Disc brake pads - rubbing

dinyull
dinyull Posts: 2,979
edited November 2018 in Workshop
Just replaced the front pads on my BR-RS505.

Before I removed the old pads, I pushed the pistons back in with a screwdriver. Replaced pads with genuine Shimano pads and when I came to put wheel back on could barely get the disc back in.

Had a bit play about with pistons again and managed to improve it a bit but still getting some rubbing - to the point if I spin the wheel it'll come to a halt after a few revolutions. Both pads look to be rubbing.

Watched a few youtube vids to make sure I hadn't missed anything, and I don't think I have - so what gives?

Comments

  • pedropete
    pedropete Posts: 227
    Few possible causes:

    - New pads may be a smidge thicker than the old ones; some after-market generic pads can vary by a surprising amount. You may need to re-centre the caliper and/or true the rotor.

    - May be some material (adhesive, swarf, paint) on the back of the pads preventing them sitting flat against the piston-face. Inspect by eye and remove any visible material that shouldn't be there

    - Pistons may not be retracting fully/consistently. Sounds like you may already have done this but, if not, do a piston advance/lube cycle on each side and try again. See below if you need a guide.

    If that doesn't work it may be that the system is over-filled (check for the first three issues first and then re-bleed the system), or, that the master cylinder is sticking (seek help from someone familiar with your model of levers).

    For a piston advance/lube cycle, you'll need:

    - Plastic tyre lever - must be plastic to avoid marking or damaging the piston
    - 2-3 clean cotton-wool-buds (ideally the eco friendly paper ones)
    - Couple of drops of brake fluid (same as used in your system)

    1. Remove pads
    2. Use the plastic tyre lever to hold back one piston and gently squeeze the brake lever to advance the other piston by 3-4mm, but no more than that!

    Advancing the piston too far could allow air into the system, or worse, you may push the pistons past the seals and have to strip the caliper completely and re-seat the pistons and seals. That's a fiddly PITA you don't need.

    3. Use a clean cotton-wool-bud to gently wipe as much crud as possible off the sides of the advanced piston - get as far round it as you can.
    4. Using a fresh bud, wipe a light film of brake fluid around the surface you just cleaned.
    5. Use the plastic tyre lever to push the advanced piston back into the caliper body.
    6. Advance the same piston again and then push back again, repeating this advance/push-back cycle 5-6 times.
    7. Change to the opposite piston (of the same caliper) and start again from step 2.
    8. Finally, clean any brake fluid out of the caliper and off the piston-faces, ensure both pistons are fully pushed back and re-fit the brake pads.

    As above, if the issue doesn't resolve it may be that the system is over-filled, or, that the master cylinder at the lever is sticking.
  • dinyull
    dinyull Posts: 2,979
    Cheers for that, will give cleaning/ lubing the pistons a go at the weekend and centre them.

    Pads are genuine Shimano pads so don't think thickness should be a problem.

    The backing plates were clean and bare metal. Only difference in pads was going from Resin to Sintered.

    Bike was new in May and came delivered without discs rubbing at the time so don't think the system is overfilled.
  • photonic69
    photonic69 Posts: 2,416
    Have you tried again with the old pads to see if rubbing persists?

    I've got the same brakes and have developed rubbing on the rear (one pad only) and this is on a new bike less than 1000 miles old.


    Sometimes. Maybe. Possibly.

  • dinyull
    dinyull Posts: 2,979
    PhotoNic69 wrote:
    Have you tried again with the old pads to see if rubbing persists?

    I've got the same brakes and have developed rubbing on the rear (one pad only) and this is on a new bike less than 1000 miles old.

    No rubbing, but there was no meat left on them so unsurprising.
  • photonic69
    photonic69 Posts: 2,416
    Dinyull wrote:
    PhotoNic69 wrote:
    Have you tried again with the old pads to see if rubbing persists?

