Useless disc brake

[Crackle]

Not one of my fleet but my son's friends bike. It's a Halfords something with disc brakes I've never heard of and they are............lacking somewhat!

He's looking at me hopefully but discs are new to me. So, what happens. Well nothing. If I put both feet on the bars and haul with all my might on the front lever the bike can still be pushed forward. It's quite new, so cables are good and the disc looks to be functioning as designed, so why won't it stop. Could it be the pads?

The back is not much better and already has the cable adjusters at the limit, so unless I can solve it, he'll have a new bike with no brakes! Apparently it is due a free service but it won't go in his mum's car so she's reluctant to take it. I however could easily take it but it means dealing with Halfords, so I'd like to be clued up before I go.

 

[lpretro1]

Some of these cable disk brakes are woefully indedequate I'm afraid - they are ok when new and everything snugged up but then get quite poor. Firstly look and see if the inner pad is anywhere near the disk - if it is not it will have a hole in the back of the caliper which fits an allen key - access it from the other side of the wheel through the spokes - use this to position the inner pad up right up against the disk and then back off 1/4 turn. Then look at the outer pad - if not anywhere near then use cable barrel adjuster either at the caliper end or the lever end (or both!) to get it as close as poss without it dragging on the disk - if adjuster is fully out then you'll need to pull some cable in - rememebr to screw the adjusters back in before doing so. Ensure you don't take too much cable and prevent the mech from pulling properly at the caliper. Also worth removing the pads - easy to do as they are usually just magnetic and pull out - they will probably be really shiny - get a piece of fine emery, blow dust of and buff them up.
If you still can;t get them to work then if it is difficult to get to Halfords then call a mobile service and they will come to you - there is a list of them here:- www.cyclefix.net/
All the busineses on this Network are qualified mechanics

 

[Globalti]

Check the pads and discs aren't contaminated with oil. A sure sign is when they squeak and judder as you roll to a stop. Take the pads out, file a small notch in one so that you can replace it on the right side then stick them in the dishwasher. While they're washing, give the discs a good clean with alcohol or something like glass cleaner.

 

[Bman]

+1 using alcohol to clean discs.

 

[Andy_R]

Remember that discs and pads also need to bed in if they are new(ish). You could also put the pads in the oven for a while to bake off any grease/contaminants (Gas mark hot for 2 hours). Just make sure you don't pick 'em up when theyre baked!

 

[Crackle]

Right. Thank you all. Quite a few good suggestions there and I'll have another look at them, armed with some knowledge now.

 

[zoxed]

I tried all sorts to get my BB5's to work: adjustment, cleaning, adjustment again, Google...
Best thing I did was chuck the BB5s and use BB7s (drop in replacement). Does the bike have BB5s ?