MTFCA Forum

Hoping I don't regret the choice, I put a set of grey "smoothie" Firestones on Lizzie, they were offered as a deal I couldn't turn down. I reckon I'm no worse off at worst - the T-Drivers that were on were worn bald, so traction is at par and they're "cute".

The T-Drivers were "oversize", and the rear 30x3-1/2" tires ran awfully tight to the running board. I presumed the Firestones are what "regular" 30x3-1/2" tires were "in the day" ? Their circumference mounted and inflated is 98-3/4", which makes the diameter 31-7/16". Oversize ? They look "big" but they're not crowding the running board as tight as the T-Drivers did.

The front 30x3" tires measure 95-1/2" circumference, equals a diameter of 30-3/8". Thoughts ?

The closest you can get to "in the day" size is Universal Ribbed tires.

Firestones and all others will come as Oversize. Riversides are about the closest to original size with an aggressive tread but are still a lot larger than the original size.

30 x 3 1/2 "Oversize" is a real, advertised thing "back in the day"...they were available alongside regular 30 x 3 1/2 tires. Some time prior to WWII (I recall) tire sizes which were considered obsolete such as 30 x 3 1/2 were severely limited by Manufacturer Association dictates and when all of the sizes were winnowed down, the "Oversize" version of the 30 x 3 and 30 x 3 1/2 was the official version that would remain in limited production. I am speculating that WWII scrap drives were the nail in the coffin for any remaining original 30 x 3 or 3 1/2 molds insofar as they would never be placed into production again (from their perspective).

I really wish I could re-find and source this information but I can't seem to locate it. It was a fascinating read when I first discovered it but failed to copy or document where I found it.

Eric Johnson gave a great photo-explanation of the different tire sizes over the years here: http://www.mtfca.com/discus/messages/82 ... 1535212847

Scott provided the answers, that today we only have the 'Oversize' or 'Extra Size' which in reality is the next size up clincher tire, the 31"x4".

Note the the article states, straight sided tires, except the two smallest, for clincher. So only the 30" x 3 1/2" and the 31" x 4". size clinchers were manufactured due to war costs. Then the market went to the Oversize for the Ford, as more miles per $$