RE: Speed ratings

["Lin, Gary" <Gary.Lin@wang.com>]

Sonia, I was only warning against nearing the 130 mph limit of an H-rated
tire, ie. get a V/Z.  I'm not going to get into the +/- of racing, just make
sure the interstate is totally clear of cars, ok? ;-)

I wrote:
> Just an afterthought, a blowout due to a failed tire above 100 mph would
> not be pretty, ... I wouldn't want an insufficient tire to contribute to a
> possible wreck ...  Play safe.
> 
Art Borin replied:
> Gary Lin wrote:
> > You both are right and wrong.  A tire's greatest enemy is speed and heat
> > combined, with more of it coming from top speed in a straight line than
> from
> > executing turns.
> 
> How am I wrong.  You proved my point. I only disagreed with the statement
> below.
> 
Art, I only disagreed with you in taking an H-rated over 130 mph, even if
just for a quick sprint before the tire heats up.  The centripetal forces
are great enough to cause the tire to disintegrate over its rated speed.

> > But highway top speed generates more heat due to the quick flexing of
> the
> > carcass as it rolls along.
> 
> This is friction, no?
> 
Correct.

> >  Plus centripetal forces, the major factor, come
> > into play above 88 mph (non-rated tires limit).  Tremendous stress is
> acting
> > upon the carcass and belts trying to make everything fly apart the
> faster
> > the speed.
> 
> What causes the failure?  Heat induced breakdown of the structure, or
> centripetal force exceeding the original design yield strength?
> 
Centripetal force over the limit, or heat breakdown near it over time; so
venturing over the speed rating, even with a built in safety margin, is
risky.

> > Tire speed ratings are determined by putting the tire on a dyno drum
> with a
> > simulated load and then increasing the speed until the tire self
> destructs
> > as explained above.  If you guys are going above 110, you're
> > cutting the safety margin on a H-rated pretty close.  Get at least a V.
> > Even a cold H can blow at or above 130 due to the speed, esp. if the
> tire is
> > slightly out of spec or previously damaged (hard pothole).  Plus a V
> will
> > generally have better handling at all speeds over an H.
> >
> > > Art Borin wrote:
> > > Sorry, I disagree.The primary factor in tire speed ratings is the
> tire's
> > > capacity to dissipate heat.  The faster the tire rotates, the more
> heat
> > > (friction) is generated over a period of time.  The speed ratings are
> for
> > > sustained speed, not a quick run like FlyinVR6 stated.  Thus, a H
> rated
> > > tire can withstand a claimed 144 mph blast, as long as that speed is
> not
> > > held for a long duration.
> 
Gary Lin