Really annoying (and I expect unfixable) problem with Shimano Deore XT brakes
Alright guys, long story short I was commuting on my mountain bike (dark, about 5am) and hit an iron gate someone had left open across the cycle path. The impact was concentrated directly on my rear brake lever, as you can see in this image:
I was traveling at a fair rate of knots, enough to throw me over the bars and unfortunately I believe it has damaged the brake internals. This video: VID attempts to show what my problem is. In the clip, I am applying light pressure to the lever and rolling it back and forth. On the forward movement of the bike, the lever sinks very slightly, and this repeats until it touches the grip. Pumping the lever reverses the effect. As you can see after the first demonstration, applying pressure when the bike is stationary has no adverse effects and this is what confuses me. There are no external leaks, no parts missing.
Anyone got any idea at all what could be the problem? I’m expecting the worst (master cylinder damage) so don’t hold back on your thoughts.
Please excuse the dressing gown and bare feet in the videoPosted 4 years agomrjmtMember
Sounds like you’ve blown a seal in the MC.
Like when your seals go in your MC on your car, you hold your foot on the pedal and it will sink to the floor as the fluid is passing past the seal. It likely won’t leak externally as its staying in the bore.
If you pull it quickly it’ll still work as the fluid doesn’t have time to pass the seal quicker than is required to move the piston.
As shimano dont do rebuild kits, i’d send it off. Might as well as it’ll need a new lever assembly anyway, unless you can find a suitable seal to fit it.Posted 4 years ago
That was my thought mrjmt, if a bleed fails I’ll get it sent. The only confusing part however is the fact that it doesn’t happen when the rear wheel is stationary.
Oi less of the sarcey, stu, it looks like a scratch but it’s actually quite a deep indentation. I was trying to show how hard the lever hit the gate.Posted 4 years agocbmotorsportMember
I had an SLX rear brake replaced after it started to become unreliable. I would pick up the bike after a few days of not riding it, and the lever would hit the grip. A bit of pumping would give me some braking force but I was having to sod around with it before every ride. I bled it 3 or 4 times, but to no avail.
I sent the brake back and just got a new one, which thus far has been fine.Posted 4 years ago
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