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Discussion Starter · #1 ·
I was involved in the testing of regular street tires at speeds from 40mph to over a 100 mph on the old Riverside Raceway. The air temps were in the high 90's and over 100 degrees over a three month period.

All of the major MANUFACTURES mentioned in the previous post "Bridgestone Eager" were used.

We were testing, because Showroom Stock cars could be exceeding the tire limits set by manufactures, due to SCCA racing conditions.

The vehicles used were Datsun 260Z, Mazda RX3SP, Alpha Romeo GT, Ford Courier? Pickup, SAAB Turbo, Mazda Rotary Truck, Toyota something, and a Chevy Cosworth Vega. Not all of these vehicles were legal to race under the rules specified.

Results? They ALL suffered from tread separation. (the air temp was never under 95 degrees). The tires were inflated to 32 psi and run with FULL TREAD. The tires would start to chunk (throw piecs of tread) after only a lap or two. Once the tires were shaved to approximately 5/32's, there was no separation from ANY of the brands, except one. If the tires were inflated to 36 lbs. to start (no shaving), the chunking wouldn't begin for another lap or two. Once the chunking began it was just a matter of time before centrifical force pulled the tread from the tire core; a few more laps. We didn't have many Blow Outs, because we immediately slowed when the tread started slapping at the inner fenders. I wish I could remember which cores seemed to hold up better (against blow outs). The front tires were the ones that usually let go first, since there was more stress put on that end of the car(racing conditions with basically stock suspension). When we put bags of concrete in the trunk (approx. 400 lbs) the rears seemed to separate sooner than the fronts (Torque?). The only tire to separate after the shaving was the Kleber (France). But, I understand that the French don't like to shave things. (Just saving Zap a post).
The only vehicle to almost flip was a truck (higher center of gravity).

My opinions are just that...nothing more. Here goes:

There is far greater heat produced in a tire with full tread.

Maybe there should be tires made with less tread, for the rear of SUV's or an extra steel cord for the rear tires, since the majority of the blowouts seem to come from that area.

The higher the center of gravity (polar moment of inertia?)the greater the chance of flipping.

Tire pressures, even a few lbs., can be critical.

SOME accidents could be avoided if there were manditory driving schools required, for SUV and truck type vehicles. The SKILL of the drivers in our test, got them out of some potential problems.

The conditions were extreme, since they were compressed in time. Nevertheless, the reality of what may happen under less extreme but prolonged duration may be worth speculation. I THINK!

743 Posts
Interesting post, there are more factors to blowouts than people think.

Originally posted by CaPPY:
I was involved in the testing of regular street tires at speeds from 40mph to over a 100 mph on the old Riverside Raceway.

Riverside, CA right? There is a mall there now

Premium Member
43,735 Posts
The thicker the tire, the more problems one seems to have with overheating. It is not a coincidence that you find big rigs shedding rubber in the summer months. Probably a combination of multiply tires, heavy loads, low inflation, and extreme heat. Aim a heat gun at one of those tires after he comes to a halt from running 70 for a few miles.

We found with our heaviest seismic trucks that the Michelins lasted far better out in west Texas with regard to tread shedding than did the Goodyears, etc in the summer time and we would only order Michelins in Libya when I worked there. Nothing else would hold up.

Circle track slicks are pretty thin and there seems to be an extreme amount of science in building the right fronts to handle the load/heat.

I would still like to see a demonstration as to how a blow out turns over a car or the Explorer. I watched the Car and Diver attempt to make one get squirrely with no success and they were popping the rear tire. I blew one on the front of mine without a wobble..but I did not jerk the steering wheel. On the other hand, I bet I can roll the damn thing at 25 mph in a hard right turn...just touch the brake and turn...most unstable feeling thing I have ever driven.

Last summer, I crawled under the front of my son's T and saw the belt sticking out the inside of one of his TA's....and it was not even vibrating.

Everyone wants cheap tires...go figure.
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