How to Make a Fender Extension
Fender extensions are soft extensions of the main fender. They are all but necessary to keep you truely dry in wet and wintery weather, fenders alone do not provide enough protection. If they hit something they will bend instead of break. These can be a soft plastic, rubber, fabric or any similar material. There are many ways to make a fender extension, here are the techniques I use.
Duct Tape
This is quick and easy and takes all of 10 minutes. It is not a permanent fender extension, but I've had them last for well over a year. It doesn't make your bike more visible, but it does give your bike a more piece-of-junk look, which can help prevent theft.
1) Clean your fender. Dirt and stuff well prevent the tape from sticking, clean it good, let it dry.
2) Stick a strip of duct tape to the center inside of the fender. This strip should be twice as long as you want the fender extension to be. Make sure it hangs straight down.
3) Carefully fold the duct tape smoothly back on itself (sticky side against sticky side) and attach the remaining bit to the outside rear of the fender. A few wrinkles are OK, they will add charactor. I like to have between 2 and 5 inches of duct tape stuck to the fender to be sure it's secure.
4) Repeat the process, but move the tape over a bit and angle it outward so you start to form a wedge shape. On strip on either side of the first one should do. Be sure that the new strip overlaps and adhere to the previously laid down strip.
5) Once you have the three strips of tape on there, I usually add a finishing piece of duct tape around the bottoms of the strips to tie them together. Sometimes I will cut the strips a bit to get a more uniform shape, but this is not necessary.
The bottom of this fender extention, on my city bike, is made out of duct tape. You can easily see how it was put together. Since the top of the fender extention was alreeady wide enough, these three strips of duct tape simpley parallel each other instead of fanning out.
Reused Platic Container
There are plenty of plastic containers you can use to make a fender exension out of. I prefer liquid laundry detergent containers because they have an optimal blend of strength and flexibility, making them ideal as a perminent fender extension. A cheeper and more readily available option are plastic milk or paper jugs.
1) Cut apart and wash your container. Try to cut it into the biggest relatively flat pieces as you can get out of it. Clean it all real good.
2) Cut your fender extension to the desired shape. The top should be as wide, as your fender, the bottom should be two to three times the width of the fender. Test it on your bike, it should be long enough to be within 1-3 inches of the ground. If you can not come up with a piece that long, you can add a fabric or duct tape fender extension to it to make up the difference.
3) Add reflective tape. This is not necessary, but if you've got this nice big flat surface on the back of your bike, it's in your best interest to use it to make you more visable. The stuff they sell at bike shops is usually crap, try to find the really bright stuff the truckers use, available at auto parts stores. Expensive, but worth it. you may wish to switch steps 2 and 3 so as to have a nicely finished product when you are done, but it does waste some of that expensive reflective tape.
4) Attach the fender extension to the fender. This can be done with a) duct tape, b) pop rivets, or c) nuts bolts and washers.
a) Duct tape will work,but the weight of the fender extention will cause it to fall off eventually. Not a big deal for cheep piece of a milk carton, but if you've invested in making something nicer, duct tape is not ideal.
b) Pop Rivet. Pop rivets are a great way to attach lots of things together. They are certainly the best way to attach your extensions to your fenders. If you can't find someone to borrow a pop rivet gun from, it's worth buying your own. To use, drill a hole through the fender and the extension (it works with fabric too believe it or not) just big enough for the pop rivet to fit. It is kind of hard to get the alignment right so be patient, an assistant is very helpful (one person holds them together, the other drills). Then, use the pop rivet gun to do it's thing, use washers if you've got them. Be sure the more flush side of the rivet is on the inside of the fender so the little nub doesn't catch on the tire. At least two attachment points are needed, three is usually the most you would need.
c) Nuts, bolts and washers will work too, especially if you'll want to be able to easily remove the extension (to remove the pop riveted extension, you need to saw through the pop rivet). The trouble with this set up is that the head of the bolt sticks out relatively far and can rub on the tire and of course, sometimes these things come unscrewed. So, choose a fairly flat headed nut. Washers are necessary to spread the force over a larger area of the fender. Also, be sure to use some lock tight a nylon locking nut to keep it all together. Drill a hole in the fender and extension, install nuts and bolts and you're done. At least two attachment points are needed, three is usually the most you would need.
This photo taken of my city bike a few months ago shows just the plastic fender extention, showing off it's reflective safety goodness.
Fabric
Fabric works well for fender extensions, especially for shorter sections. If they get too long (4 inches or more?) they tend to flap around a lot and can get caught on the tire.
Want to know where to get good quality outdoor fabric to work with? Sometimes you can find what you need at your local fabric or outdoor store. Otherwise, here's one source, and here's a list of a buch more sources.
1) Choose your fabric. Thicker. stiffer, more durable fabrics work best. Something like denim, but my wife and I prefer Cordura nylon. Expensive, but tough and water repellent (doesnıt get soft and squishy when itıs wet).
2) Cut your fabric to shape. Again, too big of a piece will flap all over, certainly keep it under 5 inches long.
3) Sew reflective fabric to your primary fabric. Good reflective fabric is expensive, but I think itıs worth it for the safety factor, especially since it GREATLY increases the visibility of your bike. Also, sewing those two sheets of fabric together makes it just that little bit more stiff, the Cordura/reflective fabric combo is almost the perfect combination of supple and stiff.
4) Drill holes in your fender with a power drill. At least two, three is usually the most you would need.
5) Put hole in your fabric. It can be tricky to get these holes in and match them to those on the fender. For thicker, stiffer fabrics, you can actually just drill right into the fabric as you drill into the fender. Itıs very tricky, it helps to have two people, and it usually results in fabric flailing around on the end of your drill bit, but it usually works. If youıre using synthetic fabrics you can heat up a nail or something and poke it through the fabric which will melt and leave a nice hold with a solid edge that wonıt fray.
6) Install with pop rivets or nuts and bolts. Duct tape will work as a temporary solution, but it wonıt hold that flapping fabric mud flap on for very long. Be sure you have washers on the fabric side to help prevent tearing.
A photo of my wife's touring bike shows a fabric fender extention hanging down from a plastic one. They are hanging off of the wussy little fender extention that came with these Planet Bike fenders, which made the whole unit flap around a lot, until we got rid of the planet bike extension.
Mix and Match
Most of my fender extensions are made by combining two of the the above methods. By doing this I not only get a fender thatıs long enough, but the extension gets increasingly flexible as it gets closer to the ground. So if I clip something or pop a wheelie or something no damage is done, and yet the top of the extension is more sturdy and stable.