Tire Speed Rating Question
I'm posting this here because the speed rating of a tire seems to me to cross all lines/types of vehicles. Reading up on warranty issues/questions just now, I came across the following language ...
Forum Discussion
The speed rating of a damaged tire does not revert to anything. A damaged tire has no rating. The maximum safe speed becomes unknown, as it depends on extent of damage and quality of repair. The only way to find out the maximum safe speed would be to run speed tests on that tire until you reach the number you want to see, or you reach the speed where the tire come apart on the test wheel.
Two things to consider:
1. We don't usually run at (typically illegal) rating speeds, so there is a big safety margin to cover damage and abuse. Experience shows that professional puncture repairs seldom fail in normal use, and repair professionals are pretty good at inspecting and deciding whether a tire can safely be repaired.
2. Most tire damage is cumulative, and does not involve punctures or repairs. Tires are degraded by hitting curbs, potholes, objects on the road, and by extended overheating from running overloaded or underinflated, which is pretty much two ways to look at the same thing. Almost all explosive tire failures, and tread separations, are the result of this damage, and occur well below rated speeds.
That's the real meaning of "the speed rating is no longer valid for a damaged tire." A damaged tire can come apart at legal higway speeds. A damaged tire can come apart at city driving speeds, often the result of an incident that would be the straw that breaks the camel's back. I had a H-rated tire throw its tread at 20 mph, about two seconds after a protruding bolt broke the steel and polyester plies in a square inch of the tread.
Speed ratings are valid for new, undamaged tires. Tire strength, safe loads, safe speeds, safe cornering loads, all degrade as the tire accumulates in use. If you are going to go racing, you race on new tires. If the use of your vehicle involves regular high speed driving, you get tires rated well above those speeds, maintain them well, inspect them often.
For unexceptional use, you keep them inflated for the load, inspect them regularly but not necessarily often, inspect them carefully (maybe have a professional unmount and inspect) any time you suspect exceptional damage. You inspect them more often, the longer you keep them in service.
Two things to consider:
1. We don't usually run at (typically illegal) rating speeds, so there is a big safety margin to cover damage and abuse. Experience shows that professional puncture repairs seldom fail in normal use, and repair professionals are pretty good at inspecting and deciding whether a tire can safely be repaired.
2. Most tire damage is cumulative, and does not involve punctures or repairs. Tires are degraded by hitting curbs, potholes, objects on the road, and by extended overheating from running overloaded or underinflated, which is pretty much two ways to look at the same thing. Almost all explosive tire failures, and tread separations, are the result of this damage, and occur well below rated speeds.
That's the real meaning of "the speed rating is no longer valid for a damaged tire." A damaged tire can come apart at legal higway speeds. A damaged tire can come apart at city driving speeds, often the result of an incident that would be the straw that breaks the camel's back. I had a H-rated tire throw its tread at 20 mph, about two seconds after a protruding bolt broke the steel and polyester plies in a square inch of the tread.
Speed ratings are valid for new, undamaged tires. Tire strength, safe loads, safe speeds, safe cornering loads, all degrade as the tire accumulates in use. If you are going to go racing, you race on new tires. If the use of your vehicle involves regular high speed driving, you get tires rated well above those speeds, maintain them well, inspect them often.
For unexceptional use, you keep them inflated for the load, inspect them regularly but not necessarily often, inspect them carefully (maybe have a professional unmount and inspect) any time you suspect exceptional damage. You inspect them more often, the longer you keep them in service.
