Tire size comparison
Shows current and new tire diameter, section width, circumference, sidewall height, and revolutions per mile.
Tire Calculator
Compare tire sizes for your Tacoma or midsize pickup.
Check size changes, speedometer error, effective gear ratio, and highway RPM before switching tire sizes.
Summary: This tire size calculator for a Tacoma or other midsize pickup compares two tire sizes with a side-by-side visual comparison of tire and rim, showing the change in diameter, width, sidewall, speedometer reading, effective axle ratio, and highway RPM for any Tacoma or other midsize pickup.
Updated
How does this Tacoma tire size calculator work?
The calculator compares two tire sizes for a Toyota Tacoma or any midsize pickup truck: how much taller and wider the new tire is, how far off your speedometer will read, how much it softens your gearing, and what it does to highway RPM. Every number comes from the tire size itself, so you can check the math.
What do I enter?
- Your current tire size, metric (265/70R17) or flotation (33x12.50R17).
- The size you are considering, in either format.
- Your axle ratio and top-gear ratio, preset to a 3rd gen V6 automatic and adjustable for any Tacoma.
What does it show?
- A side-by-side visual comparison of both tires and rims, in front and side views, scaled from the calculated dimensions.
- Overall diameter, section width, sidewall height, circumference, and revolutions per mile for both sizes, with the change.
- Speedometer error: the true speed at each indicated speed once the new tire is on.
- Effective axle ratio, so you can see how much a taller tire softens your gearing.
- Cruising RPM at 55-75 mph on both sizes for your drivetrain.
What does 265/70R17 vs 285/70R17 change?
A 285/70R17 is 32.71 in tall against 31.61 in for a 265/70R17, a +3.49% diameter change. At an indicated 60 mph you are really doing about 62.1 mph, and the taller tire turns a 3.91 axle into an effective 3.78.
| Measurement | 265/70R17 | 285/70R17 | Change |
|---|---|---|---|
| Overall diameter | 31.61 in | 32.71 in | +1.10 in (+3.49%) |
| Section width | 10.43 in | 11.22 in | +0.79 in |
| Sidewall height | 7.30 in | 7.85 in | +0.55 in |
| Circumference | 99.29 in | 102.76 in | +3.46 in |
| Revolutions per mile | 638 | 617 | -22 |
| Speedometer reads | True speed on 285/70R17 |
|---|---|
| 40 mph | 41.4 mph |
| 60 mph | 62.1 mph |
| 70 mph | 72.4 mph |
| Drivetrain | Axle ratio | Effective ratio on 285/70R17 | 70 mph RPM on 265/70R17 | 70 mph RPM on 285/70R17 |
|---|---|---|---|---|
| 3rd gen V6 6-speed auto | 3.91:1 | 3.78:1 | 1,941 | 1,876 |
| 4th gen 2.4T 8-speed auto | 3.58:1 | 3.46:1 | 1,563 | 1,510 |
| Generation | What 285/70R17 needs |
|---|---|
| 2nd gen Tacoma (2005-2015) | 3 in suspension lift, plus minor changes |
| 3rd gen Tacoma (2016-2023) | 3 in suspension lift, plus minor changes |
| 4th gen Tacoma (2024-2026) | Stock height, plus minor changes |
Full fitment detail: 285/70R17 on a Tacoma.
How is it different from a generic tire calculator?
- Tacoma baselines: stock sizes by year and trim come from the OEM tire lookup, and every factory axle and transmission ratio is a preset, so you are not guessing your starting point.
- Visible math: diameter = wheel + 2 x sidewall; true speed = indicated x new diameter / old diameter; effective ratio = axle x old diameter / new diameter; RPM = mph x axle x gear x 336.1 / diameter.
- Clearance in context: each size links to a Tacoma size page that states what each generation needs to run it, instead of a generic plus-or-minus 3% rule.
Calculator details
What does this Tacoma tire calculator check?
Rim and sidewall context
Displays rim diameter separately from overall tire diameter so wheel changes do not get confused with tire height changes.
Speed and gearing estimates
Calculates speedometer error, effective axle ratio, and highway RPM estimates from the tire size change.
Where do these numbers come from?
Every size comparison here is arithmetic on the two size codes you enter: diameter, width, speedometer error, and effective gearing are not looked up from anywhere. The Toyota documents supply the stock sizes and differential ratios you start from, and real tires can measure a little different from the math.
- Tire geometry: computed from the numbers in each size code with this site's published formulas (no outside data)
- Toyota 2026 Tacoma Owner's Manual tire and wheel specs: factory tire sizes and wheel widths
- Toyota 2023 Tacoma eBrochure: 3rd gen differential ratios (3.909 automatic, 4.30 manual)
- Toyota 2024 Tacoma eBrochure: 4th gen differential ratios (3.583 automatic, 4.3 manual)
- Top-gear transmission ratios: Taco Tires drivetrain presets, not taken from the Toyota documents linked here
- BFGoodrich All-Terrain T/A KO3 product page (measured tire specs)
- Falken Wildpeak A/T4W product page (measured tire specs)
- Toyo Open Country A/T III product page (measured tire specs)
- Nitto Ridge Grappler product page (measured tire specs)
Tacoma tire calculator FAQ.
Enter the tire size currently on the truck and the size you want to test. The calculator compares tire diameter, width, rim diameter, sidewall, circumference, speedometer error, effective axle ratio, and highway RPM.
Yes. A taller tire travels farther per revolution, so the truck usually moves faster than the speedometer indicates. A shorter tire does the opposite.
Rim size changes sidewall height. Two tires can have the same overall diameter while one has more rim and less sidewall, which changes ride feel, trail comfort, and wheel protection.
It gives sizing and comparison data, but physical fitment also depends on Tacoma generation, trim, suspension height, wheel offset, alignment, mud flaps, body mount clearance, and fender liner position.
Yes. The size math (diameter, width, sidewall, speedometer error, effective gearing, and RPM) works the same for any truck tire. What is Tacoma-specific is the starting point: factory axle and transmission presets, stock sizes by year and trim from the OEM lookup, and size pages that say what each Tacoma generation needs to clear a size. On another midsize pickup, enter your own axle and top-gear ratios and check clearance for that truck.
A 285/70R17 is 32.71 in tall against 31.61 in for a 265/70R17, a +3.49% diameter change. At an indicated 60 mph you are really doing about 62.1 mph, and the taller tire turns a 3.91 axle into an effective 3.78. The 285/70R17 is also +0.79 in wider, which is usually what rubs first at full steering lock.
At 70 mph, on a 3rd gen V6 6-speed auto it goes from 1,941 RPM on 265/70R17 to 1,876 RPM on 285/70R17, and on a 4th gen 2.4T 8-speed auto it goes from 1,563 RPM on 265/70R17 to 1,510 RPM on 285/70R17. A taller tire lowers cruising RPM by the same 3.49% as the diameter change, which is why a truck on bigger tires can feel slower to pull and downshift more on grades.