Inconsistent bite point on shinano xt brake (M785)

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Inconsistent bite point on shinano xt brake (M785)
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flag cherouvim
FL
Posted: Aug 25, 2014 at 10:39 Quote
My shimano xt M785 brakes have inconsistent bite point on the level. The inconsistency can be reproduced every 5 level pulls. It does't matter if the pulls are hard or soft. After 5 quick brake lever pulls the bite point is at a lower point, closer to the grip. The difference is around 5mm in bite point on the finger. It doesn't sound much but it is enough to make me shit my pants when riding trails because I've set my bite point pretty close to the grip.

The brakes are 5 months old and apart from this problem they work superbly. On the 2nd month of usage the front brake started having this behavior. On the 4th month the rear one started as well.

I've just fully bled the front brake (bottom to top method: push from caliper at bottom to master cylinder/lever at the top). I stopped pushing new oil from the bottom when the brand new shimano pink oil started appearing on the top at the funnel. The old oil was yellowish and foggy.

I'm pretty sure I've fully replaced the oil inside and no air bubbles are there. I've previously fully bled my old formula brakes around 15 times so I think I did it right.

The problem is that the inconsistent bite point problem on the front brake (which I've bled) didn't go away. The behavior is exactly the same. After 5 successive quick lever pulls, the bite point goes 5mm closer to the grip.

Where should I look at next?

thanks
flag Chuvak
Posted: Aug 26, 2014 at 5:27 Quote
Put your bike upside down and press the lever several times. Does it begin to touch grips?
flag cherouvim
FL
Posted: Aug 26, 2014 at 6:13 Quote
Yes. It has the same problem I described but even more exaggerated. Hmm. So maybe my bleed was not very good.
flag Chuvak
Posted: Aug 26, 2014 at 18:25 Quote
that is bad bleeding. try again. it's not enough just to press the oil from calliper to lever. you also need to squeeze the lever (press it and throw. that is a good trick for shimano). in the end of bleeding rotate the lever 30 degree up and down and press the oil in both positions. also you can not only press the oil from down to upside, but suck it back from the funnel to syringe. keep trying and all will be fine
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