Originally Posted By: CapriRacer
Originally Posted By: benjamming
Eddie,
Forget TR, let's hope CapriRacer chimes in. I would be interested to learn the "minimum nominal" cold temperature for summer tires.
You guys were doing such a good job of discussing the issue, I was hoping to stand back and watch! But if you insist!
There's a number of problems:
1) These things are curves, so to say there is a "minimum" implies some sort of break point (for you mathematical types, an inflection point) and not some arbtrary lower limit. And with one exception, it would be arbitrary. That one exception is what is called a "Glass Transistion Temperature" - the temperature where the physical properties of the rubber change. In this case, the rubber would tend to crack. But this is so highly variable that it would be difficult to pinpoint a temperature or even a temperature range.
2) It is said that if the temperature drops below 40°F, then you should use winter tires. Obviously this is somewhat arbitrary, but clearly winter tires are designed to perform at lower temperatures than summer tires - and the intent is to persuade folks to consider the temperature and not just the white stuff!
3) Obviously the higher the speed capability of a tire, the more likely it is that lower ambient temperatures might affect the grip of the tire. But I think this is so highly variable, that it would be difficult to make clear and unambiguous statements.
4) I think the same could be said of all season tires. These are more about tread pattern, than tread compound - at least compared to summer tires.
Originally Posted By: IndyIan
.......It would be nice if tire manufacturers published a friction vs. temperature curve or even more information say as detailed as specs for engine oil.
They would if traction testing took place in a lab - but it doesn't. It takes place outdoors subject to the ambient conditions at the time.
Traction testing is EXTREMELY problematic. Not only is there an effect of the surface itself, but it's hard to get consistency from run to run. as a result, multple runs with multiple tires are tested - in other words, overwhelm the inconsistency with data!
Did I mention that the road surface is part of the problem? We've seen reversals of rank order depending on what surface we're testing on!
Wouldn't most of the manufacturers have some sort of rolling road jig set up? Or maybe a portable jig attached to a moving vehicle where you where you run a tire on real types of pavement changing, load, camber, slip angle, and measure the forces created?
