4WD.ai

Gearing for bigger tires

Gear ratio calculator

On 285/75R17s, a 2026 Tacoma's 3.583 axle acts like a 3.35: 1,506 rpm at 65 mph in 8th gear instead of 1,612. A 3.91 ring and pinion brings the stock gearing back (3.84 is exact).

Stock tire

Stock
mm
%
in
31.6 in · 803 mm tall

New tire

mm
%
in
33.8 in · 859 mm tall
Maker
mph
8th gear

8-speed AT

For my vehicle

Fills in the stock tire, axle ratio and the transmission's gears from the maker's documents.

2026 Toyota Tacoma TRD Off-Road Double Cab 5-ft bed 4x4

Stock tire
265/70R17
Maker
Axle ratio
3.583
Maker
Top gear
0.651
Maker

Source: 2026 Tacoma Product Information (opens in a new tab)

3.583 on 285/75R17

Math, no slip

0.651 gear at 65 mph · 2026 Toyota Tacoma TRD Off-Road Double Cab 5-ft bed 4x4

Rpm at 65, stock

1,612

265/70R17, 3.583

On the new tires

1,506

−6.6% · 285/75R17

Axle acts like

3.35

from 3.583

Restores stock

3.84

nearest common 3.91 (+2.0%)

Engine rpm at 65 mph · 0.651 gear

  • Stock tires265/70R17 · 3.583

    1,612rpm

  • New tires285/75R17 · 3.583

    1,506rpm

  • New tires, regeared285/75R17 · 3.91

    1,644rpm

The white line is stock. Rpm assumes no slip: an automatic with its torque converter locked, as it is at a steady cruise.
Common ratios on 285/75R17
RatioActs likeRpm at 65Vs stock
3.313.091,392−13.7%
3.423.201,438−10.8%
3.553.321,493−7.4%
3.733.481,568−2.7%
3.91closest3.651,644+2.0%
4.103.831,724+6.9%
4.304.021,808+12.1%
4.564.261,917+18.9%

“Acts like” is the ratio on the stock tires that would feel the same. Stock: 3.583 on 265/70R17, 1,612 rpm.

What it means

Guidance, not advice

  • Gearing

    No regear needed

    On 285/75R17s the 3.583 acts like a 3.35 (−6.6%). Under about 7% most drivers don't regear; if you tow or climb a lot, a 3.91 gets the stock feel back (exact match 3.84).

  • At cruise

    −106 rpm

    1,506 rpm at 65 mph instead of 1,612: the engine works lower in its range, so expect more downshifts on grades and into a headwind, and slower acceleration.

  • If you regear

    Front and rear

    A 4x4 needs the same ratio front and rear. Which ratios exist depends on the axle, so check yours before you order; the speedometer needs the new ratio too if it reads speed at the transmission.

Compare these tires →Speedometer after the regear →Toyota Tacoma spec plate →

Formulas

How we calculate

The engine turns the transmission, the transmission turns the axle, and the axle turns the tire: multiply the ratios, divide by the distance one tire turn covers.

Tire turns per minute

mph × 63,360 ÷ 60 ÷ (π × tire diameter in inches)

e.g. 65 × 63,360 ÷ 60 ÷ (π × 31.61) = 691.3

Engine rpm

tire turns per minute × axle ratio × gear ratio

e.g. 691.3 × 3.583 × 0.651 = 1,612 rpm

Short form

rpm = mph × axle × gear × 336.13 ÷ tire diameter

e.g. 65 × 3.583 × 0.651 × 336.13 ÷ 33.83 = 1,506 rpm on 285/75R17

Effective axle ratio

axle × stock diameter ÷ new diameter

e.g. 3.583 × 31.61 ÷ 33.83 = 3.35

Ratio that restores it

axle × new diameter ÷ stock diameter

e.g. 3.583 × 33.83 ÷ 31.61 = 3.84; nearest common 3.91

Rpm assumes no slip: a manual, or an automatic with the torque converter locked, as it is at a steady cruise. We suggest a regear when the effective ratio moves more than 7%; a rule of thumb, not a limit.

Axle ratios, gears and stock tires come from the makers’ documents, each linked when you pick a vehicle. The common ratios are what ring-and-pinion makers usually sell; which exist for your axle is for its maker to say.

FAQ

Questions people ask

What gear ratio do I need for 35-inch tires?

Multiply your axle ratio by 35 and divide by your stock tire’s diameter. From 265/70R17 (31.6 in): 3.55 needs 3.93, so 3.91; 3.73 needs 4.13, so 4.10; 4.10 needs 4.54, so 4.56. Go a step lower (numerically higher) if the truck is loaded heavy or tows.

What rpm will I cruise at?

rpm = mph × axle × gear × 336.13 ÷ tire diameter. With a 3.583 axle and a 0.651 top gear, 65 mph is 1,612 rpm on 265/70R17s and 1,506 on 285/75R17s.

Is a higher or lower axle ratio better?

A numerically higher ratio (4.56) is shorter: more pull, more rpm at every speed. A lower one (3.55) is taller: less rpm on the highway, less pull. Bigger tires make any ratio act taller, which is why they come with a regear.

Do both axles need the same ratio?

Yes, on a 4x4. With the transfer case locked, different front and rear ratios make the axles fight each other and wear out the driveline. Regear both at once.

Where do I find my axle ratio?

On the tag bolted to the axle, the window sticker or the build sheet; some makers print an axle code on the door label. Pick your configuration above and we fill in the ratio the maker publishes for it.

Does regearing change fuel economy?

It can go either way. Restoring the stock effective ratio puts the engine back where its maker tuned it; staying taller lowers rpm but can mean more downshifts and more throttle. Fill up before and after and measure.

Data

Factory axle ratios and gears

Final drive ratios and transmission top gears per model, from the makers' own documents.

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