Front Brake Caliper Seals

[bassman]

About two months ago I was braking when I felt a strange sensation in the front brake lever.  It was very subtle, but ever since I had felt sure that the braking efficiency had reduced.  I was too lazy to take the caliper off to check it and simply bled the front brake.  It improved slightly but no great improvement.  Then, the other evening, I finally removed the caliper to find that the dust seals around both caliper pistons were forcing their way out of the barrels

Basically, the pistons have become so encrusted with crud that the in and out motion of the pistons has worked the dust seals out!!  I've got a complete set of seals (dust and fluid x 2) and am going to replace them soon (this weekend hopefully!).  I'm hoping that I can just clean the pistons without having to replace them with new.

Anyone else had experience with this job?  I've got to pump the pistons out and remove them (while draining the fluid), remove the old seals, clean everything up, then insert the new seals and insert the pistons.  I know it's not rocket science - it's just the importance of the brakes that makes me feel slightly anxious about the task .  Anyone got any hints or tips to offer?

Bassman

[ineedanap]

Sounds like you have it figured out.  It's really easy...just as easy as an oil filter change.  A couple things I'd add are

Leaving the brake pads sitting loose in the caliper is a good way to make sure both pistons come most of the way out without one popping out.  (Once one pops out you can't use pressure to get the other one out)

don't be tempted to use pliers to pull the pistons out since they're easy to damage.  Get them most of the way out with pumping so you can use your fingers.

When you're prying the old seals out make sure to use something that won't scratch the bore (piece of plastic or something).  

Lube the pistons and seals with brake fluid before sliding it all together.  

that's all I have.  It really is easier than it sounds.  

[tussey]

Hope this helps. I understand there are two different front brake designs. Mine is the older

http://gstwins.com/gsboard/index.php?topic=46715.msg524127#msg524127

[Dr.Sparkie]

//grain of salt: i dont actually own a gs500 front braking system

anyways, from my experiance with front brakes, if the pistons are corroded (rust) they will be somwhat of a challenge to clean up, the steel pistons are usually chromed, then the chrome flakes off and exposes the steel beneath to the elements. if this is the case then light sanding will only smooth the surface so much, as the chrome is way to hard to sand. a good metal polish can also improve your chances, but the rebuilt unit may leak if there are chips in the chrome.

if the piston is aluminum (SEXY!) then just try to clean it up the best you can, with a super emphasis on smoothness. metal polish never hurts as long as you dont remove too much material.

post pics so i can learn more about the brakes i never had... 

[bassman]

Thanks everyone for the advice - you all go to show what a great forum this is

I am concerned about the state of the pistons - I'll just have to renew them if they look too bad.  This experience has made me realise that I'll have to check my brakes more often.  It's riding through the British winter (and the great British summer!!) that rots everything here

I'll let you know how I get on and take pictures if I am able.

Cheers

Bassman

[gsJack]

Those outer wipers are intended to wipe the piston off when you push the piston back into the caliper to make room for new pads.  Riding year around here in NE Ohio, salt water capital of the universe, my rusted up calipers are a sight to be seen by spring.  That crud on the pistons is hard as a rock and those green Scotch kitchen pads that will readily scratch hard chrome will barely clean it off.  The pistons don't work in and out as you use the brakes they just move out as the pads wear and when you release the brake lever the piston just relaxes a bit leaving little if any clearance between the pad and rotor.  The rubber fluid seal provides a bit of spring effect to relax the pad contact with the rotor when fluid pressure is relaxed.  Those outer wipers do nothing for you if you don't try to push dirty pistons back into the seals, they will wipe off brake dust but won't touch hard crud.  I throw them away as soon as they show any sign of coming out, haven't had any in my 02 GS calipers for years and tens of thousands of miles.

