How I Installed a Full Fender and a MudFlap On a Mountain Bike with Disc Brakes (photos)

My MTB commute journey began a couple of years ago. One of my first lessons was how important fenders are – riding around town without protection from the water and the mud thrown by the tires could turn one’s bicycling adventure into a very unpleasant and “contaminated” experience.

I had to get fenders and began buying them in bulk.

My first set consisted of MTB fenders inspired by dirt bikes. The front attaches with a butterfly mechanism to the tube of the fork whereas the rear clamps onto the seat tube.

I wanted to like them, and I’m sure that they have some value if you’re doing pure mountain biking thanks to the great tire clearance, but ultimately, those fenders simply sucked for town commuting.

My next set consisted of “strut-less” plastic fenders. The front attached only to the fork’s arch whereas the rear had two points of attachments – the seat tube and the brake bridge. They offered better protection but were unstable, and the front was too short.

After a few more unsuccessful attempts, I decided to go for the real deal and invested in a set of wide full fenders that could accommodate hybrid and MTB tires.

But as you know, most MTB forks are not designed for full fenders. The entry-level Suntour forks have threading in the middle of the arch but most other models do not.

My case was even more complex since I have a Manitou fork that comes with a reverse arch by default.

Nonetheless, I found a way to make it all work. You can see the final result in the image below.

Let’s dissect the above.

My first job was to connect the struts to the legs of the fork.

This is where I got lucky.

During one of my previous attempts to find a good fender, I’d purchased the popular Zefal No Mud.

This is the classic Zefal No Mud Fender

This fender is too small and narrow for a mountain bike in my opinion, but it does have a genius mechanism that securely connects it to the legs of the fork.

I broke mine on purpose to use the mounting system as a way to attach the struts of the full fender to the fork of my bike.

My purposefully broken Zefal No Mud

Before installing them, I wrapped the fork legs with duct tape to make the design sturdier and prevent scratches.

Then, I just tightened the mechanisms and instantly had eyelets for fenders.

In the image below, you can see a close-up of the mounting system as well as how the strut attaches.

If you aren’t lucky like me to have bought 4-5 sets of fenders to afford to break one of them, you can use a pair of ultra-large P-clamps a.k.a. P-clips.

Normally, those things are designed for pipes or cable management, but if you can find one that is big enough to accommodate the diameter of a MTB fork’s legs, you can use it to attach a fender’s strut.

Make sure to use threadlocker like Loctite blue for the bolt. Alternatively, you could also buy locknuts with rubber in them.

The goal is to prevent the attachments from untightening due to the frequent road vibrations.

Attaching the Fender to the Arch of the Fork

The next step is to connect the fender to the arch of the fork.

If you have an entry-level fork, chances are that you have threading on it. If that’s the case, you can rely on the attachments that come with the fender.

But since my fork is Manitou Markhor, I had to deploy a different strategy.

My initial plan was to come up with some sort of stylish anchor point, but I didn’t have time and decided to rely on zip ties.

I wrapped the arch in old inner tubing to prevent damage caused by excessive friction, drilled four holes in the fender with the awl of my Swiss army knife, and slid two wide zip ties through the openings.

Then, I looped them around the arch and tightened them as you can see in the images below.

The zip ties loop through a set of holes parallel to each other.
From the front

The only downside of the zip tie method is the look. It isn’t professional.

Nonetheless, the fender is pretty secure. If you decide to go this route, make sure to buy UV resistant zip ties as the sun could wear the common ones fairly quickly.

The MUDFLAP

At first, I was pretty happy with the fender, but I rapidly realized that it wasn’t sufficient. My feet were often getting wet from the spray as the fender wasn’t reaching low enough.

I decided to make a simple mudflap by cutting a trapezoid piece from a plastic file for documents bought from the local office supply store.

I punched two holes, with my Swiss army knife of course, and attached the mud flap with two bolts, a washer on one side, and two locknuts.

I put the nuts on the opposite side of the wheel to keep the clearance between the mud flap and the tire as large as possible.

Questions

Is the fender sturdy?

Yes. I’ve done small bunny hops and jumped some gaps even though I use the bike mostly for commuting. There’s some movement but nothing out of the ordinary.

The mudflap sometimes brushes tall curbs, but overall, the construction has been pretty solid for me. I’ve been using this set-up for over a year now.

Is the fender effective?

It’s significantly better than everything else I’ve tried for commuting. I expected a little more from the mud flap, though. One of the problems is that it reflects water, especially at higher speeds, but this is the case even with professionally made mudflaps.

This project should do the trick if your goal is to commute on a mountain bike or a hybrid with a suspension fork and no eyelets for fenders.

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