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New to disc brakes (Sram Hydraulic) - help!

lakesludditelakesluddite Posts: 1,331
edited November 2015 in Workshop
Mornin' fettlers.

I've just become an hydraulic disc brake owner on my Spesh Roubaix disc, and now have a couple of questions:

So, coming into work this AM in the pi$$ing rain, downhill stretch - not to worry, I am now rocking disc brakes, no bother...which to a certain extent was correct, but the racket coming from the from disc when I squeezed harder was ear-shattering. Is this usual? In the dry all I could hear was a steady, quiet 'fft-fft-fft-fft..' as the gaps in the discs ran through the pads (I presume), but this was unearthly! Okay, it wasn't jet fighter loud (we get plenty of those up here), but far louder than the squeak you can sometimes get from rim calipers.

Secondly, as per usual in the downpours, I got a p*******, luckily only 10 minutes walk from work. I have just chaged the tube and put the wheel back on, but I can't seem to get it to spin without the disc rubbing the pads. It was much better before I took it off for the repair, but now it seems to rub for the whole revolution of the wheel. Is it just a case of trying to reposition the wheel until it stops, or is there something else I should be doing to make sure the disc runs true? It has QR, not thru-axles, if this makes a difference.

Any help would be most appreciated! TVM

Posts

  • bbrapbbrap Posts: 610
    The noise is probably pads not bedded in properly. Loads of info available online as to what to do.

    Rear wheel is probably not seated correctly (or more likely is now seated correctly but was'nt when they set it up). So - to make sure - loosen rear QR with the wheels on the ground, put some pressure on the saddle (lean on it) whilst doing up the QR. This should result in the wheel being located properly (straight, not to one side). Then test the brakes, if OK, all well and good. If the brake drags, loosen the disc calliper bolts a tad, apply the brake (to centre the calliper), do the bolts up tight whilst holding the brake. When you release the brake all should be centred and free running.
    Rose Xeon CDX 3100, Ultegra Di2 disc (nice weather)
    Ribble Gran Fondo, Campagnolo Centaur (winter bike)
    Van Raam 'O' Pair
    Land Rover (really nasty weather :lol: )
  • veronese68veronese68 Posts: 23,700 Lives Here
    Discs can be a bit noisy in the wet even when bedded in, different pads may help. First time it happened to me I too jumped out of my skin. Moments later a ped stepped out in front of me, I didn't shout as I thought the sound of my brakes would alert them to my presence. Completely silent braking. Presumably the first application dries them and they go quiet until they get wet enough to squeal once more.
    Check the wheel is properly seated first. Pull on the brakes a few times and it should sort itself out. Being hydraulic they should self centre. Disc brakes do not have a strong spring to pull them back like rim brakes, they can rub very slightly. You didn't pull the brake lever when the wheel was out did you? That will push the pistons out a bit. If so you might have to push them back and then pull the brakes a few times to get everything back to where it should be. Might sound like a faff but you soon get the hang of dealing with them.
  • lakesludditelakesluddite Posts: 1,331
    Cheers guys, very useful advice for a disc-novice here. No, I did not pull on the levers while the wheel was out, so I don't think the pistons will have moved.

    The noise issue seems logical - it was lashing it down and they must have been very wet, so much so that when I came to use them again they will have become wet soon after the initial 'drying' from the first application. It reassures me to hear that it's just the weather conditions rather than a mechanical issue.

    I'll give these tips a go this aft re the seating of the disc in the caliper.

    Thanks again.
  • mfinmfin Posts: 6,724
    Try to avoid getting any cleaning or oily products on the discs themselves too, some can make noises start. A can of STP Brake Parts Cleaner that you can use on a rag is handy if you do.
  • veronese68veronese68 Posts: 23,700 Lives Here
    Try to avoid getting any cleaning or oily products on the discs themselves too, some can make noises start. A can of STP Brake Parts Cleaner that you can use on a rag is handy if you do.
    Good point. Not tried the STP, but in general avoid car brake cleaners as they usually leave a light oily residue, Isopropylalcohol (IPA) is the safest bet for a cleaner. I got some in Maplin. Read some of the tips in the MTB section as they have been running discs for much longer so know most of the tricks.
  • lakesludditelakesluddite Posts: 1,331
    Yes, cheers for that. The guy in the shop suggested I use an alcohol solution to clean the discs, so I'll look into that.

    Thanks again.
  • mfinmfin Posts: 6,724
    Yes, cheers for that. The guy in the shop suggested I use an alcohol solution to clean the discs, so I'll look into that.

