Need help with center pull brakes

[Cani Lupine]

I recently picked up a used mountain bike for free, knowing it needed a little fixing up. I thought it was a pretty sweet deal, but I ended up spending about as much as I'd spend on a used bike in good condition. I've got everything fixed and put together, but now I'm having problems with the brakes. I have no idea what the names of the parts are, so searching for anything is useless, since I can't enter the proper terms to find.

Here's what I have: http://i3.photobucket.com/albums/y93/SirFratley/IMG_2298.jpg

My problem is that the round thing in the center has no way of actually securing the cable in place, so it slides back and forth, resulting in virtually no brake tension. How do you get that round thing to actually hold the cable in position so it doesn't slide around? There's two slots for the cable in the back of it, and one seems to hold it better than the other, but it still moves around, no matter what I try, and these brakes just don't work.

Here's the back side of the round thing: http://i3.photobucket.com/albums/y93/SirFratley/IMG_2302.jpg

Am I doing something wrong here, or do these style of brakes just suck? Should I just stick a screw in there and jury-rig it into holding still?

I've had bad luck with brakes on just about every bike I've had, except for the disc brakes on my last one, which was unfortunately stolen 2 years ago.

 

[dabac]

What you have are cantilever brakes, or canti/canti brakes for short.
They've been around for ages, with small changes in design.
They ARE known to be fiddly to set up, specially the ones with smooth posts(as yours are) as there's one fastener responsible for the positioning of the pad in every direction simultaneously.

OTOH, they're highly tunable, and once set up properly certainly powerful enough for just about anybody.

Probably there's nothing wrong with what you have, odds are you just haven't figured out how it's supposed to work yet.
Oh, wait - yours is indeed broken. The right side cable run in the frontal pic, the one with the frayed end, should run through a short section of tubing, to prevent the "button" from sliding down the cable. See here: http://www.vintagecyclecomponents.co.uk/bicycle-canti-lever-brake-straddle-cable-117-p.asp

If you have some brake wire housing available, you can make one yourself. Wouldn't really recommend you to toss just anything in there, brakes are kinda important. But I suppose something like plastic pneumatic line could work too in a pinch, it's fairly tough.

Or you might be able to use one section of something like this: http://www.aliexpress.com/item/Hot-Selling-10A-Dual-Row-Connector-12-Position-Wire-Barrier-Strip-Electrical-Terminal-Block/615794561.html. Slide it onto the cable, secure with both screws and it might be good enough to keep the button from sinking. Tinker at own risk though.

Or you can rewire the brakes at a modest cost to use a separate straddle cable and a yoke.

I wouldn't try to jam something in the current button, it's not meant for that kind of loads at all.

Check out this link: http://www.sheldonbrown.com/canti-trad.html, follow the instructions, then come back if there are any further questions.

 

[dabac]

But unfortunately I think I have to say that you've probably picked a lemon. What little I see of the front suspension fork screams "low-end" to me. While there's certainly a place in the world for inexpensive bikes, you don't want to sink money and effort into them.

Odds are what you have is comparable to the $200 BSO(bicycle shaped objects) sold at department stores and amazon these days. And even one of those will usually give good (if uninspired) service for some years of casual riding.

 

[alienator]

It looks like the brake cable is entirely too long. Not only is the angle between the link wire and the transverse cable too large, the transverse cable (part of the main brake cable) is too slack. I'd recommend going to an LBS to have them set the brakes up properly. While your bike is likely an inexpensive bike as someone already mentioned, that doesn't mean the brakes can't be setup to provide much better braking.

 

[Cani Lupine]

Thanks for the response! This bike is low-end, and I knew that when I picked it up. Someday I'd love to pick up a full squish KHS, but for now I have to live with the cheap BSOs. Then again, I tend to be rather rough with bikes, since I love to ride hard on less-than-smooth trails. We'll see how long this one lasts.

I ended up needing to get another cable because the end was too frayed to pass through the housing. I shortened the cable, used some spare housing to replace the missing tubing, realigned the pads, and now it actually feels like it should! Now that I have a better understanding of how they work, I'll be able to adjust the rear brake as well. I've got some automotive repair experience under my belt, but bikes have always been a trial and error thing with me.