Rebuilding the Caliper

Hi all,

Over the weekend I installed new steering head bearings and also had to rebuild the caliper because the front brakes were dragging.

I got the caliper apart and cleaned up the piston really nice (it was pretty gunked up) and did a little work to the piston bore as well. I put the caliper back together, bled the system, but the brakes still drag.

From what I've read here, I need to:
a) Clean out the bore even better. Do I take the rubber seals out?

b) Lube up any moving parts. This includes the brake pad pin (the pads were sticking and tough to move along the pin) and the piston? Is there any danger of getting grease in the brake system if it's on the piston?

c) The bolts that hold the caliper to the forks had two washers, so I assume there's one washer on each side of the caliper. Is this correct? The inner washers were a little difficult to get in, but they went without too much trouble. This is how it is right now:



Any other ideas why it might still be dragging are appreciated!

Thanks!

 

Since I have a Seca that calipers are different but I just rebuilt mine last week. how bad is the drag? so you pick up the front wheel, spin it, how many revolutions till it stops? Mine drag a Little but nothing to talk about.

polishing the bore more could only help, yes with the rubber seal removed. axle grease on the pin, and reassembly with the brake fluid - Should be all that's needed. oh, and Clean the shiny silver pad seats/guides whateva they're called. did you put the shims back in behind the pads? The manual says that's really important

 

Yes.
You carefully extract the Rubber Caliper Piston Seal.
Once the Seal is removed from the Channel ... Clean the Channel.

You have to scrape every bit of build-up and debris from the inside diameter of the Seal groove.
The build-up is backed-on brake dust and brake fluid and can be stubborn to remove.
Scrape the channel down to bare aluminum.
Lube the Channel and Seal with NEW Brake Fluid and replace the Piston.

I looked at both drawings for 550 Caliper Mounting and there is NO washer between the Brake MOUNT and the FORK.

The Mount is bolted to the Fork.
Bolt --> Lock Washer --> Flat Washer --> Mount --> Fork Tube.

 

Awesome, thanks for the help!

I imagine my misplaced washer is contributing to some of the drag. I will take apart and re-clean as well. I didn't notice the two different types of washers -- that's my fault.

yamaman, my wheel will not even do a single revolution. That's pretty bad! Also, the shim is just a shiny plate behind the pad that goes against the piston correct? If so, that's back in the same place and the shim never came off the pad. I saw that little note in the book.

Thanks again guys, I'm gonna get at this tonight.

 

I have a Seca 550. It's been a couple years since I rebuilt my calipers. I can't recall exactly but there may be a slight angle to the outer surface of the piston seal. It has to be installed with the angle it the correct direction.

I may be completely wrong about that. Could have been from a different bike I worked on. Hopefully someone more knowlegeable will pitch in some info on this.

As RickCoMatic pointed out, those washers may be the culprit.

 

Great, I'll take a look... I think you're right about that angle, I thought I noticed it. If I only I knew how it went in...

Can I reuse the seals? If not, are they readily available at auto-parts stores?

 

New seals are readily available from Chacal. install them with the lip facing away from the opening (down into the caliper). I would NOT reuse the old ones, jmho.

 

Hey all, me again.

So I fixed the washers, which helped a lot. I also cleaned out the piston bore (I didn't remove the seals as I don't have new ones). However, there is still a pronounced drag on the wheel.

I noticed the piston seems to have a slight angle to it's outer rim. I'm not sure how to line this up properly with the pad shim - is it all trial and error?

There is one point where I can see about 1-2mm space between the piston and the brake pad... I assume I'd want 100% contact piston>brakepad.

Also, how much drag is acceptable (for a safety)? The wheel spins about 1 - 1.5 revolutions on a good spin.

 

NO DRAG. Both of my 550s have "rock hard" brakes yet if I prop the front off the ground and spin the wheel it will spin for 10 minutes.

Something is still not right.

