jkuper

Hi,

I decided to convert wife's hybrid GT Tachyon 2.0 she doesn't ride since switching to a road bike into a commuter bike for me. I couldn't get used to the flat bar setup it came with so I switched to a drop bar and installed Sora ST-3500 shifters and a Sora FD-3503. The rear derailleur was a Sora 3400 so no changes were needed there. Now the brakes....the bike came with Tektro RX1 shifters and levers. They sorta work with the STI shifters but I guess the pull ratio is long vs short so I tried to upgrade to what I thought would work, which is TRP CX8.4. Problem is the mounting parts aren't matching to the frame due to both frame and TRP being female parts.

So, question - is there a way to make it work with some type of an adapter? If not, what brakes would you recommend for the frame/shifter combo?

Not sure if this is apparent in the pics or not but the frame opening is considerably larger diameter than the bolt which came with the TRPs





Thanks!

dabac

The frame has had its brake boss removed, and the brake in the lower pic has a brake boss stuck to it.
I'm not sure what is what in the brake pics. If the brake in the lower pic is what was on the bike, then you need to find a way to undo the Allen screw holding the brake arm to the brake boss, then reinstall the boss to the frame. Then the brake in the top brake pic will mount right up.

Allez3

You should be using TRP CX-9s also. Same brake, but IIRC the 8.4s are for Campy and SRAM.

Take the bike in and get then boss issue fixed.

JiveTurkey

On the original brake arm: Remove the fixing bolt with an allen wrench, then remove the boss with an open-ended wrench. Next, re-install the brake boss to the frame.

headloss 

Although the 9 won't work well with Campy or Sram, the 8.4 will work with Shimano... lots of people out there running the shorter armed mini-v's with newer Shimano; I wouldn't worry about it unless clearance for fenders and/or wider tires is an issue.

jkuper

Thanks guys, I see what you mean now. The other three came out as they should, but this one is stuck. The base of it is completely round, so using an open end wrench isn't gonna work. It's odd too because base of the boss on the other side is flattened on two sides so the wrench would fit just fine on that one.

In any case, I think I will just have to get a replacement. I am guessing it's a 10x1mm

dabac

So grab a file and make yourself some tool flats on the stubborn brake boss. Nothing particularly critical about that.
Or use some vise grips. Or drill a hole in a piece of hardwood, slightly smaller than the thread. Then cut the block in half straight through the hole to make an improvised axle vise. Clamp it and remove brake arm.
I wouldn't feel too sure about the 10x1 based on the pic. Looks like it'd be a coarser thread than that. But you may be right.
10x1 is regular derailer hanger thread, isn't it? Easy enough to scrounge up a comparison piece in that case.

fietsbob

put it in your pocket, go to a hardware store , or auto parts,, If you can find 2 nuts that will both thread over it,

then they can be tightened against each other, jam nut pair,

then you have something to hold onto while you unscrew the center bolt, from the opposite end


Or, maybe with a Loctite compound that is strong enough, you can screw the post back into the frame, then,
after the compound cures , unscrew the center bolt ..

Bezalel

The 9's are for Shimano's new pull ratio. The 3500 group set is still on the old pull ratio so the 8.4's are a better fit.

headloss 

Nice catch, I didn't even look at what shifters (specifically) were being used.

jkuper

jam nuts idea would be great if I could find nuts/wrenches in that size thread which would thin enough to engage 7mm worth of useable thread on that stud.

I soaked the parts with PB Blaster and it still won't budge. I can't do too much more to it since I still need to be able to use it. In any case, I ordered a set of studs in 10x1.25 and will run what I have until that comes in.