National Staff Greg G. Posted December 7, 2017 National Staff Share Posted December 7, 2017 TECHNICAL BULLETIN 12-6-17 ST4 NSW 282mm minimum vehicle weight 6.4.1 ST4 Tire Limitations 2) Size (See 6.5.1 for “NASA Section Width” tire measurement specifications) 1) Vehicles with a Minimum Competition Weight greater than 3100 lbs. must have a measured tire NASA Section Width equal to or less than 282mm; Or, can be any currently produced size 275, 245, or smaller DOT tire. (note: Deletion of the use of labeled tire size is probable within 6 months) Quote Link to comment Share on other sites More sharing options...
Members Jon B. Posted December 7, 2017 Members Share Posted December 7, 2017 TECHNICAL BULLETIN 12-6-17ST4 NSW 282mm minimum vehicle weight 6.4.1 ST4 Tire Limitations 2) Size (See 6.5.1 for “NASA Section Width” tire measurement specifications) 1) Vehicles with a Minimum Competition Weight greater than 3100 lbs. must have a measured tire NASA Section Width equal to or less than 282mm; Or, can be any currently produced size 275, 245, or smaller DOT tire. (note: Deletion of the use of labeled tire size is probable within 6 months) Greg - Can you share what the rationale is for this rule? How was 3100 derived? Were there really that many examples of the 'lighter' cars running 275's this past year in ST4 running away from cars running smaller tires? In NorCal we didn't see this - we had maybe one car running 275 Hankooks that posted some good times relative to others here or there, but same driver would post very similar times on smaller tires. At Western States, we saw one 'heavy' car (the winner) walk away from the field on 245's. Yes, great driver as evidenced by his record, but it was clear that tire width was not holding him back. The nice thing about the ST4 rules (at least last year), were that they were still relatively simple, while providing choice. If you wanted to run wide, great, but you'll take a HP hit. While I ended up staying with 245's all last season, it would be nice to be able to try wider - hence why I purchased 10" rims which are now useless. I know I'm not the only one in that boat. On the outside, it seems like this rule is kind of reactionary, and overly favors heavier, high hp cars, while leaving the lighter cars with fewer options. Maybe I'm missing something as I don't see what occurs across other regions. Thanks for all your help and hard work trying to get this stuff right. Jon B, ST4 NorCal Quote Link to comment Share on other sites More sharing options...
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