Do i need to bleed hydraulic brakes?
Discussion
Hello,
I have noticed that my rear brake is much weaker than the front one. It's weak to the point that i can't stop rear wheel from spinning even when pulling lever strongly, in front wheel i have the same brakes and i can stop it easily.
I tried cleaning pads and rotor two times. I have used sandpaper on pads and dish soap on rotor but it didn't change breaking force, it just stopped to squeal after cleaning but breaking is the same weak as before.
I made maybe about 400 km on this bicycle so it is quite new.
I am thinking about bleeding it but i am confused if i need it because the rear lever doesn't feel much different than front one which brakes well. I can't touch handlebar with lever even when i pull it strongly, even if there is some air inside then i think that i can make a good pressure because it is not loose and it doesn't touch to handlebars.
Maybe it is a little softer than front one but there is very small difference.
The question is if it can happen that it needs bleeding even when brake lever feels good, i mean that even when i pull it strongly then i can't touch handlebars with it because there is normal resistance when pads are touching rotors?
I thought that bleeding is necessary when lever is soft and loose so that i can touch handlebars with it but maybe i am mistaken? Did it ever happen to you that lever felt quite normal but it just braked weakly even when you pulled lever strongly?
These brakes on front and rear are Shimano BR-M355.
I have noticed that my rear brake is much weaker than the front one. It's weak to the point that i can't stop rear wheel from spinning even when pulling lever strongly, in front wheel i have the same brakes and i can stop it easily.
I tried cleaning pads and rotor two times. I have used sandpaper on pads and dish soap on rotor but it didn't change breaking force, it just stopped to squeal after cleaning but breaking is the same weak as before.
I made maybe about 400 km on this bicycle so it is quite new.
I am thinking about bleeding it but i am confused if i need it because the rear lever doesn't feel much different than front one which brakes well. I can't touch handlebar with lever even when i pull it strongly, even if there is some air inside then i think that i can make a good pressure because it is not loose and it doesn't touch to handlebars.
Maybe it is a little softer than front one but there is very small difference.
The question is if it can happen that it needs bleeding even when brake lever feels good, i mean that even when i pull it strongly then i can't touch handlebars with it because there is normal resistance when pads are touching rotors?
I thought that bleeding is necessary when lever is soft and loose so that i can touch handlebars with it but maybe i am mistaken? Did it ever happen to you that lever felt quite normal but it just braked weakly even when you pulled lever strongly?
These brakes on front and rear are Shimano BR-M355.
Agreed. It sounds like the brake itself is working absolutely fine, but the pads are contaminated with oil or something. Sanding them won't help much, as contaminants can soak into the pads, so all you're sanding off is any crap that has accumulated on the surface. The pad may look clean again, but that doesn't mean it's not still contaminated.
Just change the pads and give the rotor a good clean, then try again.
Just change the pads and give the rotor a good clean, then try again.
Is it really that hard to clean it when they are contaminated?
As i imagine when pads are dirty and i use sandpaper to remove layer of this dirt with some pad material then under it should be clean pad. Pads are thick and they became narrower with use because material goes off so if the material which is on top goes off then it can't be contaminated inside after front layer is torn off as i suppose.
Rotors are made of metal so i think it should be easy to clean it because dirt can't just soak inside it so when i clean it enough hard it then it should be clean.
Am i wrong ?
Can it really be as hard to clean so it needs to be replaced?
There are these resin pads --> http://www.chainreactioncycles.com/pl/en/shimano-a...
As i imagine when pads are dirty and i use sandpaper to remove layer of this dirt with some pad material then under it should be clean pad. Pads are thick and they became narrower with use because material goes off so if the material which is on top goes off then it can't be contaminated inside after front layer is torn off as i suppose.
Rotors are made of metal so i think it should be easy to clean it because dirt can't just soak inside it so when i clean it enough hard it then it should be clean.
Am i wrong ?
Can it really be as hard to clean so it needs to be replaced?
There are these resin pads --> http://www.chainreactioncycles.com/pl/en/shimano-a...
Edited by slawek371 on Friday 25th November 09:12
slawek371 said:
Is it really that hard to clean it when they are contaminated?
As i imagine when pads are dirty and i use sandpaper to remove layer of this dirt with some pad material then under it should be clean pad. Pads are thick and they became narrower with use because material goes off so if the material which is on top goes off then it can't be contaminated inside after front layer is torn off as i suppose.
Rotors are made of metal so i think it should be easy to clean it because dirt can't just soak inside it so when i clean it enough hard it then it should be clean.
Am i wrong ?
Can it really be as hard to clean so it needs to be replaced?
There are these resin pads --> http://www.chainreactioncycles.com/pl/en/shimano-a...
The pad might look clean when you sandpaper it, but if the contaminant has soaked into the pad, then you can sand them as much as you want, and they still won't grip properly, as the new surface you're sanding down to is already contaminated.As i imagine when pads are dirty and i use sandpaper to remove layer of this dirt with some pad material then under it should be clean pad. Pads are thick and they became narrower with use because material goes off so if the material which is on top goes off then it can't be contaminated inside after front layer is torn off as i suppose.
Rotors are made of metal so i think it should be easy to clean it because dirt can't just soak inside it so when i clean it enough hard it then it should be clean.
Am i wrong ?
Can it really be as hard to clean so it needs to be replaced?
There are these resin pads --> http://www.chainreactioncycles.com/pl/en/shimano-a...
I have just read that somebody cleaned it succesfully using few methods like puting it in paint thinner overnight, put it into alcohol and set it on fire. I think i should try something like that before buying a new pads, maybe it will become usefull again.
http://forums.mtbr.com/brake-time/contaminated-bra...
http://forums.mtbr.com/brake-time/contaminated-bra...
slawek371 said:
I have just read that somebody cleaned it succesfully using few methods like puting it in paint thinner overnight, put it into alcohol and set it on fire. I think i should try something like that before buying a new pads, maybe it will become usefull again.
http://forums.mtbr.com/brake-time/contaminated-bra...
Considering you're talking about an £8 set of brake pads, is it really worth it?http://forums.mtbr.com/brake-time/contaminated-bra...
slawek371 said:
I have just read that somebody cleaned it succesfully using few methods like puting it in paint thinner overnight, put it into alcohol and set it on fire. I think i should try something like that before buying a new pads, maybe it will become usefull again.
http://forums.mtbr.com/brake-time/contaminated-bra...
If you do that, film it for us! http://forums.mtbr.com/brake-time/contaminated-bra...
I have cleaned it for third time. Now i mixed it in boiled water with dish soap. Then heated it on fire with gas burner and saw smoke coming out of pads, used sandpaper and boiled in dish soap again. Now it brakes better maybe as good as front brake, i can block the wheel. I have read that after cleaning it might be even better after some braking.
jshell I would film it for you but i haven't seen your comment then
jshell I would film it for you but i haven't seen your comment then
I have a shimano alfine hub which has a design flaw which leaks fluid out of the hub and onto the disc is to either use car brake cleaner on them periodically and if that doesn't work soak them in ipa overnight then use a butane torch/gas hob to heat them up till they start smoking.
I think it's best to use a sintered pad for the rear wheel as they still grip even if it's oily unlike organic which do nothing at all if they get even a bit contaminated.
I think it's best to use a sintered pad for the rear wheel as they still grip even if it's oily unlike organic which do nothing at all if they get even a bit contaminated.
Gassing Station | Pedal Powered | Top of Page | What's New | My Stuff