Agassizii

Some call them Pizza Cutters, but I'm Italian enough not ever to have used one of those things (we use a long, sharp knife)...

Got that out of the way.

A big first-time -- HELLO!-- to one and all; lurking on this forum has been great, an important resource for my JK for over 2 years now. I find that I like this place as much as I need it. Thanks to everyone!

From the title of this thread you will get that I am into Overlanding, a fancy word for the love of traveling long distances over every sort of terrain and "getting lost", while still "getting there". From my tag you will get that I am not in a hurry. My almost-stocker 2008 Rubicon Unlimited will be even less stock very soon, but it has several thousand of these kinds of miles on it, buried in the 45,000 miles of SoCal commuting and Interstate travels. And all that means, is that I need new tires.

So, my first question on this forum- I am about to choose between two excellent "Tall and Skinny", Overlander type tires. These tires, though quite different, will both do the job I want them to do, and do it very well. To decide between them, I need the help of this forum:

• BF Goodrich T/A KM2 255/80R17, load index 121/118: spec sheet dia. = 33.3
• Goodyear MT/R with Kevlar 255/75R17, load index 111/108: spec dia. = 32.3

My Goals:

• 1st Priority - the "Real Life" taller tire, the one that gives me the most axle clearance.
• 2nd Priority - IF the axle clearance is much the same for both, I will choose the Goodyear for its decent ice performance (based on feedback from people I have spoken to, who use them on ice regularly).

No, the winner is not necessarily the "obvious" BFG, for several reasons which I hope will interest you enough to help me out. From research on this board and elsewhere:

• The BFG seems to run a bit small to begin with, and is also often run at 30-32psi or so (out of 80psi max) to improve ride quality, because it is a bit stiff for the JKU (load index 121/118). Lower pressure further decreases the diameter and the "static loaded radius" from the ground to the centerline of the wheel, i.e. decreased axle clearance. I have read of as much as 3/4 inch of difference between 30psi and 34psi.

• The Goodyear specs out at 1 in. smaller in diameter, but is thought by many to run true to size. Also, the load index is quite a bit softer for a JKU, implying a higher running pressure (36-40psi or so, out of 50psi max). This would tend to maximize the running diameter. Thestatic loaded radius might be quite close to what you would expect from the specs.

• As an example of this sort of difference - the Goodyear 255/75R17 is indeed the "replacement size" tire, but I have measured my stock BFG KM 255/75R17 (new) and they were indeed significantly smaller than spec, under load and not.

In short, the ACTUAL "static loaded radius" of these tires could be very, very close.

This is what I hope some you who own these tires will do for me; provide this ACTUAL measurement = the distance from the ground to the centerline of the axle (wheel), under the load of the Jeep at the inflation pressure you typically run on pavement. Real Life Measurement is the only way to go.

Many Thanks


To answer a few questions in advance...

• So what's the problem, and why should it matter? Just choose the one "I like best" and be done with it, right? It is only one inch, after all. Ahhh, but these two tires have different strengths and weaknesses that add up to a "push" for me. I could be happy with either, but I want the most for my money. So IF the BFG really does deliver 1/2 inch more ground clearance, the stiffer tire ride and (relative) lack of ice performance are things I can live with and be happy. If it does not, the Goodyear suits me better.

• I have no plans to lift the Jeep, since "true 32" or 33 inch tires are the largest my needs require.

• I have already considered tires wider than 255, and they do not suit my needs.

CerOf

I ran 255/85R16 BFGs in our old Montero Sport. I had the center lugs siped and it did as well as a set of 31"x10.5"R15 BFG A/Tkos I had on our '94 ZJ.

The 255s did well in slush and ice that we get here in North Texas. Siping helped the wet traction a lot too.

ToolManTimTaylor

I run 255/85R16 on my Duallie. They truthfully are not as thin as You think. I needed to run them so the rears would not touch each other.

Agassizii

Good point about the 255 not being particuarly skinny. It was not so long ago that this width was considered a wide tire, and a 75 aspect ratio was not really all that tall. Time rolls on...

If I go with the BFG, I am seriously considering siping. Thanks!

tslewisz

I wish we could get Simex tires in the USA!

Agassizii

"21st Century Tires is a manufacturer, wholesaler, distributor, and exporter of new tyres, inner tubes, flaps, valves, batteries, and wheels for just about any vehicle."

According to this website, they have a distributor in the US. :
If my Jeep did not have to do DD duty, I would have these tires! (16 in rims max, though.)

Agassizii

Not as exotic as Simex...

but here is a bit more info someone might find helpful. My Stock 255/75/R17 BFG KM's had (when new) an ACTUAL "static loaded radius" of 15 and 3/8 inches, with an unloaded diameter of 31 and 5/8 inches - both at 34psi.


So back to my question:

If the Goodyear MT/R with Kevlar 255/75R17 run true to size (32.3 in.), I might gain 1/2 in. under the axle. Not very exciting, but hey, I'll take it since I have to buy tires anyway. But is that gain real?

Now if the BF Goodrich T/A KM2 255/80R17 run true to size (33.3 in.), that would be a gain of roughly one inch over stock. Much more interesting, and worth a compromise (to me) of ride and ice performance. But reports on this forum and others make this seem unlikely, and I want the strait scoop.

So break out those tape measures -- come on, we all own one! -- and if you have either of these tires go out a measure them The ACTUAL "static loaded radius", ground to the center of the wheel or axle. help a guy out here

Many Thanks

m(a)ce

both the KM2s and GY MTR Kevlars have good reps around here.

and yes most people will say the GY's run more true to size.

I've been running the BFG's and have been happy with them - even through the blizzard out here last year. I'd like to experience the GY's firsthand to compare at some point but chances are I'll probably stick with BFGs for my next tire. They've been solid on road, in the mud & over rocks.

I run BFG 35's and I've seen GY 35s - they seem slightly bigger. But then again the wheel width may have differed so take that into consideration.


how about something like this?

ThreePedals

How about some 32x9.5 duratracs.

BLK08JK

Sorry to hijack a little, but what rack is that on the red 4dr? Looks like it clamps to the side of the hardtop instead of drilling into it.