A practical rule for most fleets is to hang mud flaps no more than 6 inches from the ground when the vehicle is in its typical loaded condition. Some jurisdictions allow up to 8 inches, but requirements vary by state and by vehicle class, so it’s wise to confirm your local DOT regulations before you cut or mount. In addition to height, most rules expect the flap to be at least as wide as the tire (covering the full tread) so spray is contained behind the wheel.
How to set the height correctly:
- Measure loaded, not empty. Air-ride and leaf suspensions change ride height. Set the flap height with the truck loaded as it normally runs so you don’t end up too high on the road.
- Square and even. Keep both sides the same height and square to the ground; uneven lengths look off and can attract attention during inspections.
- Allow for terrain. If you run jobsites or uneven yards, consider ½–1 inch more clearance to avoid dragging while still staying compliant.
- Use anti-sail hardware. At highway speeds, flaps can lift; anti-sail brackets or stiffeners help maintain coverage so your “at-rest” height actually performs at speed.
- Trim carefully. If trimming is needed, mark a straight cut line with a square, trim with a fine-tooth blade, and round the corners slightly to reduce catching and tearing.
- Recheck after install. Bounce the suspension, roll the truck a few feet, and re-measure.
If you’d like, share your state, vehicle type, and typical load, and we’ll recommend an exact height and hardware package that balances compliance, durability, and appearance.
