(800) 853-2651
SHOP NOW

Tire Size Conversion Chart

H

Harold H

Well-known Member
A lot of the younger users may not be aware that the American Tire Manufacturers changed the standard designations for tire sizes three times over the years.For convience I am posting a chart of the different sizes and also the different tread designations.

TIRE SIZE CONVERSION CHART
1932-1940 1940-1955 1955-PRESENT
7.00 TO 8 TO 8.3
7.50 TO 9 TO 9.5
8.25 TO 10 TO 11.2
9.00 TO 11 TO 12.4
10.00 TO 12 TO 13.6
11.25 TO 13 TO 14.9
NONE NONE 15.5
12.75 TO 14 TO 16.9
13.50 TO 15 TO 18.4
NONE 16 TO 19.2
NONE 17 TO 20.8
NONE 18 TO 23.1
NONE NONE 24.5

TIRE TREAD DESIGNATIONS
R-1 REAR FARM TRACTION TREADS
R-2 REAR FARM RICE & CANE TREADS
R-3 REAR INDUSTRIAL SMOOTH TREADS
R-4 REAR INDUSTRIAL TRACTION TREADS
F-1 FRONT FARM SINGLE RIB
F-2 FRONT FARM MULTI RIB
F-3 FRONT INDUSTRIAL MULTI RIB (I-1)

The post 1955 size designations are still in effect but do not cover many modern radial and metric and special profile tire size designations.

Harold H

I hope this will clear up some folk's future tire questions.
 
You might mention that the last two columns are the same tire, 2nd column tread width, 3rd column cross section. I am not familiar with the 1932 numbers--is that different construction? I know that in those days they put a wide tire on a narrow rim -- .
 
Reading left to right each is the same equivlent tire size.
For example, a 1939 M might have been equipped with 8.25 x 38 tires. If you need to replace that tire in the 1940's or early 50's it would be a 10 x 38. If you needed to replace that same tire again in the late 50's or later you would replace it with a 11.2 x 38 which would be the same equivlent size.

Harold H
 
Size error correction: 19.2 should be shown as size 19.6. However, I do not believe any current tire manufacturer makes the 19.6 size.

Harold H
 
The change from the first column to the second coincided with the change to wide base rims. If you look on the millertire web site (go to their FAQ's), you will find diagrams that help make this more clear. They have a size conversion table (fewer entries than Harold posted) and diagrams showing where each system measured the tire.
 
You must log in or register to reply here.

Similar threads

M
Antique Tire Size Conversion
Replies
5
Views
886
mennometis
M
R
Ford 861 with Elenco 4X4 conversion - Tire Size Question
Replies
6
Views
2K
warbaby
W
C
Tire Size, what's compatible?
Replies
6
Views
2K
Camozzi04
C
M
Lightest Brand and Model of Tire
Replies
1
Views
463
Tim Yates
T
B
tire size and brand
Replies
4
Views
1K
johns
J
Tractor Parts Tractor Manuals

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Copyright © 1997-2024 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters
Website Accessibility Policy

Back
Top