Click on the link above to see a PDF summary of results from the 2020 Buttonwillow HST Event for the first official use of the SM7.5 tire in competition.
A quick summary of the results are as follows;
- There were 19 SM entries in the Buttonwillow event with somewhere between 7 and 9 competitors ran the SM7.5 in competition.
- Average times between the current SM7 vs SM7.5 for the top five competitors over four "on-track" sessions were close to the same.
- The fastest SM7 competitor averaged 2:05.530 sec. Lap Times for the four sessions while the SM7.5 averaged 2:05.594 for 4 users.
- Fastest Qualifying time went to the SM7.5 tire with it being the only tire to break into sub 2:05.00 lap times (two competitors).
- The fastest qualifying time was 2:04.724 sec's for the SM7.5 vs 2:05.058 sec's (3rd fastest) for the fastest SM7 qualifying time.
Out of 6 potential race Podium positions, five went to the SM7.5 tire including both race wins, the remaining 3rd Place podium going to the SM7.
The performance capability of the SM7.5 seemed to be consistent with conditions over the 4 "on-track" sessions and did not show any sign that there was a "flyer" lap related to any particular Heat Cycle.
In general the wear surface of the SM7.5 appeared even and flat but their was one situation where there was tire surface irregularities that looked like a thin skin of rubber had separated from the tread surface. The Hoosier tire rep said that this issue was due to tire mold release compound getting on the uncured tread rubber as it was inserted into the mold and that this irregularity would go away as the tire wore down. I will be sending this tire back to Hoosier for engineering evaluation. We did run this set of tires on the Saturday race but we moved the tire from the most heavily loaded RR position and put it on the least loaded LF position.
Also, as a result of this condition we elected to run a second set of SM7.5 sticker tires in the second qualifying session as a precaution. Under the new Tire Limiting Program proposal, we would have lost our first qualifying time and would have had to start from the rear for the 2nd qualifying session since we used a second set of tires. We could have used a single replacement instead and kept the first set of times and started in the earned 3rd place Qual 2 start position. Ironically, at last years Buttonwillow HST, we also had a tire quality problem where we had a 7 to 9 inch long tread edge separation that was attributed to improper curing in the mold. This also resulted in our use of a second set of sticker tires at this event in 2019 due to a tire irregularity.