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Discussion Starter #1
Wow!!! Just got my KM3s installed on Quadratrac Recon rims and I gotta say they look outstanding BUT...... holy SMALL Batman!!!!! Wish they would just state the true size so we can make educated decisions when buying tires!!!! They are actually a smidge smaller new than the 315/70/17 KO2 I have after 20k miles!!!!
Hey BFG give me full credit and I will pay for 37s which are probably 35s!!!!
 

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They do state the true size. What they don't state is the conditions at which that size is determined.

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They do state the true size. What they don't state is the conditions at which that size is determined.

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32.5 mounted is no where near the advertised 34.4!!!!!
 

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They do state the true size. What they don't state is the conditions at which that size is determined.

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I guess they must use CNN for their measurements!!!!! #FAKENEWS
 

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32.5 mounted is no where near the advertised 34.4!!!!!
wow 32.5 is terrible for a 315/70-17. I would be upset.
 

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I guess they must use CNN for their measurements!!!!! #FAKENEWS
They base it using tire pressure and load. Perhaps they do it at max psi, which would not surprise me, and no load, which is how most measure it.
I like the all caps though, makes it true.

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My KM3 37x12.5R17 D2 calibrate using GPS method at 36” at 26 PSI for what it’s worth.
 

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Yeah my KM3 in 37x12.5R17 are right about 36.25" at operating pressure. That size is listed as 36.5" on BFG's website. I'd say that's pretty accurate if you were running low to mid 30s for pressure.

I'm surprised yours are off by that much. Really sucks. I know the KO2 runs really small but the KM3 seemed to be more true to size which is a big reason so I chose the KM3 over some other tires.
 

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Discussion Starter #9
I measured again today in the daylight and its pretty much dead on at 33" but they do look sweet!!
 

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I measured again today in the daylight and its pretty much dead on at 33" but they do look sweet!!

You should calibrate with a ProCal or similar and GPS app to get an accurate measurement. I am really surprised, my KM2 35s came out at 34”
 

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You're measuring the entire diameter, on the same width wheel BFG used in their listing, including the sidewall bulges like BFG does, and you're getting 33"? If so, there's something seriously wrong.

My KO2s are listed at 33.9" and that measurement was spot on. But after I put them on the wheel, inflated it, put it on the Jeep, and then measured only in a straight line I got 33.0". It makes a big difference HOW you measure them.
 
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Measuring a tire from top to bottom with the rig on the ground will never provide the true diameter because one of the radiuses (radii for the Latin buffs) is loaded and the other is not.

Instead, to determine the effective diameter double the loaded radius measured from the center of the hub to the ground.

Regardless of the method, measuring with the vehicle on the ground will never match the tire manufacturers' published diameters. Manufacturers measure with tires mounted and inflated but not on the ground. There is no loaded or unloaded radius.

BTW, the published diameter of a BFG Mud Terrain T/A KM3 315/70R17 is 34.4" mounted on a 9.5" wide wheel.
 

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You're measuring the entire diameter, on the same width wheel BFG used in their listing, including the sidewall bulges like BFG does, and you're getting 33"? If so, there's something seriously wrong.

My KO2s are listed at 33.9" and that measurement was spot on. But after I put them on the wheel, inflated it, put it on the Jeep, and then measured only in a straight line I got 33.0". It makes a big difference HOW you measure them.
Yup...just ordered a set of 285x75R17 myself in the hopes of getting a true 33 mounted without being stuck with a 315mm wide slab...or a bias-ply LTB (heh).
 

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HOLY SHRINKAGE BATMAN!! Did you measure after it got cold and wet? That sucks, my 315/70/17 Ko2 are about 33.75”.



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