Rotor rub when out of saddle

mtbrider123
mtbrider123 Posts: 102
edited May 2018 in MTB workshop & tech
Hi Guys,

I have a disc brake road bike but I think that you’re (mtb group) the best people to ask for some help. So my front rotor keeps on rubbing when I’m out of the saddle. This happens only when I lean my bike to the right. The calliper alligneremo has been checked by myself and lots of other riders + mechanics, everything is aligned properly, the disc is in the middle. Does anyone know what might be causing this, and how to solve it?

Thanks

Comments

  • JBA
    JBA Posts: 2,852
    Flex in the forks maybe.
    Have you checked your qr is tight and that the wheel isn't moving slightly in the forks?
    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • JGTR
    JGTR Posts: 1,404
    Flex, it’s normal.
  • imafatman
    imafatman Posts: 351
    Could also be wheels flexing. are all your front spokes correctly tensioned?
  • cooldad
    cooldad Posts: 32,599
    Rotors are attached to the hubs, so wheel flex won't effect the brakes.
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  • mtbrider123
    mtbrider123 Posts: 102
    JBA wrote:
    Flex in the forks maybe.
    Have you checked your qr is tight and that the wheel isn't moving slightly in the forks?

    Yes, the qr is very tight. It didn’t happen before, started doing that 2 weeks ago.
  • mtbrider123
    mtbrider123 Posts: 102
    JGTR wrote:
    Flex, it’s normal.

    I don’t think so as it didn’t do that before. Wheel flex happens towards the edges of the rim, but the shouldn’t be any flex at the hub (that’s where the rotor attaches)
  • mtbrider123
    mtbrider123 Posts: 102
    imafatman wrote:
    Could also be wheels flexing. are all your front spokes correctly tensioned?

    It’s not wheel flex as I’ve said before (responded to another person). Hmmm, I’ll ask the bike shop to check the spike tension, even though the tension seems fine on all the spokes, nothing loose.
  • mtbrider123
    mtbrider123 Posts: 102
    cooldad wrote:
    Rotors are attached to the hubs, so wheel flex won't effect the brakes.

    Exactly, so maybe spoke tension? Can a slightly loose spike cause this? By slightly I mean, not that you can feel with you hands. Hmmm, if it was the spoke, wouldn’t the wheel move side to side (but it doesn’t do that, it’s straight) ?
  • The Rookie
    The Rookie Posts: 27,812
    3 causes usually
    1/ axle loose in fork/frame allowing the hub to move (tighten up qr/nuts/through axle)
    2/ hub loose on axle allowing the hub to move (sort the wheel bearings, if cup and cone may need adjusting)
    3/ pads loose enough in calliper to move and lightly touch the disc (suck it up......)
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • figbat
    figbat Posts: 680
    You acknowledge that it isn’t the wheel flexing, then ask about spoke tension? The disc is attached directly to the hub; the spokes and rim are not going to influence how the hub and disc move (within reason).

    The Rookie has outlined the things that can physically effect the pad-disc interface. Maybe now your pads are running closer to the disc than before? Perhaps the calliper/pistons need a clean? Maybe the disc is warped? Is the disc mounted tightly? Maybe the fork is flexing.
    Cube Reaction GTC Pro 29 for the lumpy stuff
    Cannondale Synapse alloy with 'guards for the winter roads
    Fuji Altamira 2.7 for the summer roads
    Trek 830 Mountain Track frame turned into a gravel bike - for anywhere & everywhere
  • kajjal
    kajjal Posts: 3,380
    Another less likely thing to check is there may be too much fluid in the brake causing the pad clearance to be very tight. This leads to excess rubbing.

    I had this on one bike, solved by removing wheel, undoing the port on the brake leaver , gently and slowly pushing pads back with large flat screw driver while wife with kitchen roll mopped up the brake fluid that was released, while pads held back wife screwed port cover back in. After that much better, no rubbing and brakes worked fine.

