Trimming Rear Fender Lips

You know you’ve “made it” in the Mustang hobby when you get your new NPD parts catalog in the mail early.  After the past few years’ worth of investment in the NPD product line, I was kinda expecting an autographed copy…….but alas……no joy (just kidding).

On the cover of the new catalog, a beautiful cream-colored fastback is shown from the left rear ¾ view with emphasis on the rear wheel opening (to my eye anyway).  Taking nothing away from how nice the car is, this photo reminded me of a detailing trick I use in this area that is decidedly against the “concours bible”, however it makes for a nicer presentation of almost any car nonetheless:  Wheel lip trimming.

Basically, the rear wheel lips on almost all classic Mustangs are the model of variability.  Mass production techniques being what they were, you can often spot huge variances in the fender lip width from car-to-car and even from one side to the other on the same car.  Coupled with the “normal” alignment doodads and lumps-n-bumps, this bugs me considerably and is especially noticeable on lighter colored cars, like the one on the NPD catalog cover (made ya look!).

Since my Boss 302 will be a shade of “Screamin” white, the fender lips will be very obvious and any inconsistencies easy to detect.  As such, I thought it would be a good idea to document how I trim the rear fender lips to be nice and even on their exposed edges and offer a few hints on how it’s done and what to be aware of if you choose to do this to your car.

The most important rule in making this simple modification is to remember to stay outside the spot weld line, toward the lip edge and do not cut through the spot welds.  This weakens the joint and makes sealing the lip areas quite a bit more difficult.  Generally speaking this means the lip width will rarely get narrower than about ¾” on most cars.  Fortunately, this seems to allow plenty of room to clean them up, but careful measurement is still in order to make absolutely sure to clear the spot welds.

Once the appropriate lip width is established, I simply use a machinist’s square set to that width and trace along the lip to mark the cut line I need to follow with the cutoff wheel.  Then it is a relatively simple matter of carefully trimming off the lip to the line and finishing the edges with a body file, an angle grinder and/or sand paper.

For the investment of about an hour, I was able to tidy up both rear fender lips and they are now ready to be finished off nice and smooth as the body work phase approaches.  It’s simple and easy and makes quite a difference to the eye when finished.  So there ya go!  A quick tip to correct an often overlooked detail.

Ragged fender lips are a peeve of mine.  With a little work, I was able to clean up the inner lips and even the width so they present much better than when they were produced.

This poor photo shows the cleaned up edge of the passenger side rear fender lip.  Lots of bodywork yet to be done in this area, but you can clearly see how much cleaner a consistent inner edge and even width makes this area look.

Driver side rear lip is also nice and tidy.  Most times, very little material removal is actually required to get the fender lips looking nice.

The passenger side rear edges also look nice following a little trimming.  You can also see that I stayed clear of the spot welds to avoid any compromise to the strength of this critical joint.