[hc797]

I recently swapped to Michelin PS4s (x4) on my redeye and find that on rough roads the rear of the car dances around a LOT at high speed (in Mexico), my tire pressures are 32 psi cold, with a good gauge.

I have approx. 800 miles on the tires.

On smooth roads they behave fine.

Has anyone else experienced this?

 

[Blickie]

I recently swapped to Michelin PS4s (x4) on my redeye and find that on rough roads the rear of the car dances around a LOT at high speed (in Mexico), my tire pressures are 32 psi cold, with a good gauge.

I have approx. 800 miles on the tires.

On smooth roads they behave fine.

Has anyone else experienced this?

Sounds like they were not balanced correctly. Sounds like the 75 mph shimmy issue...

 

[hc797]

Sounds like they were not balanced correctly. Sounds like the 75 mph shimmy issue...

If the balance was incorrect, surely they would have the issue all the time, not just on rough roads?

 

[Blickie]

If the balance was incorrect, surely they would have the issue all the time, not just on rough roads?

Not necessarily. The out of balance condition can be on the fringe and the rough roads push it over to an imbalance.

 

[baabootoo]

I'd lean towards the low tire pressure also. What is it at "high speed"? You definitely need to raise it above 32. Track use says to aim for 40 at the end of each session. From the OWNER'S manual.

Tire Pressures For High Speed Operation The manufacturer advocates driving at safe speeds and within posted speed limits. Where speed limits or conditions are such that the vehicle can be driven at high speeds, maintaining correct tire inflation pressure is very important. Increased tire pressure and reduced vehicle loading may be required for high-speed vehicle operation. Refer to your...........**

 

[hc797]

32 psi cold - 39 psi hot , air temp 100F - speed 140 mph

Dunlop's under the same conditions were fine, the ps4s have the rear of the car dancing around, only on rough roads, the car is fine on smooth roads.

 

[GOING TO HELL 19]

32 psi cold - 39 psi hot , air temp 100F - speed 140 mph

Dunlop's under the same conditions were fine, the ps4s have the rear of the car dancing around!

Something definitely wrong. I've got the AS tires recently and I'm good to go. Wheel weights maybe? Anybody know? Sounds dangerous.

 

[ScLeCo]

It sounds to me like your alignment is off in the rear. 🤷‍♂️

 

[frictioncircle]

what setting did you have your suspension in during the dance?

 

[Xylander]

Proper sized tires for the wheel? Like, you're not trying to run 305s on a 9.5" wheel sort of thing, right?

 

[Ret.Hellcat]

Proper sized tires for the wheel? Like, you're not trying to run 305s on a 9.5" wheel sort of thing, right?

I’m running 305 on my stock 9.5 wheels. They are fine for me.

 

[Gotgap]

Zero issues with mine except for the characteristic balloon clack, triple digits are smooth

 

[hc797]

what setting did you have your suspension in during the dance?

Sport or Track, the same outcome.

 

[hc797]

Proper sized tires for the wheel? Like, you're not trying to run 305s on a 9.5" wheel sort of thing, right?

305's on 20x11 x4

 

[baabootoo]

It sounds to me like your alignment is off in the rear. 🤷‍♂️

Good point. Put the pressures at 36 cold, and give it a shot.

 

[frictioncircle]

Sport or Track, the same outcome.

try it in auto...

 

[nightrod]

Good point. Put the pressures at 36 cold, and give it a shot.

I was going to comment this too, maybe give higher psi a shot.

 

[akras]

Is there any tire other than PS4S that results in so many high-speed issues for some (death wobble, now this)?..

Not bashing PS4S (I believe this is the best tire for daily driving overall), just wondering what makes some of our cars equipped with PS4S so sensitive to alignment problems and whatever else could be at play here...

 

[Xylander]

I’m running 305 on my stock 9.5 wheels. They are fine for me.

Fine being subjective because you're running less traction than a 275 with those. It's physics. Oversized tires on the incorrect wheel will skate (because they have to). This skating action produces an irregular contact patch. If you put the same tire on the car in a 275, it would not only save weight, but offer better traction and increased road handling since the tread isn't rolled up towards the sidewall (thus causing it to not be able to transfer weight laterally as well).

 

[Xylander]

Also, is it possible that the car is "tracking" in a groove during the period where the vibration was experienced? 305s are notorious for this and maybe in the rain, the tracking is being upset by the rain channeling? No idea really, just a thought.