I wince everytime someone here tells of pushing the pistons back in to install new pads without even removing the rear caliper.  Sooner or later they will end up with brake lockup as the crud is pushed into the seals and the pistons bind unless they ride only in sunny southern CA.  I now and have for a number of years always popped the pistons out and clean them every time I replace pads, front or rear.  In spite of my year round riding I've put 80-100k miles on three of my bikes including my 97 GS and now have 74K miles on my 02 GS and have never replaced a caliper piston fluid seal.  Hondas or Suzukis I just threw away the outer wipers if they had them.  If you have those bellows type piston covers they put on cars and I had on a couple of my Hondas you can just push the pistons back in until the belows type seals get old and leak.

Make sure your brake problem wasn't/isn't caused by sticking pinsliders rather than a seal problem although when those outer wipers get out of place or twisted they can cause some piston binding and it's time to discard them in my opinion.

[bassman]

Right!  This evening I successfully popped out the front brake pistons, cleaned them up (not too corroded - but I will get new ones when I can afford it), changed the seals, cleaned everything up as much as I could, replaced the pistons (not too difficult but messy - fingers covered in brake fluid!) then put pads back in, copper greased everything that need copper greasing then bolted caliper back on to fork leg

And so to bleed...   It ain't happening...grrrrrrrrrrrr!

OK, so I have calmed down now.  It's nightime now here in jolly old blighty, so I have set the brake lever open with an elastic band and have retired to the computer with a Scotch & Coke (much to the annoyance of my oldest son who wants to get on MSN ).

I'm going to sleep on it and then try bleeding again in the morning.  I've read some posts on the site and it is clear that it is problematic bleeding the brakes when you have done major surgery like this.  I'm sorry I couldn't take pictures, but my hands were absolutely covered in crap!

It's gotta be a successful, it's gotta!...or I'm gonna be such a miserable bore 'til I sort it!

Bassman

[gsJack]

To reassemble after I pop pistons to clean them when changing front pads I hold the caliper with the bores open upwards and fill the bores with brake fluid up to the seals and push one piston all the way in holding the caliper in the bore up position.  I then start the other piston just past the seal, turn the caliper so the bleeder is up, open the bleeder screw, push the piston the rest of the way in, and close the bleeder.  I don't remove the brake line from the caliper at all and I put an oil drain pan under the caliper while doing this reassembly.  A bit messy for some I suppose but brake fluid is cheap and the caliper is almost free of air and final bleeding is quick and simple after reinstalling the caliper.  I use a similar bleed as I assemble approach on the rear.

If I ever have an assembly full of air as you now have I use a slightly different approach in bleeding to get the air out.  I fill the master, open the caliper bleeder, and hold a finger tip lightly over the hole in the open bleeder while slowly stroking the brake lever repeatedly.  Stop, close bleeder, and top up master often enough to not go dry in the master and then reopen bleeder and proceed with bleeding until fluid starts to push out from under your finger tip check valve.  Then close bleeder and finish off bleeding in conventional open, stroke, close, and release lever manner.

[tussey]

Right!  This evening I successfully popped out the front brake pistons, cleaned them up (not too corroded - but I will get new ones when I can afford it), changed the seals, cleaned everything up as much as I could, replaced the pistons (not too difficult but messy - fingers covered in brake fluid!) then put pads back in, copper greased everything that need copper greasing then bolted caliper back on to fork leg

And so to bleed...   It ain't happening...grrrrrrrrrrrr!

OK, so I have calmed down now.  It's nightime now here in jolly old blighty, so I have set the brake lever open with an elastic band and have retired to the computer with a Scotch & Coke (much to the annoyance of my oldest son who wants to get on MSN ).

I'm going to sleep on it and then try bleeding again in the morning.  I've read some posts on the site and it is clear that it is problematic bleeding the brakes when you have done major surgery like this.  I'm sorry I couldn't take pictures, but my hands were absolutely covered in crap!

It's gotta be a successful, it's gotta!...or I'm gonna be such a miserable bore 'til I sort it!

Bassman

patience. Getting frustrated leads to stripped bolts/threads and broken things. When I rebuilt my brakes they did not work when I tried to bleed them (wasn't pumping fluid down the hose). I eventually decided to take apart the master cylinder which required a very special new tool (circlip pliers)  It didn't take much time and wasn't that much of a hassle. There was some small dirt in it but nothing major so I cleaned it up. Put it all back together and it started working. Go figure.

