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fog 10-25-2006 9:47 PM

Complete front caliper service
 
Front Caliper Service

Many folks have posted here with a Varity of front brake problems. Many of which are attributable to the lack of proper maintenance. Here’s how you can always have a brake like when your bike was new.

A short list of the problems and the causes.

Soft lever or lever goes to the bar.

The usual cause is the pistons are pushed too far back into the caliper by a flexing a warped, coned, disc. Using up too much piston travel before the disc is pinched.

Juddering in sync with wheel rotation.

The disc is worn, and its thickness varies. This causes the caliper to “sink” into the thin part and when the thick part comes around, it gets wedged into a smaller space causing a tightening of the brake. Then the tight spot passes through and it like the brake is released. Then repeat, repeat.

Cupped, coned, or warped disc.

Unfortunately this is a common problem with EX’s the cause is the disc is stretched in the center due to being rigidly bolted to the wheel. The huge force of braking is transmitted to the wheel through the webbed center of the disc which gets stretched and becomes larger than the space it occupies in the center of the disc. This causes the center to push to the side trying to find room for itself. Resulting is a cone shaped disc.

Soft lever 2

The caliper has pistons only on one side, so as the pads wear the caliper must shift sideways apply even pressure on both sides of the disc. To allow this the caliper floats on two pins. If these pins get dry (no grease) dirty or bent. The caliper won’t center itself and bends the disc to wherever it is. This take up lever travel and when released pushes the pistons further back than necessary. If not fixed will eventually destroy the disc (warp it).


Ok how to prevent all of the above.

When new pad time comes around, resist the temptation to just pop in new one and go. Every time you must do these things.

Remove caliper disassemble and clean it.

Clean and re grease the sliding pins.

Polish the caliper pistons to remove dirt. If you just push the pistons back into the caliper leaks will result. Or binding.

Tools required: 12 mm socket, 8mm open end wrench, 3” or bigger C clamp, a supply of new bake fluid. Wire brush and or steel wool.

Remove the caliper from the fork leg but leave the brake line on.

Remove the old pads and the mounting frame (the sliding pins)

Remove the cover from the Master Cylinder on the Handel bar.

Attach the C clamp to one of the pistons but don’t squeeze it. Pump the lever on the bar slowly to push out the other piston almost all the way. Put the C clamp on that piston and push out the other one.

Remove both pistons by hand.

Remove all the rubber part from the caliper, the seals are in the grooves in the caliper and dull pointed thingy will get them out easy.

Disconnect the caliper from the brake line.

Soak all the rubber parts in new clean brake fluid ONLY!!!!! Rub them with you fingers till as clean as new.

The caliper can be cleaned with a wire brush or even a Moto tool for the internal grooves, NOW’s the time to paint it if you wish.

Polish the pistons till they are smooth and shinny. They are chrome plated. If any of the plating is chipped or damaged below the dust cap groove. Replace it.

The master cylinder is the subject of another write up and we’ll assume it in good working order here.

If you suspect your disc is bad, your bets bet is to replace it with an after market one fro EBC or Galpher.

Don’t remove the disc unless you intend to replace it. It will assume a new shape if it is stressed and will not be flat again. You can try to check its condition by placing a straight edge across the face of the pad swept area looking for any distortion.

Re assembly

Take the nice clean rubber seals and install them into the caliper then the Dust covers.
Wet all the rubber with new clean brake fluid and partially fill the caliper with new fluid.

Push the pistons though the dust seals and into the caliper body until the dust covers snap into the grooves.

Fill the MC with new fluid and pump the lever while holding the Line above the MC till clean fluid flows.

Connect the line to the caliper while holding it above the MC.

Pump the lever with the bleeder valve open till fluid flow from the bleeder. Hold the caliper so that the bleeder is the highest point.

Close the bleeder and pump more fluid into the caliper but don’t push the pistons all the way out.

Then squeeze the pistons all the way back in and install the new pads.

Re grease the slider pins and assemble the dust seals and re mount the caliper on the forks but leave the bolts loose.

Now clamp the caliper to the disc with the brake lever.

Look at the space between the fork lugs and the caliper, clamp and release a few times as you tighten the bolts by hand. It one lug touches much before the other the odds are you mounting bracket is bent. You can straighten it. After you get it the best you can. Some shim washers made from alum can stock can be fitted to the loose side.
What we are doing here is trying to mina muse the bedd in time and gets the best pad life.

