Steve J.

Experienced a right rear blowout yesterday. First time to use the collapsible spare and compressor. Here is what I think happened: 1) Ran over road debris. Tread punctured, air leaks out 2) Tire goes flat increasing friction 3) Tire heats up 4) Remaining air expands rapidly 5) High pressure finds the weakest point in the sidewall 6) Sidewall ruptures. Approximately one mile passes between tread puncture-

and sidewall rupture-

Pulled off the highway and found a flat place to change the tire. Jack leaves a lot to be desired! Put on the collapsible spare and inflated it with the air compressor. It did not inflate evenly - inside sidewall inflated before outside sidewall but eventually evened out. Drove slowly back to town. Replaced rear tires which were almost at the wear bars anyway - thought I could get one more trip out of them. Collapsible spare deflated and fit back in the well no problem. The car did not pull to one side or lose control. Only clue was what sounded like a helicopter landing on the car that got louder and louder!

Randy V

Whew, could of been worse.

Over the years I had always been told to have the better tires located on the front wheels, so that in the event of a blowout the car can be steered out of trouble.

The new (to me, anyway) thinking is that the better tires should be mounted on the rear, to prevent an oversteer condition that could result in the car spinning.

Think of an arrow in flight - the feathers at the rear are what keep the arrow going straight.

Makes sense to me.

Steve J.

Unfortunately, the front and rear tires are different sizes on the S4. On other cars I rotated front to back and kept the best ones on the front. The idea being that the front tires do the most braking, and steering is more important than traction.

Shane

Had a left front blow out on a 15% grade last summer. Yeah baby that was not any fun. One of those get one more trip out of the tires deals. Bent my rim to boot. So got them new tires any way, and going to upgrade wheels to 17". Was just a little POed at the wife for that one though.

Randy V

That's what I was referring to. Actually, rear traction is more important than steering in maintaining control of the vehicle.

jim912928

Had the same experience with my 83S. Was doing about 80 on an interstate and the only reason I knew something was wrong was a loud noise coming from the rear..but that was it. Pulled over and passenger side rear tire split right across tread...about 3" gap. Was amazed that the car never fluttered at all.

Worse thing about this experience (I never had a flat since I bought the car) was when I went to pull out the spare there was no air pump!!!!!laughing at myself


p.s. what engineering!

Steve J.

Vacationing in Panama City Beach, FL I was lucky to find two tires the right size. However they are only H speed rated - but cheap @ $90 ea. I thought they would get me back to Dallas where I have a brand new set of ZR rated Potenzas at home. Then I would swap out and sell these with only 850mi. for maybe close to what I paid. Now I'm thinking about keeping them since I've almost never gone over 130mph and usually drive the speed limit (maybe a little faster). I don't race the car or track it. It's my daily driver. Any thoughts on using tires with lower speed ratings than the car is capable of?

sweanders

SteveJ:

Shouldn't be a problem if you don't drive fast. Remember that winter tires rarely are recommended for high speeds and are still used on Porsches.

Gretch

Steve, I have had very good experiene with H rated tires. In fact I run them on both cars. I am an old fart and rarely ever exceed 100 mph. The bonus baby is they wear much better. This is not for everyone (especially everyone who drives a Porsche), but they work for me just fine.......

On the other hand, I have had lousy experience with top end tires.........on both cars. To each his own........

SteveG

I've never had a blow out on the Pcar, but others introduced near severe "swervability" always on a rear, not something I would want in a heavier car, but according to your experience (Steve and Jim) maybe the weight and/or Porsche engineering makes for better stability. Your description of not feeling anything except sound from the rear says something reassuring about the 928.