rebuilding a brake caliper

[Ian Barrett]

Guys (probably Les if we're honest )

Rebuilding my front caliper but I chose not to split the caliper. No real reason why but as its all painted and dry its too late to split it now.

I've got to the stage where I'm putting in the new pistons and seals.

The piston seal is in

The piston is in

Is there a knack to getting the top dust? seal in because I've already bent one metal retainer. I bought a spare set so I've replaced the bent one but I'm struggling to get the little beggars in!

Oh, I've lubed the seals with brake grease as I had some after doing the master cylinder on the TVR. I trust this is OK as rereading the Tech Doc by Les he states to lube them with brake fluid.

Thanks for your help

IanB

[Retroanaconda]

Previous topics on this subject have come down to:

• Genuine parts dust seals go in easily and fit well
• Aftermarket (Britpart etc.) ones do neither of the above

[Litch]

"Previous topics on this subject have come down to:

•Genuine parts dust seals go in easily and fit well

•Aftermarket (Britpart etc.) ones do neither of the above"

Not entirely true. I fitted Britpart seals etc and they fitted fine, they have also lasted very well.

Didn't even try to do it with the calipers in one piece as splitting them was such an easy thing to do.

[Ian Barrett]

I got Lockheed seals rather than 'after-market' from Paddock after reading the discussions on the relative merits of the seal sets.

I've fitted the seals on the caliper I had off earlier - I chamfered an edge on the seal retainer which made it a bit easier but it was still a very clumsy and time consuming job to do.

I'll certainly split the other caliper. That'll be next week as this side swivel and caliper refurb is now finished.

Thanks for your help guys, it won't be long before the old girl can go for her MOT.

[Mo Murphy]

Ian, like you I tried doing it with the caliper unsplit but it is a nightmare of a job. split and it's a whole different ball game Make sure that the recess that the seal retainer fits into is perfectly clean and clean ANY corrosion from edge of the recess and the retainers will go in more easily particularly if they are the genuine Lockheed variety.

Mo

[Snagger]

Ian, like you I tried doing it with the caliper unsplit but it is a nightmare of a job. split and it's a whole different ball game Make sure that the recess that the seal retainer fits into is perfectly clean and clean ANY corrosion from edge of the recess and the retainers will go in more easily particularly if they are the genuine Lockheed variety.

Mo

Making sure the groove is spotless (all traces of surface rust removed) is crucial to success.

[GBMUD]

Too late I know, but after having done this job a few times I have a handle on it now.

Depending on who you ask, splitting the calliper is considered a bad thing. There are tales of stretch bolts and so on but no details (AFAIK) on correct refitting. I will continue to do it without splitting the calliper where possible.

As Snagger suggests, getting everything clean and rust free is key. You can get a proper seal pick, which looks a lot like a dental gauging tool. These are ideal for cleaning as well as seal fitting.

As a matter of principal, and as the cost is so little relatively, I always use OE or brand name rubbers. I also prefer to fit stainless pistons where I can as cheap chrome ones never last and branded chrome ones cost nigh on as much if not more than stainless!

To assemble: Fit the main sealing rubber first. Lubricate the cylinder and the piston with brake fluid (or red brake grease), NEVER WD40, engine oil, baby oil, snake oil, juniper oil or anything else! Now half fit the piston into the calliper cylinder. It should slide in and out smoothly, if not something is wrong, remove and check for dirt or a foreign object in the calliper cylinder or behind the seal.

With the piston half way home, slide the dust seal onto the piston making sure it is lubricated with a small amount of brake fluid or brake grease as above. Now slide the metal ring over it and push them down towards the recess where they will sit. Do not try to push them into the recess yet. Find a piece of flat metal large enough to cover the whole area of the piston with a minimum of 3mm overhang all round. With the piece of metal in position over the piston and the metal ring, use a G-clamp or similar to bear on the metal plate and the back of the calliper cylinder such that as the clamp is tightened it drives the piston home and, as it does so, the metal plate comes to bear on the metal retaining ring and pushes it too into its recess. Tighten the clamp well before removing and inspecting. The dust seal and retaining ring should now be in position.

Before adopting this method I knackered countless retaining rings, but since doing so I cannot think of one which has been damaged.

Hope this helps someone in future.

Mods; perhaps this might make an addendum to Les's complete article in the archive?

Chris

[Ian Barrett]

Thanks GBMUD

Your method is pretty much what we adopted in the end. I use the term WE as I had two mates scratching their heads with this too.

The only difference we had was we put the caliper in the vice with the pistons oriented up / down with the ones you are working on at the bottom - so you can see the seals.

Chamfer the outside/bottom edge of the retaining ring.

We pushed the pistons in level to the piston casing, fitted the seal to the retaining ring and aligned it carefully on the recess ****

With a piece of flat 5mm steel plate we 'leaned' on the plate to press the seal in.

Any high spots were gently tapped with a socket set extension bar which has enough weight to act as a small hammer.

The problem we had with your G-Clamp method was that if the steel retainer wasn't going in it would just flatten and destroy it.

We also couldn't get the clamp on the piston where the brake pipe fits due to the large knuckles in the casting there.

**** This may have been a mistake and I'll give your method a go when I do the other side. (just the small matter of rebuilding the NSR brakes before turning the car around and I'm awaiting parts from Paddock)

[reb78]

The only think i would add to GBMUDs comments is that i use an old bent retainer ring between the flat metal plate and the new retainer ring i am fitting (like others, i had plenty of bent ones knocking around!). This seemed to make sure that the pressure was evenly placed on the new ring and stopped it going wonky as i fitted it and catching at the edge. ALWAYS use genuine parts for this, not the cheap carp you can buy (which interestingly often turns out more expensive!)

I use my ball joint seperator instead of a g clamp to add pressure to the metal plate pushing the retainer in as the jaws of the seperator get nicely in the gap between the calipers.

Others have suggested fitting the retainer ring in upside down before fitting the pistons - they are easily removeable then and this helps ensure they are the correct shape when it somes to final fitting - perhaps not necessary with genuine parts as they are manufactured pretty well in the first place!