Last-Minute New Tire Freak-out

marmotan

marmotan

New member
Hi all,

I'm having a hard time getting the answer to this question - should be easy for you off-roaders. I'm about to ditch my 235/75/15's and put 31x10.5x15's on my stock 4runner. The change would mean an increase in diameter from 29.1 to 30.3.

However, I've just read in more than one place that the increase in diameter does two major things: it increases your chance of brake failure and it may require regearing.

This website (Tire Size Calculator - tire & wheel plus sizing) gave me a warning that 'increasing your tire diameter by more than 3% can be dangerous!'

So, it is ESSENTIAL that I do the Tundra brake upgrade AND/OR regear my tranny? Will my truck survive just fine under normal use if I leave these things stock?

Many thanks...I hate this last-minute second-guessing :cry:

Oh, and feel free to post away - I want as many opinions as possible, even if they are just repeat comments.
 
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Don't sweat it. I went up more than 3% and cannot notice a difference what so ever in performance. MPG went down 1-2 but no biggie. Went from a 30 to a 32. You should be fine
 
Like everyone has said, it's no big deal. You could go even bigger if you wanted too.

You will probably notice some power loss and MPG drop though.
 
The reason they warn about the more than 3% change is because anti-lock brake systems get confused when you change tire sizes that much. do you have anti-lock brakes? Some cars are more sensitive.
As far as brake failure, the only thing I can think of is that you will brake better because you have more tire on the road, this will cause more heat in the brakes because you can brake harder. No big deal, if they get to hot they will warp.
 
Not so fast... you all have V6's unlike OP.

Just in my experience, going to 32" tires on my 2.7 was no easy walk in the park. My MPG suffered and my truck was slower than everything.

With that in mind, I had 17" rims. You should have less weight with those 15s, just don't be mad if it's not as powerful as before, because the extra diameter will give you a noticeable loss. Also keep the speedo change in mind. 60 on your speedo = 67 in real life. Overdrive on my auto (noticed you have a manual) would not keep the truck at speed on the highway, especially on hills, which was a huge b!tch. Not sure how 5th gear will fare being your overdrive gear.

Wasn't til I regeared that it was negligible (for my experience, at least), and even now I've got 33"s and 20 MPG highway on a 2.7 liter on 4.56's, soon to be supercharged anyway.

I guess what I'm trying to get across is, expect some loss in performance and MPG with stock gears (much moreso than a V6 4Runner, since we have 30hp less). It's tolerable, but you might seek some larger gears in the future. Even a used 4.30 rear end will skyrocket your performance compared to 3.91, which is likely your ratio...

I'd hold out for a larger set of rims so the Tundra brakes could be done, before I changed my brakes, I was warping the hell out of my rotors all the time. Those itty bitty brakes with the 15" rims just don't cut it.
 
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I know 4Runners weigh more than Tacomas do but my 3RZ 5 speed Taco ran 33's on stock gears no problem, I got about 19 mpg before I regeared to 4.56's and then it went up to 22.
 
Thanks everyone, all good stuff.

COB, you bring up a good point - in the back of my mind I was wondering if having the I4 with manual tranny meant that my truck might have a harder time with 30 to 31 inch tires than those with the V6.

I'm definitely not interested in supercharging my engine (the deckplate mod is as far as I want to go) or regearing. Plus, I do drive lots of hills.

I'm still mulling it over...
 
marmotan said:
Thanks everyone, all good stuff.

COB, you bring up a good point - in the back of my mind I was wondering if having the I4 with manual tranny meant that my truck might have a harder time with 30 to 31 inch tires than those with the V6.

I'm definitely not interested in supercharging my engine (the deckplate mod is as far as I want to go) or regearing. Plus, I do drive lots of hills.

I'm still mulling it over...
Click to expand...

I had 31x10.5R15s when I first bought my 4runner last year. I also have a 3rz 5spd 2wd. The brand I had were open country and it was pretty loud due to my blown shocks causing major cupping to the tire tread. I was averaging from 18-20 MPG with those tires. I could keep my speed in 5th gear if I was going 65+ mph but that was on level grade freeway. If there was any sort of incline, I'd have to down shift to 4th. Anyway I changed to 235/75r15s this past April temporarily for a road trip, those old ones were too noisy. I only saw about a 1 mpg improvement. Main thing is being able to row your own gears. It did feel slower but the 4runner is a truck style so it won't have that get up and go power like a regular car. So theres my 2 cents. I'll definately go back to 31 or 32" tires in August with my new wheels. They looked better on the car before I changed to these highway tires.
 
tv4184 said:
I had 31x10.5R15s when I first bought my 4runner last year. I also have a 3rz 5spd 2wd. The brand I had were open country and it was pretty loud due to my blown shocks causing major cupping to the tire tread. I was averaging from 18-20 MPG with those tires. I could keep my speed in 5th gear if I was going 65+ mph but that was on level grade freeway. If there was any sort of incline, I'd have to down shift to 4th. Anyway I changed to 235/75r15s this past April temporarily for a road trip, those old ones were too noisy. I only saw about a 1 mpg improvement. Main thing is being able to row your own gears. It did feel slower but the 4runner is a truck style so it won't have that get up and go power like a regular car. So theres my 2 cents. I'll definately go back to 31 or 32" tires in August with my new wheels. They looked better on the car before I changed to these highway tires.
Click to expand...

That's really good first-hand info, thanks. I calculated that the 31" tires I'm considering each weigh 8 pounds more than my 29"s, so that's 40 extra pounds to haul up hills, etc. But from what I'm hearing here, it sounds like the gearing is more the concern when we're talking about a 2.7L I4. I hadn't thought of that :redbrick:
 
marmotan said:
That's really good first-hand info, thanks. I calculated that the 31" tires I'm considering each weigh 8 pounds more than my 29"s, so that's 40 extra pounds to haul up hills, etc. But from what I'm hearing here, it sounds like the gearing is more the concern when we're talking about a 2.7L I4. I hadn't thought of that :redbrick:
Click to expand...

I have 4.10 diffs I can sell ya for cheap but I don't know what shipping would cost from Delaware to Montana.
 
Having the manual transmission helps but youll want to regear or source a v6 rear end 4.10 or 4.30. I'm gonna go with 4.88 later but not right now.
 
Just for insight, i went from the 225/75/15s on mine to a 265/75/15 with no rubbing, or anything of that nature. They fit nice and fill the wheel wells nicely. I did notice the extra weight though, i lost a decent amount of "pep". But well worth it. Much cushier ride i think
 
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