Tire Patched- any effect on performance?

WhiskeyHotel

I asked my dad - who worked at B.F.Goodrich. If they use the correct patch and procedure - the speed rating is not compromised. The biggest problem is water infiltration of the steel inside the tire belts.

He also mentioned that an under-inflated a tire has a compromised speed rating.

ChrisSlicks

Actually even a properly inflated tire can have a compromised speed rating. Typically the inflation requirements increase with speed as well as load to reduce the amount of sidewall flex and hence heat. But that's for sustained speeds above 120 mph.

Here's a decent article on tirerack.
Tire Tech Information - Air Pressure/Load Adjustment for High Speed Driving

speedworks

Here is the right answer. As an ex-tire designer, your biggest issue will be long term reliability. The biggest problem with patching is the time period before it happened. What causes a failure in the tread of a patched tire is the breakdown of the belts, by rusting - all it takes is some water that got in the hole at any time. The water travels down the belts, (and probably won't be noticed initially at all), but what happens is the belts start to rust and separate from the rubber, get weak, and then the real problem happens (break). I will patch a tire just to get somewhere or until I have the time to replace. I never run a tire that has been patched longterm. After designing tires (for one of the best tire companies), and working for a car company and being able to visit other tire manufactureres and diagnose tire failures, I would never keep and drive on a patched tire - just not worth the risk.