Canti issues - not a setup question
 

My problem is two-fold.

First, I have had an ongoing problem with the small washer/spring pin hole thing (not sure what it's called, photo below) rotating on the brake boss stud. I think I've solved it by cranking down the boss/stud as tight as I dare, but I've thought that before and it ends up loosening when I tighten the actual brakes on the boss. Any tips on getting that thing to stay still? Seems like a silly system - not sure if ALL cantis use that same plate or if it's just my shorty 6s.

Second, upon disassembly for inspection, the little pin on the spring kit that fits into the part that is rotating (photo below) fell out of the spring assembly and disappeared into thin air. I've checked ebay and the rest of the interwebz, but no replacement kits seem to exist for the shorty 6. Anyone have any ideas on anywhere else to try and find a replacement pin?

Lastly, I've considered just buying some shorty ultimates, but if they use that same spring-pin-washer-thing and it still rotates, I'm right back to square one minus $200.

Thanks for reading my wordy and poorly worded questions!

http://bikeforums.net/attachment.php...hmentid=324890http://bikeforums.net/attachment.php...hmentid=324891

I don't get it. The stop cam (washer) cannot rotate because the pin is engaged in the hole in your fork. If the fork plate itself is moving it's a defect, since it's supposed to be bonded to the fork or center post.

If you've somehow sheared the pin off the stop cam (part of the brake) you need a new one, and your best bet to to email the maker (or importer) and explain and buy a replacement directly. In many cases manufacturers will send the part at no charge.

I don't get it either. The fork plate (the silver-ish part in the center of the left photo, if I'm not using the right term) rotates freely when I loosen the boss stud. I'd actually never realized that it was supposed to be bonded to the fork. Once I started having problems and taking a look at it, I assumed that the "tightness" of the boss stud held it in place. If that's not the case...do I need a new fork?

I don't know the exact construction of your fork, but you probably have replaceable canti studs screwed into the fork. It might be that your fork depends on the studs being tight enough to immobilize the fork plate (the one with a hole).

You might look at the opposite side to see how the plate is retained in place (probably some kind of tab or pin). If it's purely frictional retension under the threaded stud, you can improve the hold by using some medium-course grit bonded to the back of the plate, or onto the fork with paint or nail polish. I'd paint the surface, and sprinkle on the grit while it was wet (or mix the grit into the paint and apply both together).

The grit will provide some mechanical bite securing the plate at lower torque on the stud. Before going the grit route, you might try making sure the front of the fork and back of the plate are clean and dry and seeing if friction alone carries the day.

Got it. Thanks for the help!

You probably are going to have to replace the fork and the brake. My cousin had the brake stud come loose and it damaged the pin. Even though I had the pin, I couldn't get it to stay in there. The factory press fit was shot.

There shouldn't be any press fit involved. This fork seems to have threaded replaceable studs (see hex at the base). so the stud is OK, or can be replaced, unless the receiver in the fork is damaged. The issue is keying the spring retaining plate (part with holes) and that calls for checking how the fork and plate were designed.

Odds are that with a bit of analysis the OP can solve this fork related problem. But he'll still have to source the correct (brand specific) stop cam for his brake. Hopefully the maker will come through for him, otherwise he now owns an expensive pair of paperweights.

That looks like the Nashbar cross fork.

If so;

The fork plate is glued onto the surface of the fork, and not with a particularly strong adhesive. unscrew the brake post and you can peel it off with almost no effort. The brake post - if tightened down enough - might pin it in place, but it might not. The entire brake boss assembly is remarkably flimsy.

I purchased mine for disc-brake applications, but was very surprised to discover how flimsy that brake boss was when I removed it. Made me glad I wasn't running cantilevers on that fork.

I will say though that as a disc brake fork it's been terrific.

I'll call SRAM. I own enough expensive paperweights.

Not sure if it's the same nashbar fork or not, but I wouldn't be suprised - it's on a BD motobecane cross bike. Maybe I'll try a touch of carbon paste on the back and then crank them down. Or maybe a touch of glue. Who knows.

BTW, when positioning the plate, match (mirror) it as closely as possible to the other one. Otherwise the difference in hole orientation will require more bias in the spring tension screws limiting the range of adjustibility for even balance.

If the fork is on a BD bike, then it's the Nashbar one. Or rather that they sourced the same open-mold generic CF fork.

The press fit pin is on the brake's spring assembly. You can't just put it back in, it's a press fit. OP-do you really want to be riding around with a carbon fork that has a messed up brake boss? A replacement fork shouldn't be too much, especially if you would consider steel.

This is a design issue. There are modifications that can be made to this fork & spring-plate to make it work. But without knowing the OP's mechanical-skills and access to machine-shop, precision measuring equipment and industrial epoxies, I recommend against it. Much easier, cheaper and safer to get a new fork of better design.

+1

One of my sus forks had exactly that setup. Instead of three holes covering an arc, there was a rather minimalist design with only one hole in a slender tab protruding from the brake anchor plate. You positioned the tab, torqued the removeable brake boss and you were done.
I had no issues with that feature as such.
Only thing was that on that particular design, there was a hexagonal base to the brake anchor plate(probably to ease positioning), so the plate got fairly thick, and the brake ended up some 10 mm further out than on the previous fork. Not a disaster, but not ideal.

guess: Boss might be loose in the fork. .. is there a metal threaded insert, in the fork, while being made,
or just the epoxy composite is threaded?

I have a BD bike with the carbon fork that is apparently the same as the Nashbar one. When my buddy gave me the frameset, one of the canti studs was out of the fork and the plate came off. The plate with the 3 holes is just held in place by a weak adhesive as mentioned above.

I just put the stud back into place using some threadlocker and positioning the plate and it has been fine ever since. I don't use those Avid brakes so I can't comment on the brake arm specific issue.

I wouldn't assume that the stop cam is bonded to the fork. It certainly isn't on my carbon fork on my Las Cruces. On mine, the brake boss keeps it in place by being properly tightened. On metal forks, they are usually attached via welding or adhesive but I'm not sure that is the case with a carbon fork. You could easily hold it in place with a bit of superglue and then tighten the stud properly.

An alternative is to go to a brake that doesn't need the stop plate. There are lots of them out there that use a different mechanism to set the spring tension. Paul's Cantilevers, for example, don't use a pin but instead use a nut on the front of the brake to set tension. They cost about the same as the Ultimates but they have a higher coolness factor.