BFG Mud Terrain actual sizing?

kiwi

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I’ve seen a few threads on this but want to confirm before buying my next tire..

Currently running 32x11x15 BFG K02 All Terrains, but from the ground up i’m hitting about 30”. I understand that BFG’s run small and i also understand that no tire will hit the exact stated size once you account for the weight of the jeep

I’m looking to go up to a true 33” tire, and there’s a set of BFG Mud Terrains for sale that are size 285/75/16. Can anyone tell me what these will actually measure out to once loaded up? Would i be better off buying 315/75/16? Especially if i get BFG’s they’ll probably end up being 33’s right?
 
I’ve seen a few threads on this but want to confirm before buying my next tire..

Currently running 32x11x15 BFG K02 All Terrains, but from the ground up i’m hitting about 30”. I understand that BFG’s run small and i also understand that no tire will hit the exact stated size once you account for the weight of the jeep

I’m looking to go up to a true 33” tire, and there’s a set of BFG Mud Terrains for sale that are size 285/75/16. Can anyone tell me what these will actually measure out to once loaded up? Would i be better off buying 315/75/16? Especially if i get BFG’s they’ll probably end up being 33’s right?

https://www.bfgoodrichtires.com/auto/tires/mud-terrain-t-a-km3?tyreSize=16

BFG says the 285/75/16 are 32.8" Diameter
 
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I’ve seen a few threads on this but want to confirm before buying my next tire..

Currently running 32x11x15 BFG K02 All Terrains, but from the ground up i’m hitting about 30”. I understand that BFG’s run small and i also understand that no tire will hit the exact stated size once you account for the weight of the jeep

I’m looking to go up to a true 33” tire, and there’s a set of BFG Mud Terrains for sale that are size 285/75/16. Can anyone tell me what these will actually measure out to once loaded up? Would i be better off buying 315/75/16? Especially if i get BFG’s they’ll probably end up being 33’s right?

See above.

For reference, I have KM3’s in a 35x12.5r15 and my son has Maxxis Razr 33x12.5r15. Mine are noticeably bigger.
 
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That’s not how you measure a tire. He shouldn’t be led to think so.

That’s the measurement he is wanting and most people when they ask. They care what it is on the jeep. BFG all run small we all know that. A metric 35 bfg or 315 will measure 33” in the fashion he is asking. I would like to see somebody post an accurate measurement of BFGs specs in relation to their tire.
 
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I have had the missfortune of buying two cars fitted with BFG ko2, the first was a brand new Triton and more recently was the TJ, these are the worst wet-weather tyres I have ever owned so I can't wait to get rid of them even though they are unfortunately brand new.

I recently put the 265 70 17 from my Amarok next to my BFG which are exactly the same size as yours and the 31.5 inch tyres tower over the 32 inch by 11.5 bfgs. Now I'm wondering if metric size tyres run bigger or if The BFG is really are that pathetic.

Screenshot_20220809-184518_Photos.jpg


Screenshot_20220809-184515_Photos.jpg
 
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Don’t get 16” wheels. You’ll wish you didn’t.

Buy something other than BFG if you want something more true to size.
 
This is all nonsense. I could start the rumor that Nittos run small, people would go out to their Jeeps and measure the height of their tires with the Jeep sitting on it, find it to be less than the sidewall says and then it would become "factual".

Look at the revolutions per mile and compare them. BFG's are generally right in the middle of the pack of tires of a given size. That wouldn't be possible if they were actually smaller and resulted in a lower axle height.
 
This is all nonsense. I could start the rumor that Nittos run small, people would go out to their Jeeps and measure the height of their tires with the Jeep sitting on it, find it to be less than the sidewall says and then it would become "factual".

Look at the revolutions per mile and compare them. BFG's are generally right in the middle of the pack of tires of a given size. That wouldn't be possible if they were actually smaller and resulted in a lower axle height.

Yeah, I hate it when I air down to 4 and realize I’m only running 35’s…

😉
 
I don't understand the compulsion to measure a tire so accurately. Tires are like Jell-O, but worse, because as you use them, they wear. The installed diameter is affected by load, tire pressure, and usage wear.
 
I recently put the 265 70 17 from my Amarok next to my BFG which are exactly the same size as yours and the 31.5 inch tyres tower over the 32 inch by 11.5 bfgs. Now I'm wondering if metric size tyres run bigger or if The BFG is really are that pathetic.

You don't think the load on the BFG and no load on the other is a factor in observed diameter?
 
Food for thought - none of the 35's I found that publish a rev/mile specification measure over 34". If we're really worried about the BFG being 1/4" smaller than an MTR then all these threads should be talking about Falken and we should all be running Generals.


BrandModelSizeRev/MileRolling Diameter
BFGMT T/A KM335x12.5R15
602​
33.50185114​
GeneralGrabber X335x12.5R17
594​
33.95305453​
GoodyearWrangler MT Kevlar35x12.5R17
598​
33.72594379​
GoodyearWrangler MT Kevlar35x12.5R15
598​
33.72594379​
YokohamaGeolandar MT35x12.5R15
600​
33.61352398​
MaxxisRAZR35x12.5R15
597​
33.78243616​
GeneralGrabber X335x12.5R15
594​
33.95305453​
FalkenWildpeak MT35x12.5R15
617​
32.68738151​
 
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This is all nonsense.