    I've got the same brakes and have developed rubbing on the rear (one pad only) and this is on a new bike less than 1000 miles old.

    No rubbing, but there was no meat left on them so unsurprising.

    I understand. I was just wondering if the pistons had moved out too much causing the issue. Tried pushing the pistons back even more? You have the new spreading spring installed?


    Sometimes. Maybe. Possibly.

  • dinyull
    dinyull Posts: 2,979
    I've tried pushing the pistons back as far as possible, but to be fair I did it after a wet ride home last night so could be that some grit got in and fouling the pistons. Installed the new spring with the new pads also.

    Will give it all a good clean at weekend and see if that solves it. I rode the bike in this morning, so it's not too bad, just bloody annoying.

    Also renews my want of a new house with garage attached/ space for bike shed as pi$$ing about in the kitchen last night was a royal PITA.
  • imposter2.0
    imposter2.0 Posts: 12,028
    Dinyull wrote:
    Just replaced the front pads on my BR-RS505.

    Before I removed the old pads, I pushed the pistons back in with a screwdriver. Replaced pads with genuine Shimano pads and when I came to put wheel back on could barely get the disc back in.

    Had a bit play about with pistons again and managed to improve it a bit but still getting some rubbing - to the point if I spin the wheel it'll come to a halt after a few revolutions. Both pads look to be rubbing.

    Watched a few youtube vids to make sure I hadn't missed anything, and I don't think I have - so what gives?

    Did you re-centre the caliper after fitting the new pads? With the wheel in, loosen the caliper bolts, pull the brake on and then re-tighten the bolts while holding the brake on. Unless there is some pre-existing technical issue with the pistons, it's unlikely to be them, IMO..
  • dinyull
    dinyull Posts: 2,979
    Nope, I didn't do that as both pads were rubbing and I didn't have my allen key to hand.

    Need to get it on the work stand this weekend and do that as well as the cleaning.

    Cheers
  • hopkinb
    hopkinb Posts: 7,129
    Old milemuncher/killer clown/bottom briquettes/tetragrammaton had a post up for a second or two banging on about one of his perennial faves - the spreader tool.

    I normally expect a bit of "tinging" with brand new pads, where it makes a noise, but doesn't obviously slow the wheels down. A couple of rides normally wears away a bit of pad material though, then I remove the pads, push back the pistons, replace the pads, shove the handle of a clean spoon in between the pads and wiggle it about to make all is back as far as it will go. Then re-centre the calliper, either using the brake squeeze technique, or by eye looking down over a white piece of paper to ensure an even gap. Nip up the bolts a little at a time, alternating, like you would for a stem.

    Sounds complicated, takes 10 minutes. Trouble free until you replace the pads again, or if you use a different wheel with a different rotor.
  • Tetragrammaton1
    Tetragrammaton1 Posts: 72
    hopkinb wrote:
    Old milemuncher/killer clown/bottom briquettes/tetragrammaton had a post up for a second or two banging on about one of his perennial faves - the spreader tool.

    I normally expect a bit of "tinging" with brand new pads, where it makes a noise, but doesn't obviously slow the wheels down. A couple of rides normally wears away a bit of pad material though, then I remove the pads, push back the pistons, replace the pads, shove the handle of a clean spoon in between the pads and wiggle it about to make all is back as far as it will go. Then re-centre the calliper, either using the brake squeeze technique, or by eye looking down over a white piece of paper to ensure an even gap. Nip up the bolts a little at a time, alternating, like you would for a stem.



    Sounds complicated, takes 10 minutes. Trouble free until you replace the pads again, or if you use a different wheel with a different rotor.

