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post #1 of 24 Old 02-24-2010, 02:12 PM Thread Starter
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Short KM2's

My new 315/75 R16's (35's) KM2's arrived on the doorstep today. Took a measuring stick to them and they barely measure 34 inches tall unmounted. I knew BFG's run small but only 34inches ??? Perhaps they'll grow up when mounted and full of air.
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post #2 of 24 Old 02-24-2010, 02:16 PM
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Perhaps they'll grow up when mounted and full of air.
Dont count on it.

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post #3 of 24 Old 02-24-2010, 02:20 PM
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BFG's always run smaller than advertised.

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post #4 of 24 Old 02-24-2010, 02:28 PM Thread Starter
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Dont count on it.

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More of a false hope I have, either way it will still be better than the 33's on now that are measuring 31.5.
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post #5 of 24 Old 02-24-2010, 10:46 PM
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Dang, I hope that the KM2 37"s that I'm ordering on Friday are a bit smaller. I have this 5.5 RK lift and if they are a full 37 then it may not fit in the garage anymore! But I'm going KM2 because I've seen them in action on the trail and they outperform my Mick Thompson MTZ's as far as traction goes.

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post #6 of 24 Old 02-25-2010, 06:13 AM
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They are tiny. Im considering going to 40's just to get close to a true 37". I love the grip, but they are borderline false advertisement when it comes to size.

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post #7 of 24 Old 02-25-2010, 12:43 PM
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The only tires I have seen come close to the advertised size are Swampers.

You really need to check the specs closely to see the actaul "mounted" height.
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post #8 of 24 Old 02-25-2010, 12:58 PM
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km2 37' are just a tad over 35"

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post #9 of 24 Old 02-25-2010, 02:19 PM
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315/75/16 calculates out to 34.6", so they are not very short actually. I bet if you do a dead accurate measurement, you'll find that they are within .5" of being accurate
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post #10 of 24 Old 02-25-2010, 02:38 PM
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My 35" KM2s are 34.25". My 33" Mickey Thompsons were 32".

Yep, swamper and Toyo seem to be the only ones that go true to advertised size (that I have seen).
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post #11 of 24 Old 02-25-2010, 05:42 PM Thread Starter
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315/75/16 calculates out to 34.6", so they are not very short actually. I bet if you do a dead accurate measurement, you'll find that they are within .5" of being accurate
Measured them from a level on top to the floor. Right at 34 inches. So fairly close to a half inch off.

Not that a 1/2" or so really matters one way or the other, just feels like we get shortchanged a bit.
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post #12 of 24 Old 02-25-2010, 06:04 PM
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my 37 KM2's are almost 36"... site says 36.8

40s are 39.8

http://www.bfgoodrichtires.com/specs...-km2/3930.html


edit: if u look.. the bigger size rim.. the smaller the tire is gonna be..

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Last edited by BiGEN; 02-25-2010 at 06:06 PM.
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post #13 of 24 Old 02-25-2010, 07:23 PM
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The mounted size will also depend on the width of the rim you are using, a skinner wheel should produce a slightly taller tire.
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post #14 of 24 Old 02-26-2010, 12:35 AM
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If you measure the circumference of your KM2 after it is mounted and on your Jeep and compute the diameter (a more accurate way to measure than trying to find the diameter), it gets worse. My "35s" measure 33.3 inch diameter mounted on an 8.5 inch wide rim. When programmed in with the AEV programmer, this size (actually 33.25 programmed as I remember) nails the speedometer with my GPS and speed calculation based on RPM. They work great. If taller, I could not get in my garage. So it all worked out for the best.

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post #15 of 24 Old 02-26-2010, 06:47 AM
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Same experience here. My 35 KM2s mounted on stock Moab wheels after mounted and aired up measure 33.75. I think I may try the Goodyear MTRs w/kevlar.

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post #16 of 24 Old 02-26-2010, 09:20 AM
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Quote:
Originally Posted by JKDoc View Post
If you measure the circumference of your KM2 after it is mounted and on your Jeep and compute the diameter (a more accurate way to measure than trying to find the diameter), it gets worse. My "35s" measure 33.3 inch diameter mounted on an 8.5 inch wide rim. When programmed in with the AEV programmer, this size (actually 33.25 programmed as I remember) nails the speedometer with my GPS and speed calculation based on RPM. They work great. If taller, I could not get in my garage. So it all worked out for the best.
Yup, my 315/75/16 KM2's required 33.25" programming to be accurate.

But of course it gets worse when mounted. You have the wheel pulling in the sidewall (decreasing the actual sidewall height) plus the weight of the vehicle bearing down on it. I suppose one could put max air into the tires to compensate for some of that, but then you would be riding on bricks
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post #17 of 24 Old 02-26-2010, 09:21 AM
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Not that a 1/2" or so really matters one way or the other, just feels like we get shortchanged a bit.
When you really think about it- 1/2" is actually only 1/4" less sidewall height.
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post #18 of 24 Old 02-28-2010, 09:17 PM
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yeah....the true height of a tire is always less that it's design height. Your average 315/70r17 is about 34.6 inches.

sadly...as I am a dork...I have a tire size calculator on my palm pre, as is available for a lot of smart phones. You can not only calculate your tire size, but the gap in speedo estmates when upgrading to such tires.

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post #19 of 24 Old 03-01-2010, 07:55 AM
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Don't think anyone mentioned this but I think tire pressure makes a difference too ... We usually run around 26-30 psi instead of the suggested 50-60 psi

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post #20 of 24 Old 03-01-2010, 07:08 PM Thread Starter
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Mounted, on the Jeep they are measuring around 33 1/2 to 33 5/8. Completely unscientific method of measuring from the ground to the top of the tire. So these are giving me an additional 1 inch of clearance over my half worn 33's.

However, they still look great. Now I need to get some time to get offroad and test them out

Last edited by seiken01; 03-01-2010 at 07:14 PM.
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post #21 of 24 Old 03-01-2010, 07:43 PM
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I just bought a new set of Goodyear MTR kevlars in 35 1250 17 on a 17x9 rim, I'll check them out. I had always heard teh BFG's were short.

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post #22 of 24 Old 03-01-2010, 07:47 PM
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I just bought a new set of Goodyear MTR kevlars in 35 1250 17 on a 17x9 rim, I'll check them out. I had always heard teh BFG's were short.
Yup, 34.25" tall at 35psi. Maybe a little compensation for the load it would be better

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post #23 of 24 Old 03-05-2010, 02:32 AM
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Don't think anyone mentioned this but I think tire pressure makes a difference too ... We usually run around 26-30 psi instead of the suggested 50-60 psi
The 50 psi rating is only for max load. If you follow a load inflation table we could get by just fine with 25 pounds or less. 30 seems to be a good comprimise between ride quality and fuel mileage. The tires on my motorhome are inflated to 95 psi cold inflation pressure. Just depends on your load.

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post #24 of 24 Old 03-05-2010, 02:53 AM
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with my previous JK 2 Door, ProComp Xtreme MTs 315x70x17s were 33.25 when mounted....anything over 35 pounds made you feel like you were riding on bricks like Terra mentioned!

With the 4 door, Coopers 35x12.5x17s measure a little over 34" and keep it under 35 pounds as well for road comfort as well.

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