Rebuilding Calipers

Think I have a sticky piston in one of my calipers.

Paddocks do rebuilt calipers for £55, not a disaster, but also sell
pistons and seals for approx £12 per caliper.

There can't be very much to a caliper (!?!), how feasible is it to do
my own rebuild (assume some mechanical competance)?

Paddocks also list stainless pistons fo an extra £1.60 ish. Sensible
investment?

David

On or around Fri, 11 Mar 2005 10:17:24 +0000, rads
<[email protected]> enlightened us thusly:

>Think I have a sticky piston in one of my calipers.
>
>Paddocks do rebuilt calipers for £55, not a disaster, but also sell
>pistons and seals for approx £12 per caliper.
>
>There can't be very much to a caliper (!?!), how feasible is it to do
>my own rebuild (assume some mechanical competance)?
>
>Paddocks also list stainless pistons fo an extra £1.60 ish. Sensible
>investment?


not a problem to rebuild 'em. You'll need a few largeish clamps, and lots
of brake fluid... basically, remove the caliper from the hub/disc. pump
the brake a couple of times. Look at the caliper and see which pistons have
moved, clamp on these ones so that they don't move any further and pump
again. once you have all 4 moving, pump 'em all out till they're mostly
out, then remove them. clean the caliper body scrupulously, fit the new
seals and dust seals to the caliper, refit pistons, push 'em home and refit
caliper and pads. bleed according to instructions, noting that 4-piston
fronts have anything up to 3 bleed nipples.

the key to long-term success is to get it all as clean as you possibly can.

Stainless pistons won't rust but may not be as hard as chrome ones. I'd be
inclined to fit 'em if they're not that much more.

--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"The great masses of the people ... will more easily fall victims to
a great lie than to a small one" Adolf Hitler (1889 - 1945)
from Mein Kampf, Ch 10

On Fri, 11 Mar 2005 13:05:21 +0000, Austin Shackles
<[email protected]> wrote:

>On or around Fri, 11 Mar 2005 10:17:24 +0000, rads
><[email protected]> enlightened us thusly:
>
>>Think I have a sticky piston in one of my calipers.
>>
>>Paddocks do rebuilt calipers for £55, not a disaster, but also sell
>>pistons and seals for approx £12 per caliper.
>>
>>There can't be very much to a caliper (!?!), how feasible is it to do
>>my own rebuild (assume some mechanical competance)?
>>
>>Paddocks also list stainless pistons fo an extra £1.60 ish. Sensible
>>investment?
>
>
>not a problem to rebuild 'em. You'll need a few largeish clamps, and lots
>of brake fluid... basically, remove the caliper from the hub/disc. pump
>the brake a couple of times. Look at the caliper and see which pistons have
>moved, clamp on these ones so that they don't move any further and pump
>again. once you have all 4 moving, pump 'em all out till they're mostly
>out, then remove them. clean the caliper body scrupulously, fit the new
>seals and dust seals to the caliper, refit pistons, push 'em home and refit
>caliper and pads. bleed according to instructions, noting that 4-piston
>fronts have anything up to 3 bleed nipples.
>
>the key to long-term success is to get it all as clean as you possibly can.
>
>Stainless pistons won't rust but may not be as hard as chrome ones. I'd be
>inclined to fit 'em if they're not that much more.

Thanks for that, Austin.

Just one more question. You mention new seals and dust seals. Are
these all contained within the seal kit AEU1547?

David

On or around Fri, 11 Mar 2005 13:39:30 +0000, rads
<[email protected]> enlightened us thusly:

>On Fri, 11 Mar 2005 13:05:21 +0000, Austin Shackles
><[email protected]> wrote:
>Just one more question. You mention new seals and dust seals. Are
>these all contained within the seal kit AEU1547?
>

dunno. I'd have thought they would be, but yer best off asking the
supplier.

