swarminglocusts

I purchased a bike this summer at the 800 price point range, the bike was fine and ran well up until about a month ago. The rear disc brakes started losing grip power. When I pumped the brakes I could get them to have stopping power again, but that only lasted about a week. Then the brakes stopped having any stopping power at all. The pads are thick and evenly worn. Any thoughts on how to adjust them? I havn't found anything good on YouTube to help. Thank you and have a good day.

allonsy

Presumably you need to bleed air from the lines? Lots of stuff on youtube about that.

allonsy

Epic Bleed Solutions has good articles on their blog. They sell a proprietary kit but you don't need it.

I'm too new to post links but search their site for "basics of brake bleeding". Also the "5 minute shimano mini bleed" is useful for potentially an even better feel after you have done a bleed"

If you have a newish bike you don't need to completely replace all the fluid, just add enough to remove the air in the system.

swarminglocusts

These are hydraulic disc brakes btw.

allonsy

Yes, hydraulic fluid filled lines. When there is air in them they don't work well or don't at all.

When your brakes were set up, some air probably stayed in the system, caught in little places in the rear derailleur or in curves in the line. Eventually that air is shaken loose and finds its way up to the hydraulic cylinder in the brake lever, where it reduces performance.

IK_biker

Brilliant!
Particularly the "caught in little places in the rear derailleur or in curves in the line" part.

I especially admire that the poster is a quick study, having registered here on BF.com today, yet has already managed to learn in depth the precise mode of air propagation in hydraulic brake systems.
I'm in awe of the power of BF.com!

swarminglocusts

I use to post in these forums a lot on a different handle. I lost my old email, so here I am. Thanks.

Marcus_Ti

You most likely need a bleed. Either learn how to do it yourself, or take it to a shop. It isn't expensive.

dmanthree

Get it to a mechanic before you kill yourself.

swarminglocusts

I've done a hydraulic disc brake change before on my motorcycle several times. I'll take it to the shop and see what they think.

Crankycrank

Try storing the bike vertical with the front wheel on top for one night. Use some sort of string, Velcro strap etc., to hold the brake levers in as far as possible. Tap on the lines a couple of times to break the air bubbles free, wait at least 8 hours and then rapidly release the levers while the bike is still vertical. This works if there is a slight amount of air in the system and you can do it a few times if necessary but if you have more than a little air you'll have to do a proper bleed. This allows the air to rise to the highest point at the levers and releasing the brakes lets some of the air escape through the master cylinder plunger.

swarminglocusts

cool trick. I'll try it tonight.