Brakes- UPDATE

[promufa]

I 've had spongy brake syndrome for quite a while now, w/o any fluid leaks anywhere. Even after bleeding several times, the problem persists. Bike has braided lines from stock by maybe they went bad... dunno. I decided to pop the calipers off the forks and give the pistons a good clean.

None of the pistons are seized or anything but they definitely don't move at the same time. Even after I cleaned them as best I good while still in the caliper, not much changed. I also noticed some pitting and surface rust on one or two pistons.

I guess I ll have to take the pistons out to give them a really good clean. Unfortunately the pistons are very long and cannot pop them out w/o spliting the caliper (I think, if there is a way let me know pls) Is there any way to repair the pitted ones or I need to fork out for new pistons? Damage is minimal really.

TL;DR are slightly pitted caliper pistons salvageable?

Thanks
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'02 Triumph Speed Four

[Casper]

Pistons dont move at the same time as you have air in the lines. Try a big syringe and pump the fluid in the nipple pushing the air up to the res.

[promufa]

Forgot to mention that, tried reverse bleeding as well
A bit better but still not great :S
Thanks for the hint though
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'02 Triumph Speed Four

[Budgetboy]

Pitting on the pistons wont help with movement also dodgy seals or cheap seals will also cause the same effect.

Pitting will cause the piston to catch on the seal and will stop it or slow it down from moving..And bad seals or old seals are just that,, they swell and cause more friction on the pistons and slow the movement.

IMO it sounds like you need to strip and rebuild your calipers.
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www.Mailorderrepairs.co.uk We service your Carburetor's, Calipers & Suspension for less Also Bike repairs undertaken.

[promufa]

[Budgetboy]

2000 grit wet n dry will get some pitting out. But imo you should not be skimping on brakes.
Do a job once and do it right is my motto mate.
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www.Mailorderrepairs.co.uk We service your Carburetor's, Calipers & Suspension for less Also Bike repairs undertaken.

[stinkwheel]

Sponginess in a closed hydraulic system is either air in the system or knackered rubber brake lines.

It's nothing to do with the pistons.

Try bleeding it at the banjo bolts rather than the bleed nipple.

Also try tying the lever down to the handlebars overnight.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Vincent]

If the pistons aren't completely smooth, they'll need replacing I'm afraid. It's a waste of time cleaning them up as it will just be back after a few days. Not all caliper pistons cost the earth, it depends how they're made. A replacement used caliper might be your cheapest option, just get a look at it before buying to make sure they're not seized/leaking too.

I wouldn't have thought any "spongyness" is down to the condition of the pistons, more likely some air trapped in the system somewhere.
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Space Is Deep

[chris-red]

[Casper]

[supZ]

right, a few confusions in this thread.

1. a little pitting on the exposed sides of the piston is fine. if the pitting runs down to the seal then you'll have a problem and they need to be replaced. otherwise dont worry. (technically, you only need to worry if the pitting is as far down as the main seal but if its reached the dust seal then its a good idea to change)

2. pistons always move differently to each other. one will always get more force than the other. its not a sign of a problem.

to the OP when you say its always spongy what exactly do you mean? does it get solid if you pump the lever but the next day its spongy again? in this case it'll be your m/c seals going and you'll need to buy a recon/repair kit off ebay (less than £20) and replace the seals/spring. easy job to do.

if its just consistently spongy then either there is air in the system or there is a bad seal somewhere (banjo washer/calliper seal). i had this with a crap washer, took me a while to realise that was the reason it wouldnt bleed properly.

reverse bleeding as mentioned above is a superb method but if you say its not making a difference then there probably is a leak somewhere. it shouldnt be that hard to bleed the brakes. when bleeding normally do you continuously get bubbles or does the fluid look air free before you nip the valve up again?

you are bleeding both callipers properly yeh?

might be worth buying some copper crush washers, replacing the old ones and buying a calliper seal kit. its very easy to change them. pop the pistons, get the seals out, soak in new fluid and replace with new ones then pop pistons back in. job done.

bit of a cop out to say 'if you cant figure it out replace all your seals and washers and start again' but sometimes its the only way to be sure
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CBR954RR - Daily toy
CBR600RR - Trackbike

[promufa]

Thanks all for you replies.
Pitting is just outside the dust seal and the pads are almost new so I guess it wont be going behind the seals (could probably leave it as it is for now)

How do you bleed from the banjo?

