><snip> The speed rating is not a rating of how a tire resists
>heat! It's a rating of how fast the tire can go and maintain its
>temperature rating (A, B, or C).
there's alot of speculation as to what the speed rating of a tire really
measures. this should help clear of obfuscate things...
SAE laboratory speed test procedure for passenger car tires (SAE J1561)
states:
Upon visual inspection of the dismounted tire, any visible evidence of
the following constitutes tire failure:
a. Tread separation
b. Cord separation
c. ply separation
d. bead separation
e. sidewall separation
f. chunking
g. inner liner separation
h. cracking
and definitions for each of these conditions are also given.
the test procedure starts from room temperature with 80% of maximum load
capability, initial pressure based on speed rating (higher rating has
higher pressure) no slip angle. The tire is taken from rest to 24mph
below the speed rating over 10 minutes, the tire is maintained at this
constant speed for 10 minutes then incremented 6 mph every 10 minutes and
maintained at the maximum speed rating for 10 minutes.
the prescribed test dynamometer is smooth steel with 67.23 inch diameter.
let the debate continue.......
Dave Yeung
Houston Region
former Space Shuttle tire engineer
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