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Why is 13.6 equal to 12?

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=204101
Printed Date: 14 Nov 2024 at 12:10am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com


Topic: Why is 13.6 equal to 12?
Posted By: StanGreen
Subject: Why is 13.6 equal to 12?
Date Posted: 10 Nov 2024 at 10:50am
As I am looking at new power shift rims for my WD45, I have figured out that my 13.6x28 tires need to go on 12x28 rims. I am just curious as to why 13.6 tires need 12 inch rims?



Replies:
Posted By: DrAllis
Date Posted: 10 Nov 2024 at 11:00am
They don't NEED 12 inch rims. That is what the tire makers recommend for best performance. You can mount them on 10 or 11 inch or even 13 inch if you want. The tire doesn't know or care.


Posted By: Rick of HopeIN
Date Posted: 10 Nov 2024 at 11:08am
The tire sizes listed in old books were based on a different design standard.  If you use tires on the rim width listed it gives the best geometry.   Some real old rims like on my WC don't fit modern tires exactly but that's all you can do.

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1951 B, 1937 WC, 1957 D14, -- Thanks and God Bless


Posted By: steve(ill)
Date Posted: 10 Nov 2024 at 12:55pm


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Like them all, but love the "B"s.


Posted By: Lars(wi)
Date Posted: 10 Nov 2024 at 3:25pm
Tires that get put on rims that are wider, tend to have the tire sidewalls too straight. Which can affect the way the tire tread grips the soil, and adversely affect tire wear, plus straight side walls may give a ‘firmer’ ride.

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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.


Posted By: DrAllis
Date Posted: 10 Nov 2024 at 3:38pm
Maybe I've misunderstood the original question.  Prior to about 1958 a WD/WD45 tire size was called a 12-28 size tire.  From about 1958 and newer, the tire industry began a new tire size system and what was a 12 x 28 now became a 13.6 x 28. Both sizes are the same actual size. A-C in about 1955 (WD-45) began advertising an optional 13 x 28 tire on a 12 inch rim. This new optional size would later become the 14.9 x 28 tire in 1958.  In my mind the 11 x 28/12.4 x 28 tire was on a 10 inch rim.  The 12 x 28/13.6 x 28 tire was on an 11 inch rim. And the 13 x 28/14.9 x 28 tire was on a 12 inch wide rim.  After all these 70 or more years you will find ANY combination out there !!!


Posted By: HudCo
Date Posted: 10 Nov 2024 at 7:16pm
if you are a little wider and change to 14.9 somtime it will work out a little bettter



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