Backcountry Pilot • Tire Size

Tire Size

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Thu Feb 19, 2009 8:29 pm

Tire Size

Can anyone explain what the numbers before the wheel size mean.

Like 8:50x6 what does 8:50 mean

or

36:00x51 what does 36:00 mean (yea, I know it's big)

thanks
UtahMaule offline
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Fri Feb 20, 2009 1:22 am

WUP would be the one totalk to about this. He should show up here soon :)

This is as much as I know about this :-k . The 8.50 relates to the tire diameter. Although, it doesn't appear to be an exact science. An 8.50 in one brand of tire will usually be a different diameter than an 8.50 of another brand tire. But the 8.50 will always be bigger than a 8.00 which is bigger than a 7.00, which is bigger than a 6.00, etc.

It seems that once you get tires larger than 8.50's the first # becomes a more cosistant represetation of tire diameter, in terms of inches. 26.00's ~ 26"'s, 29's~29"'s, 31~31"s etc.
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Fri Feb 20, 2009 2:52 am

Re: Tire Size

UtahMaule wrote:Can anyone explain what the numbers before the wheel size mean.

Like 8:50x6 what does 8:50 mean

or

36:00x51 what does 36:00 mean (yea, I know it's big)

thanks


Well, if you were to change the colon to a decimal point (i.e., 8.50), it would mean the cross-section width (not diameter, not the sidewall height, not the aspect ratio as some people claim) of the tire. And, of course, as you noted, the second number is the diameter of the wheel.

If there are three numbers (i.e. 36x13x6) then first is tire diameter, second is cross-section width, third is wheel diameter.
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Fri Feb 20, 2009 5:53 am

So on a 36:00x51 or 36.00x51 the width of the tire is 36 inches?

On larger tires I see it with a : not a . has the meaning of that number changed or . means : ? :?
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Fri Feb 20, 2009 8:47 am

Re: Tire Size

kevbert wrote:
UtahMaule wrote:Can anyone explain what the numbers before the wheel size mean.

Like 8:50x6 what does 8:50 mean

or

36:00x51 what does 36:00 mean (yea, I know it's big)

thanks


Well, if you were to change the colon to a decimal point (i.e., 8.50), it would mean the cross-section width (not diameter, not the sidewall height, not the aspect ratio as some people claim) of the tire. And, of course, as you noted, the second number is the diameter of the wheel.

If there are three numbers (i.e. 36x13x6) then first is tire diameter, second is cross-section width, third is wheel diameter.



I didn't see anyone claiming anything

8.50 is the cross section width measured at the fattest part of the tire. The reason there is no aspect ratio number as used today is because all tires used to be 1 to 1, then in the 70s they went to a letter system after that it all went metric as today.
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Fri Feb 20, 2009 12:06 pm

Re: Tire Size

mr scout wrote:I didn't see anyone claiming anything



Sorry, I didn't mean postings on this forum, just people I've encountered over the years have made those claims.

Yes, there's a real world out there beyond the internets! :D



As for the colon in the size specification of larger tires, I have never seen it. Is it brand specific, or does the industry in general use that nomenclature?
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Fri Feb 20, 2009 1:16 pm

Cool looks like my services aren't needed, goood cuz I would have gotten it wrong anyways...... I thought it would take 8.5 of those tires to equil a 31" tire..... :shock: Who knew... Have a great weekend guys!
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Fri Feb 20, 2009 8:19 pm

Jr.CubBuilder wrote:
UtahMaule wrote:So on a 36:00x51 or 36.00x51 the width of the tire is 36 inches?

On larger tires I see it with a : not a . has the meaning of that number changed or . means : ? :?


That's an imaginary tire (?) but that sizing nomenclature would fit the modern convention where 36 is the diameter in inches, and 51 is the width in inches. Usually that would be followed with the wheel size like -15 for example, so what you suggested would show up in the catalogue as 36x51-15 and it would be 36" in dia, 51" wide and fit on a 15" rim which would make great paddle tire for the sand dunes.

Since Wup makes his own tires for unique applications he gets to just call them whatever he wants.

By the way Wup if you have a surplus of 26"BWs I think a pair of those would be perfect for the old 170. Let me know if you have a sale :D



36:00 x 51 is tire found on mine equipment with a 51 inch wheel.
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Sat Feb 21, 2009 7:27 am

Like my girlfriend told me "don't worry about it- size doesn't matter anyway". Of course, she wasn't talking about tires....

:oops:
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