Jeep Wrangler Lift Kit & Tire Size Compatibility Guide (With Gear Ratios)

The relationship between lift height and maximum tire size is not a simple linear equation. It depends on your Wrangler generation, fender flare style, wheel offset, and whether you are willing to trim fenders. Here are the general guidelines that apply across JK and JL platforms. Stock height (no lift) comfortably fits up to 31-inch tires on JK models and 33-inch tires on JL Rubicon models (which come with fender flares designed for larger tires). A 1.5 to 2-inch leveling kit or spacer lift opens the door to 33-inch tires on JK and allows 33s on JL Sport/Sahara models without rubbing at full lock. At 2.5 inches of lift, 33-inch tires fit all Wrangler trims with no modifications, and 35-inch tires fit with minor fender trimming (removing the inner fender liner pinch seam and possibly trimming the fender flare). At 3.5 inches, 35-inch tires fit comfortably on most wheel offsets, and 37-inch tires become possible with flat fender flares and proper wheel backspacing. At 4 inches and above, 37-inch tires fit well, and 40-inch tires enter the conversation with high-clearance fender flares and significant additional modifications. These are conservative guidelines -- aggressive wheel offsets and flat fenders can push tire sizes larger, but at the cost of handling, bearing life, and aerodynamics.

Larger tires effectively change your final drive ratio, making the engine work harder to maintain the same speed. This shows up as sluggish acceleration, higher RPMs at highway speed (with manual transmissions), lazy downshifts (with automatics), and reduced fuel economy. Regearing restores the factory-intended relationship between engine RPM and wheel speed. The JK Wrangler with 3.21 gears and stock 32-inch tires has an effective crawl ratio that works well from the factory. When you jump to 35-inch tires, you lose approximately 9 percent of your effective gear ratio. Regearing to 4.56 restores the ratio and is the most popular choice for 35s on the JK. For 37-inch tires, 4.88 gears are the standard recommendation. For 40-inch tires, 5.13 or 5.38 gears bring the ratio back in line. JL Wranglers with the 3.6L Pentastar and 8-speed automatic handle larger tires better than JKs due to the wider gear spread of the 8-speed. Many JL owners run 35-inch tires on the factory 3.45 gears (Rubicon) without regearing, though purists still recommend 4.56 for optimal performance. JL models with the factory 4.10 gears (Rubicon with manual) do well with 35s and benefit from 4.88 with 37s. The 2.0L turbo JL has enough low-end torque to mask the ratio loss on 35s, but still benefits from regearing for towing or trail use.

Wheel offset and backspacing determine how far your tires sit inside or outside the fender, which directly affects clearance, steering geometry, and bearing loads. Stock JK wheels have a backspacing of 6 to 6.5 inches (approximately +44mm to +50mm offset). Stock JL wheels run about 5.5 to 6 inches of backspacing (+30mm to +44mm offset). For lifted Wranglers running larger tires, reducing backspacing (moving to a more negative offset) pushes the tire outward, which prevents rubbing on the frame and inner fender. However, excessive negative offset creates problems: increased steering effort, accelerated wheel bearing wear, wider turning radius, and potential legality issues in states that require tires to remain within the fender line. The sweet spot for most lifted Wrangler builds is 4.5 to 5 inches of backspacing (approximately -12mm to +6mm offset) on wheels that are 9 to 10 inches wide. This provides adequate clearance for 35-inch tires at 2.5 to 3.5 inches of lift without excessive bearing stress. For 37-inch and larger tires, 4 to 4.75 inches of backspacing on 10-inch-wide wheels is typical. Wheel width matters too. A tire that is nominally 12.5 inches wide (like a 35x12.50R17) looks and performs differently on a 9-inch wheel versus a 10-inch wheel. Wider wheels spread the tread flatter, which can increase rubbing despite having the same offset.

Changing tire size throws off your speedometer, odometer, and in some cases your transmission shift points. A stock JL Wrangler with 32-inch tires reading 70 mph on the speedometer is actually traveling 70 mph. Swap to 35-inch tires and that same speedometer reading of 70 mph means you are actually traveling about 76.5 mph -- a 9.3 percent error that can earn you speeding tickets and understate your odometer mileage. Speedometer recalibration can be done through the OBD-II port using devices like the SuperChips Flashcal, AEV ProCal, or Tazer JL. These programmers allow you to enter your actual tire size, and the vehicle computer corrects the speedometer, odometer, ABS system, and (on automatic models) transmission shift points. The cost is typically $150 to $300 for the programmer, and the process takes about 15 minutes. Most programmers also allow you to disable the tire pressure monitoring system (TPMS) warning light if you are running non-TPMS wheels, adjust the daytime running lights, and modify other vehicle settings. Regearing changes your speedometer calibration again, so if you plan to regear in the future, wait until after that work is done to calibrate your speedometer, or plan to recalibrate twice.