Yet Another Brake Caliper Thread

[Hardened Rider]

Ok, firstly I wanna say how excellent arcdef's thread on Caliper overhaul was, thats helped massively. I've got a couple of questions, I'm gonna give the Brakes an overhaul this weekend, sticking like mad cause of all the carp from winter riding.

I need to remove the pistons but I don't have compressed air, I can use the hydraulic system but I don't understand when my Haynes manual says loosen the banjo bolt and retighten lightly, what does this accomplish?

What happens if one piston pops out but one stays in, surely the pressure from the hydraulic system will no longer apply to the stuck piston as brake fluid will just shoot through the empty bore?

How do I stop brake fluid constantly coming out of the hose whilst I'm working, I could use a milk bottle or something, but surely air would get sucked back up into the system, again Haynes says to use a plastic bag, but where?



Cheers guys.

[leegriffiths128]

Once you get the one piston moving, you can then wedge something between piston and caliper to stop it popping out altogether. You can then squeeze the brake lever to 'coax' out the other piston.

I'm no expert...far from it, but its what I have done with mine in the past.

[thefallenangel]

if your worried leave them to soak overnight. if you've cleaned regularly then they should come out easily enough.

[xXBADGERXx]

I will be doing the same thing this weekend , put my rear brake on yesterday and it clamped on , bike was lethargic as hell coming out of the junction and I had to hook my toe under the lever and lift it back up to release the brake , got home a minute or so later and the rear disc was stinking .

[yorkie_chris]

Teh fook? I think you have wrong end of stick here.

Work on one caliper at a time.
Right before you remove caliper, crack the banjo bolt, then nip it again.

Crack bleed nipple, nip it again. (making sure everythings moving while it's still fixed in place aye)

Then pull the caliper off, get the pads (There's a can of worms here with the pad retaining pin... go search ... good boy) and the caliper bracket off.

Now get a G clamp ready, pump the brake lever. Use the G clamp on one piston, then the other. Make the pistons move a few mm at a time, so they're both moving out. If you do it right you will get the brake system to pop both the pistons out at the same time.

Then clean that caliper, clean the pistons, grease it all(Rubber grease where needed), reassemble and put it back on the bike.

With the other side, you will know how far to pump the first piston before you lock it off and pump the other one.

Would someone save a link to this thread to save me typing this any more times?

[flymo]

Would someone save a link to this thread to save me typing this any more times?

Ah, I like reading it over and over :-). Its like the Dave +1 channel on Sky TV.

[Hardened Rider]

Thanks for the tips, Piston removal is clearer, thanks YC. I understand what Haynes is telling me to do, but what I don't understand is WHY. Why crack banjo and bleed nipple and then nip up? What exactly is this doing, releasing pressure?

And how do I stop Brake Fluid gushing from the Bores once the Pistons pop out?

[pmapp]

Thanks for the tips, Piston removal is clearer, thanks YC. I understand what Haynes is telling me to do, but what I don't understand is WHY. Why crack banjo and bleed nipple and then nip up? What exactly is this doing, releasing pressure?

And how do I stop Brake Fluid gushing from the Bores once the Pistons pop out?

It's just easier to undo\loosen them while the caliper is still fixed to the bike.

No way to stop the fluid, just have an old bowl and plenty of paper to mop up. I personally don't pump them all the way out, tend to just stop before, then drop the fluid from the brake line.

[Hardened Rider]

Good tip, cheers pmapp.

[yorkie_chris]

Once the system is open, pull the lever and tie it back with a rag or bit of string. Stops the fluid from the reservoir all dropping out.