Front caliper rebuild

[steadythebuffs]

Evening folks
Apparently it's going to stop raining for eight or nine minutes tomorrow, so I plan to crack on with the front caliper rebuild.
I have new pistons and seals, a plan for getting my stuck piston out (put one new one in and force old one out with fluid pressure), and some questions if anyone can help

1) My pattern pistons are 'closed' at the end that touches the back of the pad - that's OK right?

2) Assuming everything is clean and then lubed up nicely with brake fluid, any tips for getting the new rings and pistons in properly?
thanks
Buffs

[dpmiller]

Closed end goes into the caliper, or are you saying both ends of the piston are solid?
If there's any corrosion in the bore, deal with it now, then soak the new seals in brake fluid and just ease'em in. If they're being a pain, use nothing harder or sharper than a plastic knitting needle to poke them into position. The lubed piston should then slide in squarely under finger pressure...

[steadythebuffs]

The pattern pistons are the same as the ones that were in place except that the normally open end has been sort of blanked off, so that instead of the outer ring of the piston being in contact with the pad, this centre 'blank' is in contact.
I would think this would work better - bigger surface area of contact - and can't see a problem, but fancied reassurance given the disastrous nature of the job so far ;D
You make putting in the new pistons sound nice and easy.
The weather forecast was wrong, it's raining again, now it looks like a job for the weekend, so if anyone else has got any further tips, I'd appreciate it.
thanks

[hovis]

Major tip mate,
make sure you slide the piston absolutely square on into the bore,take your time and do not force it or you will score the bore,lubricate it with some brake fluid prior to fitting,

good luck Hovis

[steadythebuffs]

thanks Hovis and dpmiller
this is my major concern - getting it in square.
Slowly with a screwing motion, rather than rocking?

[hovis]

thats right mate,easy does it,don't force it,slow screwing motion (ooh err misses ),just like the honeymoon

Hovis

[steadythebuffs]

;D
A cowboy and his wife had just been married and go to a hotel for their honeymoon.

The cowboy goes to the front desk. "Ah just got hitched, give me a good room with a strong bed."

The clerk: "Do you want the Bridal?"

The Cowboy: "No, I reckon I'll just hold on to her ears until she gets used to it."

[hovis]

Very good mate,
Mrs Hovis enjoyed that one as well ;D

Hovis

[honda]

I dont know about holding on on to her ears. I have been holdin on to my pockets,cards, pin numbers etc ever since. Or as the old saying goes "at one time I could have ate her now I wish I had"
Dont know what all this has to do with calipers but like hovis I enjoyed the cowboy story.

Whats the differance between your wife and your lover??


ANS about 45lbs

[steadythebuffs]

;DMrs Buffs says I can't play with you lot any more

12 hrs and counting to the great caliper rebuild. . .

[steadythebuffs]

Great caliper rebuild has hit trouble yet again.

1) popped out sticky piston using fluid pressure, after putting old 'other' one back in, and clamping it.
2) Cleaned up empty bore, removed old seals, fluid on new seals, popped them back in, both seated nicely.
3) Tried to put new piston in, gently, rotating motion etc. Can't be done - the dust ring sticks out too far, provides too much resisitance and gets mangled when I apply a bit more pressure. why oh why

I'm guessing there's some microspcopic crud in the ring seat, so clean it up using a toothbrush, a wooden toothpick, and fluid. Try again, no joy, same problem - something in the seating is making the dust ring stick out a (really) tiny bit too far in one place.
I notice a little shred of the new ring has been mangled off.

Now I have to go to work - three hours toil and really very little further.

I'm at my wit's end

[pops]

Hi Buffs
I have today done the front and rear caliper on the project bike I had no problem with either.
Saying that you are dead right in saying that you still have crud in the seal recess.A tooth pick or tooth brush is a waste of time,to soft for most of the crud.You need something like a heavy duty paper clip or thicker bent at right angle at the end.I used a welding rod flattened at the end so it just fits in the recess to the bottom.Just take it slow and make sure you have all the crud out before you try again.
Take my word for it, if all the crud is out it will be like using KY jelly.

pops

[steadythebuffs]

thanks Pops,
I was feeling proper deflated when I posted - with missing parts, and weather, this thing's just been dragging on and on, and shouldn't be hard at all - but I'll try a bit of heavy gauge wire.
Just bend it like an L, hold on to the 'long end' and scrape away slowly does it.
Is there anything I could spray on to soften it? I've got some general bike cleaner that's 'safe for brakes'?
Buffs

[pops]

Hi Buffs
Give it a go I never used anything, but it can,t harm.The crud is ally corrosion and can be a nuts to get it all out.Don,t forget to clean any cleaner off it before you rebuild it as this will contaminate the brake fluid.

[steadythebuffs]

hat's off to you, Pops!
Your scraper tip came good, and everything's back together.
I've yet to test the brakes on the road, but they are engaging and disengaging spot on.
The minor irritation is that having emptied and refilled/bled the system FOUR times during this sorry debacle, I've managed to semi round-off the bleed screw (cheap spanner, and too much wellie).
Not sure if it's tight enough (can't get a socket on it, so got the mole grips going again!), will leave overnight to see if there's any seepage, and check regularly once mobile.

But otherwise - WHAT A RESULT

Many thanks to everyone who has helped out - much appreciated.

I wonder if we could get together a series of wiki-style sticky threads/FAQs for basic jobs like these, with procedures, do's don'ts etc, and tips - with each reply updating the original message, so that the last reply is the 'final' word.

I've learned a few things the hard/stupid way on this job, and would be happy yo throw in my 2p.

Any thoughts?
Buffs