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Unread 03-10-2014, 01:09 AM   #1
73azbronco
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Is there a reference to find actual tire size versus stated size?

Any reference out there to find true tire sizes versus stated for the different brands of 33 or 35's?

Example, I have Toyo open country, they are stated at 35 inches, but measure a surprising 33.75 inflated to 30psi. Until I measured them, I would have sworn they were easily 35.

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Unread 03-10-2014, 03:12 AM   #2
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Unread 03-10-2014, 10:57 AM   #3
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Quote:
Originally Posted by 73azbronco View Post
Any reference out there to find true tire sizes versus stated for the different brands of 33 or 35's?

Example, I have Toyo open country, they are stated at 35 inches, but measure a surprising 33.75 inflated to 30psi. Until I measured them, I would have sworn they were easily 35.
No.
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Unread 03-10-2014, 11:08 AM   #4
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Actual size will vary depending on inflation, load, and wheel width. Easiest thing is to not worry about it. Second easiest thing is to find someone with a similar vehicle and the tires in question that has measured the actual size.
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Unread 03-10-2014, 11:10 AM   #5
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Rule of thumb I always use is take the listed diameter and subtract 1 inch. This usually works out great for tires under 35".

Remember, the manufacturer measures tires with the bulge of the sidewalls while mounted on a specific wheel included. You and I measure without the sidewall bulge. That's where the inch gets lost.
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Unread 03-10-2014, 04:45 PM   #6
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Look at tire height in mamufactirer's specifications. That's the height of tire when inflated to max psi.

But you won't be using max psi. So it will have less tire height.

Also perhaps what Wxmam said too.
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Unread 03-11-2014, 06:05 PM   #7
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Tire sizes are based on an inflated tire that is unloaded. Meaning not on a vehicle.

So no, there is no standardizing. Especially when dealing with different manufacturers. And when you factor in quality differences, it further complicates things.

Think of sizes as a guesstimate.
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Unread 03-12-2014, 10:54 AM   #8
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I wasn't happy that a set of Duratracs I bought (31") measured out just a tad over 29". Wasn't what I expected at all and realized I had some researching to do. Use google, many other posts on this forum and others which talk about this.

http://www.jeepforum.com/forum/f96/a...specs-1206007/
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Unread 03-12-2014, 06:15 PM   #9
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Quote:
Originally Posted by 73azbronco View Post
Any reference out there to find true tire sizes versus stated for the different brands of 33 or 35's?

Example, I have Toyo open country, they are stated at 35 inches, but measure a surprising 33.75 inflated to 30psi. Until I measured them, I would have sworn they were easily 35.
FOUND THE ANSWER!!!!
Look at the mfg's stated revs per mile.
20,168 / [insert rev's here] = more realistic actual size.
For example, your tires (MT's?) have 596 rev's per mile, which equals 33.8". Much closer than the 34.8" inflated diameter spec.

Quote:
Originally Posted by Ferrachi View Post
I wasn't happy that a set of Duratracs I bought (31") measured out just a tad over 29". Wasn't what I expected at all and realized I had some researching to do. Use google, many other posts on this forum and others which talk about this.

http://www.jeepforum.com/forum/f96/a...specs-1206007/
and yours are 681 revs, which is 29.6"


A 35" circle has 576 rev's per mile.
A 33" circle has 611 rev's per mile.
A 31" circle has 650 rev's per mile.

I've found that most 35" tires are in the 595-605 range.
33's are mostly in the 630's.
I'm not sure about 31's.

I haven't looked into it, but I believe the discrepancy comes from load bearing. The inflated diameter spec is the tire inflated to maximum psi, with no load. Revolutions per mile is probably the tire at it's maximum psi and load, meaning the tire has it's flat spot at the contact patch resulting in a shorter radius to the ground (which is half the functional diameter of your tire).
Hope this helps someone.
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Quote:
Originally Posted by HurricaneRZA View Post
JF taught me that the 2.5L, Ax-5 and D35 together are so powerful that angels weep when I shift into 4LO.
Quote:
Originally Posted by mrblaine View Post
The only thing a bicycle inner tube is good for, is tying a knot in the end of when you run out of condoms.
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