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Tire size comparison

Tire size calculator

On a 2026 Toyota Tacoma that left the factory on 265/70R17s, 285/75R17s are 2.2 in (7.0%) taller: the axles sit 1.1 in higher, the speedometer shows 56.1 mph at a true 60, and the 3.583 axle acts like a 3.35. Type any two sizes, or pick your truck.

Current tire

Stock
mm
%
in
31.6 in · 803 mm tall

New tire

mm
%
in
33.8 in · 859 mm tall

Common on 17 in wheels

Maker

Your final drive. Gives the effective ratio and the ratio that restores it.

For my vehicle

Fills in the stock tire size and axle ratio 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

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

265/70R17 vs 285/75R17

Math on the nominal sizes

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

Height

+2.2in

31.6 → 33.8 in · +7.0%

Speedo at a true 60

56.1mph

reads 6.6% low · shows 60 at 64.2

Ground clearance

+1.1in

+28 mm under the axles

Axle acts like

3.35

from 3.583 · −6.6%

NOWNEW+2.2″height+1.1″axle265/70R1731.6 in · 803 mm285/75R1733.8 in · 859 mm
FRONT11.2 in wide+0.8 in vs now
Drawn to scale from the nominal sizes; each grid square is 2 in. Dashed: the current tire. A real tire can measure a few tenths of an inch off its size.
265/70R17 compared with 285/75R17
MeasureCurrentNewChange
Overall diameter31.61 in803 mm33.83 in859 mm+2.22 in+7.0%
Section width10.43 in265 mm11.22 in285 mm+0.79 in+20 mm
Sidewall height7.30 in186 mm8.42 in214 mm+1.11 in+28 mm
Wheel diameter17 in17 insame
Circumference99.3 in2522 mm106.3 in2700 mm+7.0 in
Revs per mile638396 /km596370 /km−42
Speedometer at 6060.0 mph56.1 mph−3.9 mph−6.6%

What it means

Guidance, not advice

  • Speedometer

    Recalibrate

    Reads 6.6% low: 56.1 mph at a true 60, and 60 on the dial is really 64.2. The odometer is off the same way: 93.4 miles counted for every 100 driven. Over 3% is worth fixing: a programmer or the dealer can set the new tire size.

  • Gearing

    No regear needed

    Your 3.583 axle acts like a 3.35 (−6.6%). Under about 7% most drivers don't regear; if you tow or drive mountains, a 3.91 gets the stock feel back (exact match 3.84).

  • Fitment

    Check for rubbing

    2.2 in taller is 1.1 in more radius into the wheel well. On most trucks that takes a level or a lift; check at full lock and with the suspension compressed. Wheel offset decides where the tire meets the fender, bumper and frame.

  • Wider tread

    Check inside

    0.8 in wider: about 0.4 in more on each side at the same wheel offset. Check the inner fender liner and the upper control arm at full lock; a wheel with less offset moves the tire out.

From the math on the nominal sizes. Lift, wheel width and offset, brakes and bodywork decide what actually fits: check at full lock and with the suspension compressed. Not engineering advice.

Speedometer table →Regear for these tires →Toyota Tacoma spec plate →

Formulas

How we calculate

Every number above is arithmetic on the size printed on the sidewall. Here is each formula, worked on the example at the top of the page.

Sidewall height

width × aspect ÷ 100

e.g. 265 × 70 ÷ 100 = 185.5 mm (7.30 in)

Overall diameter

wheel + 2 × sidewall ÷ 25.4 (an inch size states it: 35x12.50R17 is 35.0 in)

e.g. 17 + 2 × 185.5 ÷ 25.4 = 31.61 in

Circumference

π × diameter

e.g. π × 31.61 = 99.3 in

Revolutions per mile

63,360 ÷ circumference in inches

e.g. 63,360 ÷ 99.3 = 638

Speedometer reading

true speed × old diameter ÷ new diameter

e.g. 60 × 31.61 ÷ 33.83 = 56.1 mph

True speed

speedometer × new diameter ÷ old diameter

e.g. 60 × 33.83 ÷ 31.61 = 64.2 mph

Ground clearance

(new diameter − old diameter) ÷ 2

e.g. (33.83 − 31.61) ÷ 2 = +1.11 in

Effective axle ratio

axle ratio × old diameter ÷ new diameter

e.g. 3.583 × 31.61 ÷ 33.83 = 3.35

Ratio that restores it

axle ratio × new diameter ÷ old diameter

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

The verdicts use rules of thumb, not limits: a speedometer more than 3% off is worth recalibrating; effective gearing more than 7% taller is worth a regear; a tire more than 1.5 in taller, or 15 mm wider, needs a fitment check.

Stock sizes and axle ratios come from the makers’ documents, each linked. Everything else is math on nominal sizes: a real tire can measure a few tenths of an inch off its size, so for a speedometer recalibration use the measured diameter or revolutions per mile from the tire maker’s spec sheet.

FAQ

Questions people ask

How do you read a tire size like 285/75R17?

285 is the section width in millimetres, 75 is the sidewall height as a percentage of that width, R means radial, and 17 is the wheel diameter in inches. The sidewall is 285 × 0.75 = 213.75 mm (8.42 in), so the tire stands 17 + 2 × 8.42 = 33.8 in tall.

An inch size says it directly: 35x12.50R17 is 35 in tall and 12.5 in wide, for a 17 in wheel. LT in front marks a light-truck tire and P a passenger tire; the dimensions work the same way.

What is a 33-inch tire in metric?

Metric sizes rarely land on a round inch, so a “33” is anything close: 285/75R16 (32.8 in), 285/70R17 (32.7 in), 255/80R17 (33.1 in), 275/70R18 (33.2 in), 285/60R20 (33.5 in).

The usual “35s”: 315/75R16 (34.6 in), 315/70R17 (34.4 in), 295/70R18 (34.3 in), 35x12.50R17 (35.0 in). Pick by your wheel diameter, then compare the exact height above.

Does a bigger tire change the speedometer?

Yes. The speedometer assumes the stock tire, so a taller one makes it read low by the same proportion. Going from 265/70R17 to 285/75R17 (+7.0% taller), it shows 56.1 mph at a true 60, and when it shows 60 you’re doing 64.2. The odometer under-counts the same way. Over about 3%, recalibrate.

How much ground clearance does a bigger tire add?

Half the increase in diameter, because only the radius lifts the axle: 31.6 → 33.8 in raises the axles, the differentials and everything above them by 1.1 in. It’s the only clearance a solid axle’s differential gains: a lift raises the body, not the diff.

Do I need to regear for bigger tires?

Bigger tires make every gear taller. A 3.583 axle on 285/75R17s instead of 265/70R17s acts like a 3.35 (−6.6%). Under about 7% most drivers live with it; beyond that, or if you tow, the ratio that restores the stock feel is the axle ratio × new ÷ old diameter (3.84 here; 3.91 is the nearest common ratio).

Are the calculated sizes exact?

They’re nominal. A real tire’s diameter depends on the brand, tread depth, rim width and pressure, and often differs from its size by a few tenths of an inch. The tire maker’s spec sheet lists the measured diameter and revolutions per mile: use those to set a speedometer.

Data

Stock tire sizes we have

From the makers' own documents, for every vehicle the “for my vehicle” picker knows. Pick one in the calculator to start from its stock size and axle ratio.

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