--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
If all be true that I do think, There are five reasons we should drink;
Good wine, a friend, or being dry, Or lest we should be by and by;
Or any other reason why. - Henry Aldrich (1647 - 1710)

>> There can't be very much to a caliper (!?!), how feasible is it to do
>> my own rebuild (assume some mechanical competance)?
>>
>
> not a problem to rebuild 'em. You'll need a few largeish clamps, and lots
> of brake fluid... basically, remove the caliper from the hub/disc. pump
> the brake a couple of times. Look at the caliper and see which pistons have
> moved, clamp on these ones so that they don't move any further and pump
> again.

It's easier to do this whilst the calliper is still attached - much less
of a juggling act. Fit 'shims' of pad and/or hardboard or whatever about
8 mm thick between the pistons and the disc (both sides - you are
attempting to ensure that the disc does not get loaded on one side
only). Pump all the pistons out (hopefully they'll all move!). The
'shim' will make sure that they don't come fully out of the bore.

If the calliper attachment bolts do not have single hex heads be
prepared to replace them.

> once you have all 4 moving, pump 'em all out till they're mostly
> out, then remove them. clean the caliper body scrupulously,

Don't forget the recesses for the dust seal retainers. If these are not
properly cleaned out the dust seal retainers will not install.

> fit the new seals and dust seals to the caliper, refit pistons,
> push 'em home and refit caliper and pads.

I find it easier to fit the piston seal followed by the piston which is
not fully pushed into the bore. You can then use the piston as a guide
to install the dust seal and retainer. I've always used purple brake
grease (the stuff that is compatible with brake fluid) as a lubricant
and to fill the space between the dust seal lips.

Use a large washer, outside diameter bigger than the dust seal retainer,
as a press tool. Press piston, dust seal and retainer in - all at the
same time. Be prepared to re-align the parts as the dust seal retainer
enters its recess. I made some bits to attach to a 3 inch 'G' clamp (a 4
inch, deep throat one might be even better) to help with this: it's been
well worth it over the years.

I would recommend doing both callipers on the same axle. If this is a
front calliper, now would be the time to replace the short transfer
pipes if they are in poor condition.

Dougal

>>Just one more question. You mention new seals and dust seals. Are
>>these all contained within the seal kit AEU1547?
>>
>
> dunno. I'd have thought they would be, but yer best off asking the
> supplier.
>

My recollection is that AEU1547 has sufficient seals to do four pistons
i.e. one front or two rear callipers. But you'd better check.

In message <[email protected]>
rads <[email protected]> wrote:

> On Fri, 11 Mar 2005 13:05:21 +0000, Austin Shackles
> <[email protected]> wrote:
>
> >On or around Fri, 11 Mar 2005 10:17:24 +0000, rads
> ><[email protected]> enlightened us thusly:
> >
> >>Think I have a sticky piston in one of my calipers.
> >>
> >>Paddocks do rebuilt calipers for £55, not a disaster, but also sell
> >>pistons and seals for approx £12 per caliper.
> >>
> >>There can't be very much to a caliper (!?!), how feasible is it to do
> >>my own rebuild (assume some mechanical competance)?
> >>
> >>Paddocks also list stainless pistons fo an extra £1.60 ish. Sensible
> >>investment?
> >
> >
> >not a problem to rebuild 'em. You'll need a few largeish clamps, and lots
> >of brake fluid... basically, remove the caliper from the hub/disc. pump
> >the brake a couple of times. Look at the caliper and see which pistons have
> >moved, clamp on these ones so that they don't move any further and pump
> >again. once you have all 4 moving, pump 'em all out till they're mostly
> >out, then remove them. clean the caliper body scrupulously, fit the new
> >seals and dust seals to the caliper, refit pistons, push 'em home and refit
> >caliper and pads. bleed according to instructions, noting that 4-piston
> >fronts have anything up to 3 bleed nipples.
> >
> >the key to long-term success is to get it all as clean as you possibly can.
> >
> >Stainless pistons won't rust but may not be as hard as chrome ones. I'd be
> >inclined to fit 'em if they're not that much more.
>
> Thanks for that, Austin.
>
> Just one more question. You mention new seals and dust seals. Are
> these all contained within the seal kit AEU1547?
>
> David
>
>

Yes!

Richard

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