    That spreader works well, but Park tool specifically say it’s not designed for ceramic pistoned Shimano Road callipers. If the brakes are rubbing after replacing the pads, you absolutely do not have to centre the callipers with the slacking the bolts off, and squeezing the lever method, or any other method. That’s a terrible idea, and quite wrong, and very poor advice because the calliper wasn’t misaligned before the pad change, unless you had a real issue with the pad replacements and had to do something to ‘encourage’ them in, they won’t be misaligned after the pad replacement. There was an article on a respected cycling journal website, by a well respected pro mechanic (which I can’t locate now ) which said the best way to correct a pad rubbing issue was to use your hand against the rotor, thus straightening it up in relation to the pad, as this is more likely to be the issue.
  • imposter2.0
    imposter2.0 Posts: 12,028
    Tetragrammaton1 wrote:
    If the brakes are rubbing after replacing the pads, you absolutely do not have to centre the callipers with the slacking the bolts off, and squeezing the lever method, or any other method. That’s a terrible idea, and quite wrong, and very poor advice because the calliper wasn’t misaligned before the pad change, unless you had a real issue with the pad replacements and had to do something to ‘encourage’ them in, they won’t be misaligned after the pad replacement. There was an article on a respected cycling journal website, by a well respected pro mechanic (which I can’t locate now ) which said the best way to correct a pad rubbing issue was to use your hand against the rotor, thus straightening it up in relation to the pad, as this is more likely to be the issue.

    Says the clown who has clearly never actually owned a disc bike. Centering the calipers is standard practice and takes about 10 seconds. Do us all a favour - please stop trolling and go away...
  • veronese68
    veronese68 Posts: 27,297
    Tetragrammaton1 wrote:
    There was an article on a respected cycling journal website, by a well respected pro mechanic (which I can’t locate now ) which said the best way to correct a pad rubbing issue was to use your hand against the rotor, thus straightening it up in relation to the pad, as this is more likely to be the issue.
    That would only be the case if the rub is at one point per revolution. If the rub is the same all the way round the disc is already true and the above is a terrible idea as the problem lies elsewhere.
    Recentring shouldn't be necessary when only replacing the pads, but it doesn't take long and who knows if the caliper was a little off before it may help. Worn pads have a greater margin of error in terms of clearance for an off centre caliper.
    As Hopkins said a bit of tinging and noise and they normally clean up and are ok after a short distance. If the wheel can manage a couple of revolutions before coming to a stop it's not a massive amount of drag.
    Kinesis Pro6
    Marin Nail Trail
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  • Tetragrammaton1
    Tetragrammaton1 Posts: 72
    Veronese68 wrote:
    Tetragrammaton1 wrote:
    There was an article on a respected cycling journal website, by a well respected pro mechanic (which I can’t locate now ) which said the best way to correct a pad rubbing issue was to use your hand against the rotor, thus straightening it up in relation to the pad, as this is more likely to be the issue.
    That would only be the case if the rub is at one point per revolution. If the rub is the same all the way round the disc is already true and the above is a terrible idea as the problem lies elsewhere.
    Recentring shouldn't be necessary when only replacing the pads, but it doesn't take long and who knows if the caliper was a little off before it may help. Worn pads have a greater margin of error in terms of clearance for an off centre caliper.
    As Hopkins said a bit of tinging and noise and they normally clean up and are ok after a short distance. If the wheel can manage a couple of revolutions before coming to a stop it's not a massive amount of drag.

    Very true. I personally would only do the full calliper slack off and squeeze, if I’d replaced the whole shebang ( callipers, discs and pads ) and I knew that the alignment of the calliper was most likely wrong / badly out. The slack and grab thing will work, but I’ve never had to resort to absolutely having to do it, just for a bit of intermittent rub after replacing pads before.
  • imposter2.0
    imposter2.0 Posts: 12,028
    Tetragrammaton1 wrote:
    Very true. I personally would only do the full calliper slack off and squeeze, if I’d replaced the whole shebang ( callipers, discs and pads ) and I knew that the alignment of the calliper was most likely wrong / badly out. The slack and grab thing will work, but I’ve never had to resort to absolutely having to do it, just for a bit of intermittent rub after replacing pads before.

