I always ask this question because it is a problem at a lot of the tracks I run here in Maine. When the rules says 44" tire, does that mean 44 by a tape measure on the truck or by the side wall lettering?

For example a lot of people around here run the 38.5x11 bogger in classes that only allow a 36.5 or 37.5 tire on the grounds that they feel it measures small. So someone like myself who runs a 37x13.5 bogger to meet the rules as written is at a disadvantage.

Any thoughts on stating a way of determining size. I don't care myself either way, just as long as everyone knows going into it and it is enforced.

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Brian Morrison
MaineMudRuns.com
brian[at]mainemudruns.com

I stood firm on "measured height" for years, but eventually caved & have "seen the light". We now run stamped height & maintain a list of the oddball tires that are considered legal - for example, MRA class 2 is a 37" stamped height limit. R85 Buckshots are considered a "37x13", so those are legal. A 38.5X11 that measures 37" would not be allowed in the 37" class.


On a side note, Interco used to make TSL's in a 13X37 size & sometime around 1985, they changed the stamp on that tire to 38X12.50 - exact same tire, same mold, verified by Interco. And ONCE in awhile, a set of those old 37's still show up. It's for that reason, I've always preferred to make the 37" stamped height class 38.0". BUT, too many guys assume that they can run 38.5's - or worse, argue that their 38.5's are in fact 38.0's. They all get that same deer in the headlights look when you wipe the dirt off & show them the sidewall stamp, though Anyway, those old 37's will be gone one day, so 37 is probably a good limit.


Oh, and the question you didn't ask but wondered, yes MRA classes limit tire diameter based on the sidewall stamp.


Scott

Oh, for those that DO stick to the measured height rule, the proper way to "measure" tires is with a rigid caliper. And here's my personal opinion on how to do that. Make it 1/8" larger than the limit & then it must pass over the tires in a horizontal plan with ZERO resistance. You have to make it slightly oversized or tires that are "at" (but not over) the limit will be snug in the caliper.