Back and Front brakes rubbing on nearly new bike

markh1961

Hi - my son's girlfriend just bought a bike for her 6 yr old daughter, sight unseen, off ebay (a pink Dunlop Disc 21). They'd left it at our house for a week until her birthday today. In typical him fashion he said to me last night - could you take a look at this bike please, the wheels don't seem to turn very freely. Sure enough both the front and back wheels are binding quite a lot on the brakes even though the bike looks in near perfect condition with very little use/wear evident. I checked the cable/levers etc and was pretty much able to eliminate them and rule out the need for adjustment. I switched my attention to the calipers and removed the front one whereupon the wheel turned fine so hub is good and it's a brake issue. I stripped the caliper back and checked the shoes etc - not really familiar with bicycle disc brakes but the pads seem seated OK and there's a little V spring to keep them apart. Pads seem to be all metal and no pad material like a car but AFAICT from images on the web they are fine. I reassembled and refitted the caliper but it made no difference. I released the cable entirely so there was definitely no pressure being applied and still there was significant rubbing. Can't see anything wrong with the discs or any mounting so am at a loss to explain it. Especially annoying is that the back wheel has exactly the same issue so I'm probably missing something basic thru ignorance but didn't want to mess too much as /I/ didn't buy the damn thing and didn't want to risk ruining it /completely/ for her birthday. Of course also annoying they didn't think to check it when they bought it or mention it to me a week ago so they could have taken it in to a shop to be sorted.

Any ideas what we should be looking for? It seems a fairly solid if cheap bike and as I said it seems to have been looked after (or refurbed).

Thanks,
M

nicklouse

what are the brakes?

the spring between the pads does not keep them apart.

sounds like they just need setting up correctly but without knowing what they are it is hard to say which way to do them.

ID them or post pics or read parktools info on brakes and take a guess.

markh1961

They have the word FLAME stamped on them and the pads are little sort of horseshoe shapes (judging by the paucity of images of them on google they may not be that common?). They have a cut out on the front of each pad that seems to need this v-spring to hold them in place and then a piston of some sort compresses the outer pad against the disc...

nicklouse

ok lets say they are single sided disc brakes.

have a read http://www.utahmountainbiking.com/fix/diskmech.htm

while I search some more.

The Rookie

Single sided cable discs?
Adjust the static pad back using the adjuster, relieve cable tension, if that has fixed the binding, then retighten both sides until it's 'just rubbing'.

markh1961

Ah yes - that looks slightly familiar. The caliper itself affixes to teh form with a couple of allen bolts and then there are 2 sprung allen bolts that I am now thinking must be used to adjust the "floating" position of the brake calipers over the disc - I did mess with these a bit (either doing them up completely or loosening them off completely) to little avail - I didn't think to try find somewhere in the middle

M

The Rookie

Yes the sprung bolts are used to centre the caliper over the disc - nasty things really!

markh1961

OK ta - that makes sense now and feel a bit daft I didn't figure it out