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Disc rotor alignment

barongreenbackbarongreenback Posts: 229
edited March 2019 in Workshop
Morning all

Have installed two new wheels with Dura Ace 140mm (rotors) - no other reason than I liked the black centre with a black bike and deep section wheels :) Paired with RS685 callipers (the old non-series Ultegra).

That said, for the life of me I cannot align the rotors properly and they are rubbing in one section. I've tried the following:

- Loosening bolts, clamping brakes and retightening
- Doing the same as the above but with a business card to try and space the pads further apart
- Eyeballing the rotor

The back rotor pad spacing is just wide enough that I can avoid rubbing but the front is still doing it.

No matter what I try, I'm still getting a bit of rub. Seems a bit odd that both rotors would be out of true. They're centre lock and the ring is done up nice and right. Wheels are running nice and true and in all other respects are fantastic, apart from the wind this weekend!

Any suggestions of anything else I can try? Thanks.

Posts

  • rafletcherrafletcher Posts: 1,235
    Do they rub on the workstand, or only when riding? If on the stand (or not under load) then something isn't straight, be it warped rotors or wheels not properly aligned.

    It may be that if it's on the stand, then riding will knock the pads back a bit and relieve the rubbing. Cleaning around the pistons may make it easier for the pads to retract as well.

    If it's when riding, well things distort / flex under load, and that's maybe something you'll have to put up with.
  • Check the torque of the thru axles...
  • imposter2.0imposter2.0 Posts: 11,964
    If these are new pads and this is just mild rubbing rather than actual binding, then it might just be that the pad surface needs to 'align' itself with the disc surface and the issue will resolve itself after a couple of hours of riding...
  • hopkinbhopkinb Posts: 7,129
    Are the pads new? Sometimes takes a while for a bit of pad material to wear away before noise free.
    Like someone else said - try and clean around the pistons with an ear bud soaked in IP alcohol. Then make sure they are fully pushed into the caliper, put the pads in again and align the calipers by eye, nipping up the bolts bit by bit alternately.
    I'll often hear a ting-ting on the stand, which I never notice out on the road.

    Oops, crossed with Imposter.
  • Thanks all. Pads were not replaced (probably have about 2,000 miles on the bike but not in a massively hilly area so no indication they are overly worn). The rub happens in the work stand rather than under load when riding. The intermittent nature of the rubbing means that something is odd but taking the rotors off the bike doesn't immediately show anything out of true.

    Thru axles are also done up nice and tight by hand (it's a Trek Domane, axles make by DT Swiss).
  • photonic69photonic69 Posts: 1,828
    You say both rotors are the same size? Can you swap front to back and see if the rub moves with the rotor?
  • AlejandrosdogAlejandrosdog Posts: 1,975
    as a separate comment, i just don't understand how people are fine accepting that their disc brakes are going to rub for a few hours whilst they magically sort themselves out.

    To solve this issue,

    1 Remove the calipers carefully from the frame
    2 remove the discs from the wheel
    douse the bike wheels calipers and discs in petrol
    3 burn

    buy a proper bike and swear to never follow the marketing guff of big bike companies.

    or take the bike to a shop that has and knows how to use a disk alignment tool (the one that sorts the posts or direct mount contact points.

    Refit and see if that works.
  • hopkinbhopkinb Posts: 7,129
    as a separate comment, i just don't understand how people are fine accepting that their disc brakes are going to rub for a few hours whilst they magically sort themselves out.

    They don't rub, they "ting" while up on a stand. There's no noticeable binding, the wheels turn freely. One commute with new pads and the noise is gone.

    I'd rather that than grab a handful of brake when some inattentive so & so in a car decides to turn left without looking and for nothing to happen until too late. Means I can ride carbon rims all year and all weathers too.

    Either that or I'm a shill for the marketeers. Or a sheeple. Or something. Or I made a choice that works for me. :roll:
  • Have you tried pushing the caliper pistons into the recess, with the proper tool, or like me using something like the end of a plastic tyre lever lever?
    ================
    2020 Voodoo Marasa
    2017 Cube Attain GTC Pro Disc 2016
    2016 Voodoo Wazoo
  • Have you tried pushing the caliper pistons into the recess, with the proper tool, or like me using something like the end of a plastic tyre lever lever?

    Not gone that far yet although the business card trick pushed them back a little. It does look like the rotor is a bit wonky when I spin the wheel although it could just be a trick of perspective. Will give those a try and failing that, worth a few quid to get the LBS to have a look at it.
  • daniel_bdaniel_b Posts: 10,694
    This is your friend.
    31aos0ALTLL._AC_SY400_.jpg
    Felt F70 05 (Turbo)
    Marin Palisades Trail 91 and 06
    Scott CR1 SL 12
    Cannondale Synapse Adventure 15 & 16 Di2
    Scott Foil 18
  • AlejandrosdogAlejandrosdog Posts: 1,975
    hopkinb wrote:
    as a separate comment, i just don't understand how people are fine accepting that their disc brakes are going to rub for a few hours whilst they magically sort themselves out.

    They don't rub, they "ting" while up on a stand. There's no noticeable binding, the wheels turn freely. One commute with new pads and the noise is gone.

    I'd rather that than grab a handful of brake when some inattentive so & so in a car decides to turn left without looking and for nothing to happen until too late. Means I can ride carbon rims all year and all weathers too.

    Either that or I'm a shill for the marketeers. Or a sheeple. Or something. Or I made a choice that works for me. :roll:

    Fair enough, the carbon rimmed world commuting race is very important :)
  • hopkinbhopkinb Posts: 7,129

    Fair enough, the carbon rimmed world commuting race is very important :)
    :D
    It most certainly is. All else pales into insignificance.
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