So I'm pretty confident with a lot of bike stuff but this parts bin build is tripping me up as I haven't had loads of experience fitting u-brakes. Long story short, am I going to be able to get this to work? (New springs are in the post to me currently..) I understand this is supposed to be used as a front BMX brake so I was going to remove the cable guide and install a pinch bolt, to fix a straddle cable so it can have a centre pull fitted. But, when the pads contact the rim, the caliper arms are touching on the side of the bottom bracket and they move very close together.. Am I wasting time with the MTB rims being narrower than a BMX rim? Is there a better rear brake to fit here?
It's an MBK tracker frame, dia compe hombre brake, if that helps.
by Tough_Ad_6463
4 Comments
just buy a v brake is my best guess
You need to post a picture of the actual situation because your description makes no sense.
From what I can see, it looks like that brakeset isn’t offset away from posts far enough to work. Look at an old set of shimano u brakes and compare.
It’s a bit hard to tell from the photo, can you move the pads to the top of the slots and pinch them in so they meet the rim square in a decent position? Take a photo of this too so we can see the clearance and angle of the arms as the pads meet the rim. By the looks of it the rim is going to be too narrow though, the pads with be arching up at quite an extreme angle on this rim. Also a plastic BB cable guide made for a front derailleur is going to get sawed into pretty quickly by a brake cable under braking tension which will create a lot of friction. In short I don’t think it’s going to work well with that brake and rim combo, unless you can find some compatible CX pads that space in a lot further. Possibly Shimano cyclocross pads (R50T2, R55C1 longer spacer versions) might make this work?
This is my understanding of your situation: When the pads touch the rim (i.e. when the brake is engaged), the caliper arms are in contact with each other (i.e. they shouldn’t be). Technically, the intersection point in the system should be the straddle wire/yoke, not the ends of the caliper arms, right? I wonder what would happen if you added a larger spacer between each pad and the caliper arm. It looks like you’re already using the larger spacer, but I’m sure you could find something longer.
Shimano BR-MT61 was a fairly common U-brake for mid-80s mountain bikes with this rear brake situation.