Rubbing disc brake

mudcow007

rebuilding my ye olde hardtail

bought a Clarks S2 hydro disc brake for the front end, spent about 2 hours tryign to figure out why its rubbing like mad (loosened mounting bolt, pull lever & tighten bolts with lever pulled in made no difference)

just been looking at the rotor an it looks like its got a radial wobble (up an down) would that have any effect on the rubbing issue?

i even thought about sanding the pads down

nicklouse

so have you used it yet? bedded the lot in?

if no that normally sorts it.

do you have a metallic noise of the rotor rubbing the caliper? no dont worry. yes add a washer between caliper and mount.

mudcow007

its brand spanking new - wheel, rotor an calliper

the brake is rubbing quite a lot, its almost like the rotor doesn't fit the calliper

the rotor isnt hitting the body of the calliper, its just rubbing on the pads

i will build the rest of the bike an take it out for a spin, see if it gets any better

cheers

bonezy

As long as it's not binding, a little rubbing is fine, both surface are very hard and won't slow you down. As nick said, bed them in properly and see if it's any better

mudcow007

went on a maiden voyage last night (rode home from work as my commuter has been recalled)

brake is still rubbing after 15 miles an is slowing the bike quite alot

any ideas? im currently thinking about sanding the pads down? bad idea?

nicklouse

center the caliper. re set the pads.

mudcow007

right after a weekend of riding Coed-y-Brenin i thought the brake would have bedding in...nope!

its still rubbing, i have found if i push the whole calliper inwards towards the wheel it stops rubbing so i will try a few washes on the mount to sort that

any ideas why there is absolutely no power in the brake though? i reckon i have ridden about 40 miles on it so far (and have been using it!)

nicklouse

just adjust it then no washers needed.

mudcow007

how do you adjust it though?

i have tried pushing the pistons back but they didn't move. the rotor looks very very very close to the body of the calliper

The Rookie

Very close is fine, touching is not.

If you have radial wobble it imlies the disc is not concentric with the hub, I get this on my crossrides as there is no centre location for the disc (Shimano hubs all have centre location) and you need to loosen the bolts and centre the disc before nipping them up.

If you get no rubbing by pushing the calliper over it implies you're not centring it properly, my callipers twist slightly when I do the bolts up so I have to be very slow and careful to do each bolt up a little at a time to stop the calliper twisting slightly (worse on Avids with the centralising cones than other callipers), clamping it on the disc doesn't help as the disc isn't stiff enough.

New discs - you did remove the protecting oil when you fitted them right?

Simon

mudcow007

The Beginner wrote:

New discs - you did remove the protecting oil when you fitted them right?

Simon

erm....

not exactly

i just bolted them straight on to be honest.....contaminated pads?

i will try an loosen the caliper an see if i can find a sweet spot where it doesnt rub, if i can find it i will try an tighten up

The Rookie

Not sure about clarks, but most discs come with a light oil film to protect from corrosion, needs to be removed before you fit them if so and yes it won't do the pads any good.

Simon

johnsav

you sure about that?
I didn't think stainless steel would rust in packaging, on a shelf in a shop

I've never cleaned off any of my discs before anyway

Jomox

Sorry to bump an old topic. I have the exact same problem with the S2 that I just brought for the front. The rotor rubs hard and the wheel hardly spins, it's like it's not been setup for the rotor (Like the rotor being to thick) I very much doubt bedding in will do much as it's impossible to ride like this (It's like trying to pedal a tank) I've tried to use shims, and adjust it with all advise on this thread but to no avail. There is no pre fluid on the rotor (and I gave it a good wipe before putting it on the hub also)

Will this require a new bleed?

supersonic

Is the rotor straight and true?

Jomox

Yeah it's straight & true, it catches all way round. It's not like catching when the rotor is a bit warped where only certain parts of it catch.

supersonic

Try pushing the pistons all the way back into their bores, then realign the caliper.

Jomox

Ok will do, will I have to push quite hard?

supersonic

Usually quite a lot! You also want to see if the pistons are not sticking ie retract after the lever has been pressed, and pretty equally. Never press the lever fully with the rotor/pads out though!

Jomox

Ok, I got it just a very tiny bit better but not much. From what I can see only one piston is pushing the pad while the other one don't do anything. It looks like the disc is closer to the pad that is moving so I guess I'll try some shims again. I'm not sure if the pistons moved though much (maybe just one a little, which is the piston that seems to be doing the work now)

Jomox

Ok I am getting there, moved pistons a bit more, one shim not enough though,rotor is touching other side but both pistons are moving (unlike before with one not doing anything) I just need to add shims I think to get it more center now, my only problem is don't have any more small ones! But it's not catching as much just need to get it positioned right now as still not good yet.

cooldad

I put a big screwdriver in and turn it like a key. And also leave the pads in (or better still put an old pair in) so if you damage anything it's the pads not the pistons.

Jomox

My theory with the shims did not work as it made it worse actually. It's like the position where the hub lines the rotor is off compared to the caliper. I made it a bit better at least but it's not ridable like that and i may need pro help with this I think.

Jomox

Just a little update. I gave up on the S2, need a pro to fix it. As shims can only put caliper one way it makes it worse. The disc is almost touching caliber and pushing pad in so it needs some adjusting (Maybe different mount or something) Nothing wrong with the brake just seems like wrong mount with this hub / fork combination.

I put my Juicy 3 back on the front which I had problems with to begin with, but pushed pistons all way back into their positions, put pads back in, followed manual and all is good, just a bit of rub from the warped rotor (I'll get a new one or it unwarped)