Mudflaps: A Elementary Treatise on Their Design and Construction

After last weekend's very wet ride through rural and exurban Maryland, I thought it time to collect my thoughts on the subject of the seldom used, oft-misunderstood mudflap. Not merely a place to display lewd or political images on your semi truck or bike, they actually serve a purpose. Material choice, shape, and placement all affect how well they fulfill that purpose.

What is the purpose of a mudflap?

• Keep as much water off you and your bike as possible when riding on wet roads
• Keep water off the people riding behind you

The photo in this post by Jan Heine show how much of a difference a good mudflap can make in keeping your bike clean. But we are interested in going even further into the fluid dynamics that allow your feet to get wet.

Water leaves the tire tangent to the wheel in the direction of rotation. 

Another Jan Heine post demonstrates how much extra protection a longer fender provides.

But we are also interested other paths the water takes. When riding through standing water (anything deeper than 1/8"), the tire plows through the water sending it simultaneously back toward your feet and outward. Anyone who has watches a car go through a puddle at full speed will appreciate how much water can be moved and how far. A narrow mudflap will fail to stop the water that isn't thrown straight back. Result? Soaked feet.

I have also found that wide tires (more than 38mm) going through puddles throw up enough water into a fender that a significant amount leaks around the edges and onto your feet. So, the less water that is directed into the fender, the better.

Front fender wraps around the sides of the wheel, offering maximum protection when riding through standing water. (from book Rene Herse by Jan Heine)

So what is the ideal mudflap for very rainy rides? It should hang as close to ground as possible (less than an 1" away), it should be wide enough to provide protection from puddle tidal waves, and it should direct as much water as possible toward the ground and not up into the fender.

The result:

hangs low and wide and is attached behind the fender, not in front

Which can also be seen in countless classic photos of cyclists riding and racing on fully equipped bikes.

One of the lower-rung teams of the VCCA competes in the Coupe Herse in 1956. Lucien Detee leads Rene Delahaye. Marcel Pineau is in third position, apparently pushing a rider going through a  difficult patch.
(from book Rene Herse by Jan Heine)

I use 1/16" Neoprene on my fast bikes because it is more flexible in the wind while still providing good protection. On my utility bikes I use thicker 1/8" Neoprene.

Now that we've addressed the design and placement of the front mudflap we should note that the rear mudflap has different design considerations.

If you want to be courteous to the rider behind you, you would like to protect them from as much of the water off your back wheel as possible. This means a low hanging mudflap. Since the rear fender typically ends 12" off the ground, 12" of Neoprene flapping in the wind doesn't offer much protection. In this case, it is better to go with a stiffer material, usually thin, hard plastic. Perhaps a piece of a trashcan or something similar. It also doesn't need to be as wide because the following riders feet are considerably further back (roughly 3') than in the case of the front fender and your own feet.

Severna Park 200K

The DC Randonneurs organized the Pastries and Coffee 200k on Saturday, March 14th starting and ending in Saverna Park, Maryland. It was rescheduled from the 7th due to snow on all the roads. Here's a brief report with some pictures.

Weather was low 40's with a light steady rain at the 7am start. Rain continued until about 1pm with temps steadily rising into the upper 50's. Rain recommenced at 3pm and lasted until 5:30pm.

Ride start @7am

Things that worked?

1. Wool, Wool, Wool. Everything wool that I was wearing was great: socks (feet were a little chilly when soaked, but tolerable), gloves, hat, sweater, knee warmers. Other people had waterproof shoecovers and their socks were still soaked. Sometimes, less is more.
2. Waxed handlebar bag. Everything stayed dry and I was able to carry some backup clothes I didn't end up needing but gave me some peace of mind.
3. Full Fenders and mudflaps. I had to fiddle with my front mudflap a little before the start since it was scooping water up instead of directing it down to the ground. After that was solved, they worked beautifully. My feet still got soaked, partly from other riders who didn't have fenders, but the rest of me (jacket, and from the knees down) stayed a lot drier because of the fenders. And I'm sure other riders behind me appreciated the extra long coverage on the rear. I chose to keep riding with another person in part because they had similarly complete fenders and mudflaps.
4. Tweezers. Had to use them twice to pull tiny (very, very tiny) shards of glass out of tires. Thanks for the tip Jan Heine.

Things that didn't?

1. Could use a little more gear range in my drivetrain at the low end for longer or steeper hills, currently 35 inches, hoping to change to 27. But I've known this for a while, and change is imminent.
2. Some knee pain, not sure if it due to pedals or saddle adjustment. May trying changing pedals first.
3. Glue in the patch kit had dried out. Make sure to check your glue or replace glue every year or so.

Rode with Nick who had 4 flats. First was on the front tire. Second was on the rear, third was on the rear and was probably the same piece of glass as before that we didn't find. Fourth was on their car after finishing the ride. Two cans of fix-a-flat/inflator seemed to solve that enough to get home.

 Flat #1, on the front

Flat #2 on the rear. Near BWI Airport

What a day.

Post ride drop-off on New York Ave. in DC

Waxing Poetically

Would you believe I've been riding my bike?

Well, I have...and gettin' crafty.

I decided to add some wax to my Velo-Orange Grand Cru handlebar bag to make it a little more waterproof. I haven't actually ridden in anything more than a drizzle yet, but it pays to be prepared. Plus, who doesn't like to wax stuff?

Fifteen minutes of internet research led me to purchase 4 ounces of beeswax and 1 lb of paraffin wax.  One or both may be available at your local hardware store. Mixed in a ratio of 1 part beeswax to 4 parts paraffin, it makes a good wax for applying to cotton.

Some people seem to have lots of trouble applying waxing products to cotton ("had to throw away my Carhartt jacket, it was RUINED!!!" says The Internet). I'm not sure what they did differently, so here's what I did.

After heating in a jar in a water bath on the stove, I used a cheap paintbrush to apply to the cotton. The wax instantly dried when it hit the room temperature cotton. That's the white stuff on the bag below.

Then I used a hairdryer to melt the wax into the cotton and a rag to rub the wax in and take off any excess. Pretty straightforward, but time consuming. When finished, the cotton looks a little irregular, about the same as something well aged. I also did the leather accents, since beeswax and paraffin are ingredients in most leather waterproofing products. You can tell in the picture below, the leather on the left is a little darker, it got a little more wax.

I only did the front and the inside of the top. There is a plastic stiffener which is in between the inside and outside cotton layers. It runs down one side, under the bottom and up the other side, acting as a reasonable moisture barrier. And the rear pockets are covered by the top flap and don't get rained on as much because when riding, rain mostly hits the front and top.

Total time, 1 hr.

I would pay an extra $30 to have the whole exterior  of the bag treated like this during the manufacturing process.

Here are some pictures after riding for 11 hours on a rainy day. Rain was light but steady for 6-8 hours and there was a lot of road spray off other riders hitting the front of the bag.

Front, completely soaked on the outside

And completely dry on the inside

Ride more, even in the rain.