I thought this was exactly what S, V, Z ratings were supposed to
address--what speed a tire could sustain without self destructing.  As to
the "gumminess" of tires, I don't think it's a question of speed.  Racing
tires are so soft that you can dent them with your fingernail, which means
they grip really well.  But, they also wear quickly for the same reason.  If
you've ever sat on the outside of a corner at a grand prix, you get showered
with little balls of rubber for the whole race.  They feel like chewing gum.
At Indy, they go about 100 miles on a set of tires before changing, but also
take 90 degree turns at 240+ miles per hour.
bmc  :)
"Faith will move mountains, but you'd better bring a shovel...."

> From: Stan Wilder <wilden1@JUNO.COM>
> Reply-To: Stan Wilder <wilden1@JUNO.COM>
> Date: Mon, 7 Oct 2002 09:05:54 -0500
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Porsche's SUV
>
> In visiting with a tire dealer he disclosed that the wide low profile
> tires that are on many high performance BMWs, Porsche have a life span of
> only 12 to 15 thousand miles because they get gummy at high speed and
> just use themselves up.