Tire decision help

[magoh76]

It is high time to get new treads for my Montero. Currently running the stock 265/70/16. I've been convinced by ExPo forums on the advantages of the skinny tire. However, 255/85/16 only comes in a few choices now, none that seem right for me. So I'm looking at 235/85/16, lots more choices and no need for a lift, which I can't afford right now anyway. Since the Monty is used as a daily driver right now, I am thinking something along the lines of a Cooper AT3. My dad has them on his truck and loves them, but he rarely goes offroad. Do any of you have another recommendation?

 

[Kaisen]

Points to consider:

There is a reason your Montero runs 265mm wide tires. It's a tall, heavy vehicle. Going to a 235/85 takes away nearly 3 inches of lateral contact patch (stability, handling) and transfers that load to sidewall flex (folding the sidewall under lateral load).

Also, most 235/85-16s are light truck tires with an E load range. 10-ply sidewalls. Tough tires, but can be very stiff. Are also typically more expensive. And there are fewer choices......for a reason: it's not a very popular or modern size.

I'd recommend a 265/75-16 in whatever load, brand, and tread you prefer. There are dozens to choose from and it won't compromise the on-road safety of your truck, nor its off-road capabilities.

But lots of ExPo'ers won't agree with me

 

[magoh76]

Those are good points Kaisen. Doesn't the stiffer sidewall of an E help counteract your point about the sidewall flex, though? Is it the size of the contact patch that matters as much as the width of the track? And smaller contact = greater contact force, right? Or am I simplifying it too much? As for price and choice, it seems to be similar to what I am seeing in a 265/75-16, the other size I am considering. Hmmm, lots to think about.

 

[Kaisen]

Those are good points Kaisen. Doesn't the stiffer sidewall of an E help counteract your point about the sidewall flex, though?

No, not really. The sidewall of an E-load range LT tire is engineered for load-bearing, not lateral forces. A stiff sidewall makes for a less progressive breakaway when lateral grip shears. And by then the sidewall is folding, lifting the inside corner of the lateral patch, and allowing the truck to list a few degrees more than it would with 70 or 75 series tires.

Is it the size of the contact patch that matters as much as the width of the track?

Yes and no. It's just as much the shape as it is the area. When you're presenting a lateral force, the width of the contact patch is important.
Think of it this way: put on foot in front of the other, toe-to-heel. Then have your buddy push you from the side. Now try it with your feet side-by-side. Same contact patch area, right? I know this oversimplifies, but it's one way to think about it.

And smaller contact = greater contact force, right? Or am I simplifying it too much?

A 255/85 doesn't have a smaller contact patch, it just deforms more to the road radially due to the taller aspect sidewalls. The patch isn't that dissimilar in total area, just its shape. A 235/85 is smaller. More pounds-per-square inch would be good in the rain, and in the snow/ice. Everywhere else, it's not desireable.

As for price and choice, it seems to be similar to what I am seeing in a 265/75-16, the other size I am considering. Hmmm, lots to think about.

Really? You can find a 235/85-16 in a C or D load range tire? That's news to me. Your Montero has no 'need' for an E, unless you want it.

 

[magoh76]

You can find a 235/85-16 in a C or D load range tire? That's news to me. Your Montero has no 'need' for an E, unless you want it.

I quote from a local deal for a 235/85-16 AT3 that was 4 dollars more than the quote I got for the same tire in 265/75-16

 

[Kaisen]

And there are fewer choices.

As for price and choice, it seems to be similar to what I am seeing in a 265/75-16, the other size I am considering.

I quote from a local deal for a 235/85-16 AT3 that was 4 dollars more than the quote I got for the same tire in 265/75-16

"Choice" means that there are more brands, tread designs, and load ranges to choose from in a 265/75-16 than a 235/85-16

If you've decided you want a Cooper AT3, then you only have one choice in 235/85, an E-load
However, you have three choices in a Cooper AT3 in 265/75-16:
51769 - LT265/75R16XL 2505# @ 44 psi - $139
51721 - LT265/75R16C 2470# @ 50 psi - $169
51720 - LT265/75R16E 3415# @ 80 psi - $189

BTW, the AT3 in 265/70-16 (your oem size) is exactly two inches wider at the tread (8.70" vs 6.70") than their 235/85 x 2 tires = 4.00" narrower footprint overall

 

[huntsonora]

I like the LT235 tires and think it would be a good choice. A lot of 1 ton trucks that are a lot bigger than your Montero run those 235's. You would be fine and they will be tough tires. I have been contemplating 235's on my 4Runner

 

[Kaisen]

I like the LT235 tires and think it would be a good choice. A lot of 1 ton trucks that are a lot bigger than your Montero run those 235's. You would be fine and they will be tough tires. I have been contemplating 235's on my 4Runner

It's been years (decades) since single-rear-wheel pickup trucks ran 235/85-16s. Duallies, yes. But not singles. Times change.

And if your truck was engineered for 235s, that's fine
When it was engineered for 265s, why run a narrower tire?
Makes zero sense to me
It's an ExPo thing

 

[bat]

I've been convinced by ExPo forums on the advantages of the skinny tire

 

[Hilldweller]

The 235 would change the scrub radius marginally too ---- it would steer lighter. The narrower tire would also contribute to that.
Fuel economy could also increase.

 

[Kaisen]

Fuel economy increase from the narrower tread section is a myth. It is negated by the increased deformation of the taller sidewall at the road. The overall rolling resistance is the same. Aerodynamics don't play a role. However, a taller tire can change effective gearing, lowering rpms at speed, reducing fuel consumption.

A 235/85-16 would not have any advantage over a 265/75-16 in efficiency

 

[LR Max]

I have a dissenting opinion on E rated tires. For a normal-people SUV (Your montero, LC100s, LR3s, etc), go with a load rating of C. MUCH better ride.

Just put 265/75/16s on it. Good looking tire. Will be roughly an inch taller than your current tire. Edit. Just looked, most are load range E. I guess you are stuck.

Also if you are just doing fire roads and not hitting up the local mud holes or Off Road parks, stick to an AT tire. The Cooper AT3 is a great tire. Personally I'm a huge fan of the BFG AT, but I am a BFG fanboy.

If you know you are going to be in mud, but want to compromise, the Goodyear Duratrac is a great compromise tire. Originally I was concerned about sidewall strength but if you don't go full retard you should be fine (now that I think of it, vehicles typically don't hold up for long in this mode).

 

[Kaisen]

The Cooper AT3s he wants are available in C-load in 265/75-16s. See my post above
The Goodyear Duratracs are also available in C-load in 265/75-16s. They run ~$189 each
Kumho and Yokohama also offer C and D load ranges

265/75-16 are also readily available in non-load tires....basically a half-ton truck tire

 

[evilfij]

Just go 265 75r16

They are fine. I would run a load range D or E as I think they are tougher than the C and non load rated ones.

 

[huntsonora]

Don't listen to these guys, if you want to run 235's then get after it, they will be just fine. There are plenty of examples of guys running and loving 235's. I've run taller skinny tires and I like them a lot