Road Fan

Question is, how close to the ground should the bottom of a front fender rainflap be? Want to keep my feet, drivetrain, and the lower frame mostly dry.. Tires are 42 mm Grand Bois Hetres (actually 39 mm), at least for now.

Koyote

I’ve got Brooks leather flaps on a couple bikes… The only mistake you can make is not going close enough to the ground. I’d say get it about one and a half inches from the pavement. Remember, the whole idea of using leather – – as opposed to something more rigid – – is that you can go down steep driveways, over curbs, etc., and it will just kind of bend out-of-the-way.

PS: it might be a good idea to wash it off thoroughly and apply some leather conditioner every year or so… Though to be honest, I probably haven’t remembered to do that for the past couple years, and mine are both still going strong at seven years and eight years, respectively.

pdlamb

Long-winded answer: In my case, I've got to cross some lawn to get my bike from the back of the garage to the street. That means I'm dragging it through tall grass (until I get around to mowing it), and the long mudflap is great for sweeping up leaves in the fall, which then get jammed between tire and fender until either they disintegrate or I stop to clear them out.

On the other hand, it's really nice when the mudflaps are catching the spray coming off my front tire, so my shoes take longer to get soaked on wet roads. If you imagine (or draw with CAD) a tangent to the circumference of the tire, you want to place the bottom of the mudflap so it gets in the path of the spray going to your foot at the bottom and back of your pedal stroke.

Short answer: an inch or two off the ground in front for maximum effectiveness, maybe an inch higher if you're bothered about dragging. Four inches in the back -- it'll still catch the majority of the spray.

SpeedyBlueBiker

I would say about two inches off of the ground for both the front and the rear.

TiHabanero

When I commuted year round I made a mud flap for the front fender out of a sheet of foam that was used to line a back pack. It hung 1-1/4 inch from the ground and was 2 inches wider than the fender on either side of said fender. I came up with this design after finding the traditional narrowish and short mud flap did not offer any real protection when riding in slush. My home brew design lasted over 10 years and finally was given a proper burial when I stopped commuting in the winter months.

Keep in mind when riding in wet weather the front tire spray not only comes off the bottom of the tire directly back at the bike, but also fans out as wide as the feet on the pedals. Make the thing wide, my friend.

Maelochs

I have seen people add a split two-liter bottle to the bottom of a fender, with a split old tire underneath it, to get down as low as possible---the rubber flexes as leather would, but if it gets toen up, no one cares---you can get ten out of a single used tire.

Road Fan

Thanks, all! 1.5" sounds like a good target. The point about flexibility is well-taken. I have a new set of fenders and will move my Berthoud flapper over to it, but that flap has not seen water for a few years. I may want to to do a full soak and scrub, then use some gentle hear to "motivate" the absorption of the oil. Got a choice of Proofide fron the tallow days (a ittle smelly, now!), some newer veggie Proofide, and regular veggie Obenauf's. The soak also gives me the chance to curl the leather bottom back, togot the most of the "blockage geometry" pdlamb is talking about, even though we're just improvising here! Maybe if I can score some more scrap leather I can try a few concepts, though I don't really have bandwith for more projects at the moment.

BobbyG

On my old commuter I repurposed an old yoga mat and cut flaps to experiment with length. I ended up less than an inch off the ground.
On the new commuter I got SKS longboards and rotated them backwards by attaching the bracket to the rear of the front fork crown. I never felt I needed a flaps on that one.
My only other fendered bikes is my 20" folder whose "flap" is about 4 to 5 inches up. On that bike my toes will sometimes get wet going through puddles and on wet streets.