Just take it slow and steady and you'll get it worked out. 

[bassman]

Well, it's nealy Saturday lunchime and I've finally bled the front brakes and taken a test ride.  All seems OK - it stops the bike!  I forgot to add earlier in the post that my bike is a GS500E year 2000 (naked - single front caliper).  It took me a total of about 3 hours to bleed the brakes!  I've got one of those non-return valve bleeding pipes that I used.  It just seemed like the master cylinder was not pushing the fluid down to the caliper - but eventually it did come through.  I had a false dawn though...I was going great guns - loosening the bleed nipple couple of pumps of the brake lever, bubble bubble, and so on, then 'SLURP SLURP!' - I'd taken my eye off the reservoir and sucked air in all over again   It had been getting nice 'n' firm up until that moment 'Ooh err Mrs!).

Anyhoo, I'm leaving it to rest now with an elastic band under the (mistaken?) assumption that that will assist any further air to rise.  The thing that is bugging me is that the brake lever travel, although not excessive, is a lot more than my Yamaha XJ600N (those brakes are really short and sharp compared to the GS).  The GS travel is around one and half inches or thereabouts.  I probably never thought about it until I got the Yamaha - does that sound about normal?  The pads are only about halfway through their wear.  I'm seriously contemplating braided brake lines now to firm things up.  I'm sure evrything's OK - it's probably just the dear old GS's 'character'.

Bassman

[tussey]

was going great guns - loosening the bleed nipple couple of pumps of the brake lever, bubble bubble, and so on, then 'SLURP SLURP!' - I'd taken my eye off the reservoir and sucked air in all over again   It had been getting nice 'n' firm up until that moment 'Ooh err Mrs!).

damn....sucks.

I probably never thought about it until I got the Yamaha - does that sound about normal?  The pads are only about halfway through their wear.  I'm seriously contemplating braided brake lines now to firm things up.  I'm sure evrything's OK - it's probably just the dear old GS's 'character'.
Bassman

The brake lever is adjustable from "squishy" to "firm". (1-4) I think 4 is firm. It might be 1. Just pull the brake lever forward (toward the front of the bike, OPPOSITE direction of squeezing the brakes) just a TINY bit then with your other hand rotate the small dial that says 1,2,3,4.

[bassman]

No 1 is the 'firmest' if that's the way to put it.  I rode to work today and the brakes work fine.  But being the nit wit I am, I had to bleed the brakes one more time when I got home.  I even 'cracked open' the master cylinder banjo bolt in case there was air trapped in there (every time I think of 'banjo bolt' I hear that 'duelling banjos' tune in my head )

The thing that bothered me was a slight 'notchiness' when squeezing the brake lever and the seemingly long travel of the lever.  But I read about a similar experience that someone had with 'notchiness' either on this forum or another, which was cured by simply lubricating the lever

So what did i do?...I lubricated the lever...and my world is now all fluffy and happyness.  The travel of the lever has lost its notchiness and I don't care about the brake lever travel length anymore.  I'll try and remember these happy thoughts as I career headlong into that brickwall...

Bassman

[bassman]

Just a quick update.

Still don't like the feel of the brake post piston seal change.  Have bled the brakes 'til I was bleedin' fed-up!  Have diassembled the caliper and cleaned and greased every bit which needs greasing.  Have come to the conclusion that the master cylinder is at fault - and is what probably caused the original strange 'sensation' through the lever.  I reckon, by a process of elimination, that the master cylinder seals have got old or become contaminated with crud.  So I have ordered a rebuild kit (£25...is that around $30??).  Also need to cough-up for circlip pliers.  Would appear that I need internal circlip pliers (as opposed to the 'external' ones you need for the front sprocket circlip for instance).  I'll let you know how I get on if anybody is interested.

Bassman  

[jeremy_nash]

my circlip pliers at work are reversible, that would probably be the best way to go, then you will have it both ways when u need them in the future