Michelin Pilot Sport 4S - Tire pressures

[Jimbo's M]

Your hot pressure is only 2 psi over the cold pressure? How is that possible?

I'll play...

Nitrogen.

[Estoril]

I'll play...

Nitrogen.

The air we breathe is 78% nitrogen.

[Jimbo's M]

The air we breathe is 78% nitrogen.

I've been aware of that since elementary school. I'm sure you know that nitrogen filled tires are less susceptible to heat transfer compared to regular "air". Besides, I was as I said.."playing along."

[jbfrancis3]

There’s another possibility, too

[Estoril]

There’s another possibility, too

Valve stem cap variances?

[Casa de Mesa]

Valve stem cap variances?

I rotated my valve stem caps so I took that out the equation. Also, filled the tires with pure hydrogen to help with unsprung weight.

Thanks for all the replies. Heading out today to align the car. Seems like pressure values people are running are all over the place. So many different wheel/tire combos out there, probably no 'silver bullet' of an answer for me here.

The reason I asked is with 275 rears (Michelin Pilot Super Sport) running at 31-32 psi cold, I got significant wear on the center of the tread. Or, a clear sign of over-inflation. I recently put ~5k miles on the tires without really scrutinizing the tread pattern and the wear is surprisingly significant. At 31-32 psi (already 3-4psi under the door placard), the only thing I can think of is that the load rating is so different from stock that the tires just do not need that much air.

Hence, I was hoping others might corroborate my theory. Which is: When going a good bit wider than stock, given all other things equal, running lower pressure than what the door placard calls for makes sense. That's why I was highlighting the load index of the tire. Going up even further from 275s to the 285s I just put on, they need even less air to hold the same weight. Which is typically just me + the car.

I may try to chalk the tire, but I haven't had good luck with that in sportscars. I've had great luck doing this with truck tires, but can't seem to get it right with a low profile tire. I will most likely start with low pressures (30 psi rear), use a pyrometer to measure the heat across the face of the tire, and go from there.

[Casa de Mesa]

For reference, here is the offending rear tire. It has about 20k miles on it when I took it off the car.

[Redline]

I run 36 front 38 rear for street.

[Arith2]

For reference, here is the offending rear tire. It has about 20k miles on it when I took it off the car.

The proof is in the pudding. That looks like an overinflated tire if I've ever seen one, and I've seen many. How often are you above 100mph versus regular driving?

[Nate047]

33-35ish front 35-ish rear cold for street.

28 front and rear for track as a baseline which obviously will need to be adjusted case by case.

[Casa de Mesa]

Went with 28R / 31F. Will report back on tire temps once I measure them. This isn't used on track, but will push it on mountain roads.

Edit: I kept trying to upload the photo in my next post with this post, but apparently I'm inept at such an activity.

[Casa de Mesa]