Quote:
Originally Posted by CapriRacer
When it comes to these performance categories, it's a trend,
but there are enough exceptions to make it difficult to sort out.
In the old days, All Season tires were pretty much S and T rated and Touring
tires were H rated, but high performance tires were V rated. Further, it used
to be that high performance tires were stiff riding, All Season tires soft riding,
and Touring tires in between.
Lots of changes since then. In particular, the Ford/Firestone thing back in 2000
pointed out the need for higher speed capability - that is, problem tires were all
S rated, but H rated tires hardly had any failures. To insure that the tires
coming from the vehicle assembly plant were of higher quality, the vehicle
manufacturers started specifying higher speed ratings. However, the ride quality
was specified at the same level as the S rated tires.
The good news is that ride quality isn't tied to the same tire components that
speed rating is, so it was possible to get the same ride quality in a V and higher
rated tire (albeit by sacrificing steering crispness.)
Nowadays we have a mixed bag, and while the tendencies are still there, it is a
lot harder to see them.
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The "Ford/Firestone thing" had more to do with Ford specifying '60s-era pressures - 26PSI if I recall - for their then new Explorer utility, to counter vertical stability issues in that new platform. By 1990, a contemporary competitor, S10 Blazer, recommended 35psi cold at all four corners.
Running 26psi in any recent RAV4, Explorer, New Blazer, or Grand Cherokee, is almost begging for a blowout, even on just a long drive home from the dealer you picked it up from.