As I work for a major tire company (not Firestone) I feel compelled to comment. The H, V, and Z ratings validate the tire's ability to continuous duty at a certain speed rating. I am a process engineer, not a tire engineer, so the speeds I do not have memorized. I have however sat in with Tire Development Engineers and the following are tire truths:

High speed rating generally indicate a tire with a Cap Ply. This is made of nylon plies in various solid or wound patterns. Basically this ply is a reinforcement hoop which keeps the steel belts from seperating (or growing to a larger diameter) from the radial tire body plies. The steel plies are held only by the rubber compound adhesion between body plies and steel belt skim rubber (i.e. what FIRESTONE tires did NOT do, and cap plies they did not have).

The sidewall construction has NOTHING to do with this speed rating system!
However there are several types of sidewall reinforcement, and this portion of the tire is what gives it lateral stiffness, which leads to handling improvement & road feel. Of course the complete tire is a system, and this requires the tread compound to be suitable for good adhesion in trying circumstances (TRANSLATION - LOW TREADWEAR LIFE).
When we develop a tire for BMW , FORD , or any other OE, they all seem to specify different constructions to "tune" the vehicle suspension with the tire. This adds further to the plethora of sidewall reinforcements.....

If you note when you look at V & Z tires typically you will see the DOT treadwear index on the outside sidwall rated at a low number such as 150. This indicates either a bargain basement tire (car for sale) or also a high performance handling tire. Sticky tread compounds = minimal tread wear & many resales for replacements.

I recommend you research perhaps Car & Driver, JD Power, or some other
performance publications to find the good handling tires you desire!


DET

• difference in performance between H,V,Z rated tires, moby, Wed, 29 Nov 2000 15:39:37
  • Re: difference in performance between H,V,Z rated tires, DET, Thu, 30 Nov 2000 20:24:59 <-- Viewing This Message
  • Technically it tells you nothing about hanlding performance, saw, Wed, 29 Nov 2000 19:04:08
    • Correct. But..., Mike H, Thu, 30 Nov 2000 08:21:14
      • as a side note:my left rear tire was flat this a.m., moby, Thu, 30 Nov 2000 15:41:42
    • best thing I've read all day!, dave n, Wed, 29 Nov 2000 19:28:06
  • Re: difference in performance between H,V,Z rated tires, GM, Wed, 29 Nov 2000 16:12:18
    • Re: difference in performance between H,V,Z rated tires, moby, Wed, 29 Nov 2000 16:57:11
      • Re: difference in performance between H,V,Z rated tires, GM, Wed, 29 Nov 2000 17:25:22
  • PS 1990 SPG w/106k Bilsteins and some other mods, moby, Wed, 29 Nov 2000 15:41:41

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