Fork Shudder SOLVED!!!.....
...well at least on my bike.
I posted this in the recreational CX section too (since I use my race CX bike as a commuter as well), but this mod works for race rigs as well.
Here is the story and what I did.
Bike: Empella Bonfire SL
Problem: INSANE fork shudder that I could not tolerate anymore. I've tried 5 different cantis (I know how to set them up), 4 pads types, different toeing settings, various hanger heights and even mini vs (which I hated). Nothing relieved the terrible shudder the bike was plagued with.
This is likely due to the [awesome] carbon fork that Empella designed not having the provisions to mount a hanger in a front brake caliper hole like many new cx frames are turning up with. So, I was stuck with the under-the-stem-hanger which, I'm sure everyone knows by now, facilitates shudder for all that use it (in addition to making front brake cable routing sucky).
The issue became so terrible that I began to consider swapping the fork, but then came to my senses and devised a plan to get the cable mount off of the steerer and onto the fork somehow. You will need:
-a cheap aluminum MTB brake booster with a hole at top center. Mine was $7
-a Tektro straddle cable hanger with the allen screws for cable securing. $12 for 2
-a Tektro fork mount cable hanger. $12
The idea here is to use the booster to mount the cable hanger, thereby mimicking bikes that actually have a hole for mounting the cable hanger directly to the fork. If you have that hole, don;t read on as your problem is easy to solve. If you have a holeless fork like me then this solution is for YOU!
1) Ditch your straddle cable hanger and old straddle cable. Remove canti bolts from bosses.
2) The MTB booster will have holes that are wider spaced than your CX bike's brake bosses. Use a round file to enlarge the inner edges of each bolt hole opening until it fits the spread of your fork.
3) With the longer bolts that are included with the booster, install it over your cantis using the spacers that should have come with the booster. If none were included, you will need to space the booster about 3/4 of an inch off of the cantis (for cable alignment) with aluminum spacers.
4) Mount the Tektro cable hanger through the hole in the top of the booster (see pics). You want it "curving" toward the steerer tube. The hanger comes with a long nut like you's use on a road caliper in your fork. You can use this to mount it, but it would look pretty funny. I found a bunch of bits in my parts drawer to make the mounting a bit tidier, but functionally it is no different.
5) I use Nokon cabling on my CX bike, so I just added a few links to make up for the slightly lower cable position in the hanger. If you are running plastic housing you may need to cut and run a new piece of housing to get mounting length correct.
6) Instal the new straddle cable and the Tektro straddle hanger. I chose this one to avoid the bolt style hanger, as I knew it would be a tight space to work in. If you are more patient than I, you can just reuse whatever hanger you have and save a few bucks. For me the ease of the small allen screws was worth the $12.
7) Retune your cantis
All done! Even though this is admittedly a bit clunky looking, I was AMAZED at the instant departure of chatter. Power is better as well as modulation, even with the crappy Shimano cantis and v pads I have on there now. This absolutely solved the problem. Do it you your bike too!