October 2025 Fastrack Preliminary Minutes/Tech Bulletin
09/18/25 - Preliminary Minutes
09/18//25 - Preliminary Tech Bulletin
09/18/25 - Preliminary Minutes
09/18//25 - Preliminary Tech Bulletin
October 2025 Fastrack
- Thread starter Greg Amy
- Start date
Well here's my chance to win the Runoffs. Come in 23rd and protest everyone on front of me based on a poorly worded wheel dimension rule.
Strikes me that as worded somewhere between "all" and "half of all" wheels that are nominally at the max size for the class would be in violation of this, depending on interpretation, roundness, and production tolerances. I interpret "absolute maximum" to mean that 0.001" oversize is illegal.
Ironic that the next item adds a tolerance to throttle body ID.
Strikes me that as worded somewhere between "all" and "half of all" wheels that are nominally at the max size for the class would be in violation of this, depending on interpretation, roundness, and production tolerances. I interpret "absolute maximum" to mean that 0.001" oversize is illegal.
Ironic that the next item adds a tolerance to throttle body ID.
A little bit of language evolution regarding wheel regulations, is this perhaps some foreshadowing and structuring for a forthcoming wheel update? 2 years and going on that letter...
"Rim width and diameter are
This is an edit to GCR Appendix G, so not affecting Prod specifically. And since it was done mid-year it's clearly an "errors and omissions" to clarify intent, not a regs change (which requires BoD approval).
And do note that listed diameters were already "max" allowances; see column labels in the spec sheets.
If you're worried about adding these as diameter tolerances (which cannot be measured to .001") then why were you not worried about it when width was already in there as an absolute? Wouldn't it be a lot more useful to exceed width, and a lot harder to measure (because of the tapered walls)? Are you implying that competitors have been fabricating wheels that are larger than the allowed diameter (which must be one hell of a fun thing to deal with when installing standard-sized tires) and they'll now get dinged for exceeding that? I find that hard to believe, honestly.
I can't offer why the PAC proposed this (other than to remove the word "max" in the spec lines column label) but I see concern over this as "a tempest in a teapot". - GA
The only reason that I even thought about it (with respect to width OR diameter) was the change. But when I DID think about it, I remembered Prod cars (at least one anyway) being DSQ'd for a valve 0.001" over the maximum dimension.
No, I have no thoughts that anyone is specially making marginally oversized wheels, especially wrt diameter, which as you say would only serve to make tires harder or impossible to mount. Nor do I really think that anyone is really making 7.1" wide wheels as a cheat, though it might be tempting..
It just seems a bit unwise to use the term "absolute maximum" on something that is extremely difficult to actually measure and subject to largely unknown tolerances. I was perhaps inspired by the wisdom of an Internet sage who once said something to the effect of "If a rule can't be enforced it isn't a rule".
In this case I'd modify it to "If a rule shouldn't be enforced as written it should be written differently".
I'm really not in the least personally concerned, and probably being a bit pedantic, but I do think that using the words "absolute maximum" on something that is in many ways a nominal dimension (unless you are armed with an SAE or ISO standard) is maybe setting a landmine in the rulebook that may or may not ever get stepped on.
Anyone wondering what I'm on about - go measure a road wheel and tell me EXACTLY - down to the thousandth - the diameter and width. No cheating by looking at the cast in nominal dimensions.
No, I have no thoughts that anyone is specially making marginally oversized wheels, especially wrt diameter, which as you say would only serve to make tires harder or impossible to mount. Nor do I really think that anyone is really making 7.1" wide wheels as a cheat, though it might be tempting..
It just seems a bit unwise to use the term "absolute maximum" on something that is extremely difficult to actually measure and subject to largely unknown tolerances. I was perhaps inspired by the wisdom of an Internet sage who once said something to the effect of "If a rule can't be enforced it isn't a rule".
In this case I'd modify it to "If a rule shouldn't be enforced as written it should be written differently".
I'm really not in the least personally concerned, and probably being a bit pedantic, but I do think that using the words "absolute maximum" on something that is in many ways a nominal dimension (unless you are armed with an SAE or ISO standard) is maybe setting a landmine in the rulebook that may or may not ever get stepped on.
Anyone wondering what I'm on about - go measure a road wheel and tell me EXACTLY - down to the thousandth - the diameter and width. No cheating by looking at the cast in nominal dimensions.
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I was perhaps inspired by the wisdom of an Internet sage who once said something to the effect of "If a rule can't be enforced it isn't a rule".
Sure, I get it. But I do think, in that context, that concern about wheel diameter as an absolute max tolerance is less worrisome than wheel width...which was already in there. We didn't complain about it, though...
Curious why the PAC pursued that. There's gotta be a back story.
I agree 100% that any actual physical discrepancy (ie cheating) would be width, not diameter. And of the two, width seems harder to measure and thus more subject to incorrect measurement. And yes, width was already there - I simply hadn't thought about it.
Sure, I get it. But I do think, in that context, that concern about wheel diameter as an absolute max tolerance is less worrisome than wheel width...which was already in there. We didn't complain about it, though...
Curious why the PAC pursued that. There's gotta be a back story.
But I DON'T think it's amiss to point out possible points of disqualification that are very likely prone to error, even if they have been in the rule book that way forever.
If you haven't, take a tape measure to a cast road wheel. An acquaintance (I forget who) was looking for a particular old VW wheel, I dragged out some old stock Scirocco wheels (yes I'm a packrat) and was surprised that I couldn't quickly decide within a quarter inch or so how wide they (nominally) are. There's just no obviously correct place to measure the width, it's to a certain non obvious place in the curved bead seat profile as defined by somewhat obscure industry standards.
Here's a diagram poorly photographed from the Bosch Automotive Handbook. Notice that the diagram even uses the term "nominal rim diameter".
Gordon Jones
Well-known member
It's a poorly written rule. Where on the wheel is the measurement to be taken?
jimmypet
Well-known member
Wouldnt the easy button be to make the width measurable by something easy like the rim width calipers the tire shops use when balancing?
www.carliftparts.com
SnapOn Wheel Balancer Rim Width Caliper Measurement Measuring Tool EAA0247G21A
This is a HIGH QUALITY wheel width caliper / rim measurement tool for Snap On & John Bean Wheel Balancers. It Measures from 3' up to 14' wide wheels and increases by 1/2' increments. The numbers are raised and in Bright white to make them easy and quick to read. This caliper is made out of ...
Those are measuring on the outside of the wheel rim, and presumably have a built in thickness assumption, as the actual dimension is to the inside of the bead seat at some hard to define point. I'd assume that they would get you to the nearest half inch - probably. Which in practical terms is probably all that matters, but when I see "absolute maximum" in the rule book I'm thinking (rightly or wrongly) thousandths not half inches.
Tires are not all the same size. The tire and rim association size guidelines are wide and there is no requirement to comply with them. In other words one 245 is 240 another is 253. The rim being 6.95”, 7”, or 7.1” gonna have less performance benefit than the allowance already available in the tire dimensions.
Except the Prod rules limit wheel size, not tire size.
My issue with the rule as written isn't that I think that there is a significant performance advantage with a 7.1" wide wheel, but rather the enforcement (or possible overzealous enforcement) of an "absolute maximum" dimension that nobody really know how to measure accurately. AFAIK no such issue has ever arisen and maybe it won't, but Prod cars have been DSQed over a valve that was 0.001" oversize.