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Being the cheap skate that I am, I saw various places selling off older versions of XTR dual control levers and XT calipers individually for not much cash.
I bought 'em along with a Clarkes hose kit, and done all the assembly.
The front brake works like a dream.
The rear brake is doing my nut in! When the bike is left for a few days, or even a few hours, the brake goes all spongey and pulls right back to the bars. Now, to me that suggests air in the system. But the thing that riddles me is that when you pump the lever 10-12 times, it returns to normal operation, for between 1 minute and 1 hour. So it can be a bit disconcerting when you grab a handful of brake only for it to come right back to the bars with no bite.
Anyone got any thoughts as to what the issue could be? I've bled the system 4 times now, with no change in the symptoms. I've checked all the banjo's and fittings are tight, and can't see any brake fluid escaping from anywhere.
Any tips for things to try would be grand.
Cheers,
Kevin
Anyone?
sorry vague answer but surely must be a seal on its way out somewhere? prob in the master cyclinder?
Change the olives, I had this and it turned out one of the olives wasn't seated right and was slowly letting air in the system, new olives and it's fine, worth a try, olives are cheap
Cheers guys. Sincerely hope it's not a seal in the caliper - they were brand new. Glad to hear someone else has had the same problem and managed to fix it - just ordered some new olives. Thinking I should probably replace the o-rings on the banjos at the same time. Anyone know where to get them?
Sounds like it just needs bled. What with air being a gas and all that...
Elastic band around the brake lever, pull it back to the bars, wrap elastic band around bars , leave overnight. Job done
My first though is a master cylinder seal. Bleed the system through. Tie the lever back to the bar so the system is under pressure. Leave a while and check for leaks. If air is getting in, fluid will also get out. Look for the wet patch. If there isn't one, fluid isn't escaping, it's just bypassing an internal seal. This would again, lead me to think it was a master cylinder seal.
Bled it 4 times now, with no improvement. Left it overnight with the lever cap off and the lever compressed hard to force air out...all with no real effect. Will try again tomorrow and will check for oil.
Would it not be a bit odd for a new caliper to have a bust seal?
Classic symptoms of a system that needs bleeding - in a car the brake pedal will do exactly the same thing.
Re-bleed the brakes - you STILL have air in there
I had the same problem with my brakes, have you tried lifting the front end of the bike up when bleeding your brakes as there is usually some air trapped in the top of caliper because of how it is postioned, this worked for me, hope it helps.
I had the exact same issue on both my dual controls. Basically I just kept pumping oil through then holding lever back overnight and repeating. Eventually it worked but a royal pain in the ass. The rear is never as good as the front despite this.
But I do like the flippy paddles mind!
Definitely air in the system - persevere and eventually you'll cure it.
Well had another look today. Took the caliper off the frame and dangled it down towards the ground with the frame in the workstand (and the levers on the bars).
Took the reservoir cap off and was surprised to see some tiny pico-bubbles coming out of the hole when I pulled the lever. Quite a few of them really. Left the brake all day with the lever pulled in tight (they had firmed up by this point). Went out this evening, took off the cable tie, and pulled the lever a few times - still lots of pico-bubbles coming out. No oil escaping anywhere from what I can see. Brakes still firm though, so will see how they are in the morning. Can't help thinking the top olive hasn't seated properly, letting in the pico-bubbles. But as someone else mentioned, if the air is getting in, I'd have thought oil would be escaping.
Will post up the results, I'm sure you're all on the edge of your seats. 😉