Fender Clearance How-to

Updated Apr 18, 2016

GM Inner Fender Modification

How-to get another 2″ of tire clearance between the rear of the front tires and cab-side of the fenders on later-model GM pickups


by Bruce W. Smith


Taller, wider tires look good on pickups and their larger diameter is an easy way to gain additional ground clearance.

The downside is on later-model GM pickups installing larger tires creates clearance issues with the cab side of the fender well. Even going up one tire size can result in the rear of the front tires contacting the rear of the inner fender.

A lift or leveling kit is one way to gain clearance. But it’s not the only way.

We prefer a far less expensive approach: Modify the rear of the inner fender so there’s enough tire clearance to run 2- to 3-inch taller tires without any clearance issue.

This technique is particularly good for fleet managers who don’t want their pickups sporting suspension changes.

The process is straight-forward and involves a couple minor sheetmetal cuts and a few taps of a hammer. The end result is a gain of about 2″ in rear tire clearance without any body or paint work.

We did this modification on Big Red, our 2008 GMC Sierra 3500HD dually after installing a Cognito adjustable 4-6″ lift kit and 35×12.50R22 Toyo M/Ts.

The new front tires just clipped the back of the inner fender. After the modification Big Red had plenty of tire clearance.

(We plan on making the same modifications to Project Bedrock, our 2011 GMC Sierra 1500 4×4 so it can run 285/70R17s. Right now those taller tires rub under full-lock.)

The gallery of images below show the step-by-step process, which takes less than 45 minutes to do. — Pro

Area of tire interference

Mark cut line

First cut inner fender

Bend down inner fender edge

Cut edge support

Cutting edge brace

Hammer pinch weld flat

Ready for paint

Cab pinch weld flattened

Painting inner fender area

Folding bottom edge up

Inner fender closed up

Inner Fender after mod

Inner Fender mod after top view

Added Tire Clearance