-the holding block goes directly against the fork leg, no washers, but I think you got that already.

-you HAVE to replace the seals, and no, you can't get them at the auto parts. Get them from chacal or Yamaha.

What happens is this: Over time, "crud" consisting of accumulated dirt and old dried brake fluid builds up in the channels BEHIND the seals. You have to remove the seals, and spend some time getting the channels completely, religiously, DENTALLY clean.

If not, your caliper will continue to hang up and drag; this is a potentially unsafe situation.

If you can't find sufficient resources doing a forum search, I can pop up a couple of pics from an article I'm working on about the relationship between all the parts in the "holding block" style calipers like we have. Just say the word.

Order some seals as long as the piston is fine. Gotta do it.

 

The Channel for the Caliper Seal is: Perfectly round.
The Caliper Seal that goes in the Channel: Perfectly round.
The Caliper Piston: Perfectly round.

When everything is perfectly round ... the Caliper Piston is forced out against the Brake Pad when the Brakes are applied and retreats a few thousandths ... when the Lever Pressure is relaxed.

When the combination of Brake Dust, Brake Fluid, Road Grime and moisture combine ... they form a type of mud which collects in the "Perfectly Round" channel behind the "Perfectly Round Seal" and what WAS Perfectly Round ... isn't, any more, and the Piston starts to SEIZE ... instead of relaxing.

You've a Mission to eliminate all Crud.

 

I took an hour or so today just patiently de-crudding the bore and behind the seals and it worked! Brakes aren't dragging.

Thanks a ton everyone!

 

How would you rate the difficulty of cleaning that Caliper based on a scale of 1 -to- 10?

Based on your experience, ... would you recommend others having sticky Calipers to give this job a shot?

 

Difficulty-wise: 4 or 5. It's not very difficult, though you ought to know what you're doing (no gouging!) and it can be messy (damned brake fluid) and time consuming (bring beer). For reference, cleaning the carbs properly is a difficulty 6, replacing steering head bearings is a 7 and fine-tuning would be an 8. Re-doing your electrical system is a 10.

Sticky calipers can be a dangerous situation as the brake pads generate heat, which heats up the brake fluid, which then expands, which pushes the piston which locks up your brakes. At least this is what I've been told. I'd recommend anybody do this if their wheel doesn't spin 4-10 revolutions on a good hard spin. I had to do it to pass my safety.

The play-by-play:
- Caliper off
- Pads out
- Pump the piston out and catch the fluid
- Clean, clean, clean, beer, scrub, clean: seal channels especially
- Clean it a little more (or risk repeating steps 1-4 several times like me)
- Piston lubed with brake fluid and zero dirt, reservoir lid off, push in piston slowly (c-clamp) - it squirts brake fluid out the reservoir pretty far if you rush the c-clamp
- Pads in (lube/grease the pin)
- Brakes on
- Bleed system
- Watch that wheel spin

I had the brakes on, off and bled about 5 times before I actually did it properly and got it working. Remember kids, do it once, properly.

Special thanks goes out to Ricky and Fitz on this one.

 

Nice work.

When you Press the Piston back into the Caliper, ... its less messy to crack-open the Bleeder and let some Fluid and Air escape at the Caliper, ... than to Uncover the Master Cylinder and have Fluid squirt-out all-over the place.

Looks like your close to the bottom of that long list.

 

Yo Rick... stop making so much sense.

 

Well done. Wasn't it amazing just how much crud had built up in the channels? And the consistency and PERSISTENCE of it?

It's one of those things you can't really wrap your head around until you actually see it.

Congrats on a job done right.

 

Thanks. It is pretty crazy how persistent it is... and how much is there. There some gross stuff in there. I used all the tools in my arsenal to get it out, but it was more a matter of time with some 1500 sandpaper than a matter of tools. Actually, an old flat-head screwdriver with a bent tip became my best friend.

Thanks fitz!