I'm currently deciding on which tire size I want to get, 285/75r16 or 265/75r16. I go skiing in Colorado so I'm driving up I70 pretty regularly and 3rd gens are already not fast vehicles especially at altitude. Can anyone in CO with 285s comment on what the power loss is like on I70?

Anywhere in the world non-aspirated engines loose 3% power per thousand feet of elevation.

I-70's peak is at 11,158 so that is about 33.5% power loss.

I have to have mine pegged (just about) to maintain 50, uggg....

So yeah less rubber would help, how much, probably not much difference.

Having taken my stock 5th gen to Vail from Denver a number of times I can say you'll prefer the smaller tires on the highway. That said, if you hardcore offroad and need the prowess of the larger tires it may be worth it to lose highway performance.

Going up i-70 with stock tires, O/D off, ect engaged our trucks are slow. 285's will be slower. With 285's when going around big rigs drop into 3rd rpms screaming get back into right lane put it in 4th, and repeat until you get to the top. Regear and 285s will give you more pep at lower speeds but the traffic in the left lane is almost always way over 55mph so your rpms will go up and gas per mile will go down. Is it doable? Yeah just have to get used to it.

edit; 265/75r16 will be the compromise.

Maybe consider the 255/85/16? The MTs I am looking at weigh about 10 lbs less than comparable 285s and are a bit taller at 33.2. The biggest negative seems to be the lack of tire options in that size. Rotational weight on the axle is what seems to really kill the power on these rigs. I currently run 265s Milestar Patagonia MT that are 56 lbs ea, live in Denver, and have an auto. It is totally doable getting up I70 but I would love to have a regear in the future. I often have to hold 2nd gear at a higher RPM to keep from losing speed at certain points and also end up shifting back and forth from 2nd/3rd often for the same reasons.

It's definitely not fun, and not fast, but it's do-able. I'm thinking of eventually doing a re-gear/supercharger, but I just deal with it for now. Speedo is also about 5 mph slow at highway speeds, but I just use GPS to make sure I'm not doing too bad.

I'll second KamKoz, that 255/85r16 could be a good size, I'm currently running some Maxxis Bighorns in a 255. The acceleration was affected but it wasn't as bad as I thought it would be. One consideration with that size is that you'll need a small body lift or you'll need to extend your front bumb stops a bit to avoid hitting the fender at full compression. I achieved this with 3rd gen Tacoma front bump stops.

Could be worse. I'm running 285s with 4.88s and have none to minimal power loss but suffer from horrible gas mileage due to leaking/burnt valves. 9.2 MPG average and cruising....

That's about 150miles a tank

Couple weeks away from the motor rebuild so no worries here.


Sorry not helpful to thread...

@fishy3G , what gears do you have ? I'll guess 4.10's.
285's n 4.10's your going to be disappointed big time, 265's better choice.
285's n 4.30's not so bad a power lose, again 265's better choice.
I say this being a flatlander 350' elevation most times, have run both sizes and ratio's, will be worse your travel route.

@96RedRunner I have 4.30's so maybe it wouldn't be that bad with the slightly better gears.
@Ben336 I hadn't read about using 3rd gen tacoma bump stops before, that's a good tip if I go the 255 route. How much larger were the tacoma ones to prevent hitting the fender?

@fishy3G They are about 1/2" taller, I think they remove around an inch of up travel. The tire has 1 1/2" of clearance at full compression.

4.30's not so bad at your elevation, 4.30's & 285's on eastern mountains was to me needing more gear when loaded with trip gear.
Go 285's if to your liking all is good if not plan B time.

295/75/16s and 4.10s with a 5 speed here, not great climbing at highway speeds but i’ve driven much worse and now i just hang in 3rd, far right lane and embrace the slow. Also, i always have recovery gear and “oh shit kit” in the wooden storage platform with a fullsize spare on a heavy ass swingout hanging off the rear.

Like several others have said, if power and gas mileage are most important than stick with 265. Otherwise be ready for a dog


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Reeee-geeeear. I know it's not cheap but will make a world of a difference.

This is from LCE, a major supplier of aftermarket Toyota parts (it's all they do):

"Once you've determined your gear ratio, the next step is to determine which gear ratio is right for your application. This is a
highly subjective subject, but We base our conclusions on the factory ratios. The following chart shows what gear ratio / tire
combination will maintain stock or better performance, in my opinion. The following applies specifically to 4x4's, with either a 5
speed manual or overdrive automatic made through 1995. While We believe it would be applicable to 1996 and later Tacoma's and
4Runners, these models did receive higher gearing from the factory, so using this chart would make the rpms significantly higher
than what you may be used too.

As always, if you are unsure which ratio to install in your truck, be sure to seek a second opinion.
What you see recommended below, may not be to your liking depending on your driving style.

TIRES SELECTION A SELECTION B
225/70R-15 Tires = 4.10 or 4.30 gears
31 x 10.5-15 Tires = 4.56 or 4.88 gears
32 x 11.5-15 Tires = 4.56 or 4.88 gears
33 x 9.5-15 Tires = 4.88 or 5.29 gears
33 x 12.5-15 Tires = 4.88 or 5.29 gears
35 x 12.5-15 Tires = 5.29 gears

For factory stock performance, or near factory stock performance with larger tires, selection A should be used with 5
speed manual transmissions, selection B should be used with automatic transmissions. For better off road
performance and better highway acceleration, selection B should be used, but you will experience higher rpms on the
highway than you may be used too. How these ratios affect fuel economy depends entirely on how you drive and the
weight you carry. In some cases a lower ratio, combined with reasonable driving, will return stock gas mileage, on a
truck with larger tires.

When regearing with an automatic transmission on pre-1995 trucks that have larger tires, We recommend going with the next lower gear ratio to maintain factory performance. I.E. if you have 31" tires, you should use 4.88 gears, if you have 33" tires, you should use 5.29 gears. The lower gearing is recommended to offset the extremely high 1st gear in the automatic and the high overdrive. Toyota installed 4.30s in stock automatics, while similar 5 speed models got 4.10 gears. This is not as critical on Tacomas since they have more powerful engines."

LC ENGINEERING Differential Tech

I should also say, I plan on putting 4.88's soon in my 31" tire 4Runner, or stock 265/70/R16. This thing is gonna rip