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Whats wrong with my disc brakes? Please help!

boxrickboxrick Posts: 38
edited April 2019 in Workshop
I had a bike with full Ultegra 6800 and hydraulic disc brakes, the bike was not the right size no matter what adjustments I made, so I sold the frame and my dad who is pretty handy with bikes transferred most of the pieces off onto a Roubaix frame I picked up.

However the brakes were squealing massively and basically not stopping me. I purchased a new set of pads and took it to a bike mechanic.

The bike mechanic had it for 6 months and replaced the tubes, got the front shifter replaced by Madison ( who sent out an umatched R8000 shifter ) and a new caliper.

He also did a variety of unrelated things to the bike to do with the drivetrain, the bike mechanic said he has bled it countless times and tried loads of different things. I also cycled home and around 15 times cycled up to around 20 mph and braked hard to try and bed in the pad.

Ultimately the rear brake is now fine, locks on and brakes as you would expect. The front one has 2 issues:

1) The first couple of pulls has loads of travel, then subsequent pulls lock on quite quickly. This gradually reverts back to loads of travel in a couple of minutes.

2) When fully locked *hard* the brake still allows the wheel to move. When I am cycling this simply means it is not functioning correctly.

This whole issue is driving me crazy and I would really like some advice, I am happy to spend the money to get this fixed. I am thinking of purchasing some new rotors and picking up a matching R8000 for the left shifter since these feel completely different on the bike.

Additionally is there anyone around Manchester who may be able to help me out?

Video and pictures below, I have also included a picture of my Red Roubaix which is perfect:

https://www.youtube.com/watch?v=ZEp8iDmIrPo

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Posts

  • cyclecliniccycleclinic Posts: 6,865
    It should be trapped air. I have taken to pulling the syringe back to pull fluid back from the resovioir. Alot of trapped air can be drawn out. Once that in the syringe reinject the fluid and repeat until there is not trapped air. That solved the problem for me a few times.

    This is not a official Shimano bleed process but it seems to work and causes no harm.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • oxomanoxoman Posts: 11,173
    Just sounds like they need bleeding and setting up correctly.
    https://m.youtube.com/watch?v=TYhb8tGUzbs
    Hope this helps.
    Too many bikes according to Mrs O.
  • sparquinsparquin Posts: 69
    It should be trapped air. I have taken to pulling the syringe back to pull fluid back from the resovioir. Alot of trapped air can be drawn out. Once that in the syringe reinject the fluid and repeat until there is not trapped air. That solved the problem for me a few times.

    This is not a official Shimano bleed process but it seems to work and causes no harm.

    Funnily enough, you've just described the Magura bleeding process, which is the fastest and most effective way to get air out of your brake lines.
  • boxrickboxrick Posts: 38
    You still think it's bleeding despite being bled numerous times by an experienced mechanic?

    I'll buy myself a bleed kit and give it a go I guess then.
  • ugo.santaluciaugo.santalucia Posts: 27,696
    boxrick wrote:

    The bike mechanic had it for 6 months...

    That's quick service for you...
  • photonic69photonic69 Posts: 1,828
    If any mechanic has a bike for 6 months I'd hardly call him an expert/professional/experienced!!!
  • DeVlaeminckDeVlaeminck Posts: 8,305
    PhotoNic69 wrote:
    If any mechanic has a bike for 6 months I'd hardly call him an expert/professional/experienced!!!

    Well he's had at least 6 months experience now.
    [Castle Donington Ladies FC - going up in '22]
  • apreadingapreading Posts: 4,535
    First piece of advice is get a new mechanic. If he has had access to the bike for 6 months and not fixed it but you think a bunch of people on a forum might be able to suggest the problem without seeing it, then there is something seriously wrong there.

    Air in the system or a really flexible tube seem the most likely causes for the long travel and the latter of those unlikely unless he bought cheap hose intended for some other purpose.

    I wouldnt worry so much about 'problem' number 2 unless the wheel still moves REALLY easily - pulling the brakes on hard when cold and being able to move the wheel is a totally different circumstance to when you are moving and the friction at the pad generates heat and makes it bite.
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