Racing slicks or DOT tires?
Ibve been autocrossing an old highly modified 1967 Triumph Spitfire in EM for
the past 15 years (1600lbs, running a Mazda 2.5L V-6 170hp, with custom
suspension). During this time Ibve always accepted the conventional wisdom
regarding running in this class and have blindly run on racing slicks
(20.0x9.5-13). Ibve run on Hoosier, Goodyear and Bridgestone road racing
tires, usually on the softest compound available. But, none of the tire
companies actually makes racing slicks especially for autocrossing. The slicks
are made for road racing. And from what I can tell theybre made to last a
weekend of racing, consisting of multiply 30 minute heats at considerably
higher speeds than one encounters in autocrossing. In these 30-minute heats
the tire temperature can be brought up to the proper working temperature for
their best performance. But in a 40-80 second autocross I canbt seem to get
the tire temperature up to what the manufacturer suggest. During all my racing
Ibve never gotten a tire temperature past 140 deg F, and Ibve only gotten up
in the high 130bs on days when the outside temperature was over 100 deg. Most
of the information I can find on tire temperatures talks about getting
temperatures up in the 180 to 230 deg ranges. Basically I donbt believe Ibm
getting the performance possible out of the tires.
Recently Ibve been looking at some of the new DOT tires made by Hoosier and
several other companies made especially for autocrossing. From what I can get
from their web sites, it appears these tires are made with a rubber compound
especially for autocrossing. From the pictures Ibve seen of the tires
theybre not much more than a racing slick disguised as street tires with a DOT
rating. So my question isb&.. Am I better off going with the conventionally
wisdom and blindly running a racing slick (my current usually Hoosier
20.0x9.5-13 R25A) made for multiple 30 minute heats at high speeds or one of
the modern DOT racing tires made for autocrossing (such as the Hoosier A3S04
225/45ZR13).
Anxiously awaiting the collective wisdom of the list...
Dave
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