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My bros M615 rear brake keeps needing bleeding otherwise within a short period of time the lever goes from firm to floppy . They have had relatively little use so unlikely to be worn seals ....also no sign of leakage .
I seem to remember some Shimano brakes are quite notorious for this issue and wondered if there is any fix apart from buying new ?
Any suggestions much appreciated .
Cheers
Bill
First double check that the bleed is done properly: I always forget to unwind the reach adjustment on the lever and that results in a bubble of air. The M615 design appears to be quite good at catching bubbles of air in various places, I suspect that's why the newer calipers bleed differently.
I always forget to unwind the reach adjustment on the lever and that results in a bubble of air.
Ah, I don't do that, I didn't think that the reach adjuster affected anything. I am aware that if the brakes have a bite point adjust, this should be fully out.
OP, I was really surprised how much air I pulled out of the rear calliper after filling it (and I'd been careful to remove the air from the syringe before filling).
Shimano recommends using a plastic bag on the end of the tube to let the oil flow back, but I top up the oil in the cup and just draw back on the syringe until no more bubbles come out.
It might be worth trying another bleed. The rear brake has a longer hose and more convoluted run so there's more chance of getting air in the system.
Your probably not doing anything wrong and you just have bad brakes
However, saying that I have had much better results with a gravity bleed with my shimanos and now do this exclusively.
Ah, I don’t do that, I didn’t think that the reach adjuster affected anything. I am aware that if the brakes have a bite point adjust, this should be fully out.
Yeah, I'm not sure how the reach adjuster can affect anything (at least on my brakes), as it's just a mechanical adjustment between lever and master piston.
OP, I was really surprised how much air I pulled out of the rear calliper after filling it (and I’d been careful to remove the air from the syringe before filling).
If you're pulling on the syringe, is it possible that you're actually pulling in air where the hose connects to the nipple? I've certainly done this.
Shimano recommends using a plastic bag on the end of the tube to let the oil flow back, but I top up the oil in the cup and just draw back on the syringe until no more bubbles come out.
I always push fluid up from the bottom. If you've got bubbles in the reservoir at the top, I'm not convinced that drawing from the bottom pull them all through. Certainly, you'll have quite a lot of fluid to draw through before you get them. Also, make sure that the last thing you do is gently push fluid into the system with the other end closed so that the reservoir is full.