📋 Quick Facts
+1 size
1-2 MPG
Stock to 33s
1-2 MPG
Stock to 35s
2-4 MPG
Stock to 37s
3-6 MPG
Going up one tire size typically costs 1-2 MPG. Stepping from a stock 32" to 35" costs 2-4 MPG. The bigger jumps come from rotational mass, rolling resistance, and the fact that bigger tires lower your effective gear ratio.
Why bigger tires kill MPG
- Rotational mass. A 35" KO2 weighs ~65 lbs vs. ~45 lbs for stock. Multiply by 4. The engine spins all that extra weight up at every acceleration.
- Effective gear ratio drops. A 35" tire vs. a 32" lowers your gear ratio by ~9%. The engine has to work harder for the same speed.
- Rolling resistance. Wider footprint, more aggressive tread compound.
- Aero impact. Wider tires increase frontal area slightly.
- Speedometer error. Stock 32" reading 60 mph is actually 65.6 mph with 35" tires. Your "MPG" calculation by dash is off too.
Tread type matters
- Highway/touring tires: Stock-like rolling resistance.
- All-terrain (KO2, AT3W, KO3): 1-3% additional rolling resistance.
- Mud-terrain (KM3, MT, ATX MT): 5-8% additional rolling resistance.
- Snow/winter: 3-5% additional rolling resistance (softer compound).
How to recover some MPG
- Re-gear the differentialOne step lower gear (e.g., 3.55 to 3.92) recovers most lost low-end torque and 1-2 MPG.
- Recalibrate the speedometerNot for MPG directly, but it makes your fuel economy reading accurate.
- Stick to load-rated, not overbuiltA 10-ply tire on a half-ton truck is heavier than needed and costs MPG without benefit.
- Check pressure weeklyBigger tires lose MPG fast if under-inflated. Run door-jamb spec.
- Avoid mud-terrain unless you need itThe MPG difference between A/T and M/T is huge on a daily-driven truck.
🔗 Related Guides
❓ Frequently Asked Questions
Will plus-one (taller wheel, shorter sidewall) hurt MPG?
Slightly - typically 0.5-1 MPG. The larger wheel adds rotational mass at a worse leverage point.
Why does my MPG seem worse than the calculation says?
Speedometer reads low when you have bigger tires. Actual distance is longer than dash-recorded, making MPG seem worse.
Will narrower but same-diameter tires help MPG?
Slightly. A narrower tire reduces rolling resistance and frontal area. 1-2 MPG improvement is realistic.
Will skinnier sidewalls (lower profile) help MPG?
Yes - less flex, less rolling resistance. Trade-off is harsher ride and pothole damage risk.
Do bigger tires always look better?
Subjective. Going too big visually unbalances the car and worsens ride, MPG, brake performance.
Is the gas tank still good for the same range?
No. Same gallons, fewer MPG = less range. A 24-gallon F-150 going from 20 to 16 MPG loses 96 miles of range.