the 19/20 sizes and OEM fitment are SL (standard Load) tires and may require a higher inflation level as the GM OM suggests.

Many of us purchased the PSS in 18/19 sizes and they are not ZP's. Those tires come with an XL (extra load) rating and will run at high speeds at normal pressures and still well within the tire load rating. The original Goodyear EMT's that were on the C6Z06 in 18/19 sizes were LL (low load) rating and would need more pressure to run at the higher speeds.

One of the drawbacks of running higher pressure in the C6 Z06 is that at 42 PSI the DIC will give you a high tire pressure warning. Since I run the DIC to display oil temperature and it is quite inconvenient to try to bring up the oil temperature while doing high speeds/ HPDE's I generally favor tire pressures that will not trigger the high pressure alarm once the tires get hot. I run the 18/19" M PSS non-ZP's in Xl load rating for the street. I do 150 MPH 90 mile events and have run to 195+ at other events in my stock LS7 C6 Z06.

JRS 94

Update, called Michelin, went to discount tire, Michelin has warranted my tires at 75% and 55%. No challenge. Hate to give up on these but, Going to try Nitto INVO's. Any experience with these tires? Car is 2008 base with ECS kit at 540rwhp. stock front size and 305/30/19 rears. looked at NTO5;s but they are a bit taller. Thanks

AzDave47

Invo's are a value, quiet, high tread mileage tire suitable for cruising, not any performance work. The NT05's are more of a performance tire than the Invo, but I pulled .93G and .98G s in two local back to back roundabouts with the 295/335 NT05's and 1.12G in both with the PSS so you will give up a lot of traction leaving the PSS. If you are a straight line guy, maybe try the NT05R's in back?

JRS 94

Agreed , mostly a DD with an occasional blast. I've been drag racing for a long time (I have a bracket car) this PSS wobble thing is worse than anything the slicks ever did. I hate to give up on them.

MarMPB

Now I'm afraid to get another set of the MPSS and get the same problem after some miles on them.

When I bought my set of MPSS tires I went to 190+mph on a 3 km top speed event.

Now I get the death wobble!

Last news: No more doubt! I changed my MPSS for a track day event. ( I'm still using them on the street at low speeds only )
On track I used the Nitto 05R at the front and the Michelin Pilot Super CUP at the rear.
Didn't change any set up.
No wobble at all!

Shoecat

^^^ You put nt05r's on the front?

MarMPB

I think it'll work!
I just happen to have a set of rear 345-30/19 Cup tires, so I got a set of the front Nitto nt05r to have semi slicks/ track day tires all around.
The wobble problem as far as I know was only with the PSS in the rear!

Shoecat

Awesome, thanks for clarifying
Mine were just out of balance as it turns out.

AzDave47

I know it happens, but 20K miles on my PSS and no problems, I've been to 196 MPH and have over 400 miles at 150+ MPH on them.

dart.deanda

Got my Z06 in June with fairly new MPSS on the car, 345s in the rear. Car was fine, I did a 4th gear pull early one morning on an empty freeway to 145 mph no wobble. I took the car to the 1/4 mile track, and at the top of 2nd, 3rd, and 4th, the wobble was so bad I had to back out of it. It felt like the car was going to fly off the track. Violent side to side shaking. I'm going to contact Michelin and see what they can offer. I have had an alignment and balanced all tires with suspension inspection, nothing to see, no fix. Where is the date code on MPSS? Kind regards, d'Art

Ninety-Nine FRC

I have a 2008 Z with 19/20 265/345 PSS non ZP. I get the death wobble getting on the interstate at the top of second gear. I don't normally get to the top of 3rd gear driving around, but the first time it happened it scared the daylight out of me. Tires have around 2500 miles on them. I called michelin and they are sending me to the tire shop for inspection for warranty replacement. Tires are almost brand new. Hopefully a new set doesn't cost me much and solves the issue.

Tires are under 2500 miles and the car is under 7500 on the clock. Both basically brand new.

