Tire sizes that are actually the advertised height. - JeepForum.com

 
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post #1 of 10 Old 01-29-2016, 06:14 PM Thread Starter
737mechanic
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Tire sizes that are actually the advertised height.

Bought my son a 2007 JKU and it has Terra Grappler 285/70R17 which should be about 33" tall according to the size comparison charts I have found but they actually measure about 31. They are worn somewhat but i do not think they would have been 33 when new.

What I would like to know is what brands and sizes are actually 33" tall.

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post #2 of 10 Old 01-29-2016, 06:31 PM
UTAH
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The 34x10.5 BFG's on my JK-8 measure out to 33" tall mounted.

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post #3 of 10 Old 01-29-2016, 06:36 PM
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Wondering why 1/2 inch of ground clearance matters that much ? Nearly all tires measure smaller than their stated diameter, sometime as much as one inch smaller.

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post #4 of 10 Old 01-29-2016, 08:12 PM
sketchy
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I've seen tire vendors online that list the measured size of the tires (and the wheel width used for the measurement). I can't find one now though. Anyone know who I'm talks nag about?

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post #5 of 10 Old 01-30-2016, 02:04 PM
LouC
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tire rack does

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post #6 of 10 Old 01-30-2016, 02:21 PM
LouC
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http://www.tirerack.com/tires/tires....l=Grabber+AT+2
just click on 'specs'
General and most tires have the same thing on their websites...

http://generaltire.com/tires/light-t...uv/grabber-at2

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post #7 of 10 Old 01-30-2016, 03:47 PM
UTAH
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Keep in mind Tirerack's specs, like most vendors, are provided by the tire companies. So, their "official" specs are just as prone to err on the large side. Having said that, they're a good place to start.

And, even when tire specs are right, there's still a difference between un-mounted and mounted diameters. You can lose another 1/2" to 1" in diameter.

Bill

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post #8 of 10 Old 01-30-2016, 10:30 PM
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Tire manufacturer specs don't err on the small side. They're correct for tire inflated to max pressure with no load/weight on it (wheel not mounted on vehicle).

Loaded static height mounted on vehicle (what you care about) will be less because you don't have max pressure and you have load/weight on it (wheel mounted on vehicle).

Actual height while rotating will vary according to inflation pressure, load/weight on it, and rpm.

I wish I had a dollar each time this topic comes up.

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post #9 of 10 Old 02-01-2016, 10:40 AM
mike_dippert
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Using the "rotations per mile" spec is the closest I've seen.

A true 35" circle has 576 rotations per mile.
A true 33" circle has 611 rotations per mile.
A true 31" circle has 651 rotations per mile.

The average 33" AT is 638rpm, which equates to a 31.6" diameter.

It doesn't matter though, because that undersized 33 is still a 33, not a 31.
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post #10 of 10 Old 02-05-2016, 07:31 AM
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Virtually all tires run short. It's just the nature of the beast.

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