How to Fit 305/35R20 Tires on a 2015-2023 Mustang GT Without Rubbing

Getting a 305-wide tire to fit on a S550 Mustang GT is one of the most searched topics in the muscle car community — and for good reason. The factory rear wheel well has just enough room to make it work, but only if you nail the offset and backspacing.

## What You Need to Know First

The S550 Mustang (2015–2023) runs a 275/40R19 from the factory on the rear. Moving to a 305/35R20 adds roughly 30mm of width and changes the overall diameter slightly. The key measurements you need to control are:

- Wheel width: 10–10.5 inches is the sweet spot for a 305 - Offset: +25mm to +35mm rear offset works for most builds - Backspacing: 5.5–6.0 inches keeps the tire away from the inner fender

## Step-by-Step Fitment Process

Step 1 — Measure your current clearance. With the car on a lift, measure the gap between the sidewall and the inner fender liner at full droop. You want at least 15mm of clearance before adding the wider tire.

Step 2 — Choose your wheel offset. A +25mm offset pushes the tire outward for an aggressive flush look. A +35mm offset tucks it slightly more. Most builders run +28 to +32mm for a clean street fitment.

Step 3 — Check the control arm clearance. The rear lower control arm is the most common rub point. With the suspension at full compression, the sidewall of a 305 can contact the arm. A simple fix is a 5mm–10mm wheel spacer if you are running a higher offset wheel.

Step 4 — Inspect the fender liner. The plastic inner liner has a small tab at the rear that contacts wide tires during suspension travel. Use a heat gun to roll it back or trim it with a utility knife — this is a 10-minute job that prevents a constant rubbing noise.

Step 5 — Test drive slowly first. After mounting the wheels, drive over a few speed bumps and make tight turns in a parking lot before hitting the highway. Listen for any rubbing at full lock.

## Recommended Tire and Wheel Combos

For a street/strip S550 build, the most popular combination is a 305/35R20 on a 10-inch wide wheel with a +32mm offset. Brands like Mickey Thompson Street Comp and Nitto NT555 G2 are proven choices that fit without modification on most stock-suspension Mustangs.

## Final Notes

If you are running lowering springs or coilovers, drop height changes the clearance equation. At a 1.5-inch drop, you may need to roll the rear fender lip slightly to prevent contact during hard cornering. A fender roller tool makes this a 20-minute job and is far cleaner than cutting.