Disc brake trouble

[montage]

I have very limited experience with disc brakes (read as "none") and have recently aquired a 2nd hand carrera kraken which needs some work doing to it.

I have a couple of issues, firstly, rubbing on the disc brakes....
- The wheel and the disc run true, so I can only assume this is an issue with the brake itself. By loosening it off an realigning the brake I can minimise this, but it is still there. I assume that the reason for this is to do with the second, larger problem.


There is very little space between the brake pads, and I reckon the pads may be worn (how do I check, should there be a rubber compound or are pads just metal?). Apart from the rubbing, the rear brake works ok ish, but the front brake applies no resistance at all - when the lever is squeezed the pads don't appear to move in enough to apply force on the disc, how do I adjust this?

I've also heard it is bad to squeeze the lever when no wheel is in...I have done this...major problem?

Many thanks

 

[MacB]

if they are cable operated then a good read of thsi is very helpful:-

http://www.twowheelblogs.com/avid-bb7-disc-brake-set-and-tuning

it shouldn't matter what type of brakes they are the info around proper cable prep etc will be valid. Then you can search on line for a download of the specific brake manufacturers instructions.

If they're hydraulic then I haven't got a clue.

 

[montage]

Cable operated, Cheers MacB, I'll have a look...hope you had a good birthday yesterday!

 

[MacB]

Yep, nice day thanks mate, you'll find a few posts, and threads, from me as I worked to understand cable disc brakes, here's a quick and dirty summary:-

actuation - the only ones I'm aware of have one side fixed and one side that moves, ie one pad stays where it is and the caliper pushes the other pad across deflecting the rotor into the fixed pad. The postioning of the rotor between the two pads seems to make a difference to brake feel. The consensus seems to be that better brake performance is achieved with the rotor off center and closer to the side of the caliper that doesn't move, giving better modulation.

pad wear and replacement - not had them long enough to know much about wear but have taken pads in and out and its easy on the BB7, you need to check manufaturers pdf download to be sure. But as the pads wear they need to be manually dialled in and again checking pdf to see how. Mine are just a little wheel you turn and there's one each side, I'm aware that some have single sided adjustment only and might need an allen key.

lever pull - as soon as you touch the lever the brake should actuate, if it doesn't then refer to all the info on cable outer prep and cable inner installation. I bought special compressionless cable outer from Goodridge and also a little dremel tool to get the ends totally neat and square. This may be overkill but I can certainly say that the calipers react to the slightest touch on the levers.


Let us know how you get on and post up details of what you have so that we can research a bit better

 

[rusky]

I'm guessing they are Tektro brakes, I have a Vulcan disc with Tektro brakes & a Marin Muirwoods with hayes brakes.

The pads are metal backed with a very hard friction material - like car brake pads. My Marin always rubs & the brakes are a pain to set up. I don't think it matters if you pull the lever with no wheel in, but with hydraulics, the pistons can pop out.

I'll see if I have the manual for the tektro brakes later.

 

[montage]

Cheers for the help.
I couldn't find the adjustment bit for the moving pad, but was able to work with changing the stationary pad to eliminate rub (combined with the trail and error movement of the whole brake). Front brake working as well!....for now.... some fine adjustments to the gears and then I'll take it out for a snowy spin tomorrow afternoon

Thanks again