Tire Size

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Model T Ford Forum: Forum 2018: Tire Size
Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Govoni Fredericksburg, VA on Sunday, July 22, 2018 - 06:24 pm:

So soon I'll be taking care of a lot of things on my 26 touring that I bought two years ago. One of the things I noticed was my tire size. The tires read 4.40/4.50-21. They are on wood wheels with split rims. I know that the fist number is the with and the 21 is the rim size but when I read about tires people talk about 3.5-21's. Are my tires an odd size? Do I have to stay with 4.5's? will 3.5's work as well?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Sunday, July 22, 2018 - 06:42 pm:

4.40/4.50x21 are the right size for your year/model.
3.5x30 are for earlier T,s. I don't think 3.5x21 is a tire size, well not listed at my end of the world anyway.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Sunday, July 22, 2018 - 06:47 pm:

What you have is a standard size for 1925/'26/'27 as well as the '28/'29 model A Ford and a bunch of other cars of that era. Any "3.5" was never a common standard size for a 21 inch rim (there may have been a few motorcycles or equipment tires that size?).
The "3.5" size usually referred to are the 30 inch OUTSIDE measure tires that fit a 23 inch clincher rim (a totally different animal). Earlier tires were measured by outside X tire (doubled) to reach the rim size. (30 X 3.5 times two equals 7, means 30 - 7 equals 23, the rim size) (That confusing enough?)

Have fun! I hope you enjoy tinkering with old technology. Most of us do.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Arthur Babitz on Sunday, July 22, 2018 - 06:51 pm:

My '27 Roadster has 4.50/4.75-21 tires on wood spokes.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Govoni Fredericksburg, VA on Sunday, July 22, 2018 - 07:22 pm:

Thanks everyone. So why did they label them 4.40/4.50? Why not just 4.50?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Sunday, July 22, 2018 - 08:07 pm:

Back in the day, some cars had 4.40 inch tires and others had 4.50 inch tires. Some had 4.75inch tires. Now days the 4.40/4.50 is used for either size. They will work just fine. The tire manufacturers just don't have enough market to make the individual sizes. Only one tenth inch difference.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Govoni Fredericksburg, VA on Monday, July 23, 2018 - 09:41 am:

Thanks Norm and everyone else. I'll have to get some tires soon. The ones on the car have very little mileage but were bought in the 70's!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Monday, July 23, 2018 - 10:50 am:

Your determination to install new tires is wise. Yes, I know, some folks run on tires that are fifty or sixty years old and have never had a problem. But I believe that the risk of failure increases with the years, because rubber DOES deteriorate with the passage of time. On a car that moves only a few miles a year for an occasional slow visit to the local ice cream parlor, those ancient tires may not be a high risk. But for a car that does any serious driving, I'll go with new.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Govoni Fredericksburg, VA on Monday, July 23, 2018 - 11:02 am:

Steve, I have never driven the car (yet). I've got a transmission issue to resolve first. I'm just making my anti death and crash to do list before I take a ride. Lot's of work to do yet.


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