Dan;
I think wide tires, per se, are getting a bum rap. Racing on salt may be
unique but it doesn't seem like the principles would be different than other
types of racing.
Fat slicks (no tread pattern whatsoever) are not even suitable for wet
asphalt so I'd guess they wouldn't work on wet salt, either. On the other
hand, big wide rain tires work pretty well on asphalt-- even at high speed.
Here's a quote from mulsannecorner.com:
"At nearly 3.5 miles long, the Mulsanne was such a high percentage of the
overall lap time at Le Mans that anything you could do to make your car go
as fast down the Mulsanne as it could would more than likely lower your lap
time. The aerodynamic specificity that was needed to tackle the Mulsanne
Straight was different than any other track during the racing season. The
Mulsanne straight was the fastest piece of racing real estate on the planet!
(sic) In 1970, Vic Elford in the Porsche 917 LH ran over 240 mph down
Mulsanne at night, in the rain, through the "kink" flat out. It took Indy
Cars nearly 25 years to reach straight line performance levels that the
sports cars were achieving back in the early 70s!"
Doing 240mph in the rain (and at night, yet-- shudder) seems to confirm the
fact that big wide APPROPRIATE tires can work at high speeds on damp or even
wet surfaces such as asphalt, so I can't see any reason they won't work on
salt. It's important to note that rain tires have a very special tread
pattern that literally pumps the water out of the contact patch as it rolls.
Their tread compound is usually pretty stickey and they operate best at
lower tire temperatures than "normal" slicks. Just any treaded race tire
won't work as a rain tire. Ordinary tire tread helps wipe away some
moisture, oil, dirt, etc. but it isn't capable of running at the same speeds
in the wet as true rain tires.
One of the advantages of wide tires over narrow tires (confirmed by talking
to Dunlop & Michelin tire engineers) is that they offer far higher lateral
stiffness. This makes them far more stable and this helps make a car handle
well; in fact, the concept of running on skinny tires at high speeds gave
the tire guys the Willies.
On cars with exposed front wheels (roadsters, top fuel dragsters, etc) their
special circumstances may make the lower frontal area and drag of the skinny
tire outweigh the higher stability and traction offered by a wide tire. On
streamliners with very high speed capabilities, the tire design necessitated
by the terrific centrifugal forces in the tire body & tread may make a wide
tire unfeasible.
I wish I had a good contact at Goodyear...it would be helpful to get
information from them as they do have LSR experience as well as with
virtually every other area of motorsports. They should be the last word in
this controversy.
Regards, Neil Tucson, AZ ...are we tired --no pun intended :)-- of
this subject yet?
-----Original Message-----
From: Dan Warner [mailto:dwarner@electrorent.com]
Sent: Friday, September 13, 2002 7:23 AM
To: land speed
Subject: GT40 spinner
Why was the GT-40 so prone to
doing 185 MPH dados? I assume short wheel base but it couldn't be
much shorter than some of the lsr roadsters I've seen.
******************************
Don't know a lot about aero instability. The GT40 in question had the fat,
treaded tires used for asphalt road racing. No grip and tendency to
aquaplane
on the salt.
Dan Warner
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