Best Mud Flaps & Quarter Fenders for Semi Trucks: Poly vs. Stainless Steel Explained
Share
If you haul freight for a living, you know mud flaps and quarter fenders aren't optional — they're required by law in most U.S. states and critical for protecting your rig and other drivers. But with so many options on the market, choosing between poly and stainless steel can feel overwhelming. This guide breaks down the differences so you can make the right call for your truck and your budget.
What Are Quarter Fenders?
Quarter fenders mount behind the drive axle to deflect road debris, mud, and water. Required on semi trucks in most states, they come in two main materials: heavy-duty polyethylene (poly) and stainless steel.
Poly vs. Stainless Steel — Key Differences
| Poly | Stainless Steel | |
|---|---|---|
| Weight | Lighter | Heavier |
| Durability | Impact-resistant, won't rust | Corrosion-resistant, premium finish |
| Maintenance | Easy to clean | Polished look, easy to wipe down |
| Price | More affordable | Higher upfront cost |
| Best for | Daily work trucks | Show trucks or premium fleets |
Do You Need Mud Flaps Too?
Yes — most states require mud flaps behind all axles. Pair your quarter fenders with heavy-duty rubber mud flaps for full compliance and maximum protection. Skipping mud flaps can result in fines and liability if road debris damages another vehicle.
How to Choose the Right Size
Semi truck fenders and mud flaps are sized to match your wheel configuration. For standard 18-wheelers running 22.5" or 24.5" wheels, make sure your quarter fenders are rated for dual axle setups. Always check your state's DOT requirements for width and overhang coverage.
Shop HEYDAY Truck Parts
At HEYDAY, we carry mud flaps and quarter fenders built for 18-wheelers, Peterbilt, Kenworth, Freightliner, and more. All products ship from stock — no waiting, no compromises.
Shop our full range of semi truck fenders and mud flaps today.
