BF Goodrich - KM3's - Info and opinions needed

Paul R

Well-Known Member
Location
SLC
I am a BFG Fan, but also a capitalist theorist. I suspect they make them smaller so you are willing to buy the next size up for a price premium to get that next size up...:spork:🤷‍♂️
My guess is most never bother to measure and it has more to do with what they can get away with. Smaller tire = less material. I bet it adds up.

Either that or French men must be used to measuring small things things and then exaggerating! :rofl:
 

BlackSheep

baaaaaaaaaad to the bone
Super Moderator
Supporting Member
Interesting info. Is there a reason why BFG's specifically are (nearly always) smaller when compared to a identically labelled tire from a different manufacturer? I assume they are still in the "window" you mentioned for that size designation, but why always at the low end of the range?
I am a BFG Fan, but also a capitalist theorist. I suspect they make them smaller so you are willing to buy the next size up for a price premium to get size you really want...:spork:🤷‍♂️

When I go to put 37's on my cruiser, I will be looking at 37's from most manufacturers, but 39's from BFG and paying a premium for the 39's...
I'm still looking for the details on the TRA Window. I'm not in the light truck side of the business so I don't have access to the tools necessary. I will say that the tires will fall in the window. These windows - the range of sizing - is probably going to be bigger than you think for a given size.

There can be performance reasons to position the tire in a specific area of the window. If that is the reason for a specific position, it is usually taken to an extreme (i.e. into the far corners). I'm sure cost plays into the equation as well as industrial considerations. Sometimes history (of the tireline and dimension) also plays into the decisions on a new tireline.

What I think we'll find is that for a given group of tires they are probably all relatively near the middle of the window. I've pulled specs on 7 tires in 35x12.50R15 so I can plot their SW and OD. Once I get the data for the window sizing, I can complete the chart.
 

BlackSheep

baaaaaaaaaad to the bone
Super Moderator
Supporting Member
Sorry for the delay - Had to get the information on the TRA design window. TRA actually has specifications based on tread depth. The way TRA defines the tread depth is not always perfectly clear if your tire's tread depth is not exactly at the depth at which they define the demarcation. I'll show both the Highway tread design window and the traction tire design window.
TRAwindow35x12p5R15compare.png

TRAwindow35x12p5R15compareTRAC.png
The blue box is the design window. This window is the industry standard for tire sizing for the 35x12.50R15. Every dimension has a design window similar to this according to that dimension. As you can see, in Green, approximately the center of the window is the TRA Design size. This is essentially the nominal sizing for the dimension with the window as the allowable range of sizes.

I've plotted 7 tires on each chart - I pulled the SW and OD from the specs listed on Tirerack.com. The individual tire dimensions don't change position on the chart, only the window position changes depending on whether you choose Highway or Traction tread.

The observation from several that 'BFG is smaller diameter than others' appears to be an accurate statement (certainly for this dimension at least but keep reading). If you look at the table in the lower right (for each chart), you'll see that the difference is about 1/2 inch between the tallest tire (Grabber X3) and the two BFG models (which fall on the exact same point). You'll also note that the BFG products do fall within the window regardless whether you look at the Highway or Traction TD chart. Note that one of the 7 actually falls outside the window.

Recall that the OD and SW reflected in this chart - as well as the TRA Design size and the window - reflect a tire mounted on the design rim which is the 10" width. Mounting on a narrower rim will change the SW pretty significantly and the OD very minimally (if at all). The entire window and all the points will shift.

The range of the window can also be seen from the table. For section width the range is 11.9" to 13.4" - this is consistent for both charts. The OD range for highway tread is 33.9" to 35.1" and for traction tread it ranges from 34.1 to 35.3 - about 1/4" taller for traction tread.

Keep in mind, this is just an example using the specs for one dimension - for any other dimension, you'd have to go through this same exercise.

Back to the difference in OD - Here are the tread depths for the 7 tires I've plotted:
TractionTireTD.png

Note that the BFG Mud-Terrain is 18/32nds inch while most of the others are 21/32nds. That's a 3/32nd inch difference in tread depth, which is a 6/32nd difference in OD. That's just shy of 1/4" and it is solely due to the difference in tread depth. For the All Terrain - the OD difference due to tread depth is about 3/8"!

One can now begin to see that the positioning on the window is affected by the actual tread depth of the tire. If the BFG had the same tread depth as all the other tires on the chart, the difference would be less and perhaps not as noticeable when compared to some of the other tires on the chart.
 
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Kiel

Formerly WJ ZUK
So bfg is doing a rebate right now on the km3s looks like it can be up to 150 total so I'm glad I waited. I also got my local place to price match the 4 wheel parts price which saved another 150 over 4
 

spaggyroe

Man Flu Survivor
Location
Lehi
So bfg is doing a rebate right now on the km3s looks like it can be up to 150 total so I'm glad I waited. I also got my local place to price match the 4 wheel parts price which saved another 150 over 4
thanks for the heads up Keil!

Here's the hyperlink
Looks like the promo is valid 6/27/20 through 7/6/20

I ordered a set from Summit, so HOPEFULLY they ship soon, and HOPEFULLY they recognize Summit as a "participating dealer".
 

spaggyroe

Man Flu Survivor
Location
Lehi
So, because of Covid, BF Goodrich was shut down for about 2 months, and now has an immense backlog to work through. I couldn’t find any in stock in the size I wanted, and couldn’t get a firm commitment as to when they will be available again.

Long story short, I cancelled my order.
 

BlackSheep

baaaaaaaaaad to the bone
Super Moderator
Supporting Member
So tires are not an “essential “ business?
Truck tire plants were running at a reduced capacity. Passenger car plants were down significantly more. The demand for tires dropped significantly especially with the vehicle manufacturers.


I got mine, but discount had to ship them in from all over the place. I'll do a measurement when I get them on the ground
Remember that the overall diameter isn't measured with the tire loaded so you will get a number significantly lower than what you are expecting. If you really want to have a number to compare to the tire specifications, it's best to measure the circumference of the mounted and inflated tire, then convert to diameter.
 

Paul R

Well-Known Member
Location
SLC
I got mine, but discount had to ship them in from all over the place. I'll do a measurement when I get them on the ground
I'm looking forward to seeing what it comes out as. I currently have Toyo MTs in this size on our 200 and love the size but hate the tire. I am confident that the KM3s will be smaller but hopefully not too much...
 
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mbryson

.......a few dollars more
Supporting Member
What did you hate about them?

I bought the Toyo's in lieu of the BFG's due to the shortage... :grimacing:

They just rode like they should be on the Stuper Duty. You'll likely get 80k out of them on a Jeep? I got 60k+ on my Stuper Duty and still sold them for $150-200 when I bought new tires. Not the greatest traction on the lighter Jeep vs the 7500 lb pickup. SUPER heavy tire for the 3.6 to turn even with the 4.88 gears. For a Jeep (maybe not a JKU as they are not the most svelte rig out there), I like a C load rating. For a JKU, I think a "D" would probably be ideal but I'd lean to a "C" if they are available.
 

DAA

Premium Member
Supporting Member
Mine took a lot of weight to balance and wouldn't stay balanced. Were obnoxious loud. Poor lateral stability. Traction, meh. Wore out fast - 30,000 on a CTD. And were expensive, too.

There was nothing I liked about them.

- DAA
 

ID Bronco

Registered User
Location
Idaho Falls, ID
Toyo MT's on my duramax were fantastic, I would have done them again except for the cost. I did sipe the inner tread blocks, and they gave me awesome wear and good traction in the winter. (for an MT)
 
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