Front brake rubbers: BMW R100 1982

Discussion in 'Airheads' started by Kiwicruiser, Nov 13, 2017 at 8:58 PM.

  1. Kiwicruiser

    Kiwicruiser n00b

    Sep 9, 2017
    Melbourne Australia
    Hi folks,

    I have taken my front brake callipers off and removed the brake pads. I was just hoping to inspect and give a bit of a clean, but notice one of the circular rubber seals that sits over the cylinder just behind the pads has had it (fell right off, where as all the others are still nicely held in place). Can I simply order a new seal and replace this one by pressing it on ... or is this a bigger job? (new to brakes and was hoping to avoid a service/rebuild at this point, but have a healthy respect for their purpose in life...).

    Any help most appreciated as always.

    Thanks, Ty
  2. Cogswell

    Cogswell Spudly Adventurer

    Jan 3, 2005
    Riding with my pal Richard Cranium
    yes, should just take a few minutes to clean and replace.
  3. disston

    disston ShadeTreeExpert

    Mar 22, 2011
    Silver Spring, Md
    It's a dust seal. Under it is the piston and another seal deeper. The second seal keeps the brake fluid in the caliper.

    It's very possible that all you need is the dust seal but I think they, dealers, only sell a kit that contains both seals. They also sell another kit that contains the seals and a new piston. At this point you need to look at what is really going on before you buy parts because you can't buy the pistons without the seals so if you got the seals and then discovered the pistons were pitted you'd have to buy the seals again.

    This is general info concerning BMW brake calipers but you don't say what year your bike is. Are they ATE calipers or Brembos?

    If the dust seal went bad then it's possible there is damage inside and to do it right I would take all of them apart to see if new seals all around would work or if they needed new pistons.

    The pistons rust and pit in the bores from water in the brake fluid because of not enough changing of brake fluid.
  4. Warin

    Warin Retired

    Aug 30, 2012
    If the outer seal is gone .. then clean the area (old tooth brush, detergent and water) then look for any signs of corrosion. Extend the piston, say, half a pump on the handle bar and recheck for corrosion, you may need to clean again to remove any further dirt.
    If no corrosion - replace seal. Corrosion .. I'd disassemble to make a good examination and make a decision then on parts required.

    If you simply decide to replace the seal - after cleaning with the above soap and water allow it to dry and then clean with methylated spirits - this combines well with any remaining water and helps remove it - thus reducing any corrosion in the future.

    The brakes are brembo - you can get parts from a Ducati dealer, a motoguzzie dealer .. they can be cheaper than a bmw dealer.