Ok with everything tight you should be through, Notice we don’t need to bleed the brakes, but if you screwed up in any of the above steps, you might do that here.

Care full to Bedd in the new pads gently. Too much pressure too soon will burn the pad material as only a small area will be gripping at first. You also won’t have full braking power till the pads are fully familiar with the disc.

Good luck Ride Hard.

FOG

knightslugger 10-25-2006 10:58 PM

Re: Complete front caliper service
 
Thanks FOG! would the service portion be near universal to any brake system?

**Stickified**

fog 10-26-2006 6:50 PM

Re: Complete front caliper service
 
Yes pretty much, Except some systems behave better than others. and four piston setups don't have the sliding pins to foul up. The best new Radial mounted four(or more) piston ones are the best.
Prolly the one thing that is common is pushing dirty pistons back into the caliper. Depending what type of dust seals are used, this can or not be a problem.

FOG

budlight 2-3-2007 11:01 AM

Re: Complete front caliper service
 
Interesting way of bleeding the front brakes, I might try it sometime. I prefer never to mess with disconnecting the brake line if they aren't broke or imminently breaking. One thing that should be noted for anyone new to brake work, is that brake fluid is a very corrosive substance and will take the paint off of near anything given enough time.

Mulcibre 2-14-2007 7:22 AM

Re: Complete front caliper service
 
Yeah, wear rubber gloves, brake fluid is some evil stuff

yttfdyvt 5-21-2008 6:06 PM

Re: Complete front caliper service
 
Alright, I messed this up despite your instructions.

I had one of the pistons clamped and was pumping the brake lever to push out the other piston. However I went too far and the second piston was pushed out all the way, when this happened all the brake fluid inside came out (over my jeans). So I put the piston back and crammed it in (without pouring in more brake fluid in the, which I'm guessing was a mistake) and pumped the break lever to try again. Now neither will move, I'm guessing its because the chamber behind them is now empty. Is there a faster way of filling up the caliper then squeezing that damn brake lever for 80 freakin hours?

*edit
Alright, managed to get them both out, guess all it takes is time.

zeroaffiliation 6-11-2008 8:03 AM

Re: Complete front caliper service
 
forgive possibly the most newbie question, but, I am assuming that the rear caliper would be done in the same fashion? (still waiting for my clymer book to get here)

Great breakdown FOG, thanks!

fog 6-11-2008 9:24 AM

Re: Complete front caliper service
 
Quote:

Originally Posted by yttfdyvt
Alright, I messed this up despite your instructions.

I had one of the pistons clamped and was pumping the brake lever to push out the other piston. However I went too far and the second piston was pushed out all the way, when this happened all the brake fluid inside came out (over my jeans). So I put the piston back and crammed it in (without pouring in more brake fluid in the, which I'm guessing was a mistake) and pumped the break lever to try again. Now neither will move, I'm guessing its because the chamber behind them is now empty. Is there a faster way of filling up the caliper then squeezing that damn brake lever for 80 freakin hours?

*edit
Alright, managed to get them both out, guess all it takes is time.

Yeah, About the same time it take to write a "help!" to the forum.

FOG

gogi 7-22-2008 11:34 AM

Re: Complete front caliper service
 
did you bench bleed the brake MC? Also I put teflon tape on the bleeder threads as they tend to leak air while bleeding.

fog 7-22-2008 12:15 PM

Re: Complete front caliper service
 
If you were Bleeding properly there would always be positive internal pressure on the bleeder nipple and thus the only thing it should leak is the internal air or fluid.

FOG

yakfish 7-24-2008 2:12 PM

Re: Complete front caliper service
 
FOG, thanks for the cookbook instructions. I'm a newb to working on brakes and there are a few details that aren't clear to me, if you'd be so kind as to enlighten me.

"Remove caliper disassemble and clean it."
"Clean and re grease the sliding pins."
...what do you use to clean the caliper and pins? I'm guessing "brake parts cleaner", but since it's not in the list of items in your posting, I thought I would check. What kind of grease do you use on the pins?

What do you use to polish the pistons? Is that what the steel wool is for? Use any chemicals along with that?

Thanks again. I'm gonna give this a try in the next weekend or two.

fog 7-24-2008 6:32 PM

Re: Complete front caliper service
 
Quote:

Originally Posted by yakfish
FOG, thanks for the cookbook instructions. I'm a newb to working on brakes and there are a few details that aren't clear to me, if you'd be so kind as to enlighten me.

