Tires

Hi, Not at all.

I will disagree and say "yes!'

A question of tire ratings came up in the Yahoo! Prius forum a couple years ago. The speed ratings were debated to death, especially the meaning of the ratings. It turns out the meaning of the speed rating differs from one manufacturer to another, with a few rating a tire for a speed after testing at that speed for as little as ten minutes and a few rating it at that speed if it passed tests for long periods (simulating indefinite runs at that speed.) But the most surprising data was from somebody who had a response from a Dunlop tire engineer who provided the explanation about the variability of the tests:

"But, in order to pass an H speed rating, a tire more or less has to have a cap ply. This change has a profound effect on failure rates, way beyond what the increase in speed rating suggests. The failures rates are so low for tires with cap plies that court room 'experts' claim that tire manufacturers are negligent for not using cap plies even in their S rated products. (My response to that is that these 'experts' must also be saying that tires ought to have a minimum of an H speed rating - and if that is true, the "experts" ought to be lobbying NHTSA to specify H rated tires for any tire sold in the US.) But the point I want to make is that the step between T and H is enormous from a tire durability point of view. And I don't recommend anyone use anything less than an H rated tire. Considering that the risk of a tire failure includes fatality, the cost / benefit seems to be there."

Since reading that I have specified H speed rating for all the tires I buy, snow tires excepted.

Mike

Oops - I noticed the OP wanted to go down to an H, not up. Anyway, H is fine.

Mike

thanks for re-posting that.