A rear fender for bikes with low clearance.

Most road bikes sold today have no way to mount a full set of fenders.  There are a few commercial options that are easy to install and work ok, like SKS Raceblade, which are short fenders attached with rubber straps. Being not very into commercial options that are easy to install, I decided to make my own after reading a post on BikeForums by stausy, who was looking for a good way to attach fenders to his bike.

The bike I usually have here at the shop is an older Giant OCR Elite, set up as a single speed with a White Industries ENO Eccentric Hub. With the hub rotated upwards, and with the shorter replacement fork I have installed, it uses short reach brakes, rather than the usual spec medium reach.  With 25mm tires, there’s not enough clearance for a normal fender under the rear brake.  Another problem is the lack of a chainstay bridge with the carbon rear end.  To mount the fender at the chainstays, I had to make this bracket, which attaches to the frame with the bottom bracket cable guide screw.

At first I tried to make one of these by flattening out a p-clip and bending it to the right shape.  It was far too flexible, so I made one out of the clamp band from a Shimano STI lever.  This just happened to be exactly the right size for my bike, about as big as a #10 p-clip, for reference.  You could make this bracket out of just about anything you could bend and drill two holes in.

Before

After

These are really (really) hard to bend, but eventually I got it into this shape, which is about what you see mounted on the bike above.  I made it so that it would press up against the frame when tightened down, so it wouldn’t vibrate. I don’t think it would work so well without being supported in the middle somehow.

Fitting this to the frame gives you your first fender attachment point, and a good reference point for your second.   To get the fender to fit between the chain stays without rubbing the tire I needed to cut some material off.  Make sure you line up the fender where you want to attach it to the mount, I used the third hole up from the end to extend the fender a bit below the bottom bracket shell.

I marked the fender around the chainstays as a guide to where I would cut the relief, while keeping it aligned with the bracket.

I then cut into the fender, removing a small amount at a time, and test fitting as I went.  It’s best to remove as little as you can because the fender gets weak quickly if you cut the sides out.  I used a pair of diagonal cutters to cut the fender, and a half-round file to smooth out where the fender contacted the stays.  Here’s what it looked like in the end:

Plenty of clearance to go around now, and no rub at the chainstays.  If you’ve got a steel or aluminum bike, and can’t fit the fender between the tire and chainstay bridge, try using a bracket and modifying the fender to mount it in front of the bridge.

Now that I had the fender attached at the chainstays, I could measure where to cut the fender in half to clear the seatstays and rear brake.  Make sure you take into account the shape of the bracket that clips on to the fender, it might extend a bit forward of where it bolts into the frame.  I didn’t do this, and have a larger gap in front of the seatstays than I needed to.  This design of carbon seatstay uses a normal recessed nut to attach the rear brake, so I was able to substitute it with one of the Sheldon Fender Nuts.  Here’s the hardware I used to attach the fender and brake:

The Sheldon Fender Nut works just like a normal recessed brake nut, except it has an internal thread that accepts a 6mm bolt.  I used a long 6mm bolt and a spacer to attach the fender bracket, like this:

I have no idea where this spacer came from, but it was just right.  The Sheldon Fender Nut anchors the brake caliper, then the spacer, the fender bracket, a washer, and the bolt attaches the fender to the bike.

To attach the rest of the fender, I made a bracket that comes up from the brake bolt, over the brake, and back down near the wheel to anchor the fender.  Here’s the part I used, the single stay from a Blackburn Rack:

I bent it using a vise and some pliers, and attached it in front of the brake behind the seatstays.  You should probably make this bracket and attach the fender to it, before attaching the brake and front portion of the fender, or you’ll just have to take the brake off again like I did.

It’s important to make sure you leave enough room under the bracket so it doesn’t rub on the brake at all.  I had to make mine go up pretty high to clear the triangulated arm of the Rival brake.

After this, I lined up the rear portion of the cut fender under the bracket, and drilled a pair of holes to attach it.  Using a center punch is really helpful when drilling holes in fenders to keep the drill from walking around.  I found a couple of short 5mm button head bolts with nylock nuts, and attached the rest of the fender.

There weren’t any eyelets at the dropouts, so I attached the fender stays to the seatstays with p-clips.  Make sure your p-clips are small enough to tighten down completely.

The finished product:

The fender almost looks like it belongs there.

Addendum: After putting this article together I was able to put a front fender on, by just cutting the front of the fender past the bracket off, and using a Sheldon Fender Nut to attach it to the back of the front brake.  I get some spray splashing back from the underside of the fork crown, but not that much.  If it gets to be too annoying I’ll probably build a bracket similar to the one I used on the rear.