Bicycle Mechanics - hydraulic brake problems
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07-18-11, 02:12 PM
Hi, I know this is a learning curve, keeping on top of bike maintenance, but it is an expensive one! Ok, i was cleaning the bike, and took off the rear wheel, then accidentally pulled the brake lever whilst the disc rotor was not between the brake pads! Arghh! So i have undone the torx screw on the brake lever resevoir and pushed the pistons back into place, then re-tightened the torx screw back up on the brake lever resevoir, have put the wheel back on the bike, with the rotor back in the right place. Now, however, there is no power in the brake. I have pumped the lever many times, but to no avail. I don't think i have lost any brake fluid from the resevoir. Can anyone help?
07-18-11, 02:18 PM
Ooops! Sorry, the brakes are avid juicy5
07-18-11, 02:28 PM
If the bike was in an extreme position such as upside down or on its side when you did this you may or must have pushed some air down the line. And if you do this again there's no need to loosen any screws. Just push the pistons back and all is well.
In any event it sounds like you'll need to bleed the brake.
07-18-11, 02:35 PM
I got a very large screwdriver to pry the disc brake pistons back
when I replaced the pads on the Car.
pretty much the same thing in miniature..
07-18-11, 02:45 PM
Erm, yes the bike was upside down when i done the job. Oooops! Does this now mean i need the bleed kit? at 35 quid! Thanks for all your help btw. Does pushing the pistons back with a screwdriver damage the piston seals at all?
07-18-11, 02:58 PM
fietsbob has the right answer, personally would use an allen key to push the pads back in, Hydraulic brakes although an open system are sealed, and although you shouldn't depress the brake lever when the wheel is not inserted, it shouldn't require a bleed.
When you have pushed the pistons out, re-fit the wheel, and pump up the system by squeezing the brake lever until you have the desired feel to the brakes / lever.
For the future, did you bike come with a travel / set-up insert for the brakes, as you can install this when the wheel is removed and then depress the brake lever when ever you want.
07-18-11, 03:04 PM
No, it didnt come with a set up insert, but i suppose i could improvise something to use as one.
07-18-11, 10:03 PM
Just don't ever touch the brake lever while the wheel is out.
If you hit the lever while it was upside down then you pretty much certainly have a bubble or two in the line. You can try the method of rubber banding the lever to the grip and leave it over night. If it doesn't work the first time do it again. With any luck the bubble will migrate back up and into the master piston and then into the reservoir and you'll be back in business. If this doesn't do the trick you'll need to bleed the brake system.
Seldom is the stuff in a bleed kit all that special. Perhaps post a link to a picture or list of what's in the kit. The biggest thing is to fine a bleed nipple that fits into the caliper and connects to a plastic tube if one doesn't live in the caliper as it comes.
07-18-11, 11:06 PM
I wouldn't look forward to trying to improvise on Avid hydraulics, since both ends use threaded fittings. The consumer-oriented bleed kit is US$51: http://aebike.com/product/avid-disc-brake-bleed-kit-with-2oz.-of-5.1-dot-fluid-sku-br6850-qc30.htm If there's one nice thing about Avids, it's that the bleed tools are first-class.
Also, I wouldn't suggest inverting your Juicys if you can help it. Wheels down. Besides keeping any air at the top of the reservoir and out of your master cylinder, you won't risk fluid leaking out the weep hole, getting on your bike and stripping the paint.
07-19-11, 12:38 AM
They include the "keeper" for a reason. Id recommend having them handy..
like in the puncture patch kit.
lobster boy may need the LBS to do the bleed , or read the service PDF..
07-19-11, 01:00 PM
How much fluid should be in the resevoir? Should it be full? Thanks for all the great advice.
07-19-11, 01:18 PM
Yes, the reservoir should be full. If you need bleed instructions, here's a PDF file: http://www.sram.com/sites/default/files/techdocs/95-5015-029-000_hydraulic_disc_brake_bleed_and_hose_length_adjustment_rev_a.pdf As I said before, this really calls for the proper tool kit, which is capable of pulling a vacuum on the system to get all the air out, as well as de-gassing the new fluid you'll be pushing into the system from the caliper end.
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