KidVermicious
New member
Do you have a reference for that? The local wisdom here is that the MTR Kevlars have a much better sidewall than the KM2s, but that wouldn't make sense if the KM2s have the same sidewall as the Krawlers...
Why not 255/85/16?
- Thread starter Dous
- Start date
Do you have a reference for that? The local wisdom here is that the MTR Kevlars have a much better sidewall than the KM2s, but that wouldn't make sense if the KM2s have the same sidewall as the Krawlers...
spectre6000
New member
I'm going to weigh in (against my better judgement) on this subject. For starters, I feel most people base their decisions on these sorts of things based on aesthetics, W-esque feelings, and "what Bobby-Joe did" rather than anything all that objective or substantial...
The best tire for a given rig is dependent on where and what that rig will be doing its thing (and definitely not what other people in the area or on your favorite forum are using, sheep). If you wheel mostly in sand and mud, yes a wider tire is probably a better bet. If you wheel just about anywhere else (to include mall parking lots) the narrower tire is better.
The standard theory on tire size as I see it stated in the myriad discussions on the subject is that wider tires provide better grip because the tread covers more square inches. This is excellent justification for a wider tire IF your surfaces you're getting traction on are smooth and regular like tarmac. The alternate side to that theory is flotation; this applies only to smooth regular surfaces that are soft like sand or mud. These are the only instances in which that theory holds water.
Most of us, however, do not do our wheeling in sand and mud, we do it on rocks and sticks and dirt and such. These surfaces are hard and irregular, and do not require or benefit from any sort of flotation or distributed surface area (you're only going to be contacting the highest spots). If you read the white paper (the link), I don't think you have to get through more than the intro to see the point illustrated that a narrower tire grips these few high spots BETTER than the wider tires at the same pressure.
When wheeling you air your tires down not to increase the footprint of the tread, but to allow the tire to conform to the terrain and "grip" it. The paper uses the more appropriate term "mechanical keying". A narrower tire aired down and compared to an identically inflated wider tire will grip the available terrain BETTER than a wider tire due to the exact same effect as the flotation advantage had by the wider tires in soft terrain. Since the load on the wider tire is spread out more, it can't grip the available grippy spots as tightly (because that grip is spread out over more potential grippy spots) as the narrower tire.
Think in terms of specific scenarios:
A big rock:
Smooth, rounded, probably some sand or something dusted over the top
Advantage: draw. Unless the big rock is really big and really smooth, they're pretty much going to be contacting the same area
A bunch of smaller, but still decent-sized rocks:
Jagged, irregularly distributed, firm
Advantage: skinny tire. The narrower tire grips more firmly on fewer points as it deforms over them than the wider tire which is "floating" (borrowing the term) more loosely over the top of several rocks with less overall deformation.
Hard dirt:
Distributed, gives some but not much, irregular surface, will displace
Advantage: skinny tire. The narrow tire will, for the same reasons as the smaller rocks scenario, grip the parts of the terrain that are firm. Where the terrain is loose, the narrower tire has a better chance of cutting through to the more firma terra.
Slick Rock:
wide, generally flat textured surfaces with gentle curves, firm
Advantage: kind of a draw really... It's like driving over sand paper. You could pretty easily get by with just about any tire. It's called slick rock because it was slick for horses with their shoes and the hard wagon wheels, not because tires didn't stick to it like glue.
Mud:
Mud
Advantage: Depends on the depth... Narrower tire wins if the mud is shallow, wider if it's deep and soupy.
Sand:
sand
Advantage: see mud.
Snow:
snow:
Advantage: wider is better for deep snow to stay on top, narrower is better for less deep snow to cut through to the grippy terrain.
I'm going to go ahead and stop with the scenarios. Apply the logic to whatever you want. Don't like it, see what Bubba's doing and copy it slavishly.
Edit: Oh! I forgot! If you use your 4Runner for anything other than occasional (or even regular) wheeling like, I don't know, a general mode of transportation, the narrower tires are better period. Better fuel economy, larger tires without body modification, etc. All those reasons stated a million times elsewhere. If your rig is built for extended adventure travel (long, unsupported trips over any and all terrain), you're generally better off with the narrower tires as they're better suited for a wider variety of uses. If you just want it to look cool in the parking lot with the tires sticking out, get the wider ones and don't post anymore.
The best tire for a given rig is dependent on where and what that rig will be doing its thing (and definitely not what other people in the area or on your favorite forum are using, sheep). If you wheel mostly in sand and mud, yes a wider tire is probably a better bet. If you wheel just about anywhere else (to include mall parking lots) the narrower tire is better.
The standard theory on tire size as I see it stated in the myriad discussions on the subject is that wider tires provide better grip because the tread covers more square inches. This is excellent justification for a wider tire IF your surfaces you're getting traction on are smooth and regular like tarmac. The alternate side to that theory is flotation; this applies only to smooth regular surfaces that are soft like sand or mud. These are the only instances in which that theory holds water.
Most of us, however, do not do our wheeling in sand and mud, we do it on rocks and sticks and dirt and such. These surfaces are hard and irregular, and do not require or benefit from any sort of flotation or distributed surface area (you're only going to be contacting the highest spots). If you read the white paper (the link), I don't think you have to get through more than the intro to see the point illustrated that a narrower tire grips these few high spots BETTER than the wider tires at the same pressure.
