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Regearing for Bigger Tires

The short answer

Bigger tires make your gearing taller, so the engine turns slower at the same speed. To restore it, raise your axle ratio by the same percentage your tire grew: a 4.10 Jeep on 33s needs about 4.3 for 35s and about 4.57 for 37s. Jeep uses 4.56 on its factory 35s, Ford uses 4.70 on its 35s and 37s, and published guides suggest 4.56 to 5.13 for 37s.

By 4x4 Tire Review EditorsLast verified: From 19 owner reportsFrom maker specs

This draws on vehicle makers’ spec sheets, the gearing guidance gear specialists publish, and counted reports from owners who regeared. See how we research.

Work out your ratio

Enter your current and new tire sizes, your axle ratio and your transmission’s top gear. The example below is a Wrangler on 4.10 axles with the 8-speed automatic, going from 33s to 35s.

Type the size from your sidewall: metric like 285/70R17 or LT285/70R17, or flotation like 35x12.50R17. Results are calculated from the size code; real tires vary slightly by brand.

Gearing and engine RPM

Top gear is your transmission’s highest gear: 0.67 on the Wrangler and Gladiator 8-speed automatic, 0.72 on the Wrangler 6-speed manual, 0.64 on the Bronco 10-speed, 0.651 on the 2024-and-later Tacoma 8-speed. Leave it at 1.00 to compare in a 1:1 gear, like most gearing charts.

Result

Enter both sizes

Current
New
MeasureCurrentNewChange
Diameter
Width
Sidewall
Revs per mile

When your speedometer shows 60 mph, you’re actually going – mph.

How it works

Engine RPM = speed (mph) × axle ratio × top gear × 336 ÷ tire diameter (inches). A taller tire covers more ground per turn, so the same speed takes fewer engine revolutions.

The shortcut: raise your axle ratio by the same percentage your tire grew. Jeep’s 33-inch and 35-inch Wrangler tires turn 637 and 604 times per mile, so a 4.10 Jeep needs about 4.3 to feel the same on 35s. On 37s it’s about 4.57. Most people round up to the next ratio they can buy.

What the factories choose

From maker specs
VehicleFactory axle ratiosWith bigger factory tires
Jeep Wrangler JL (2026)3.45; 4.10 (Rubicon, Willys); 4.56; 4.88 optional on the 3.6-liter Rubicon4.56 with the 35-inch package
Jeep Gladiator (2026)3.73; 4.10 (Mojave, Rubicon)No factory 35s
Ford Bronco (2026)3.73 automatic, 4.46 manual; 4.70 available on both4.70 with the 35-inch Sasquatch package and the 37-inch Raptor
Toyota Tacoma (2026)3.583 automatic, 4.300 manualThe 33-inch TRD Pro and Trailhunter keep 3.583
Toyota 4Runner (2025)3.583The 33-inch trims keep 3.583

From Jeep’s and Ford’s 2026 spec sheets and order guide, and Toyota’s product information sheets.

What gear specialists recommend

Published advice agrees on direction but not on exact numbers, so here’s each source’s own figure:

  • Randy’s Worldwide: 4.88 for a Wrangler JL with the 6-speed manual on 35s, coming from 3.45. It adds that 5.38 is not unusual for towing on 35s.
  • Quadratec: 4.88 or 5.13 for 37s.
  • 4 Wheel Parts: about 4.56 to 4.88 for a Gladiator on 37s. Its worked example takes 32-inch tires on 4.10 axles to 37s: about 4.75, so 4.88.

None of these splits its advice between today’s 8- and 10-speed automatics and manuals. Jeep’s own pairing for 35s with the automatic is 4.56.

Engine RPM at 65 mph

Tire3.734.114.564.885.13
33 in.2,4692,7203,0183,2303,395
35 in.2,3282,5652,8463,0453,201
37 in.2,2022,4262,6922,8813,028

From Quadratec’s gear chart, in a 1:1 transmission gear. In an overdrive top gear the engine turns 15–30% slower than shown; use the calculator above for your exact gear.

To read it: find your current tire and ratio, then pick the ratio on your new tire’s row with the closest RPM. A 33-inch Jeep on 4.11 turns 2,720 rpm; on 37s, 4.88 gives 2,881.

What owners report after regearing

What owners report From 19 owner reports

  • 9 chose 4.88, 6 chose 5.29, 2 chose 4.56 and 2 chose 5.13.
  • 13 say the truck drives better or fine afterward; one wasn’t fully satisfied.
  • The 7 who reported fuel economy saw anything from slightly better to about 2 mpg worse.

Most of these owners drive 3rd-gen Tacomas and 5th-gen 4Runners. We found no regear reports yet for the 2024-and-later Tacoma or the 6th-gen 4Runner, with their 3.583 axles.

Deciding on a tire size first? See 33s vs 35s vs 37s.

FAQ

What gear ratio do I need for 35s?

Jeep pairs its factory 35s with 4.56 and Ford with 4.70. From 4.10 on 33s, matching the original RPM works out to about 4.3. Randy’s Worldwide recommends 4.88 for a manual Wrangler JL coming from 3.45.

What gear ratio do I need for 37s?

Ford uses 4.70 on the Raptor’s 37s. Quadratec suggests 4.88 or 5.13 for a Jeep, and 4 Wheel Parts about 4.56 to 4.88 for a Gladiator.

Does regearing improve gas mileage?

Not reliably. The 7 owners in our log who reported it saw anything from slightly better to about 2 mpg worse.

Sources

Show all 21 sources

Manufacturer data (6)

  1. Stellantis, 2026 Jeep Wrangler specifications
  2. Stellantis, 2026 Jeep Gladiator specifications
  3. Ford, 2026 Bronco technical specifications
  4. Ford, 2026 Bronco order guide
  5. Toyota, 2026 Tacoma product information (forum-hosted copy)
  6. Toyota, 2025 4Runner product information (forum-hosted copy)

Owner reports (9)

  1. Bronco6G, Anyone go with 5.13 or 5.38 gears on 37's?
  2. Bronco6G, Regearing and doing 37s right
  3. Tacoma World, Effect of tires and gears on MPG
  4. Tacoma World, 4.10 gears and 33's
  5. Tacoma3G, 5.29 fuel mileage thread
  6. Tacoma3G, 4.88 gears
  7. Trail4Runner, 4.56 regear on a 5th gen 4Runner
  8. Trail4Runner, Why did you re-gear?
  9. Trail4Runner, 4.88 gears on a 5th gen

Other references (6)

  1. Quadratec, Tire and gear ratio calculations
  2. Quadratec, Best Jeep gear ratios for larger tires
  3. Quadratec, How to fit 37-inch tires on your Jeep
  4. RANDYS Worldwide, Re-gearing a JLU Wrangler with 35-inch tires
  5. 4 Wheel Parts, A guide to gearing
  6. 4 Wheel Parts, What tires fit on the Jeep Gladiator JT?
  • Updated October 26, 2026: First published from vehicle makers’ specs, gear specialists’ published guidance and 19 counted owner reports