BFG MTs vs. KM2s...a size difference for 255's

[Beowulf]

This is for 255/85R16s. I thought sure a new KM2 would be very similar in all dimension to the old MT. Especially since the BFG site say it would have a 10" casing width on 7" rims and was 33.3" tall. However, I just got the new KM2 and it seemed much narrower. At first I thought this was an optical illusion. Since I kept my old MT spare to sell, (which has already sold) I figured I measure everything. Height and casing width are similar enough. What surprised me is the tread face measurements. From measuring the widest and narrowest section of lugs I was amazed at the difference.

Old MT: 7.25" wide to 8" wide.
KM 2: 6.75" wide to 7.25"

This is a difference of 1/2" on the Narrow section of lugs and 3/4" on the widest section. I not really sure this matters, but the width in lug face is quite noticeable and makes the tire seem not only narrow, but makes the tire appear more rounded (bulgie), like the side walls are not as straight and squared off as the old MT.

Now you make ask, does it matter? The truth, I don't know. But, with physics there is always a difference due to contact patch. Will this increase pounds per square inch, decrease rolling resistance, decrease floatation.....etc. Time will tell. I just wanted to point out my findings in case this would matter to anyone else.

 

[MotoDave]

What wheel width are you running? Are the measurements both off of mounted, aired up tires?

 

[Beowulf]

These are measurements mounted to an 8" rim and off the rig.

 

[78Bronco]

A 255/85 has no place on a 10" wide wheel.

 

[Beowulf]

78Bronco,

Sorry if the size description was not clear. That meant to convey the site has always indicated a 10" casing width on 7" rims. I edited that sentence up top.

 

[alexrex20]

post pics of the KM2s on your vehicle. i'm interested in these exact tires and would like a perspective view.

 

[Beowulf]

Here are a couple really bad Cell phone pics. These don't do any justice to the visual difference you see when in person.

 

[alexrex20]

thanks for the pics! just to confirm, the older BFG MT KM in the pic is also a 255/85/16?

 

[Beowulf]

Yes, that is correct. The old BFG MT is also a 255. Please don't compare height as one is on the rig and the other is not.

I can tell you that when I took my Spare KM2, put the level on top of and measured the height it was a perfect 33.5". Unfortunately, I did not do that to the old MT for comparison.

 

[Desert Dan]

Beowulf you are at the max rim width according to BFG which might explain the bulge and rounded sidewalls??

http://www.bfgoodrichtires.com/specs/mud-terrain-t-a-km2/3930.html


LT255/85R16/E

Rim Width
Range (inches)

6.5" - 8"

 

[thecriscokid]

I noticed the same thing when I purchased a pair. Although I was shopping for the 285/75 and ended up getting the 305/16. I think the 305 km2 is still narrower than the 285 AT's that I ran prior

 

[Beowulf]

Desert Dan,

I would have expected by going to the widest rim range the tire would seem more square. The BFG MT KM was definitely very square compared to the New KM2.

 

[Stumpalump]

I think any visual distaste you have for the tire will wane quickly as you use the tire. I love my 255/85/16 KM2's.

 

[Beowulf]

There is definitely not true distaste for the tire. It seems narrower and even that has grown on me considerable when I was finally able to see them in the daytime and not just parked in my garage.

In fact, now the old MTs look too wide.

I do have to say they ride great. Of course going from a tire with near 40K miles just about any tire is going to seem smooth.

 

[Redline]

Very accurate description.

I had a set of 255/85 BFG KM, and for a very short time a set of 255/85 KM2. The extra narrow tread width was quite noticeable.

For a 255/85 tire that is closer to the dimensions of the old 255/85 BFG KM I would suggest the Maxxis Bighorn. The Bighorn is about the same if not a hair wider than the old BFG MT (tread face about 7.75-8.0" wide).

This is for 255/85R16s. I thought sure a new KM2 would be very similar in all dimension to the old MT. Especially since the BFG site say it would have a 10" casing width on 7" rims and was 33.3" tall. However, I just got the new KM2 and it seemed much narrower. At first I thought this was an optical illusion. Since I kept my old MT spare to sell, (which has already sold) I figured I measure everything. Height and casing width are similar enough. What surprised me is the tread face measurements. From measuring the widest and narrowest section of lugs I was amazed at the difference.

Old MT: 7.25" wide to 8" wide.
KM 2: 6.75" wide to 7.25"

This is a difference of 1/2" on the Narrow section of lugs and 3/4" on the widest section. I not really sure this matters, but the width in lug face is quite noticeable and makes the tire seem not only narrow, but makes the tire appear more rounded (bulgie), like the side walls are not as straight and squared off as the old MT.

Now you make ask, does it matter? The truth, I don't know. But, with physics there is always a difference due to contact patch. Will this increase pounds per square inch, decrease rolling resistance, decrease floatation.....etc. Time will tell. I just wanted to point out my findings in case this would matter to anyone else.