Nickle size bubble in sidewall - Need Advice Please
A replacement will be here Monday.
The bump is on the sidewall of my pass rear Pirelli Pzero Rosso.
I've got them underinflated. Wrong idea? What should they be inflated to with this bubble. Currently at 34psi.
Late to ask but what range should I have these inflated to normally. Guy at chain tire shop said it should be filled to five less than the MAx marked on the sidewall fore a performance tire. Not heard that before.
Lastly how crazy is it to be considering a three hour drive to Keene, NH for a MINI meet this weekend? And back? Will a temp used 205/45 do the trick when the rest are 215?
Frankly, I wouldn't drive the car much, if any at all, before you get a replacement on that wheel. That bubble indicates the sidwall is failing - think anuerism that's about to pop. If it goes whlie you're underway, you may have large strips of tire tread flailing away at the rear of your car and it could cause a LOT of damage. That's assuming you don't loose control and hit something and/or roll.
Underinflation causes excessive sidewall flex, which generates heat. Rubber, when overheated looses it's structural integrity and tends to delaminate. That nicle size bubble may just be a fraction of the hidden damage underneath.
This is not a flame. It is genuine concern first for your health and then for the car.
I'm still left wondering what the proper inflation on a high performance tire is. I've been going by the door jamb. I've been told as of yesterday that the proper inflation is 5psi below max. Those are two greatly varied numbers.
I'm not driving it except home after work. i will fill up the air along the way. I'm left with the correct psi, or correct range thereof, as a veritable black hole.
I was alway taught to go by the car manufacturers recommendation ... the max as printed on the tire is the max for the tire itself not what is proper for the car. Every tire gets installed on a variety of vehicles so tire manufacturers have no way of knowing but the people who make the car do
just my 2 cents and how it was explained to me by my father (retired mechanic 60+ years experience)
I'd go with what pressure gets you the best wear pattern across the tire.
Pressure is also load dependent.
32-34 psi should be a good starting point.
Do not do any high speed driving if you can help it. And the the diameter difference of the 2 tires might be enough to trigger your flat tire light but that's a lot safer than driving with the crap tire.
The flat tire light shouldn't go on if you reset it with the new tire.. Though if you try it without reseting, if the light doesn't go on, that supports it not being a big deal..
I agree with what other people have said follow the car's directions. If you want maximum performance, crank up the PSI, but only for short term situations such as track days or autocrossing. I know someone who flipped a miata because he accidently left his tires overinflated from an autocross session and it botched the handling on normal roads. Perhaps that's what the guy at the tire place was thinking?
It may just be me, but I trust tire engineers way more then some guy at the chain tire shop.
Magic 8-ball was correct. All be in awe of Magic 8 ball.
Parking the car is best, until you get a new tire fitted. The bubble could pop at any time, resulting in sudden deflation and loss of control of the car.
For inflation - I usually run 2psi over what the door jamb says (which isn't the easiest chart in the world to figure out). I get very even wear, and at 13,000 miles I've still got a good amount of tread left (probably 40% remaining). I also rotate at 5,000 mile intervals.
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and all around good-guy 
