Roadtripr

I would agree, but in reality you might only have dropped 0.75mpg.
Say before you got 300 miles to 16 gallons (18.75mpg), now you only go 268 on the same 16 gallons. But add 7.5% in larger diameter and you are actually going 288 miles (18 mpg). Anyway we drive trucks and inherently get bad mpg

My bigger concern is if it feels slower when accelerating, old threads seems to point to that for 5 sp owners

cackalak han

Maybe someone can shed more light on this, but I get 3.4% change in diameter. The overall diameter of the 265/70/16 is 30.61". The diameter of 265/75/16 is 31.65". The difference is 1.04. The % increase is 3.4%.

But I did account for the larger tire size when I was inputing it into my Excel spreads. Still came out to about 2mpg drop. However, with my current 235/85/16's, I am about 0.5-1MPG drop (still need more tanks filled). The pep is still there. I think it's a really good compromise between a bigger (taller) tire and MPG.

4biker

Your numbers are right - it's not 7.5% difference.

There are a number of factors to consider as well, above and beyond just the tire dimensions. The lug size, depth, and spacing, noise levels, carcass weight, and tire pressure (which would deform different size tires differently) are the ones I can think of right now. When I had my cherokee I went from the stock 225's to 30x9.50x15's and my mileage actually got obviously better with the larger, heavier tire. I attributed that to the strong, broad torque range the 4.0L jeep motor has, along with the 4.10 gear ratio.
In your case, I would suppose that the rotational mass has decreased significantly with the 235 width, as well as road friction, and maybe noise. Also, depending on the air pressure, they may not deform as much when coming in contact with the road, all of which reduces the amount of drag created on the road/rubber contact patch. If the tires are considerably lighter, that would help accelerate you quicker than with the wider tire as well.
I definitely want to go with a tall skinny tire next. Somebody want to trade?

B. Graves

i just put pro comp 75s on mine. very slight rub while offroading or something. i cant even tell where it rubs i can just hear it.

Roadtripr

Cackalak
yeah, it should only have been 3.5% or so.
So how much firmer is the ride with 235/85 (as they must be load range E) compared to the 265/70s. I need new tire in 5000 miles or so and starting to look at options.

4biker
You are not happy with the heavier larger tire?

cackalak han

Yes, they are load range E (BFG KO's). The ride is actually very nice. It is a bit firmer than the P-rated 265/70's I had, but it is still very nice everyday tire (I daily drive on these). Yours should ride even better with the coil springs out back instead of leafs like mine. I highly recommend these. Cheaper, too!

Roadtripr

cool I will consider them

Gerdo

It looks like the 235/85R16s are 4 lbs lighter also.

Don't inflate to the sidewall max pressure and they should ride well. (back to the chalk test) Any LT tire is going to have a harder ride than a P series tire.

I may have to look at this sixe when I need new tires.

Remember a narrower tire is better in the snow on the road where you want the tire to cut into the snow and hit pavement but worse on trail snow and sand where you want to float.

MV181AA

Do you people realize that a p265/75r16 tire from one manufacturer will NOT be the same size as one from another manufacturer? You will find up to a 5%difference easily. Example: A BFG of the above size in the t/a KO will be shorter and narrower than a Bridgstone Dueler A/T Revo. These differences are way more than the 3.4% based on "theory of tire size" making MPG, odometer and speedometer correctness a case by case application.

Atwater27

I read in consumer reports that the rolling resistance of the tire can make up to 2 mpg differance. They tested them all on chev pu and suburbans. Most of the AT tires had average to below average rolling resistance. They had the Bridgeston Revo as a Recomended tire. Now I'm starting to look at them. Wow never thought it would be so hard to decide.

Opreds98

1 thing no one has mentioned is what brand of fuel. "ALL" the suppliers are different. So to get the best reading you need to buy from the same station over a 2-3 week period. Hopefully they buy from the same depot in that period of time.
I have a 91 4-Runner, 5spd with 280k miles. I went from 31x10's to 315/75/16 (excellant price from 4 wheel parts) gas mileage dropped maybe .3 - .8mpg.
So if you want mileage - keep factory specs and drive the blue-hair speed limit!

cackalak han

Yeah, I have mine at 40lbs f/r. Seems like a good pressure for the road (max is 80PSI!).

And narrower will be better for snow and rain on the road. On the trail, it really depends. Although the tire itself is narrower than say 265/75's, when aired down, it will deform more, creating a longer contact patch, giving good floatation comparable to the wider tire. This is a choice tire (meaning tall and skinny) for many African/Austrailian rigs who drive on rocks and sand constantly. <-- This is how it was explained to me. As far as application, I have not tested this out. Seems logical, though. I've seen 235's and 255's (both 85 aspect ratio) down to 15psi and they really do deform and perform well.

4biker

Yeah, I'm commuting about 55 miles per day now, where my last office was just a block away from home. The Yokohamas I have now are pretty hard on the mileage numbers. I've only got 1.5-2" of lift, so if I had to do it over, I'd get a 70 profile tire. I don't get to wheel much anyway.

4biker

I think that's a really good point, but most companies don't go out of their way to publish the difference. Also, if you consider that 5% difference is from small to large, you'll get up to 2.5% smaller than theoretical, and 2.5% larger. Most will probably fall somewhere in between, probably less than +/-1.5% for most companies. If we have to base it strictly off of theoretical sizing, it's probably close enough. I agree that it's important to remember that actual diameters and widths will vary depending on company and actual tread pattern.
(those percentages were based on the 5% you threw out there, and I don't know if it's verified or not)

Roadtripr

Ouch that is a long commute anyway

MV
I actually felt my 265/70 Revos are smaller than a friends 265/70 BFG A/Ts. That is part of the reason I was thinking of going larger on my next set. I will see what I can find from the manufacts.
Here are the stats, it seems it depends on model chosen:
Rotations per mile BFG A/T KOs Bridgestone Revos
265/70/16 675 679 (so slightly smaller than BFGs)
265/75/16 656 655
235/85/16 656 649 (so slightly larger than BFGs)




Btw, I only saw maybe <1mpg drop compared to the tires the truck came with. The tires have been great all round, but expect to get about 40k out of them.

4biker

I loved my revo's on my old ranger. You'll be looking at a true 3.5% difference if you go bigger. It would be interesting to see if you stick with the same tread pattern on a larger circumference, what the difference will really be. Although when your old tires are worn out, the change will be from a worn-out set of 70's to a brand-new set of 75's, so the difference will be considerably more than 3.5%. You'd have to measure the old tires to be sure.

Man, this is too complicated

Roadtripr

It will depend on how long the commute is to my next job, I would like the look of a slight larger tire but not sure about the lower mpg and slower accelaration. Or if a long commute I might just pick up a small commuter vehicle and keep the 4runner for weekend and trips
New tires would look bigger anyway. If you like the Revo why did you choose Yokos

4biker

I picked these up used for $300 after lifting my 4runner (and then sold my old tires for $300). My only problem with the revo's is they're not a very aggressive looking tire, but I didn't have that much money anyway. I loved them for quiet ride, and amazing wet and snow traction.

Roadtripr

For looks the BFG A/T is probably the best, but I value the surefootedness of the Revos over their lack of aggressive looks. Wet and snow performance is amazing

Gerdo

A taller tire will lower the your RPMs when cruising down the highway. If you have a long flat highway commute you should get better MPG with a taller tire.