"bleedin brakes"

[Stul]

Hi all, I have a Raleigh with Shimano hydraulic brakes, (never had them before). The front brake is fine, but the rear brake seems to lose "power". i got myself a hydraulic bleed kit and after watching various youtube vids I preceded to "syringe" from the caliper end back up to the handlebar mount end. No matter how many times I tried it did not seem to make any improvement, so I then proceeded to go from the other direction, (ie syringe applied to the handlebar end and drain tank on the caliper end. Although still a little "lose" for my liking it seemed to make a big improvement?
Nit sure uer I really see the point going hydraulic, a friend has a mechanical disc brake system and this seems far simpler, and at least you can make adjustments simply?...or am I missing something here?
of

 

[iluvmybike]

Have you changed the brake pads?

 

[Ming the Merciless]

Bleeding is about getting air out of the hoses. It should be a 15 min job. You shouldn’t need to do it that often with Shimano and mineral oil. Perhaps once every two years if that.

 

[iluvmybike]

You said " syringe applied to the handlebar end and drain tank on the caliper end " - if you do that you will just be sucking air in!

 

[CXRAndy]

If you're talking about a lever with too much travel- I have a method to improve.

Soft lever, spongy, will most likely be air or piston seized. First check both pistons move by looking down carefully for both pads moving. Try tipping the caliper to make the hose connection the highest point when bleeding.

Now to reduce lever travel

Take the pads out and wrap in clingfilm. Before you have wrapped them place a piece of printer paper on the brake surface side. This is for both pads.
This paper gives the clearance once the job is done. Refit covered pads.

Bleed the brakes as normal, then put the sealing cap on the lever reservoir. Apply fluid under slight pressure from the syringe at the caliper. This will force the pistons to take up all the slack in the system. Whilst holding pressure, lock off the bleed nipple.

Remove clingfilm and paper spacers, clean up, refit pads. You should have virtually no free play before pads bite disc rotor.

 

[Stul]

You said " syringe applied to the handlebar end and drain tank on the caliper end " - if you do that you will just be sucking air in!

..yes syringe full of fluid, and pumps fluid from the handlebar end to a "waste" bottle at the caliper end...

 

[Stul]

Have you changed the brake pads?

..no, the bike is fairly new. I note that most youtube vids show the pads left in place, but just found one that suggests taking the pads out and putting a spacer in?..very confussed now! (NB It's a belt drive so a bit of a pain to get the rear wheel out to take the pads out...)

 

[Ming the Merciless]

Most bleed kits come with a spacer you put in. Definitely don’t bleed with pads in. Just likely to contaminate them.

 

[iluvmybike]

..no, the bike is fairly new. I note that most youtube vids show the pads left in place, but just found one that suggests taking the pads out and putting a spacer in?..very confussed now! (NB It's a belt drive so a bit of a pain to get the rear wheel out to take the pads out...)

The reason for remving the pads is so if you spill any fluid it doesn't get on the pads and contaminate them. I'd remove and check yuor pads for contamination anyway - if you have bled the brake and it is not better then that may be the cause - it is easy if you use spray lube at the rear of the bike for tiny airborne droplets of lube to get on the rotor and then picked upo by the pads. If in doubt swap the pads before you mess about any more.

 

[CXRAndy]

..no, the bike is fairly new. I note that most youtube vids show the pads left in place, but just found one that suggests taking the pads out and putting a spacer in?..very confussed now! (NB It's a belt drive so a bit of a pain to get the rear wheel out to take the pads out...)

The spacers are usually too wide and leave you with a slacker lever. In my early days I made my own width spacer to get the correct lever travel. I was always a tad tight, a few rides with binding pads, freed up

You remove the caliper if pads come out of bottom. Most pads come out of top.

Clingfilm is the protection against the mineral oil

 

[Kajjal]

I used a bleed kit from below and a top up bleed worked fine to remove air from the brake line. They have plenty of useful info on the site.

https://epicbleedsolutions.com/

 

[Stul]

Most bleed kits come with a spacer you put in. Definitely don’t bleed with pads in. Just likely to contaminate them.

..oops...

 

[Ridgeway]

Just did one of mine as the LBS (bought as a second hand bike) had nicely included some free air within the system.....

For the rear brake it can help to raise the front end so any air can easily rise up when you fill the new fluid from the calliper end.

Definitely brake pads out and use a block, normally you'll need to prise the pistons back to get the block in.

 

[Pumpkin the robot]

I tried the syringe method and could not get a decent feel at the lever, so I went to the tried and tested method of doing it as I would on a car or motorbike.
Plenty of oil in the reservoir and then pull the lever back to the bar, release the bleed nipple to expel the air, tighten bleed nipple and release the lever. repeat until there is no air in the system. Just make sure the reservoir is always full of oil.
Worked for me and I have not had to rebleed in 2 years of use.

 

[Supersuperleeds]

I used a bleed kit from below and a top up bleed worked fine to remove air from the brake line. They have plenty of useful info on the site.

https://epicbleedsolutions.com/

Thread resurrection time.

I’ve just used one of their kits to bleed the rear brake on my hybrid. I’m happy with the result, took me about 15 minutes and normally I am useless at anything manual.