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-   -   Poor braking - hydraulic disc brakes (https://www.bikeforums.net/bicycle-mechanics/1142533-poor-braking-hydraulic-disc-brakes.html)

MarcoCee 04-28-18 11:53 AM

Poor braking - hydraulic disc brakes
 
Greetings

The brakes on my new Giant Rapid 1 (Shimano M315 Hydraulic Disc) seem to have pretty poor braking power. No doubt a little adjustment is needed, however, I've never touched disc brakes before. Not sure if a simple diagnostic/adjustment is needed, which I can do myself, or a trip to the store is needed.

Any advice? Calipers are so much easier to figure out!

DrIsotope 04-28-18 12:01 PM

Are they brand new? When applying the brakes, are the levers firm, or mushy? Brake pads/rotors take a little time to bed in, so it could be that simple. If it just feels like too much lever travel, they might just need to bed in. If you can pull the levers all the way to the bars and the bike doesn't fully stop, the brakes need to be bled, which is a job for the LBS if they sent it out the door that way.

fietsbob 04-28-18 12:03 PM

Needs Bleeding air bubbles out,/ got contamination on the brake pads or/ there is a problem with the system,
master or slave end , And you need to replace the whole thing near new it should be under warranty..

Try the dealer- bike Shop ?, they who can see what you have, rather than blind guessathons here.. ?

Maybe look it up online, and RTFM? buy the bleed kit?





....

MarcoCee 04-28-18 12:06 PM

There's a little bit of give on the levers, but they're far from firm. Is that normal?

MarcoCee 04-28-18 12:08 PM

I'll most likely take it in tomorrow for a look. Just wasn't sure if there was an easy way to identify the cause.

DrIsotope 04-28-18 12:08 PM

There will always be a little lever travel on hydraulics, but once you start squeezing and the pads engage, the lever should "firm up." If it doesn't, they need to be bled. Systems now generally come pre-bled, and sometimes the guy building the bike will get lazy and just figure all is well. A good tech will test ride it before the bike leaves the shop.

MarcoCee 04-28-18 12:11 PM


Originally Posted by DrIsotope (Post 20311948)
There will always be a little lever travel on hydraulics, but once you start squeezing and the pads engage, the lever should "firm up." If it doesn't, they need to be bled. Systems now generally come pre-bled, and sometimes the guy building the bike will get lazy and just figure all is well. A good tech will test ride it before the bike leaves the shop.

Thanks. I'll take it in to the local Giant store tomorrow and hope it's nothing to worry about.

italktocats 04-29-18 12:49 PM

is the disc centre of the caliper? loosen the bolts on the caliper a bit, press lever, tighten bolts again

if you keep "pumping" does pressure build up? then its a air/leak/bleed problem


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