Whats the rule on where mudflaps can be placed?

While there are no federal rules on mudflaps, each state/province sets their own. From what I could gather having them mounted in front of the DOT bumper should suffice.

 

There is no federal regs pertaining to mudflaps other than the requirement for reflective tape if they are on the back of the tractor. Placement, length, etc. is left up to the states. For example, MO & TX want them within 8" of the ground...IL just has to be within 12". Some states use a formula based upon the angle between where the tires contact the ground and the rear of the vehicle...if you have enough overhang, you're good to go even without mudflaps, and even if they ARE needed, the farther back from the tires they are the shorter they can be.

Doing the research is time consuming and confusing...better off just picking one of the standard methods of mounting them and not messing with 'em unless you know that what you want to do different will be legal in all of the states you'll be operating in.

 

putting them behind the tires is best

 

I have a step deck with sliding axle. Mudflap used to slide with axle. I mounted mudflap on inside of rear bumper. DOT must be ok with it. I haven't received a ticket yet. It has been a couple years now.

 

I pulled cans with stationary mudflaps and wonder the same question. Never had a problem so far with dot.

 

Distance and MountingMost states share a common formula for mud flap placement. Although the mathematics seem esoteric, they're simply intended to keep water and debris from slipping from under the tire and hitting the car behind at an angle greater than 22.5 degrees. In inches, measure the distance from the tire's rearmost point of contact (with the trailer fully loaded) with the road to where you'd like to mount the mud flap, and multiply it by 0.4142. Take that measurement, and measure upward from the ground at your desired mounting point; this is your maximum allowable mud flap ground clearance. Example: if you wish to mount the mud flap 18 inches from the rearmost contact point of the rear tire, multiply 18 by 0.4142; this gives you a maximum of 7.45 inches from the ground. A simpler calculation often used by roadside officials to determine angle is 5 inches of vertical rise for every 12 inches horizontal from the contact patch.

 

mine have always been inside the ICC bumper, never heard nary a word

i moved mine for the same reason when i was blowing maypops

 

Some of these truckers I've seen could use a mudflap someplace other than their tires.. Sometimes for the same reason we keep them behind the tires...

 

I don't mean to be rude, but why are you blowing so many tires. Running those junk recaps?