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Shimano Deore M615
What kind of damage can dragging the brakes too much do, if any?
After three bleeds I still can't get them sharp. They bite, but still too much lever, still too spongy.
It was the result of ending a full days coaching on Innerleithen steep which left, not only me a shaking wreck, but my brakes levers pulling all the way to the bar. I admit I was dragging the brakes pretty much the whole time down Repeat Offender and Community Service. Top notch trails but I was out of my depth once at low energy levels.
Overheated and damages seals? Any leaks? Replaced fluid completely?
Glazed the pads? Tried new ones?
Thanks for the response. That's what I was wondering, had I overheated the seals.
Yeah, I did a full fluid replacement. The front brake fluid was brown, the rear looked fine, however, the rear is the worst.
I've tried sucking air out of fluid using a vacuum in the syringe before attaching to the calliper and extending pistons to maximise fluid in system. Bike has been rotated in the stand to get the calliper and hose vertical.
Yeah new pads are in
What state are the rotors in, worth a measure for thickness.
Also I've found that since coming to live in the Tweed Valley I've had to go up from 160/140 rotors to 180/180 (and now got a 200 on the front of the 29er) - mincer also.
How old are the brakes?
I seem to be hitting a point at about 2 years old (XT in my case but internals will be no different) where the lever-feel deteriorates and becomes inconsistent.
If still in warranty (2 years), I'd send them back anyway. Chances are they'll just replace with new.
i'm crap at riding bikes, years ago i dragged my (then already) ancient deore brakes down the MegAvalanche. 2 years later i did it again, with the same brakes.
They never missed a beat, I'd be surprised if you'd done any permanent damage to your brakes.
a spongy lever suggests air in the system, it can be quite tricky to get all the bubbles out, you've almost got to think like a bubble, dude.
I did the epic bleed solutions 5 minute bleed on mine last week and it was amazing how many air bubbles there were. Could do with a full bleed though as the oil was a bit discoloured. If the oil is like that is it worth draining all the old oil from the system before putting new stuff in or will the cause an unforeseen (by me) problem?
Thanks for the suggestions guys.
Rotors still have loads of meat on them. I can't pick up any wear on them with a fingernail test. I have 180/160 rotors.
Brakes are a year old.
I'll have one more go on each end, this time thinking like a bubble 8) If it fails then I'll hand it over to a pro. If that fails then I'll see what my LBS who sold the bike say about a warranty claim.
The odds that you overheated them enough to damage them at the golfy are basically zero imo, it's just not that big a hill. But harder use than your normal can show up setup/service issues that have been fine up til now, I think probably this catches out everyone sometimes... So I'd bet it's just that, and a service will probably bring them back up to scratch.
Oh yeah, the Epic 5 min bleed was tried. It felt perfect immediately after that, but a short ride later that "stiff feeling" had gone.
Have you tried the motorbike bodge of tying the levers back overnight? It doesn't fix any problems permanently but it helps air to gather at the top of the circuit making it way easier to get out
(sometimes it'll get it all into teh reservoir, meaning the brakes feel great, but it'll get back in and sabotage you again. This works better for motorbikes with their huge, elevated reservoir and lesser tendancy to be turned upside down)
Ah, I've heard of that, but I didn't understand what it was meant to achieve. Now I see, so I'll be trying that tonight! Cheers
I've used Northwind's solution/bodge on a couple of bikes and it has worked.
what fluid have you used?
newer Shimano seem to be pretty sensitive about using their own proprietary oil.
Yep I always use the Shimano branded oil.
Are you still in Innerleithen? I could take a look at them if so.
Have you checked the brake alignment and the pistons are retracting evenly? Try shining a torch from behind the calliper to check all is even and straight.
Thanks for the kind offer [b]goodgrief[/b], but I'm back home in Aberdeenshire.
Solamanda, I've got good brake alignment. I've cleaned up the pistons twice and get good movement. Though it isn't totally even, its pretty close.
[i]The odds that you overheated them enough to damage them at the golfy are basically zero imo, it's just not that big a hill.[/i]
If he took 10 mins coming down Repeat, and dragged the brakes all the way - they'll be fairly 'warm'...
how much space between the pads and the rotors do you have?
I know it's a long shot but have you checked the 'reach screws' haven't loosened.....I thought my rear brake had gone the other week, checked the grub screw and it had unwound itself putting the lever pull closer to the bars....wound it back where it should have been and hey presto, perfect rear brake! It's often overlooked not just by me....
Cheers guys,
[b]b r[/b]: almost exactly what happened, though I had to stop as my legs were trembling and forearms pumped, haha!
[b]poah[/b]: will need to check that, but it's not excessive. The problem is after the pads make contact the lever will pull further.
[b]Suggsey[/b]: Yeah, I loosened out all the way for bleeding then readjusted after a bleed.
Another full bleed done over the weekend, bike vertical, all new fluid in and passed it back and forth several times until no bubbles. I was amazed that even on the third go I was getting some tiny air. Fairly happy that they are purged now, though not had time to test ride.
What should I realistically expect at the lever? I think I've lost sight of what a good brake feels like. Will pulling with all the strength of a finger give some, eg, do seals compress a little, hose expand a little, allowing lever to move further?