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  1. #1
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    Damaged SLX hydraulic brake system???

    Hi guys, i'm new of the forum and I wisg to have some of your expertise to help me finding out what's wrong with my bike.
    I have a Trek 6700, 2009 model mounted SLX.

    I have been riding it gently mostly to work and short trips. Lately the brakes have lost sognificantly power, both front and rear. Since I noticed that the calipers (do i write it right?) inside the brakes were kind of stiff, I lubbed them with some spray oil (following the advice of youtube).
    Since then the situation has just worsened, now the brakes are squeaking every time I have to come to a complete stop and the stopping power is further reduced, especially when I hold the brakes for a long time. I have tried to bleed the system and to change pads but there is no effect whatsoever. When I unmount the brakes I always find traces of oil on the pads and on the discs.

    My question:
    1) Do you think I have dameged the seals of the brake system?
    2) If yes, is it possible to repair or do I just have to trash the whole thing?
    3) How come that I have been searching the web for weeks for similar cases and have never come on anything like that...Are these problems not common with hydraulic brakes?
    4) Could you suggest me a good mechanical disc brake to eventually replace mine. I got kind of fed up of hydraulic systems...

    Thanks for all the help you guys are gonna give me

    Best Regards
    Alessandro

  2. #2
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    did you use a spray lube from a can and did you remove the brake pads first?? If you didn't remove the brake pads first you've probably contaminated the pads and will either be lucky and can burn/clean the contaminant off or will need to buy new pads.
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  3. #3
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    well when i sprayed for lubbing the calipers i definetely removed the pads.

    but now the pads are contaminated for sure since there's oil leaking all the time I brake very hard.
    The question is where is that oil coming from? In my opinion it can only come from the system and I guess that the seals have been damaged...
    But how come that something like this has happened simultaneously on front and rear brake??? How come that nobody has encountered my problem...I searched thoroughly the net and found nothing...

    Thanks for help

  4. #4
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    The reason you are not finding anything on the web about your problem is that it is not a common problem. What you did when you sprayed oil in the caliper is likely used a lubricant that was not designed to be compatible with the piston seals. That's why it is recommended to use DOT fluid (for DOT brakes) or mineral oil (for mineral oil brakes like yours) when lubing piston seals. From the sound of it, whatever oil you used, has damaged the piston seals and they are now leaking. The solution is to tear down and rebuild the calipers, replace the pads, and clean the rotors.

    Good Dirt
    "I do whatever my Rice Cripsies tell me to!"

  5. #5
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    mmm i see. But realistically, is it anything doable for me (rebuilding the calipers?) how could I fix the seals? If you mean that this can be done with a reasonable expense I will take it into consideration, otherwise I will just buy a new mechanical system.
    Thanks a ton!

  6. #6
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    Here is a current version of the SLX ready to go and a significant improvement over your model from 2009. $70 from Bluesky.
    Clean your rotor and bed in the new pads.
    BlueSkyCycling.com - Shimano SLX M666 IceTech Disc Brake w/Adapter

  7. #7
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    Quote Originally Posted by eb1888 View Post
    Here is a current version of the SLX ready to go and a significant improvement over your model from 2009. $70 from Bluesky.
    Clean your rotor and bed in the new pads.
    BlueSkyCycling.com - Shimano SLX M666 IceTech Disc Brake w/Adapter
    I am with eb1888. More expensive than a rebuild but you only have to do it once: Buy new brakes. Installing new brakes takes about 10 minutes. Don't even worry about cutting your brake lines if too long (assuming they come pre-bled). Just loop them with cable ties and have them cut appropriately next time the bike is in the shop (assuming you don't have the tools and expertise to cut hydraulic lines). You'll enjoy your new brakes. Consider upgrading to XT while you are at it.

  8. #8
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    Another vote for eb1888's suggestion.

  9. #9
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    Hei guys, just wanted to update you.
    I have done a thorough job cleaning rotors and pads and apparently I succeeded fixing 70% of the problem.

    I have boiled for 15 min in soap water rotors and pads, then I baked the pads 220 celsius for 15 min and finally I cleaned everything again with gasoline. I cleaned the calipers and removed every particle of grease and dirt.

    Now the bike is stopping without squeaking, no sounds at all and so far I couldn't see any trace of oil leakage on the rotors or pads. However I noticed that the rotor width is 1.7 mm and the pads are quite used so I reckon that with new pads and new rotor I should be able to get a 100% full working system...

    So my theory is now that the pads and the rotors were soaked wet with the lub fluid that I used to clean the calipers. Even though I tried to sand-paper the pads several times I was not able to improve the situation. Is it my understanding correct that braking pads can get really soaked with oil (i mean it penetrates deep in the material like it was a sponge)?

    Thanks again for your tips.
    I hope that I managed to fix this issue...and that it will last...:-)
    happy riding!

  10. #10
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    Glad to hear you got it sorted, just remember, gasoline comes from oil and still has some lubricating properties in it, best to use alcohol in the 99% range. I'd have to concur with your reasoning of running those brakes for 5 years and needing new pads (more than likely) and new rotors wouldn't hurt FYI, I can't even imagine what it would be like to ride a bike for even a year with one set of pads I thankfully decided to check my XT pads last night after coming to a hard road stop and feeling like maybe metal on metal, found out I'd worn down the front pads to just that, well starting. Have had these brakes for 8, maybe 9 months, but then again I ride this bike prob 3 times a week and recently found and made a nice 11 minute steep descent, so that prob hasn't helped

    Quote Originally Posted by abo_83 View Post
    Hei guys, just wanted to update you.
    I have done a thorough job cleaning rotors and pads and apparently I succeeded fixing 70% of the problem.

    Thanks again for your tips.
    I hope that I managed to fix this issue...and that it will last...:-)
    happy riding!
    One day your life will flash before your eyes, will it be worth watching??
    MTB Barbados
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