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Discussion Starter #1
alright, just got a question about tire height. i noticed the other day that my friends 31x10.5r15 swamper tsl's (on a jeep, im assuming 8" wide rim) looked taller than my 32x11.5r15 buckshots on stock 15x7 alloys. so i measured them and sure enough, his measured 31" from ground to top of tread. mine only measured 30" from ground to top of tread. now he has slightly less tread wear than mine, but only like 1/8'' to 1/4".

so my question is, do my tires measure short because it's such a wide tire on that narrow of a rim? that's the only reason i can think of. am i on the track here?
 

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Tire size can be affected by several factors.

1. actual tire size may not be as stated - a 32" tire may only measure 31.2"...
2. air presure - will affect axle height, as well as overall tire height - A flat tire is not as tall as a fully inflated one.
3. tread wear.

Rim width may make a little difference.
There may be other factors, too.
 

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all the above are all true, and to add if your rim were narrower your tire would be slightly taller than if same said tire were on a wider rim. By how much depends on tire construction.

One thing to add is if your tread is only 1/4" less than your buds, when you measure you have to account for that 1/4" on the top and bottom of the tire, since you are measuring the diameter of the tire (tire height) rather than just radius of tire (from hub center to outter tire tread). 1/4" less tread adds up to 1/2" difference and couple that with differrent rim widths, could be as much as 1" overall.
 

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I know exactly what you're talking about. I just bought a set of 33x12.5 15 Pro comp A/T's and they measure just about 32" in diameter.

But I knew this when I bought them. Manufacturers specs for this tire are 32.4" in height.

It actually measured a bit over 32".

I wanted a tire the was wide but not overly tall and I couldn't find a 32x12.5 15 in the tire I wanted. So I found the closest one to this, and thats what I got ( a 33" tire that actually measures 32".)

I have these monuted on 10" Wheelers steelies for the record.
 

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Discussion Starter #5
yeah, i just looked on maxxis's website and the tire actually 31.3". and yes, goldentaco, i did forget to count the difference in tread wear twice. and im running 36 psi if that means anything.

okay, half way through this post i did some math and i now i get it. the way my numbers add up, ive lost about 1/2" of tread. i guess the buckshots had deeper tread than i thought.( i bought the truck used, tires already on there) Ok, well i guess i got it figured out now, unless someone has anymore relevant info thay wanna add. thanks for the responses.
 

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drinkintedbr said:
you should normally run what it says on the inside of the door.
thats only true with stock size and type...

you should run as much pressure as you can and still have a flat contact patch, every tire/wheel combo is different. I can only run 18 in my 35 BFG's on a 15x8... they dont overheat thou, so its fine... on the hwy with camping gear they get about 26....

The more pressure you run will give less resistance, and more mpg... but at a loss of traction, so in winter and when wheeling drop it as low as you feel safe.

My wifes 03 get about 32 in the summer, max per sidewall, and 27-28 in the winter for added traction. OEM tires still...
 

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The only reasoning I can see why the tires are spec'ed larger than actual diameter is for customer fit issues. If you know you can fit a 32 and get new tires that are slightly smaller, even though you buy a 32 they'll fit. If the manufacturer made em close to 32 but erred on the large size, they may have product return issues due to close fit tolerances that exist as we are all aware of.

Way I see it, the're coverin their asses.

Another thing to consider (I know this is wheeling land and all) offroad tirea have deeper tread depth than road tires so when they wear down you'll notice more power fluctuations(differences in gear ratios)/ speedometer discrepancies than with road tires which have normally shallower tread depth. Optimal tire diameter stays more constant...only matters if that's what your after though.
 

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My bfg all terrains are only measure 30 1/2 inches tall, and they are supposed to be 33x1250s i bought them about 3k miles ago..
 

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honca2k said:
My bfg all terrains are only measure 30 1/2 inches tall, and they are supposed to be 33x1250s i bought them about 3k miles ago..
is that on the rig? if so thats about normal... take them off and measure, they will be taller.
 

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ah64id said:
is that on the rig? if so thats about normal... take them off and measure, they will be taller.
Or measure them across (front-back) instead of high (up-down). I use two 18x24 carpenter squares to measure diameter, instead of a tape measure. Just orient them like a sliding caliper...
 
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