    So it's obviously not 'a terrible idea, and quite wrong, and very poor advice' then. Seriously, do you ever check what you've written previously, before spewing more of your utter nonsense?
  • joey54321
    joey54321 Posts: 1,297
    Tetragrammaton1 wrote:
    That spreader works well, but Park tool specifically say it’s not designed for ceramic pistoned Shimano Road callipers. If the brakes are rubbing after replacing the pads, you absolutely do not have to centre the callipers with the slacking the bolts off, and squeezing the lever method, or any other method. That’s a terrible idea, and quite wrong, and very poor advice because the calliper wasn’t misaligned before the pad change, unless you had a real issue with the pad replacements and had to do something to ‘encourage’ them in, they won’t be misaligned after the pad replacement. There was an article on a respected cycling journal website, by a well respected pro mechanic (which I can’t locate now ) which said the best way to correct a pad rubbing issue was to use your hand against the rotor, thus straightening it up in relation to the pad, as this is more likely to be the issue.

    I know you're just trolling but in case anyone reads this and takes it seriously, you have undermined your own logic.

    You've said that aligning the calliper is a bad idea because before the pad change the caliper was aligned, but that would also be true for the rotor.
  • imposter2.0
    imposter2.0 Posts: 12,028
    I've said this before and I'll say it again - I actually think the guy gets off on being criticised like this. I can't think of any other reason why he keeps coming back and spouting the same old drivel, knowing what will happen...
  • photonic69
    photonic69 Posts: 2,416
    Sometimes you have to re-align the caliper to the rotor. Usually in the case of removing and replacing the wheel. On two of my previous MTBs with hydro disk brakes I found this really annoying when arriving at a place with the bike in the car with wheels removed and on replacing had really bad disk rub. Turns out it was the position of the axle in the drop outs. I filed notches into the flats of the lock nuts. If I placed the notches uppermost the rub would not occur. If it was 45/90/135/180/270 degrees out etc it would rub. This was with QR axles. With through axles on my road bike this is not the case.

    I've now got disk rub on my road bike but that is (quite literally) a whole other thread.


    Sometimes. Maybe. Possibly.

  • shortfall
    shortfall Posts: 3,288
    This recurring saga would be comedy gold if it wasn't so tragic. Part of me thinks that the chap who receives all these bans richly deserves all the mockery aimed at him, and another part of me thinks that he's absolutely desperate to be liked, suffers from a mental illness, and has to carry some real baggage around with him (and I don't mean the 40kg rucksack).
    Sad.
  • imposter2.0
    imposter2.0 Posts: 12,028
    Shortfall wrote:
    This recurring saga would be comedy gold if it wasn't so tragic. Part of me thinks that the chap who receives all these bans richly deserves all the mockery aimed at him, and another part of me thinks that he's absolutely desperate to be liked, suffers from a mental illness, and has to carry some real baggage around with him (and I don't mean the 40kg rucksack).
    Sad.

    Completely agree and I share the same sentiment, although I do still have my doubts. But even if that is the case, then his constant lying and misinformation (plus his refusal to even acknowledge these) is not going to be endearing him to the forum at large...
  • apreading
    apreading Posts: 4,535
    PhotoNic69 wrote:
    Sometimes you have to re-align the caliper to the rotor. Usually in the case of removing and replacing the wheel. On two of my previous MTBs with hydro disk brakes I found this really annoying when arriving at a place with the bike in the car with wheels removed and on replacing had really bad disk rub. Turns out it was the position of the axle in the drop outs. I filed notches into the flats of the lock nuts. If I placed the notches uppermost the rub would not occur. If it was 45/90/135/180/270 degrees out etc it would rub. This was with QR axles. With through axles on my road bike this is not the case.

    I've now got disk rub on my road bike but that is (quite literally) a whole other thread.

