How To Replace the Mud Flaps on Your Semi-Truck

Mud flaps are large, durable mats you place behind the tires of your semi-truck to protect it from road debris like mud, rocks, and water. Because the whole point of these flaps is to take a beating so your undercarriage doesn't, they can wear down faster than other truck parts. On average, a set of mud flaps will last anywhere from a few months to a few years before they crack and need to be replaced.

If your mud flaps are starting to look worse for wear, but you've never replaced a set before, this guide on how to swap out the mud flaps on your semi-truck will help you make a clean transition when it's time.

Get Your New Mud Flaps Ready

Before you can start the replacement process, you’ll need a new set of mud flaps. It’s useful to have them on hand so you can swap them out immediately after removing the old ones. This preparation minimizes your truck's downtime and gets you back on the road faster.

When you select new flaps, you have a few options. Some drivers prefer standard, no-frills flaps that get the job done, while others might look for ones with custom logos or designs. The choice is yours, but you'll want to select a set that matches the durability and size requirements for your truck.

Park on a Level Surface

Your safety comes first, so pick a safe location to perform the swap. You should find a flat, stable area to park your semi-truck. A level surface prevents the truck from rolling unexpectedly and injuring you.

Once you’ve found your spot, engage the parking brake. Even on a level surface, the truck could still roll, especially when you're pulling, pushing, or using tools that cause vibration. The brake is an extra measure that helps keep the truck stationary while you’re underneath it or working around the wheels.

Gather Your Tools

Having all the necessary tools within arm's reach makes the job go much faster. You won't have to stop mid-task to search for a missing wrench. What tools do you need? Typically, you'll need a set of wrenches or a socket set to remove the bolts that hold the mud flaps in place. Lay out these tools on a tarp or a piece of cardboard next to your work area so you can easily grab them as you work.

Take a Look at the Old Flaps

Before you start unscrewing bolts, take a moment to examine how the current mud flaps are attached. Are they bolted directly to the frame or to a separate bracket? Seeing the existing setup gives you a clear picture of what you need to do.

You might even snap a quick photo with your phone. A picture can be a handy reference if you run into any confusion when you're attaching the new flaps.

Remove the Old Bolts

Now it's time to get to work. You'll use your wrench or socket set to loosen and remove the bolts holding the old mud flap. These bolts can sometimes be tight due to rust or road grime, so you may need to apply a bit of force.

If a bolt is particularly stubborn, try spraying penetrating oil to loosen it. Let the oil sit for a few minutes to work its way into the threads. This should make the bolt much easier to turn and remove without causing any damage.

Detach the Old Mud Flap

Once all the bolts are out, the old mud flap should come off easily. You can carefully pull it away from the mounting bracket or frame. Sometimes, it might be stuck on with a bit of dirt and grit, so a gentle tug might be necessary.

With the old flap removed, you have a clear view of the mounting area. This is a good opportunity to check the condition of the bracket and the surrounding frame. You can look for any signs of rust or damage that might need attention.

Clean the Mounting Area

A clean surface is the secret to a secure fit for your new mud flaps. You should take a few minutes to wipe down the mounting bracket and the area where the new flap will sit. A wire brush is quite effective for removing any caked-on mud or rust.

After brushing away the debris, you can wipe the area with a clean cloth. This helps your new mud flaps sit flush against the bracket, which leads to a stronger, more reliable installation that will hold up on the road.

Position the New Mud Flap

Now for the exciting part. You can pick up your new mud flap and align it with the mounting holes on the bracket. You'll want to get the positioning just right so the flap hangs straight and provides maximum protection.

It can be helpful to loosely insert one of the top bolts to hold the flap in place while you align the other holes. This frees up your hands and makes it easier to get everything lined up perfectly before you tighten any of the hardware.

Secure the New Bolts

With the new mud flap in position, you can start inserting and hand-tightening the new bolts. It's best to start with the top bolts and work your way down. This keeps the flap stable and properly aligned.

You should check that you're using the correct bolts for the job. New mud flap kits often come with their own hardware. Using the provided bolts and nuts guarantees you have the right size and thread for a secure connection.

Tighten Everything Down

Once all the bolts are in place, you'll go back and tighten each one with your wrench or socket. You’ll want them to be snug and secure, but you should avoid over-tightening. Applying too much pressure can strip the threads or even crack the mud flap.

A good rule of thumb is to tighten the bolts in a star pattern, similar to how you'd tighten lug nuts on a wheel. This technique distributes the pressure evenly across the mounting surface. The result is a flat, secure fit that won't warp or buckle over time.

Replace Your Worn Mud Flaps with Higgs Parts

When you know how to replace the mud flaps on your semi-truck, you don't have to panic when you notice your current flaps are starting to look worse for wear. You'll be able to quickly and effectively replace them with a new, durable set.

If the day of reckoning is coming for your mud flaps, preemptively pick up a replacement set at Higgs Parts. We're a dealer for East Manufacturing trailer parts, and carry many of their products, including their mud flaps. Their high-quality, tear resistant flaps will help you protect your semi-truck from whatever the road throws at it.