TallRider

Fork-mounted brake cable hangers are supposed to help avoid brake judder that often happens when using a top-of-headset cable hanger with cantilever brakes. This is particularly an issue with larger bikes (that have longer head tubes and fork steerer tubes). The mechanism, as I understand it, involves steerer tube flexing, which leads to alternately grabby-then-loose-then-grabby brakes. Explained here by Lennard Zinn.
Andrew Stewart points out that this is particularly a problem on relatively modern cyclocross bikes using cantilever brakes on carbon forks with aluminum steerer tubes. Most older (and modern) bikes using steel forks (including steel steerer tube) with cantilever brakes don't have a problem with brake judder, even with cable hanger atop the headset. That said, I have experienced significant cantilever brake judder on one older steel bike. Note that I am 6'5" and the bike in question has a 21 cm head tube, so lots of steerer tube that can flex and cause the judder.

My question here: is it possible to install a fork-mounted cable hanger on an older steel bike? Most newer-ish (pre-disc) 'cross bikes don't have headset cups protruding well beyond the fork crown, whereas bikes with 1" headsets always have this issue.

This picture shows a Tektro fork-mounted cable stop attempting to fit on a Trek 520 touring bike with Velo-Orange threaded headset. The headset gets in the way of the cable hanger. This cartridge bearing headset has 45mm diameter headset cups, but the narrowest-loose-ball headset cups I've seen are 41mm diameter, which would only buy me 2mm (radiums = 1/2 diameter) of space. How long of a spacer would you trust before starting to worry about shearing, or at least significantly bending, the bolt which holds the hanger to the fork crown?

nfmisso

It depends on how strong a bolt is used. With a class 12.9 bolt, all the way thru to the fork, same grade nuts and a cr-mo spacer, 10-12mm should be okay. The strength of the fork will come into play. You could fill the end of the fork around the bolt with low temp metal: https://www.amazon.com/Low-Melting-P.../dp/B001QUVQGK to help stabilize the fork.

TallRider

I asked a friend who does this regularly at his shop, and he sent me an example picture and had the following advice:

It sounds like the bolt will be fine with just enough spacer to let the brake bridge clear the headset cup.
That said, his picture shows a bike with a fork crown that is thicker (front-to-back), as well as a less bulky headset.
The bike I'm working on (pictured in my initial post) will need thicker spacer(s).