MTFCA Forum

I have a set if round wood fellow wheels for a 14 T w/o the hubs installed. The diameter of two of the wheels are slightly smaller than the other two. Which are the rears and which are the front?

R/Mark

23" wheels = rear

24" wheels = front

The rear wheels are smaller than the front wheels. The tire nomenclature for clincher tires is counterintuitive. The first number in a clincher tire is the outside diameter of the tire (or think of it as the diameter of the outside of the tread). The second number is the tire height as measured from inside diameter to the outside diameter of the tire (or think of it as the measurement form the rim to the tread). The early USA non-demountable model T tires were 30x3.5 for the rear, and 30x3 for the front, that means the front and back tires have the same outside diameter of 30" but the height of the tires as measured from the rim to the outside diameter is .5" taller for the rear wheel than the front wheel. Therefore, to have a taller tire in the rear with the same outside diameter as the front tire, the rear wheel rim is smaller than the front. Ye Gads, what a counterintuitive and confusing sizing system!!!

Math for Jeff's explanation above:

30 x 3.5 rear tire
30" - 3.5" - 3.5" = 23" rear wheel

30 x 3 front tire
30" - 3" - 3" = 24" front wheel

Thanks everyone for the detailed explanation. This is the first t I've owned that had 30x3 tires, so i never gave it much thought. I always thought the second # was the tire width since the 30x3 tires are narrower, at least the ones I have are.

Look at it this way Mark: you cannot increase a circle's height without increasing it's width. A clincher tire with a taller sidewall will always be wider as well, and vice versa...make sense?

straight wall tires on locking ring rims are an entirely different story