I bought a new bike with hydraulic brakes in september 2019. It was working fine for a few weeks but after that I started to notice my disks blackening and the brakes lacking power.I got told that there was probably air in the system so went to the shop to get it fixed which they did for free as it hadn't been over 6 weeks since the purchase.This is a link to the old thread which helped me a lot but I haven't had a chance to visit the shop due to bad weather. Hydro brake disk blackening It's been about 2 to 3 months since that thread and the weather finally settled this weekend so I took my bike out only to find that none of my brakes work at all now.Im not sure what to do now.Id be grateful if anyone can help.BTW they are Clarkes brakes

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    It could be the brake fluid leaking and contaminating. If your bike is still covered by warranty, you should claim it as a warranty problem if it is indeed a leak caused by a fault. Commented Mar 8, 2020 at 16:31
  • How long would the standard warranty cover because I think mine was only 6 weeks
    – Jash2204
    Commented Mar 8, 2020 at 22:44
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    That is ruled by the consumer laws of your country (which you did not mention). However, six weeks sounds ridiculously short for any developed country. Even though perhaps anything is possible in the land of unlimited possibilities. Commented Mar 9, 2020 at 8:05
  • I'm in the United KingdomEngland
    – Jash2204
    Commented Mar 10, 2020 at 11:04
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    Then your bike must be covered by warranty. You should claim it before attempting to fix it yourself. Or at least before making any larger changes. Normal maintenance is allowed. Commented Mar 10, 2020 at 11:10

1 Answer 1


Black stripes on the disks usually means contamination. Disks should look shiny and clean.

This could have been picked up from the road e.g a splash of oil or diesel, or the callipers are borked and leaking fluid or oil depending on what Clarkes use.

Take the callipers off the bike and examine them. They will be dirty but shouldn’t look “wet” behind the pad or near the bleed valve or anywhere really. That would be a sign that they are leaking. If they are leaking they need to be fixed or replaced.

You need to decontaminate the disk by removing it from the wheel, sanding lightly with very fine grade sandpaper on a flat surface and cleaning with isopropyl alcohol. You can get the isopropyl from a car supplies store very cheap. It’s called brake cleaner.

The pads might be able to be decontaminated by cleaning with isopropyl and sanding lightly. More extreme is setting them on fire (outside) with the alcohol and again cleaning/sanding but also likely is that you need a new set of pads. Organic pads soak up contaminants and emit them like a sponge.

You can tell if your brake lines have air in them if the levers are spongy/springy when you pull them hard. The bite point should be relatively hard in air free lines. Do this with the wheels installed, don’t pull your brake levers when there’s no discs between the callipers.

All these cleaning things are super easy to do at home with a hex wrench and screwdriver. There are many good YouTube videos on the topic. GMBN has a good one on decontaminating disk brakes.

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    Please note: Do not test if the brakes feel spongy when rotor and or pads are removed. It may push out pistons too far.
    – gschenk
    Commented Mar 8, 2020 at 16:25
  • I understand what you have advised however I'm not sure how to do that at all.Do you have any idea how much I SHOULD be paying if I had to go get it done at a shop and I think there is air in my system.How much would it cost?
    – Jash2204
    Commented Mar 8, 2020 at 17:21
  • Cost depends on where you live and the average rate for the bike shops there. But a bike shop is unlikely to do these deep clean tasks They will tell you to replace the rotors and pads and charge you at least 1 to 2 hours of shop time plus parts and markup. A bleed will probably attract an hour of shop time plus fluid. I’ve tried to point you in the right direction, either spend the $ with a shop or take the time to learn about your bike by reading about it and watching some videos. I’m not a pro bike mechanic and have never worked in a bike store so I’m just guessing rough times. Commented Mar 8, 2020 at 18:52
  • Thanks for the help Warren I think I'll go to the shop and see what they can do for me because on ny previous thread someone stated that since it has been under 6 months of purchase I'm covered by consumer rights for defects which arent caused by me so I'll try and see if they can fix it for free.If not I'll try to fix it myself
    – Jash2204
    Commented Mar 8, 2020 at 22:43

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