Let’s talk about the F word. Fenders

My next “gravel” bike would like the option for fenders.
What are you go to fenders and how do you go about adding the mounts? Max tire size?

Thank you.

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YES ALWAYS!

I might be biased living in places with this weird thing called “rain” but fenders to me are a necessity on any bike that isn’t an mtb or race-specific frame. I am a bit of a fender snob and only run nicer fenders - imo Honjo are the gold standard and Velo Orange are a close (but more economical) second. You can get Honjo fenders from Sim Works, EAI, or Rene Herse - there’s a bit of overlap but it’s worth checking out all the different options.

I generally design around the widest fender I can for maximum coverage - for example the all-road bike I made has clearance for 62mm H80 fender, but will usually see 42mm tires. Sim Works is nice in that it gives you the full dimensions of the fender so you can put your bridges in the exact right spot, along with recommendations for tire size.

As far as mounting locations, I tend to stick to a chainstay bridge, seatstay bridge, and some sort of boss near the rear dropout. There’s a bit of flexibility there - sometimes I’ll put a water bottle boss on the inside of the seatstay near the dropout for “stealth” mounting, but sometimes putting a rack mount boss near the dropout is easier and multifunctional.

If you want to get fun and funky with it, you can also do what I did for my PBE show bike last year:

It’s hard to see in the photo, but I put a water bottle boss directly on the BB, one on the seat tube, and used a regular bridge on the seatstay for the third. I used some spacers from McMaster to get the fender at the exact right distance from the frame.

Here’s another fun mounting method I did for one of my MADE show bikes. I didn’t want a full bridge so I made these little arms with machined stainless balls:

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Great. Thank you for the info. I like the bottle bosses on the BB and ST.

+1 to everything @liberationfab said.

Some tips:

  1. Your fender width should be around 20mm wider than your tire width.
  2. Fender gap from the tire should be around 20mm.
  3. While fender line should be consistent for high fives from all the rando nerds, it’s not a bad idea to slightly reduce the fender gap at the leading end so any rock that makes it between the tire and fender will be small enough to spit out the other end.
  4. Expect to take a loooong time to properly install fenders. Don’t rush it and don’t force the fenders to fit. There should be no build-in stress in the connections.
  5. Rene Herse includes a really nice instruction manual when you purchase fenders from them. If this is your first attempt at working with aluminum fenders, the manual is super valuable.
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Another great resource for learning how to install metal fenders is at How to install metal fenders, Part I: achieving a proper arc radius – Eléctricalités A.T.

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4-part series. The one on dimpling fenders to clear tight forkblades and stays is valuable.

Mark Beaver
Tamarack Cycles

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Long unsupported spans of fenders will eventually crack. Fenders mounted with only a single mount will wiggle annoyingly and then crack.
Some builders try to get away with skipping the chainstay bridge and using a boss on the back of the seattube instead… This will crack and fail also.
Fender bosses in the bridges, racks and fork crown should be normal to the fender. Little 90 degree brackets will crack and fail.
Hahn" resident rando nerd"Rossman

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Somewhat related to this conversation:

Titanium fenders? Amazing. I wonder how they get that shape. It must not be easy, given the price.

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I talked with them about the manufacturing process when they were first launched and it is definitely not easy. Especially difficult given the propensity of titanium to work harden when formed and the tight compound radii involved. It’s a great recipe for cracking sheetmetal. I believe they had mentioned about 2 years of prototypes before it was ready for production?

This is probably the most impressive thing that I’ve seen in the framebuilding world from a manufacturing engineering point of view.

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I’d hoop roll a tube to the right radius, then cut along the centreline with a bandsaw and curved guide profile to give a fender shaped blank.
50% wastage of materials, but pretty quick, and uses standard tooling.

The degree of springback would need to be tested, so the blank ends up at the right radius. The remaining material radius will spring open when the compression side of the tube is removed.

I used this method on hundreds of wheelguards for racing wheelchairs. Aluminium, so the springback is far less than with Ti, but should work in principle.

All the best,
Dan Chambers

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Wow, that is REALLY cool! It looks like a hot rod!

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:slightly_smiling_face:

All the best,
Dan Chambers

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Thank you for all the info. It will help a lot on the next frame build.