A little bedtime story about drag tires:
Once upon a time a guy was returning from Bandimere (Denver) to California.
Due to a lack of planning, the spare for the tow vehicle was left behind.
So of course, a truck that had brand new tires on it, and had not had a flat in over 100,000 miles, got a flat.
Luckily, the racecar used the same rims as tow truck. And the race car was VERY heavy at 6700lb.
So it was assumed that the DOT rated drag tire that was rated at over 200mph for dragracing, and easily went 130mph many times at heavy loads would be OK for 20 miles to the next town.
But, the heat generated by sustained 55mph operation was not something the tire enjoyed. After 10 miles, it began to develop delamination on the sidewalls. Another 2 miles later it exploded. The tire was 3 months old (by date code) with only 1 event on it.
While this tale does not necessarily apply to Goodyear (these were M&H's that I and hundreds of others continue to use today), speed ratings for drag tires are not tested for sustained operation, not even DOT models.
By comparison, DOT street tires with only a 149 mph rating easily endure huge loads at high speeds for years and tens of thousands of miles. In fact, one model required 35? miles at 2200lb loading spinning 215mph before a piece of tread came off. The tire did not fail, it only went out of balance. The reason the tire was not tested at higher speeds or loads was simply because the testing lab could not go higher.
Sadly DOT street tires are frowned upon for high speed use by the SCTA. Tires that don't even get warm at 175mph for 50 miles straight aren't good for 175mph operation.
Cars and tires have changed dramatically in the last 80 years. There are over 50 models of new cars that are capable of speeds over 200mph today. Tires today ran out of speed ratings. (Y) is the highest rating possible (more than 186mph) and doesn't have a top speed rating. They had never expected cars to go over 150mph until relatively recently, hence the Z rating ratings the SCTA uses. Z was the highest letter. But as time went on, they had to scramble to find tire designations. W rating came out to remove the Z rating, but cars went faster still. So they added a Y rating. Surely no OEM car will exceed 186mph. Right? DOH!!! They were now out of letters and gave up. Today's supercars that run their tanks dry at 250mph use a (Y) rated tire, which means (Why didn't we see this coming?). They shortened it to simply (Y).
And then they lived happily ever after (until the 300 mph street cars come out that is).
The End.