When wheeling you air your tires down not to increase the footprint of the tread, but to allow the tire to conform to the terrain and "grip" it. The paper uses the more appropriate term "mechanical keying". A narrower tire aired down and compared to an identically inflated wider tire will grip the available terrain BETTER than a wider tire due to the exact same effect as the flotation advantage had by the wider tires in soft terrain. Since the load on the wider tire is spread out more, it can't grip the available grippy spots as tightly (because that grip is spread out over more potential grippy spots) as the narrower tire.
Think in terms of specific scenarios:
A big rock:
Smooth, rounded, probably some sand or something dusted over the top
Advantage: draw. Unless the big rock is really big and really smooth, they're pretty much going to be contacting the same area
A bunch of smaller, but still decent-sized rocks:
Jagged, irregularly distributed, firm
Advantage: skinny tire. The narrower tire grips more firmly on fewer points as it deforms over them than the wider tire which is "floating" (borrowing the term) more loosely over the top of several rocks with less overall deformation.
Hard dirt:
Distributed, gives some but not much, irregular surface, will displace
Advantage: skinny tire. The narrow tire will, for the same reasons as the smaller rocks scenario, grip the parts of the terrain that are firm. Where the terrain is loose, the narrower tire has a better chance of cutting through to the more firma terra.
Slick Rock:
wide, generally flat textured surfaces with gentle curves, firm
Advantage: kind of a draw really... It's like driving over sand paper. You could pretty easily get by with just about any tire. It's called slick rock because it was slick for horses with their shoes and the hard wagon wheels, not because tires didn't stick to it like glue.
Mud:
Mud
Advantage: Depends on the depth... Narrower tire wins if the mud is shallow, wider if it's deep and soupy.
Sand:
sand
Advantage: see mud.
Snow:
snow:
Advantage: wider is better for deep snow to stay on top, narrower is better for less deep snow to cut through to the grippy terrain.
I'm going to go ahead and stop with the scenarios. Apply the logic to whatever you want. Don't like it, see what Bubba's doing and copy it slavishly.
Edit: Oh! I forgot! If you use your 4Runner for anything other than occasional (or even regular) wheeling like, I don't know, a general mode of transportation, the narrower tires are better period. Better fuel economy, larger tires without body modification, etc. All those reasons stated a million times elsewhere. If your rig is built for extended adventure travel (long, unsupported trips over any and all terrain), you're generally better off with the narrower tires as they're better suited for a wider variety of uses. If you just want it to look cool in the parking lot with the tires sticking out, get the wider ones and don't post anymore.
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rebelbowtie
New member
The BFG website references this. MTR's though have always been regarded for strong sidewalls so I mean you can't really argue that.
rebelbowtie
New member
He pretty much owned the thread
spectre6000
New member
Haha! Probably worth taking that single post and making a new thread with some easily searchable title as much as the subject comes up. I think the white paper that was linked to previously is pretty excellent. Lacks a bit in academic rigor, but spot on all the same. It's a white paper not a dissertation.
04rnr
New member
very true, and Im sorry I didnt mention that, I figured, that people that wheel, already do air-down, and know how much it helps, glad it was pointed out :girl:
Airing-down is a whole other thread lol
PhdNPrerunners
New member
Here is a fellow members rig that is running 255's on his sport. Its not the best picture but you kind get the idea.
spectre6000
New member
Why do you think this? With 285s sure, but 255s from what I've seen and heard are pretty much plug and play. You'll want a little body lift (just like you would with the 285s) to keep things from rubbing at the extremes, but that's the only modification necessary.
Just get toyo's Dous. call it a day lol. they're gonna be quieter and at 33.5 in height why not. IMHO expedition portal is gonna have way more input on the 255/85 size. A good majority of the rigs on there use that tire. Depending on how much you're willing to drop on pizza cutters I'd even consider the toyo M-55. Ask ProudRunner how he's liking those toyos.
Dous
New member
I am really tempted to get the Toyo's, but...
-They have quite a bit of siping and I am worried about chunking them up
-The sidewall is a little "busy" I like the clean look of the BFG
The second thing is an aesthetic deal and will not play into my choice that much. Price wise I can get the KM2's for about $20 cheaper a tire, so no big deal there. It might come down to which tire the shop can get there faster lol.
curtperry
New member
Most SUV's, 4runners included, are not very resistant to rolling over. The wider tires and spacers that usually accompany a lift are both helping to increase the lateral stability of the vehicle. If I were going with 255's I'd retain the spacers for that reason... and yeah I think it looks better with the limited flares too.
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spectre6000
New member
255s are something like 3/8" narrower than the stock tires. The increased risk of rollover is negligible.
curtperry
New member
I agree with what you said. But this thread is about ~33" tires (wide or skinny) and therefore assumes a lifted vehicle (in almost all cases). So, I don't think it's productive to try to dismiss my point about rollover risk by comparing to stock.
If you run off-camber trails, or need to make evasive maneuvers at highway speeds, then you might appreciate every millimeter of extra track width.
