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I'm no expert, but I was thinking about doing this and the big think that came to mind was reinforcement. The rear triangle wouldn't be as much as an issue as the fork--more force little option to brace it. However, it wouldn't be hard to swap the fork for a disk compatible one.

You can find adapters out there. I had to get one for my rear brake, the 2002 fisher did not have the mounts on the frame. So it was a $14 adapter, but worth every penny.

i have mig'd a few of these tabs on some projects og my own. scroll down to frame parts and you can see 'disc tabs'...

http://ticycles.com/TCF/hardware.html

you can then find one of several locals that do a nice job TIG welding thin wall bicycle tubing. Mike Brown from Maestro Cycles could get this project turned around for ya in short order....

http://maestrocycles.com/custom-bike-frames/

Based on my understanding, it's a bad idea. Basically what Nick said regarding reenforcement.

Something might be doable on the rear stay, granted there is enough metal there to support both the weld and the brake torque. It's not something I would even consider unless I found a frame shop that has experience with such a modification.

It would be cheaper and make more sense to just buy a disc fork rather than trying to modify it.

Have you considered using v-brakes? Mini-v brakes will work with STI/Ergo shifters and Tektro has some reasonably priced options

I've seen a Salsa Vaya disc fork on ebay for just a little over $100... I've considered throwing that on my Trek 520 to replace the v-brakes. I wouldn't even bother replacing the brakes (in my case) but given my desire to change out the shifters I need to change the fork and grab a BB7 road caliper. .

http://www.ebay.com/itm/271088405247?_trksid=p5197.c0.m619

[double post]

pbeaver, where did you find an adapter for $14? What kind of adapter? Similar to the tabs in Lenk's link?

There is a Surly fork that looks like it would work for me. Its about $110. Add in a BB7 calliper an disc for another $70 or so, that would put me in the $180 range. Then I'd also have to find a compatible wheel. I haven't been able to find one. Any suggestions? Seems like it would be a pricey switch even for the fork. I wonder if just switching the front brake to disc brakes would be sufficient? I kind of dislike that kind of asymmetry though.

I highly recommend trying a quality v-brake first.

With salmon kool stop pads.

dmtroyer, did you have a particular brand or model in mind? Or at least some quality to look for?

I have Avid Single Digit 5's on the 520... they've been around for a while. I don't recall ever having a moment where I thought "gee, I wish that I had my disc brakes today." Actually, I have thought that... but not while riding. I like the adjustibility of disc brakes better and the .5 seconds less time it takes to remove a wheel. :p Seriously, save yourself the headache and go with v-brakes! Money spent on a disc conversion is better spent towards another bike! ;)

According to what I read on Sheldon Brown's site, if I went to v-brakes I'd also have to switch to special brake levers. I have shimano tiagra shifters/brakes on this bike. What are you using? I am using salmon kool stops right now. They work alright, but squeal horribly despite toe-in.

I'm not currently using STIs (although, I am in the process of swapping out the levers for a campy 10spd system with mini-v's). If clearance for racks isn't an issue, mini-v's will work without question; lots of cross guys are doing that. I'm not sure how they will fit with racks, but I might find out soon. :p Another option is the travel-agent, but it's not the prettiest option: http://problemsolversbike.com/products/travel_agents/ Also, if you grab a pair of the current gen 105 or greater (the ones with the cable routed under the bar wrap), they have a different cable pull and some people are reporting decent braking with standard v's... Of course, that's just internet word fo mouth.

Brybot, mini-Vs are your ticket for road levers. The lever arm is shorter, so your cable pull ratios should be spot on. I use Tektro 926AL 8cm mini-Vs with Koolstop Salmon cross pads on Dura-Ace 7800 shifters, and it's incredibly powerful. Maybe too powerful.

+1 on tekto mini v-brakes. I just put them on my cross check with road brake levers.

That sounds like a good option, but I've got both fenders and front/rear racks. I guess I forgot to mention, but this bike is my commute/touring bike and I frequently have heavy loads on it which make braking even more of a problem.

I'm going to try the Tektro RX5 out (especially since rice rocket states that the 926 "maybe too powerful.") LOL Maybe I'll go with the TRP CX9 if someone wants to buy them for me! :p If you can fanangle the RX5 to work with a rear rack and use a disc fork in the front... I don't know. That's my plan, but I haven't gotten around to making it work yet.

So I ended up trying a total of 3 different brake pads with a variety of yoke angles and toe in angles but nothing fixed the shudder. Finally, at the recommendation of the kind people at Performance, I tried a new canti brake, the Tektro CR720, rebranded as a Forte. Interestingly, this seems to have cured the brake shudder and I'm finally getting good performance. The brake pad is a smaller road size as opposed to the longer mountain style that was on the Tektro Oryx stock brakes. I'm not sure if it was the pad length or that my original brakes were just defective. Either way its fixed. Thanks for all the advice.

brybot wrote:

So I ended up trying a total of 3 different brake pads with a variety of yoke angles and toe in angles but nothing fixed the shudder. ... .

Sounds to me like you need a Fork Mounted Cable Hanger. They work wonders for canti brakes.

@unicyclemike That was going to be my next step, but the new canti's seem to have fixed the issue. I may swap to a fork mounted hanger anyway just to increase rigidity. Thanks for the tip

Hurray for working brakes! Glad you found a solution.

I went the front fork route. I had a wheel sitting around so I had Thick order me a Surly disc fork and BB7 brake. My existing Tektro levers work for both the rear canti and front disc. It works great.