"Remove caliper disassemble and clean it."
"Clean and re grease the sliding pins."
...what do you use to clean the caliper and pins? I'm guessing "brake parts cleaner", but since it's not in the list of items in your posting, I thought I would check. What kind of grease do you use on the pins?

Ans: any sort of cleaner will work fine I like those super one Like Greqased lightning or the castrol purple stuff, nasty but effective. Any sort of grease will do , this is just a mechanical set of pins.

What do you use to polish the pistons? Is that what the steel wool is for? Use any chemicals along with that?

Yes you can use the steel wool if you need it. Caution here only brake fluid for the pistons and all the rubber parts.


Thanks again. I'm gonna give this a try in the next weekend or two.


medwards82 8-10-2008 9:39 PM

Re: Complete front caliper service
 
Here's a rookie question.

I think my brakes work great, but I noticed that on the front brake, the rubber cap is off the nozzle, and on the rear brake it is on the nozzle. Does it matter if it is on or off? Should it just go on to keep dirt out?

zeroaffiliation 8-10-2008 9:52 PM

Re: Complete front caliper service
 
it's a good idea to keep the bleeder nozzle covered, so dirt doesn't collect in the hole.

bachieeee 8-16-2008 8:19 PM

Re: Complete front caliper service
 
I think I am in deep now. My front brakes lever not pushing anything the brake fluid to the front caliper. I tried filling the caliper with some fluid, but that doesnt help. Help FOG!!

fog 8-16-2008 10:16 PM

Re: Complete front caliper service
 
It's because you have air in the MC piston. Try loosening the banjo fitting on the MC and pump it . FLuid should flow in a few pumps then tighten the fitting and bleed the caliper . Never let the MC fluid level go too low or it will happen again.

FOG

brianp 8-26-2008 2:24 PM

Re: Complete front caliper service
 
Has anybody done his procedure with pictures ?

It sounds straight forward but the fact is i do not know what most of the parts mentioned are so just reading it still leaves me a little puzzled. I had a pad swap coming up soon and would like to do this. Does anyone know of an exploded view image of the caliper so I can learn? Also what do you use to re-oil stuff? Particular brand or type i should look for ?

ratchet 8-26-2008 3:36 PM

Re: Complete front caliper service
 
can't help you with the pictures....

here's the exploded view:
http://fiche.ronayers.com/Index.cfm/..._Brake(D11/D12)

oh... and I don't know about everyone else... but I always use brake caliper grease.

zeroaffiliation 8-26-2008 4:13 PM

Re: Complete front caliper service
 
I had done the rear using this (FOG's) write up as a reference and took pictures then posted to the wiki.

https://www.ex-500.com/wiki/index.php...aliper_Service

'cept I used high temp multi-purpose grease on the slider pins

vvolfgang 9-10-2008 5:52 PM

Re: Complete front caliper service
 
Thanks zeroaffiliation!

I used your procedures but only needed to bleed the rear brakes. I finally found the AMPRO one-man bleeder kit which really simplified things.

Vv-[/color]

Dalemac 9-28-2008 6:09 PM

Re: Complete front caliper service
 
Went to do a front pad change and realised that the large piston has siezed! couldnt move it at all in or out, even when pumping the lever. the pistons were in bad shape, corrosion all over them and the seals looked terrible.

Bought a different caliper from ebay, should be here in the next few days, during which time i will doing a full rebuild of the caliper.

Once i have reconditioned the new caliper, i will be wanting to recondition the current caliper. Does anyone have any tips on removing this sieze piston? like i say it wont move at all, even under pressure.

Cheers,

Dale

fog 9-28-2008 9:20 PM

Re: Complete front caliper service
 
Drill and tap a hole through the bottom of the piston in the center. The use a screw in that hole to push against the bottom of the caliper thus pushing out the piston. You'll need a new one anyway.

FOG

triple88a 11-2-2008 10:14 PM

Re: Complete front caliper service
 
hey fog, is there a problem for using dot 3 vs 4 vs 5 brake fluid? Whats the difference?

fog 11-2-2008 11:28 PM

Re: Complete front caliper service
 
3 or 4 are fine do not use 5 as it'd silicon and only for Harley's.

FOG

Forbin 11-3-2008 9:57 AM

Re: Complete front caliper service
 
Motul RBF600 (DOT4 racing fluid) is what I used in my EX.


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