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So, I was checking the rear brake pads on project K1 the other day and I noticed there was a bit of fluid around the pistons on the caliper.
Because I have just fitted some freshly painted wheels, I decided to go the safe rather than sorry route and check and reseal the caliper rather than risk having brake fluid spoil my lovely new paint.
So I thought I'd do a few pics for people to see how it's done.
Maybe it's been posted before but what the hell, i'll do it anyway.
It's a very simple job and can be messy depending on how grotty your shit is. Being a rear and having only two pistons, it was pretty quick but the principles are the same for front calipers, there's just more pistons and more fucking around, particularly when getting the pistons out.
The only tools you need are decent spanners or socket set and allen keys, an o-ring pick/scriber/pointy screwdriver, some compressed air and maybe some small G Clamps which we'll get to shortly.
Also some cleaning fluid, i like white spirits, some use kerosene.
Some brake fluid, i'm a bit anal and I always use a new bottle of fluid.
Some CLEAN rags.
After talking to McCullochs about new seals, I ended up getting seals plus pistons for not much more than just the seals. So I just went that way, instead of maybe pulling the pistons out and finding them half rooted.
A big warning here.... Brake fluid messes paint up. If you do anything with brake fluid, keep your mits away from your bike and make sure you clean them properly before touching anything with paint on it. Except your calipers which are impervious to brake fluid.
If you happen to spill brake fluid on any painted surface, use water and a rag to clean it off. Don't panic, just do it quickly and don't be shy with the water.
So.......
First up we need to remove the caliper.
Make sure you crack EVERY bolt you will need to undo during this job BEFORE removing the caliper, a lot of these will be tight and undoing a tight fitting or bolt while holding the caliper in your hand after removal is virtually impossible.
Here I crack the pin that holds the brake pads and anti rattle bits in place.
Then I crack the banjo bolt carefully so as not to spill fluid. Then I nip it back up to prevent spillage to be undone later when the caliper is off the bike and away from the paint.
Most wheels are powder coated so you probably don't have to be so anal, but I am being very carefull here.
At this stage, if I was going to split the caliper in half to give it a really thorough clean, I would also crack the two large allen head screws (you can see one there on the bottom left of the caliper). But my caliper is pretty clean so I am not going to bother.
The next thing is to remove the caliper, please note that I have already unbolted the arm that holds the caliper to the swingarm.
I also put a piece of rag down to protect delicate bits.
With the caliper removed, I put the brake line into a bottle so it could drip any fluid without causing any damage.
This, is a banjo bolt.
It doesn't play music.
It has a hole going from the bottom of the bolt to the hole you can see in the side. This is how the fluid gets from the brake line and into the caliper.
Note the two washers, these are extremely important so don't lose them.
One washer goes on either side of the banjo fitting (on the end of the brake hose)when you bolt it up, make sure they are not damaged or crushed. They are very cheap if you need to replace them.
Make sure they are clean, I buffed the bolt up on the wire wheel on my grinder before reassembly but it was already pretty good nick. If you don't have a wire bush, elbow grease and light sandpaper will do. Make sure you don't leave any contamination in the fluid holes after cleaning.
Never EVER put an old rusty bolt in when you reassemble your brakes, stoopid.
Here I am removing the pin the holds the pads and everything together, this is the pin I cracked in the earlier photo.
These are the main components removed from above.
Make sure the pin is cleaned and greased before you reassemble the caliper and don't lose any of the anti rattle plates. You can see one I popped off one of the pads. They both have them.
At this time, if your pads are worn, think about whether they should be replaced.
Mine are still low klms so i am re-using them after a clean.
Now the fun part.
Use some safety glasses here just in case you get a spray of brake fluid or grime in your eyes.
I use some compressed air to push the pistons out, do it gently, don't just crank open the blow gun or you will regret it.
But you'll notice here that only one is moving. If I let this pop out, I may have trouble getting the other one out as i can no longer pressurise the caliper with air due to the gaping hole the piston would leave.
Here I used a piece of wood to stop the free piston from coming out.
DO NOT EVER, EVER try to hold the piston in with your fingers.
The piston may come out and crush your fingers, it fucking hurts and makes you look silly running around the yard with a brake caliper slammed shut onto your fingers.
Here is where a small G clamp might come in handy to hold the piston in place while the other one begins to move.
Here I used a scriber to remove the old quad seals after getting the pistons out.
There's nothing worse than trying to reassemble something with parts that don't fit.
Here I checked the sizes of the parts I removed against the new parts, all good.
Note two things here.
The small seal sitting by itself is to be used if I was to split the caliper into two sections for a really thorough clean. I won't need this.
The other thing is that my pistons were in very good condition with no pitting, scratches or rust. A good wipe over could have had me using them again, but since I have new ones, i will fit them anyway.
In the past, I have used fine wet and dry to remove rust from pistons. All the time, keeping in mind that if the damage is too great, then they will just leak, and I hate doing jobs twice. So if they had been bad, i would have changed them.
So the next step is to thoroughly clean the caliper, making sure there is no contamination left inside where the pistons go. Be sure that the seal grooves are free of grit before fitting the new seals.
I pour a little fresh brake fluid into the bottle cap and smear some brake fluid on the seals before I put them in. I also coat the piston to act as a lubricant for when I refit it.
Use finesse rather than force to get the piston in. It needs to go in straight, you will need to give it a good push to get it past the seals but if you're not lined up properly, you will struggle.
Next, with the pistons pushed all the way home, I refit the pads with rattle plates, and the top rattle plate with the freshly cleaned, buffed and greased pin.
It's now ready to go back on the bike.
Make sure you assemble it with the pads all the way apart to make it easy to get back on the disc.
And here it is, bolted back up, everything tight (checked twice) and ready to get a guts full of fresh fluid and a good bleed up.
Remember, when it comes time to bleed the brake, once you get fluid coming out of the bleed nipples, you will need to shut them off and pump the pedal or lever to push the pistons out until the pads are on the disc before you will start getting any pressure at the lever.
Then you can resume bleeding and go chasing those last few air bubbles.
I hope this helps people out.
it's not a difficult job, but it can be a little messy.
Take your time, use your brain and all will be fine.
Cheers
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Originally Posted by Rocket 
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