Originally Posted By: y_p_w
I thought that CapriRacer had explained that speed rating is largely independent of the tread.
Quote:
http://www.barrystiretech.com/speedratings.html
In speed rating tests, failures are almost always belt area separations - and in particular "belt leaving belt" separations. In other words, tire construction, not tread compound, seems to be the limiting factor.
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To get a tire to pass an H speed rating almost requires the tire to have an overlay - commonly called a "cap ply" and nylon is a commonly used material.
This overlay restricts the growth of the tire due to centrifugal forces as well as the movement caused by the standing wave. Not only does this result in reduced stresses in the tire, it also reduces heat generation.
Adding further overlay layers results in higher speed capability. That is, you achieve higher speed capability with just changes in construction. Rubber compound changes are almost incidental.
So the speed rating doesn't necessarily correlate with handling or performance. Granted - I think it's far more common for winter tires to have lower speed ratings and the inherent nature of a winter tread is going to mean a squishy feel. However, this doesn't necessarily correlate with speed rating. I've also noticed that I can't find many V speed rated tires in the 205/55R16 size for my car. There used to be several on the market.
Originally Posted By: krzyss
I think above statement from Capri is generic and may not apply to Q rated winter tires. I do think that their Q ratings come from tread not from construction. Or rather since tread cannot sustaing high speed no need to make carcas handle it either.
When I read what I wrote, and applied it to the subject here (winter tires), I realized that winter tires are very likely the exception to the rule - that tread compound DOES play a role in the speed rating.