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Chris_W 12-03-13 05:13 PM

Rear Fender/Mudguard Length and Shortening
I'm thinking about trimming my rear fender down. The only advantage of a long rear fender or adding a mud-flap to it is to benefit people who are riding behind you. When riding around town, I'm mostly riding alone, especially when it's raining. Plus, I'm getting ready for a long-distance, self-supported ride next year (over 2000 miles in 2 weeks, the Transcontinental Race) for which I want to trim off all the weight I can while still having full fenders; and drafting isn't allowed in that event, so there shouldn't be anyone on my wheel.

So, how far do you think I can go with fender trimming if my goal is purely to keep myself dry? It's currently about level with the axle and has no mud flap. Of course I can start experimenting easily enough, but does anyone have some useful advice/experience?

nyrikki 12-04-13 02:58 AM

This is a very rough rule and ignores the complex physics and wind but if you look down from where the highest portion of your body is you should only see fender.

Of course the real issue is that once you start to really shorten a fender the water that is ejected onto it will drip off onto the tire and if short enough into the cassette. This will dramatically increase the amount of grit and dirt that your drive train is exposed to.

I live in an area where I have to cross a ship canal where I have to walk the bike on one wheel and I also work in a place with vertical hanging bike locks. Both of these require me to have a bit shorter of a fender and mine is cut at about the 10 o'clock position. I do have a planet bike "hardcore" fender that has a bit of a flap on the back so the drip edge is behind the tire. The rooster tail at 18 mph with no wind seems to be about two bike lengths long or below safe following distance in wet conditions IMHO.

Look for pictures of "race blades" IMHO that is as short as I would go if you use it in the rain often. The angle seems to be typically in line with the top of the chain stays. All of this is just opinion, but in my opinion, rain is just wet but road grime filled water just plain nasty.

Note: I have a "cascadia" front fender because dry feet rule but this would not be "ultra-lightweight"

Chris_W 12-04-13 09:59 AM

Thanks a lot nyrikki, that's exactly the kind of info / experience I was looking for. I know the Race Blade fenders, and your suggestion of matching their length seems like a good one, I think I'll at least start with that.

As for the front fender, I agree that dry feet are more important than weight, which is why I have a full-length SKS model with a long mud-flap extension, it's probably similar in length to the Cascadias.

fietsbob 12-04-13 01:44 PM

you got a weird sense of priorities


Plus, I'm getting ready for a long-distance, self-supported ride next year
you wheelie-ing the whole way? , will it take you months to unscrew a few bolts?

wphamilton 12-04-13 04:23 PM

I've experimented just a little (you run out of clean white t-shirts too quickly to be real scientific about it). Short version, you need the fender to be down to the vertical tangent if you want to avoid splatter. Sad but true, any trimming will get you splashed.

Chris_W 12-05-13 01:25 AM

I've tried trimming my rear fender to about the 10 o'clock position (it was at 9 o'clock), and we'll see how that goes. The big advantage with this is that I can get rid of the lower set of stays, so the total weight saving was about 80 grams :) I already got rid of the upper set of stays by attaching the fender to the rear rack instead, which makes it really stable. I also got rid of the upper stays on the front fender, and that seems to be keeping it's position just fine.

My next step is to get a Planet Bike mudflap for the front while I'm in the US over Christmas because they look to be at least as long as the SKS one I have now, but a bit narrower, and so slightly more aero (I'll either be running 25 or 28 mm tires, so I don't need much width). Plus, for just $5 for a pair, it's worth a try.

I know all this won't provide perfect rain protection, but based on the photos from last year very few people had fenders at all, so my trimmed-down version is going to be way better than that.

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