    A normal symptom of this is it can be hard to get the wheel in without the pads rubbing or the clearance is extremely tight compared to the other wheel / brake.
  • figbat
    figbat Posts: 680
    Yep, I have almost killed myself riding against a dragging, overfilled caliper! My method was to apply a little brake pressure with the lever and open the bleed port slowly until a drip or two came out, nip the port back up and then release the lever.
    Cube Reaction GTC Pro 29 for the lumpy stuff
    Cannondale Synapse alloy with 'guards for the winter roads
    Fuji Altamira 2.7 for the summer roads
    Trek 830 Mountain Track frame turned into a gravel bike - for anywhere & everywhere
  • JBA
    JBA Posts: 2,852
    OP - what brakes have you got on your bike?
    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • mtbrider123
    mtbrider123 Posts: 102
    figbat wrote:
    You acknowledge that it isn’t the wheel flexing, then ask about spoke tension? The disc is attached directly to the hub; the spokes and rim are not going to influence how the hub and disc move (within reason).

    The Rookie has outlined the things that can physically effect the pad-disc interface. Maybe now your pads are running closer to the disc than before? Perhaps the calliper/pistons need a clean? Maybe the disc is warped? Is the disc mounted tightly? Maybe the fork is flexing.

    It’s definitely not the disc as I’ve put a brand new one. Don’t think that it’s flex in the fork as i didn’t have this problem before. Maybe removing 1–2 drops of the fluid will help as others suggested?
  • mtbrider123
    mtbrider123 Posts: 102
    Kajjal wrote:
    Another less likely thing to check is there may be too much fluid in the brake causing the pad clearance to be very tight. This leads to excess rubbing.

    I had this on one bike, solved by removing wheel, undoing the port on the brake leaver , gently and slowly pushing pads back with large flat screw driver while wife with kitchen roll mopped up the brake fluid that was released, while pads held back wife screwed port cover back in. After that much better, no rubbing and brakes worked fine.

    A normal symptom of this is it can be hard to get the wheel in without the pads rubbing or the clearance is extremely tight compared to the other wheel / brake.

    Thank you for your idea, I’ll try that and see how it goes.
  • mtbrider123
    mtbrider123 Posts: 102
    figbat wrote:
    Yep, I have almost killed myself riding against a dragging, overfilled caliper! My method was to apply a little brake pressure with the lever and open the bleed port slowly until a drip or two came out, nip the port back up and then release the lever.

    I’ll try that, thank you!
  • mtbrider123
    mtbrider123 Posts: 102
    JBA wrote:
    OP - what brakes have you got on your bike?

    Sram Red etap hydraulic brakes
  • JBA
    JBA Posts: 2,852
    I used to have SRAM/Avid brakes on one of my bikes and every summer I would get brake drag or the pads clamping the disc.
    The DOT brake fluid expands in the heat and effecrively operates the brake. The only solution was to bleed a drop or two of fluid from the brake.
    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • JGTR
    JGTR Posts: 1,404
    It’s flex, the fork flexes when you are out of the saddle and you get a bit of rub (in fact the whole bike will flex to some degree) especially if you have replaced the disc and the clearances may be less. It’s common, it’s normal.....you many need I bleed a bit of fluid or there may be other contributory factors but the cause is exactly the same, flex.
  • 02gf74
    02gf74 Posts: 1,168

    It’s definitely not the disc as I’ve put a brand new one. Don’t think that it’s flex in the fork as i didn’t have this problem before. Maybe removing 1–2 drops of the fluid will help as others suggested?

    The fork is flexing.

    You didn't get disc rub with the old disc so it is the new disc that is causing it.

    If the old disc was worn, a new disc, assuming it is not warped and is same type as the old one, will be slightly thicker.
    Did you spread the pads apart before fitting the new disc, you need to do that to get the clearance.
  • mtbrider123
    mtbrider123 Posts: 102
    I’ve just noticed that one piston is coming out more than the other. So one comes out and goes back to its original place, however, the other comes out but doesn’t go back. If I press again, it comes out even more, so I think this causes the brake pad to get closer to the rotor. Any idea how to fix this?
  • figbat
    figbat Posts: 680
    Strip and clean.
    Cube Reaction GTC Pro 29 for the lumpy stuff
    Cannondale Synapse alloy with 'guards for the winter roads
    Fuji Altamira 2.7 for the summer roads
    Trek 830 Mountain Track frame turned into a gravel bike - for anywhere & everywhere
  • kajjal
    kajjal Posts: 3,380
    A quick way is take out the wheel, gently and slowly press both brake pads back to reset the pistons. Then put the wheel back in and do a few hard stops from speed. Assuming the caliper is lined up that should sort it. It is not unusual for one piston to be a little slower than the other but not by much and it should not stick or cause rubbing.