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Replacing Hydraulic Brake Caliper

photonic69photonic69 Posts: 1,537
Hi All,

I have 105 BR-RS505 brake calipers with the corresponding ST-RS505 shifters. The front caliper suffers from a sticky piston. I'm constantly having to clean, fettle and adjust the caliper to stop it rubbing. Brake lever action is also excessive despite freshly bled system etc.

I want to replace just the caliper with another. That specific caliper is now obsolete so I need a compatible item. I have read that any Shimano caliper (road and MTB) are OK to use and conversely read the exact opposite. Given that parts are hard to find at the moment what is my best, quickest, cost effective remedy for this? What about hose type? 59 vs 90? I guess I'll need a new olive but will the barb be ok to leave in place? I'm just disconnecting and replacing.

Thanks.

Posts

  • photonic69photonic69 Posts: 1,537
    So I took out the pads and gave the outside of the pistons and good scrubbing with degreaser and a sawn off toothbrush, rinsed and lubed with GT85 whilst holding back alternate pistons with a lever and operating the brakes to free up the sticky pistons. Removed all excess lube and put new pads in and realigned the caliper. All is well again - but this lasts for a max of 2-3 months before I need to do it again.

    I'm using Sintered pads from Gorilla Brakes. They do leave a lot of black brake dust around the calipers and pistons. I live in a very hilly area so they get a lot of use.

    Any one have an idea of a replacement caliper for me so I don't have to do this all the time?
  • andyrrandyrr Posts: 1,669
    I’m not familiar with hydraulic bicycle callipers but am with automotive ones - if yours have a rubber seal on the piston I wouldn’t use GT85 or similar but would be using a lube compatible with that material. Red rubber grease is what is most often used for cars and motorbikes, it can be tricky to get hold of but doesn’t degrade seals or cause them to swell.
  • photonic69photonic69 Posts: 1,537
    @andyrr - gt85 is largely a silicone based lubricant and safe for use on most rubber compounds. If I was stripping down the caliper completely and removing the pistons I would either use red grease as you suggested or just lube them with the shimano brake fluid.
  • ibr17xviiibr17xvii Posts: 988

    So I took out the pads and gave the outside of the pistons and good scrubbing with degreaser and a sawn off toothbrush, rinsed and lubed with GT85 whilst holding back alternate pistons with a lever and operating the brakes to free up the sticky pistons. Removed all excess lube and put new pads in and realigned the caliper. All is well again - but this lasts for a max of 2-3 months before I need to do it again.

    I'm using Sintered pads from Gorilla Brakes. They do leave a lot of black brake dust around the calipers and pistons. I live in a very hilly area so they get a lot of use.

    Any one have an idea of a replacement caliper for me so I don't have to do this all the time?


    I have discs on my winter bike & I find that I need to clean / regrease the pistons every couple of months or so for the same reasons. They start rubbing when I'm out of the saddle which is the tell tale sign for me. I use a light coating of Shimano mineral oil which seems to work well.

    I'm not sure there is any better answer than what you are already doing TBH.
  • photonic69photonic69 Posts: 1,537
    ibr17xvii said:



    I have discs on my winter bike & I find that I need to clean / regrease the pistons every couple of months or so for the same reasons. They start rubbing when I'm out of the saddle which is the tell tale sign for me. I use a light coating of Shimano mineral oil which seems to work well.

    I'm not sure there is any better answer than what you are already doing TBH.

    Yeah, this is something they never tell you when saying how great disc brakes are!!

    Conversely my wife has a Giant Rapid, flat bar road bike with Tektro M285 Hydraulic Disc brakes. She's done over 6000 miles in all weathers, the pads are still original, has great lever feel, I've not had to bleed them and they have been problem free over the 3 years shes had it.

    I believe Chris Froome doesn't like discs either due to them rubbing.

  • ibr17xviiibr17xvii Posts: 988

    ibr17xvii said:



    I have discs on my winter bike & I find that I need to clean / regrease the pistons every couple of months or so for the same reasons. They start rubbing when I'm out of the saddle which is the tell tale sign for me. I use a light coating of Shimano mineral oil which seems to work well.

    I'm not sure there is any better answer than what you are already doing TBH.

    Yeah, this is something they never tell you when saying how great disc brakes are!!

    Conversely my wife has a Giant Rapid, flat bar road bike with Tektro M285 Hydraulic Disc brakes. She's done over 6000 mailes in all weathers, the pads are still original, has great lever feel, I've not had to bleed them and they have been problem free over the 3 years shes had it.

    I believe Chris Froome doesn't like discs either due to them rubbing.


    Without going down the whole disc v rim rabbit hole, performance wise mine (once you have them set up spot on) have been flawless particularly in the wet.

    Maintenance wise there is no doubt in my mind they are a wee bit more of a faff than my rim brakes.
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