I completely agree. The "BFGs run small" BS has been perpetrated for years by people who don't have a clue how tire manufactures measure/advertise diameter and who refuse to be enlightened.

Tire manufactures do not measure diameter with a tire mounted on a vehicle and on the ground. It is a diameter, either measured or calculated, of a tire mounted on a wheel of specified width at a specified tire pressure, unloaded. Visually, imagine a spare mounted on a carrier rather than a tire in use on one's jeep.

In practice, I find the most useful values to be the revolutions per mile published by the tire manufactures, and if one wants a physical measurement, the "rolling radius" of the tire mounted on the vehicle and on the ground, i.e., from the center of the hub to the ground. X2 if one wants a "diameter" to plug into a gear calculator.

Some may find the tire diameter experiment in this post enlightening. Some won't.
https://wranglertjforum.com/threads/tire-size-measurement-methods.38648/page-5#post-641879
 
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I just read this, Mr. Bills, and in your "Extra Credit" section, you left out the most important way to measure the tire with regards to speed and gearing. In the automotive engineering world, it's known as the "rolling circumference." Modern radial tires do not deform circumferentially any significant amount due to the steel cables running around the circumference (even with them being biased in most cases.) The easiest way to measure the rolling circumference on a vehicle is to paint a dot on the tire, and then roll the vehicle forwards or backwards in a straight direction on flat concrete until two dots appear, then measure the distance between them. That gives the rolling circumference, which is how far the vehicle travels with every wheel revolution.

Incidentally, this rolling circumference is generally used by the manufactures to calculate the tire diameter that is given in their literature by dividing the rolling circumference by pi (3.14...). The number of revolutions per mile can then be calculated either directly from the rolling circumference or from the resulting diameter. Of course, as the tire wears, this number changes. However, if you change tire pressure or load on the tire, it doesn't significantly change because you still have the same length of steel running around the tire.

So, if you're doing gear calculations, you have to work with the rolling circumference. If you are looking at ground clearance issues , you simply look at the vertical distance from the ground to the axle center. If you are considering the "visual tire size" as CaptainBanana's picture shows, you look at the ground to top of tire distance, but make sure you are comparing apples-to-apples and have the tires inflated to the proper pressure and loaded (on the vehicle). These measurements are only loosely related to each other. It's important to be considering the right parameter, depending on your "calculations."
 
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I’ve seen a few threads on this but want to confirm before buying my next tire..

Currently running 32x11x15 BFG K02 All Terrains, but from the ground up i’m hitting about 30”. I understand that BFG’s run small and i also understand that no tire will hit the exact stated size once you account for the weight of the jeep

I’m looking to go up to a true 33” tire, and there’s a set of BFG Mud Terrains for sale that are size 285/75/16. Can anyone tell me what these will actually measure out to once loaded up? Would i be better off buying 315/75/16? Especially if i get BFG’s they’ll probably end up being 33’s right?

Your definition of a true 33 means you will be running 35's. I've run true 33's, true 35's, and true 37's. Unfortunately for you that means I started with 35's, 37's, and 40's to get there.
 
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I just read this, Mr. Bills, and in your "Extra Credit" section, you left out the most important way to measure the tire with regards to speed and gearing.

Actually, I didn't.

What I was interested in was determining the effective tire diameter for purposes of a gear calculator by using the gear calculator itself to determine the necessary value for tire diameter of my tires on my wheels taking into consideration the actual tire pressure and actual load on the tire.

I was not interested in "rolling circumference" because, as you noted, the rolling circumference doesn't change appreciably with tire pressure or load. The published revolutions per mile provide the same basic information and I had no reason to doubt those numbers. In any event, while "revolutions per mile" and "rolling circumference" are both great for calculating a diameter, both are of little value for determining the optimal gear ratio because neither value can account for changes in tire pressure or load. If one wants to use a "rolling" measurement to calculate potential gear ratios, doubling the rolling radius and using that value as the tire diameter will provide far more useful results than calculating a diameter from the rolling circumference.
 
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Actually, I didn't.

I was not interested in "rolling circumference" because, as you noted, the rolling circumference doesn't change appreciably with tire pressure or load. The published revolutions per mile provide the same basic information and I had no reason to doubt those numbers. In any event, while "revolutions per mile" and "rolling circumference" are both great for calculating a diameter, both are of little value for determining the optimal gear ratio because neither value can account for changes in tire pressure or load.

What I was interested in was determining the effective tire diameter for purposes of a gear calculator by using the gear calculator itself to determine the value for tire diameter of my tires on my wheels taking into consideration actual tire pressure and the load on the tire.

You missed my point. Changes in tire pressure or load have an insignificant effect on gearing calcs because they don't affect the rolling circumference.