    Thanks again.

    eBay is a good place to buy IPA (anyone wanna make a blindingly obvious real ale joke and think they're being quick witted?)
  • kajjalkajjal Posts: 3,380
    Disc brakes being noisy in heavy rain is not unusual, they can make a screeching, honking noise. Any other conditions they will be fine. Once the rain calms jam the brakes on firmly a few times and it will stop. Any mud etc will rub until cleared.

    There is no need for disc brakes to rub if you remove and replace the same wheel. For QR wheels make sure the tiny springs are either side, put the wheel in and while pushing down on the stem do up the QR. Pull the brake a couple of times and then spin wheel to test. Reseat and try again if needed. Make sure the QR is done up tight enough or the wheel will move and rub on braking.

    If still rubbing check pad clearances on disc. Then undo both caliper bolts and position caliper so even gap either side of disc. Then carefully do up bolts one at a time maintaining gaps by holding caliper in place. Pull brake and test. If still rubbing check action of pads as sometimes one will move in slightly faster than the other. If this is the case loosen caliper bolts and adjust to compensate. It will then run without rubbing.

    Main thing is to take your time and not get frustrated. Once properly set they will not need adjusting for a long time normally.
  • I find if I don't tighten the QR lever to exactly how it was before, it throws the disc slightly out of alignment and it catches the pad. To get around this, I now always turn the QR 8 times anticlockwise to remove the wheel and vice versa to refit. Doing this it's now 50-50 on whether the disc will catch on the pad.
    To stop it catching, loosen both caliper fixing bolts off half a turn; spin the wheel, then whilst holding the brake on, alternately tighten the bolts back up a little bit at a time (it helps stop the caliper twisting) until they are tight enough. Test and repeat of necessary.
  • wongataawongataa Posts: 916
    Try to avoid getting any cleaning or oily products on the discs themselves too, some can make noises start. A can of STP Brake Parts Cleaner that you can use on a rag is handy if you do.
    Good point. Not tried the STP, but in general avoid car brake cleaners as they usually leave a light oily residue, Isopropylalcohol (IPA) is the safest bet for a cleaner. I got some in Maplin. Read some of the tips in the MTB section as they have been running discs for much longer so know most of the tricks.
    Why would a car brake cleaner use an oily residue? You don't want that with car brakes either.
  • veronese68veronese68 Posts: 23,700 Lives Here
    Try to avoid getting any cleaning or oily products on the discs themselves too, some can make noises start. A can of STP Brake Parts Cleaner that you can use on a rag is handy if you do.
    Good point. Not tried the STP, but in general avoid car brake cleaners as they usually leave a light oily residue, Isopropylalcohol (IPA) is the safest bet for a cleaner. I got some in Maplin. Read some of the tips in the MTB section as they have been running discs for much longer so know most of the tricks.
    Why would a car brake cleaner use an oily residue? You don't want that with car brakes either.
    Automotive discs are made of cast iron and rust very easily so automotive brake cleaners leave a very light oily residue. Cars are much heavier than bikes and the brakes vastly more powerful so they can burn this light oil off easily, a bicycle can't.
  • Try to avoid getting any cleaning or oily products on the discs themselves too, some can make noises start. A can of STP Brake Parts Cleaner that you can use on a rag is handy if you do.
    Good point. Not tried the STP, but in general avoid car brake cleaners as they usually leave a light oily residue, Isopropylalcohol (IPA) is the safest bet for a cleaner. I got some in Maplin. Read some of the tips in the MTB section as they have been running discs for much longer so know most of the tricks.
    Why would a car brake cleaner use an oily residue? You don't want that with car brakes either.
    Automotive discs are made of cast iron and rust very easily so automotive brake cleaners leave a very light oily residue. Cars are much heavier than bikes and the brakes vastly more powerful so they can burn this light oil off easily, a bicycle can't.


    I don't know if this stuff leaves an oily residue or not (presumably solvent based?), but the points you mention about cars being heavier and more powerful means that every time you use the brake, rust gets swept off anyway, so no reason to have anything left on the disc to combat it.
  • veronese68veronese68 Posts: 23,700 Lives Here
    I don't know if this stuff leaves an oily residue or not (presumably solvent based?), but the points you mention about cars being heavier and more powerful means that every time you use the brake, rust gets swept off anyway, so no reason to have anything left on the disc to combat it.
    OK, use car brake cleaner on your bike then, I really don't care.
  • I don't know if this stuff leaves an oily residue or not (presumably solvent based?), but the points you mention about cars being heavier and more powerful means that every time you use the brake, rust gets swept off anyway, so no reason to have anything left on the disc to combat it.
    OK, use car brake cleaner on your bike then, I really don't care.

    My brakes are fine, but thanks ;).
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