It doesnt look like there is a leak in the system. I have checked every washer/piston seal, no sign of brake fluid around it.

The bike has an over-the-mudguard link setup. I start reverse bleeding for the left caliper (further away from the M/C). I pump about 2-3 reservoirs worth of brake fluid through and the repeat on the right. I also tap the line lightly while pumping the fluid through.

[stinkwheel]

[Vincent]

None of us has asked what the bike/caliper type is yet If it's in two halfs, could be that the seal in between is leaking.
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Space Is Deep

[Vincent]

None of us has asked what the bike/caliper type is yet If it's in two halfs, could be that the seal in between is leaking.
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Space Is Deep

[map]

[supZ]

[promufa]

Ordered a master cylinder kit, new piston seals all around, fluid washers etc.

I 'll get the pistons out when everything is here and have a go at cleaning them properly. I hope I wont need new ones

The bike has braided lines from stock. Do they go bad at some point or is it just an issue of not bending them? Bike is 10 years old now around 29k miles

Thanks all for the help
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'02 Triumph Speed Four

[supZ]

nah braided lines should, within reason, last forever. its only the standard rubber hoses that can perish and weaken over time.

when i cleaned my pistons up i used a wire attachment on my dremel to get the grime off and then swapped to a polishing end to bring it up. worked wonders

not the best pics but..
https://farm9.staticflickr.com/8286/7723865456_c1e519edba_b.jpg
to
https://farm9.staticflickr.com/8281/7723867134_d1f681559b_b.jpg

you can just see the pitting at the end of the piston. no where near the seals so it wasnt an issue for mine.

with mine i took everything apart. cleaned all anti-rattle springs, replaced slider boots..

its perhaps a bit late now but i presume when you ordered new seals for the callipers you also ordered new dust seals as well? ideally you'd get new slider boots but that all depends on the condition of yours (if your brakes are similar to my trackbikes)

good luck! let us know how you get on
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CBR954RR - Daily toy
CBR600RR - Trackbike

[promufa]

[supZ]

so how'd you get on in the end?

all fixed?
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CBR954RR - Daily toy
CBR600RR - Trackbike

[promufa]

Just finished the whole job today.

Pistons cleaned up quite nicely with a green kitchen scourer and 2-3 hours worth of scrubbing. 1 of the pistons has a small ship but that is on the exposed surface just past the dust seal so it should be ok.

The seal seat where completely clean, no corrosion or gunk of any kind. Replaced all seals after sparingly coating them with rubber grease.

Light coat of rubber grease on the pistons and back in the caliper they went.

Replaced the crush washers on both calipers.

The rubber rings on the M/C piston were perished and I suspect that was the source of the problem. Now changed.

Filled up with brake fluid from the nipple. On the plus side the brakes work so I didn't fuck it up. It still a bit spongy but much better than what it was. I will let it settle and bleed again tonight or tomorrow.

The only things that are now used are the brake lines, 2 crush washers on the M/C and the small seals inside the caliper halves.

Those seals were in really good condition and had no signs of leaks when I split the calipers (ie brake fluid only on the inside of the seal, outside and seating completely dry)
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'02 Triumph Speed Four

[promufa]

On a different note, how tight do the caliper bolts need to be? I am talking about the 4 bolts that keep the 2 halves together - workshop manual doesn't say anything about it. I 've done them up to 25ft/lb atm.
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'02 Triumph Speed Four

[map]

[supZ]

sounds like you're on the right track now, nice one

personally though i wouldnt have used any rubber grease, id have just soaked them in new brake fluid for 10mins before fitting the seals (as per haynes recommendation)

and definitely wouldnt reuse crush washers.. from the very name, they crush as you use them so unless you've been annealing them in the oven id use new. you can end up with a bad seal by reusing old ones.

just my opinion.

as you say though.. see how it goes, hopefully any air thats left in will work its way out and your brakes will be back to how they're meant to be again
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CBR954RR - Daily toy
CBR600RR - Trackbike