AzDave47

On the outside sidewall, you will find in small letters "Treadwear 300". Directly under that (toward the center of the wheel) will be a four number code. The first two numbers will be the week manufactured and the last two numbers are the year, thus 2414 would be the 24th week of 2014 and 5211 would be the 51st week of 2011.

This four digit code is also the second grouping after the DOT marking. M made it easy as some companies put the code on the inner side of the tire, making it difficult to see when the car is on the ground.

Ninety-Nine FRC

Oddly I took it to get inspected today and they checked tread depth and called Michelin. Michelin asked a few questions and told the tire guy that I'd get the fronts replaced but had to pay 10% of the cost of the new rears. Tires have around 2500 miles on them but were installed two years ago. Garage queen. Gotta say I never pushed for new tires just explained what I read and the issue I experienced. Michelin customer service has been beyond great with this issue. Tires should be in in a week or so I guess.

v8sten

here is my 2 cents. I could be completely wrong but if the OP is talking about the problem where the car sways to the left and right under full power and at speed, this worked for me. I had a "factory spec" alignment done and it was on the money, I hads Nitto INVOs on my car at the time. and it did this to me once at the track and I had to let out and regain control. fast forward a few months. On my car and the inside of the rear tires were extremely worn compared to the outside. We rechecked the alignment and it was still dead on. I had them take the camber down from -1 deg to -0.5 deg on all 4 corners. havent had a problem since, and it gets better traction now due to a bigger foot print actually touching the ground.

AzDave47

That may work for the straight line guys but not us road racers as we'd lose a lot of cornering power with those settings, which would be fine for street driving.

Mcar, with 4+ year old PSS non-ZP's is currently set at -1.7* front and -1.1* back for camber and no problem at 165 MPH (275/325's). I'm wondering, the problem seems to be more prevalent with the 345 size rear PSS tires than with 325's.

Freebird427

I've been surprised how much wind up or lack of steering precision there is on the front end of these cars when the front is under side load. This goes to what LD mentioned earlier on control arm bushings.

Speed (areo lift) and hard acceleration will tend to unload the front. Add to this more neg camber at the front, possibly unevenly worn tires that are already wide with stiff sidewalls. We know that crown or seams in the road have an effect on the cars tendency to hunt at the front, especially with the tires like what we running. Everything has a natural frequency.

II guess I'm wondering how much movement we might be seeing here in the control arm bushings here and how much a simple change here might make? I'd like to think that more lateral stiffness here would tend to help. Curious, how many of the posters have updated their control arm bushings ?

FB

racerxrick

I am starting to catalog this issue and saving links to threads...THIS IS NOT JUST A CORVETTE ISSUE! I have found threads on GT500 and even BMW forums with just a little research. Michelin was kind enough to swap my rears out for $96 (sarcasm implied) and I still have the issue.

I posted the following to another thread today:

I have been following threads like this on multiple forums (it's not just a Corvette problem) and the issue is ALWAYS the same and ALWAYS related to Michelin tires! 100% of the time after reading through a typical thread eventually it comes out the owner with the "wobble" has Michelin's. To be clear not all owners with Michelins experience this.

Me: (702whp 2010 GS) I have been fighting this and I have two other sets of rims (drag pack and DR's on spare 19" rears)...with these other rears there is NO WOBBLE! Switch back to the Michelin PSS and under hard 3rd and 4th accel the rear end wobbles and it is VERY scary!

Michelin "exchanged" my rears and denied ever hearing of this problem (despite others reporting the issue and a friend reporting the issue directly to a race engineer at COTA). And yes I have another friend locally with his 675whp GS experiencing the EXACT same issue on his low mileage car.

BTW, I was charged $96 to exchange the rears for another set.

What really sucks is I love the wet/dry traction (lateral and straight line) but cannot trust these at high speeds as under accel the car "at times" will wag it's tail like a dog with a bone!!!!!!!!!!!

Going back to Discount this week to work on exchanging for another brand.

Ninety-Nine FRC

So discount called me and said the 345/30/20s are discontinued and I'm getting 335s instead.