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MG MGA - Old calipers need rebuilding!!

I just bought brake calipers, hubs, and rotors (rotors are useless) from a MGA 1600. Is it possible to rebuild them myself? Do I need any special tools?


gerard hutchinson

This is a picture of the hubs, rotors, kingpin, etc.


gerard hutchinson

I wouldn't bother as there is a replacement kit available for £199.
Cam Cunningham

Yes they are easily rebuilt without special tools. What are your intentions? Are you adding disc brakes to an earlier car? Disc brake housings are almost always rebuildable. Hardest part may be getting the pistons out. Piston surface may be rusted beyond use but pistons are available. MGB pistons can be used. Moss list MGA at $62.95 while MGB are $21.95.(http://www.mgaguru.com/mgtech/brakes/bt104a.htm)
The kingpin and spindle are the same between drum and disc. The hard to get part is the caliper bracket,not shown in your pics, but I assume they are there.
R J Brown

Hi again Gerard - here is the link to a kit now on ebay -
they are a direct replacement for the original callipers.
seem to be OK unless you want concours originality - if you are converting a 1500 you still need the adapter bracket. cheers Cam
http://www.ebay.co.uk/itm/bek172-MGA-FRONT-BRAKE-CALIPER-KIT-/120703656702?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item1c1a7fa2fe#ht_3788wt_1163
Cam Cunningham

You can sand blast the calipers, install new seals, also new pistons if the old ones are corroded. You can use the cheaper MGB pistons if you remove the center guide pins from the caliper. New hoses, new rotors, and you're in business.
Barney Gaylord

Gerrard I have rebuilt my calipers once but used Bigg Red in Worcester last time. http://www.biggred.co.uk/. Bob West can supply the correct MGA pistons in stainless steel at a reasonable price. Todd Clark in the US can supply the locking tabs for the caliper bolts holding the two halves together. He can also supply new high tensile bolts. The workshop manual advises not reusing the bolts.

One problem I had with Bigg Red was that they put the pistons with the cut away section on the pistons on the outer ring upside down and had to redo them.

I hope that the bores for the pistons are not badly corroded especially around the seal grooves.
John

John Francis

I rebuilt my MGA calipers a good few years ago. Original pistons for the MGA were very expensive then so I decided to use MGB pistons.

I don't see any advantage in using MGA pistons the MGB ones are great and have been no problems. The orientation refered to by John is very interesting. If you read the MGA workshop manual it suggests they shold be across the bottom of the caliper. Whereas the MGB workshop manual suggests they should be to the sides?? Which one is right is I suppose anybodies guess or indeed what is the purpose?

Robert (Bob) Midget Turbo

The caliper bores are not the critical sealing faces. The piston surface is, along with the bottom of the seal groove, maybe even the walls of the seal groove. How to proerly clean that area so the fluid does not leak around?
Art Pearse

Soak them in Molasses and see what happens. I am waiting for a reason to try this trick!

http://www.youtube.com/watch?v=b-_z4tinnXk

JIM in NH
AJ Mail

Great advice as always fellas!!! I will definitely use the MGB pistons!!

I plan to have the hubs and calipers bead blasted. should I remove the bearings first and if so how?
gerard hutchinson

First remove the outer bearing by inserting a suitable round socket and bar into the inside of the spacer and hit from the big bearing side, so you are forcing onto the inner race of the outer bearing. Not good for the bearing, but you will replace it? Definitely don't leave them in while blasting. No matter how well you wrap it you will get grit. Once the inner is out, you can see the inner race of the outer bearing. Push on it and the bearing will come out. same applies about new bearing. Best to use push rather than hammer if you plan to re-use them.
Art Pearse

You might take the time to grind in a few notches in the inner hub to access the outer races in the future. This way you could access the outer race with a punch in the future to safely drive out the bearings. Handy if you need to R&R the bearings for any reason later on.
Chuck Schaefer

Art, the bearing seem to be in really good shape and the outer seal seems to have little wear. I am willing to damage the seal but not the bearings!! Is there a way to remove the seal without damaging the bearing?
gerard hutchinson

ALSO!!! How do I remove the caliper pistons?! They are stuck and rusty! Should I apply heat?!
gerard hutchinson

See here: http://mgaguru.com/mgtech/hydraulics/ht105.htm
Barney Gaylord

Gerard

I have emailed you some info on doing the job with MGB pistons
IHTH

Bob
Robert (Bob) Midget Turbo

I'm interested in the choice to go to MGB pistons instead of original MGA because in the workshop manual it describes the role of the post in limiting the amount that the piston withdraws once the pressure is relieved by way of a friction stop. When my calipers were overhauled I elected to stay with the posts because of this so I'm puzzled how MGB pistons manage?
J H Cole

The retraction on MGB and on other modern calipers is simply by the elasticity of the seals and any slight wobble in the rotors. as long as the hydraulic pressure is off and the pistons are not stuck, there is no more brake drag. Originally it was thought necessary to positively disengage the pistons.
Art Pearse

A second intent of the center post arrangement in the MGA caliper was to prevent the piston from retracting too far on long runs with vibration and no touch of the pedal. It turns out that neither function is required, because the rubber seal ring performs both functions well. As such, the center guide pin arrangement was deleted for MGB production. The guide pins can be removed form the MGA caliper to allow use of MGB pistons.
Barney Gaylord

This thread was discussed between 24/11/2011 and 28/11/2011

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This thread is from the archive. The Live MG MGA BBS is active now.