I have a xt front disc brake ( one of the servo wave ones) when i first squeeze the lever it comes close to the bars but after a couple of quick pumps the lever becomes solid with hardly any movement at all, i let it go and the lever gets its full movement again. My rear one just works normally as does my mates front one. why is this happening? cheers.
air in the system somewhere, give it a bleed see if that sorts it
definately an air leak. Visually check for any leaks or splits in the hose, tighten the coupling between the hoses and caliper/lever. Replace as much of the fluid as possible with new stuff and bleed any remaining air out of that. If it still does it try once more for luck before looking at things like seals on the calipers etc.
Its been bled a few times by shops but still has the same problem, is there any other things that could lead to this problem, dodgy seals etc
did the shop bleed it or replace the fluid? Brake fluid can become infected by air whihc is why you shouldn't leave the cap off for too long etc. Give the entire system a really good clean so things are easy to spot.
Does anyone else think this typically sounds like issues with the lever?
I am having the same problem with my rear leaver. After a long bleeding session using the syringe at the calliper end and the official clamp at the lever end I still have air getting in from somewhere. I think in my case it is the lever because when I cycle the lever with the cap off air appears in the master cylinder on the return stroke. It is really annoying. 🙁
Brake fluid can become infected by air
hydraulic brake fluid (DOT) absorbs moisture out of the air
shimano brakes use a different type of fluid, not DOT, but the principle is the same, contaminated fluid is a problem.
sounds like master cyclinder to me, too.
Other liquid mixed with oil? Like something off the hands, i.e. GT85 for example.
I found oil leaking down the brake hose on mine so I have just tightened the hose/lever screw and see if that works.
i have just tightened the connector to my lever and it has stopped the squishy air noise, and the brake does not seem to pump up. Not all good news though as the lever seems ok, the pads hit the rotor and it feels normal but then if I squeeze a bit more the lever comes all the way to the bars in a very spongy manner! I am going to get some mineral oil tomorrow and re bleed now it is all tight. my fingers are crossed but I don't feel very confident 😕
If it feels spongy then its most probably air in your system, with the hose/lever fully tightened, try rebleeding your brakes. I did mine at the weekend before going for a ride but lost all power in the rear brake. I'm sure it is to do with oil leaking out (and air getting in) from the lever/hose connection as it wasn't fully tightened - which I just found out tonight.
Any body know which parts I can get for the 775's? Hose, olive, inset and the coupling between hose and lever as I think I may replace these too while I am at it. There seems to be nothing listed for the 775's on chainreaction. cheers
Ignore the last post, I was being a numpty. I have found the spares now! cheers 🙂
Lock your brake lever to the bar overnight...position the bike so the lever is the highest point and the cable from caliper is as near vertical as possible...overnight the trapped air in the system will work it's way up to the reservoir and the air will be at the top of the system...you could remove top cap and top up with fluid but a full bleed is best - but takes time.
Locking the lever leaves the system open (internally) so the air can travel up (as it is lighter than the fluid) and then get stuck at the very top of the system...this will fix the brakes for a couple of weeks but the air will eventually get back in...so best bleed to remove the air.
