• There has been a recent cluster of spammers accessing BARFer accounts and posting spam. To safeguard your account, please consider changing your password. It would be even better to take the additional step of enabling 2 Factor Authentication (2FA) on your BARF account. Read more here.

Pushing pistons back in

hyo650

hyo650

New member
Joined
Jul 11, 2008
Location
San Francisco
Moto(s)
Hyosung GT650R (Sold), '06 636 (Sold), '96 PC800
Name
Vlad
The question I have is this....when changing brake pads, generally speaking, how much pressure does it take to push the brake pistons back into the housing?

I know its hard/almost impossible to quantify but there are several techniques to do this.

1) Loosen the bleeder valve, and push the pistons back in with the brake fluid escaping through the bleeder screw

2) Just exert enough force on the pistons to push fluid back through the house and up into the reservoir.

It seems from the various posts/articles I've read on the subject, most people tend to just force the pistons back and the fluid back up the lines. My question is....how much pressure does it generally take? Something that can be accomplished by hand? Or does some sort of mechanical device need to be used? Vice? Channel Locks? Etc...?

Just a general question guys....I'm not about to take a pair of channel locks to my caliper pistons.... :laughing
 
If it takes more force than your fingers can exert then you've got some issues. Don't open the bleed screw either.
 
Jello_Biafra said:
If it takes more force than your fingers can exert then you've got some issues. Don't open the bleed screw either.
Click to expand...

See, but my question is...are you using your hands directly on the pistons themselves, or what? Because another option would be to take a flat piece of wood (for example) lay it across the face of the piston, and use the leverage you get from that to push the piston back in....which is what I've done in the past. But this method is also kinda tough to do...

EDIT: Also, why do you say not to open the bleed screw. If you can compress the caliper that way and not get air in the system (although I bleed the brakes after changing the pads anyway) its a good way of removing a bit of resistance when compressing the calipers...right?
 
Last edited:
hyo650 said:
2) Just exert enough force on the pistons to push fluid back through the house and up into the reservoir.
Click to expand...

This. I can do it with finger pressure (and I'm hardly a brute).

I also take the opportunity, grab an old toothbrush and a mix of 20% dish soap / 80% water by volume and scrub all the crusty dust off the calipers and pistons before pushing them in. Can even carefully push the pistons *out* a little more, scrub scrub scrub, pour a cup of water over to rinse, then reassemble. Yay brakes.
 
hyo650 said:
EDIT: Also, why do you say not to open the bleed screw. If you can compress the caliper that way and not get air in the system (although I bleed the brakes after changing the pads anyway) its a good way of removing a bit of resistance when compressing the calipers...right?
Click to expand...

theoretically yes since you are bleeding the system anyway.

The issue as stated, is getting air in the system considering how cumbersome the process can be of pushing in a piston and cracking open the bleeder, then closing it.

Personally, i make sure the pistons are clean, deck the pistons out while watching the MC reservoir fill up, prying carefully with a small prybar while the old pads are in the calipers. It shouldn't take long or much effort.
 
Karbon said:
theoretically yes since you are bleeding the system anyway.

The issue as stated, is getting air in the system considering how cumbersome the process can be of pushing in a piston and cracking open the bleeder, then closing it.

Personally, i make sure the pistons are clean, deck the pistons out while watching the MC reservoir fill up, prying carefully with a small prybar while the old pads are in the calipers. It shouldn't take long or much effort.
Click to expand...

AH HA!!! So you ARE using some sort of leverage to push them back in....

Like I was saying, the reason for the weird way this question was formatted was to see if my caliper pistons are sliding smoothly enough, or if they need to be taken out and maintained! yadada mean?
 
hyo650 said:
Like I was saying, the reason for the weird way this question was formatted was to see if my caliper pistons are sliding smoothly enough, or if they need to be taken out and maintained! yadada mean?
Click to expand...

Sure. If you carefully push them out with the lever (leave the other caliper on the disk for this) do you see a line of grime a few mm in?

That's your most likely enemy. Kill it :)
 
That's the thing, if you leverage them back in using the pads then you're missing the chance to clean them. Either way you have to push them back in with your hands to get the new pads in.
 
imortlfool said:
Sure. If you carefully push them out with the lever (leave the other caliper on the disk for this) do you see a line of grime a few mm in?

That's your most likely enemy. Kill it :)
Click to expand...

The eye-sight....its not so good....:laughing

Honestly though, its IS difficult to see the pistons while on the rotor...so I figure if I'd do this, I'd just want to take the caliper off the rotor, and stick a piece of wood in there to prevent them from popping out completely? no?
 
He's saying leave the OTHER caliper on so that those pistons don't come completely out while you're pumping the lever to get the ones that you're working on out.

I'm not really sure what answer you're looking for here. Plenty of people clean their pistons without using a piece of wood. *shrug*
 
Jello_Biafra said:
He's saying leave the OTHER caliper on so that those pistons don't come completely out while you're pumping the lever to get the ones that you're working on out.

I'm not really sure what answer you're looking for here. Plenty of people clean their pistons without using a piece of wood. *shrug*
Click to expand...

Just a general answer about how much force you guys are using to push the caliper pistons back in....thats all...
 
Jello_Biafra said:
If it takes more force than your fingers can exert then you've got some issues. Don't open the bleed screw either.
Click to expand...

However, the process can be slow and take a fair amount of force. I used some blocks of wood and a C clamp. Makes the job much easier.
 
If the pistons are dirty, pushing them back into the caliper body is not a wise choice.

Cleaning them is.
 

Attachments

  • DSC09584%20(Large).jpg
    DSC09584%20(Large).jpg
    137.2 KB · Views: 14
Hooli said:
0.00160739092 kg2. :nerd
Click to expand...

fuckin ehh....

and it only took 14 responses to get the answer I was looking for! :laughing

But on a more serious note, I find myself taking a piece of wood, and forcing the pistons back in that way using the extra leverage I get from this.

I do, however, think its about time to at least pull the calipers off and take a better look at whats going on.....just not something I'm looking forward to doing....
 
I use brake cleaner and brake fluid to clean before pushing

Should I use something else?

I want to keep water as far away as possible
 
c_clamp_2.jpg
 
TT120 said:
c_clamp_2.jpg
Click to expand...

but with that you'd have a chance of pushing the piston in unevenly into the bore.... :dunno

On a side note, was watching a few Youtube videos, and ran across this one....truth be told, this is the first time I've seen something like this

[youtube]1qoPqN2GBdw[/youtube]
 
You must log in or register to reply here.
Back
Top