    If that were the case then you would need to re-index the gears every time you take the wheel out too?
  • photonic69
    photonic69 Posts: 2,416
    apreading wrote:
    PhotoNic69 wrote:
    Sometimes you have to re-align the caliper to the rotor. Usually in the case of removing and replacing the wheel. On two of my previous MTBs with hydro disk brakes I found this really annoying when arriving at a place with the bike in the car with wheels removed and on replacing had really bad disk rub. Turns out it was the position of the axle in the drop outs. I filed notches into the flats of the lock nuts. If I placed the notches uppermost the rub would not occur. If it was 45/90/135/180/270 degrees out etc it would rub. This was with QR axles. With through axles on my road bike this is not the case.

    I've now got disk rub on my road bike but that is (quite literally) a whole other thread.

    If that were the case then you would need to re-index the gears every time you take the wheel out too?

    With a MTB and 8 cogs on the rear the 0.5mm or so it takes either way to induce disk rub was not really enough to have a bad effect on indexing. Plus on a MTB over rough terrain you don't notice like you do on a road bike


    Sometimes. Maybe. Possibly.

  • dinyull
    dinyull Posts: 2,979
    Thanks all (before it all went a bit c*ck waving).

    Cleaned the bike, pushed the pistons back and et voila - jobs a good'un.

    Must have been a bit of grit fouling them from the wet ride before I swapped them out.
  • N0bodyOfTheGoat
    N0bodyOfTheGoat Posts: 5,844
    I had intermittent pad/rotor rub with both the default Fulcrum RacingSport 77 DB 6-bolt rotors and the Hunt Aero Disc Light centrelock ICE rotors, especially when I got out of the saddle up climbs on my Cube, despite pushing the pistons back several times. A tiny adjustment of the caliper alignment to the frame and forks fixed it.
    ================
    2020 Voodoo Marasa
    2017 Cube Attain GTC Pro Disc 2016
    2016 Voodoo Wazoo
  • haydenm
    haydenm Posts: 2,997
    PhotoNic69 wrote:
    apreading wrote:
    PhotoNic69 wrote:
    Sometimes you have to re-align the caliper to the rotor. Usually in the case of removing and replacing the wheel. On two of my previous MTBs with hydro disk brakes I found this really annoying when arriving at a place with the bike in the car with wheels removed and on replacing had really bad disk rub. Turns out it was the position of the axle in the drop outs. I filed notches into the flats of the lock nuts. If I placed the notches uppermost the rub would not occur. If it was 45/90/135/180/270 degrees out etc it would rub. This was with QR axles. With through axles on my road bike this is not the case.

    I've now got disk rub on my road bike but that is (quite literally) a whole other thread.

    If that were the case then you would need to re-index the gears every time you take the wheel out too?

    With a MTB and 8 cogs on the rear the 0.5mm or so it takes either way to induce disk rub was not really enough to have a bad effect on indexing. Plus on a MTB over rough terrain you don't notice like you do on a road bike

    I agree. A very tiny amount of misalignment can cause brake rubbing (in mild cases anyway) and it's easily fixed with a quick realign. (It's not poor/terrible advice as milemuncher says, it's standard advice that works in most cases). I've had this many times but never had to re-index the gears because of it so it must be a tolerance thing.

    I've had similar issues to the OP and most of the time it's fixed by a short ride around the block and some on/off braking, it should loosen up even you've had to force the rotor back into the caliper (say, if you were a lazy teenager and didn't have a piston spreader :oops: ). I don't know if these specific brakes do but some MTB brakes auto adjust for pad wear and it takes a short while to rectify
  • pedropete
    pedropete Posts: 227
    Dinyull wrote:
    Thanks all (before it all went a bit c*ck waving).

    Cleaned the bike, pushed the pistons back and et voila - jobs a good'un.

    Must have been a bit of grit fouling them from the wet ride before I swapped them out.

    Result. Start with the simple stuff and work up to the more awkward bits if that doesn't work. And yes, I'd forgotten how quickly things could escalate round here too :wink:

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