cormacf

I have a bike I absolutely love (a Lynskey Sportive Disc), but I love it even more when I'm rolling on 650x42 than I do with 700x28. The only problem is that I can't fit unmodified 650b fenders on the back--the fork has oodles of clearance in the front.

I can't find my calipers, but eyeballing it with a ruler (imprecise, because there's a 700x23 tire in there now and it's locked in a trainer, I'd guess I probably have 48mm of clearance where the fender would be at its widest, so I'd need to cut into the sides of your typical 50mm fenders a mm or 2 (to be safe) on each side.

1. Has anyone done this successfully and had no long-term problems?
2. If so, structurally, which fenders would be better to cut--plastic or AL?

Thanks!

phughes

I wouldn't give it a thought. I trimmed my fenders in 2011 to fit my Surly LHT. No issues. They are Planet Bike Cascadia fenders. Mine had to be trimmed near the bottom, but I wouldn't stress over trimming them. Fenders have a history of needing fitting.

Koyote

I agree with phughes . Fenders often must be modded a bit for a good fit. I think metal (steel or aluminum) is probably best for your purpose, but will admit that I have little experience with plastic fenders.

SpedFast

I have Planet Bike's plastic on one of my old steel steeds and had to mod them to fit. I think they were intended for 700c wheels and not 27" with 32mm tires. If you really need them then mod them to work. I used a dremel with little grinder on the plastic and it cleaned up really nice. Just try not to scuff the exterior surface. Mine have that black glossy look on the exterior with adjustable stainless mounting rods.

cormacf

Thanks, all. I'm trying to build a set-and-forget config for randos, and the 650s are just more comfortable for super-long rides (plus, I already have a 650b dynamo wheel built up), so I'll give it a go.

79pmooney

Exact material and method of construction matter. Aluminum - it may have a rolled or folded edge. If you cut it where it is seeing bending while in use, you will have removed the reinforced edge and weakened it. (Usually true of plastic fenders as well.) Plastics for fenders vary a lot, The soft Planet Bike plastic cuts neatly with a sharp trim knife and is not crack prone. The hard plastics on many fenders is crack prone and the dremel and good rounding is a sound choice. I've have very good luck tailoring the Chromo-plastic (or whatever their term is) fenders from SKS but I make the cuts in a key place structure-wise, I reinforce the inside with fiberglass and epoxy.

Reinforcing I have done - shaped aluminum sheet to the inside of the fender, drilled out the fork crown bracket rivets and re-riveted or machined screwed though the bracket, fender and aluminum sheet underneath to fit narrow forks and prevent fender shimmy. (Planet Bike.) And I've hacksawed through the flanges of an SKS rear fender, stretch it to be a full 3" longer, then epoxied fiberglass inside to hold that stretched shape. (SKS . To stretch the fender and allow several inches of fix gear hub travel in the dropout.)

Edit: Another approach - cut the fender at the seatstays and use a "reacharound fender bracket" from River City. https://www.rivercitybicycles.com/pr...ckets-4486.htm I've never used them but I know many who do. They work very well. I made my own for that SKS on my fix gear. (I hadn't seen the local River City ones yet and mine is basically my invention. But we arrived at nearly the same place so I can vouch for those others. (And they humbled me on finish, workmanship and looks.)

rumrunn6

plastic

the whole reason I justified buying a rotary tool was due to a fender install. bought some rivets too. take your time, be patient, post up some pics, others will chime in & help you. they may kick yer butt a little but in the end you'll be wiser for it. I think most of my wounds have cleared up ... ;-)

btw in order to get around really tricky spots, one can also cut a fender in 1/2 & mount the 2 halves independent of each other

ironwood

I have cut plastic fenders to fit, and found a crack developing at the cut.


I have VO aluminum fenders on a couple of bikes. To make them fit at the seat stay, I simply dented the fender slightly. On one bike I indented the fender at the chain stay, on the other i cut the fender to fit. I think cutting the fender at the chain stay is better, and if I remove the fender on the first bike , I'll cut it to fit.


Bicycle quarterly has had a number of articles on fitting fenders.

rm -rf

Is this for fitting the fender in between the seat stays, or at the chain stays down by the crankset?
Or is the fender too tall to fit under the brakes?

rm -rf

I have Portland Design Works 700 - 45mm fenders. They are quite/very expensive, but well made. It's aluminum, with no rolled edges, so bending or trimming is easy. I like the aluminum stay design, easy to install.
I had to extend the brake bridge attachment with a small length of 1/8 inch thick aluminum, with two holes drilled (the supplied hanger was just slightly too short, so I bolted this on as an extension). And I got a selection of nylon spacers and longer metric cap screws at the hardware store to reach my frame's bottom bracket fender bolt hole. That worked well.

I think my one complaint is that the front fender could extend farther forward.

PDW 650 65mm fenders

Kedosto

Got nothin’ to add other than the fact that on more than one occasion I anticipated hacking, cutting or grinding only to be pleasantly surprised that none was necessary. Fender mounting is quirky like that.

In your case, the 650b x 42 are really close in diameter to the existing 700x23’s. You might be surprised.