What gauge of steel should I use for custom fender wells?
Documented on the Ford Mustang build
Published February 26, 2026
Typical practice is 18 gauge (around 1/16") for inner wheelwell and patch panels to match OEM thickness and maintain formability.
Full Answer
Typical practice is 18 gauge (around 1/16") for inner wheelwell and patch panels to match OEM thickness and maintain formability. Heavier steel makes shaping and welding more difficult and can add unnecessary weight.
Documented In This Build
Related Knowledge
How do you prevent warping when welding large panels?What finish work is needed after welding the new wells?Do I need to remove the fender to make custom wheelwells?How do I prevent warping when welding thin sheet metal?What wheel/tire sizes can this modification accommodate?How much extra tire/wheel clearance can I expect?How difficult is this for someone with limited metalworking experience?How much wheel/tire clearance should I leave when shaping the fender well?
Related Parts
Seam sealer (tube)
$8
Body filler (Bondo or equivalent)
$12
MIG welding wire (ER70S-6 spool)
$25
Grinding/flap discs (pack)
$20
Sheet steel (18 ga / 1/16")
$40
Preformed inner fender / wheelwell panel (replacement or donor)
$120
Plastic fender liner / wheelwell liner
$60
Weld-through primer
$15
Pop rivets / fasteners (kit)
$10
Self-tapping screws / hardware
$10
Related Tools
Angle grinder with cutting and flap discs
MIG welder
Drill and drill bits
Hammer and dolly set
Spot weld cutter / chisel
Clamps and magnets (panel clamps)
Jigsaw / reciprocating saw (for rough cuts)
Body file / sanding block
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