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MG MGA - Calliper Cut-away

The Workshop Manual shows the cut-away on the piston 'pointing' down - the lower end.
The new callipers I have fitted as supplied, show that 'pointing' in.
Is there a problem here? Should I rectify?
Barry.





Barry Gannon

Barry

It looks like your new calipers are aftermarket and I was just about to post a thread asking about user satisfaction with aftermarket calipers.

Apart from piston orientation, does anyone please have any comments on these aftermarket calipers?

Cheers
Dave
Bolney Coupe

Morning Dave
I have fitted aftermarket calipers with no problems to date (4years+). I believe there are 2 types using different pistons, with either original type centre pin or without as Mgb pistons.
Brian Paddon

Hi Barry
Intriguing subject, As you say the MGA book has the cutout downwards, MGB's have the cutout inwards towards the stubaxle and I've seen pics of them with the cutouts 20 degrees from horizontal, then there are some new calipers that have full circle pistons without a cutout-
I can understand having the cutout at the bottom which in theory should reduce the pressure on the leading edge of the pad and promote more even pad wear
Being new they should spin around easy enough, so just for the sake of it I'd spin them to the bottom as in your w/shop book---If nothing else, at least you'll know you have them as per the book
Some high end multi piston calipers actually have a smaller piston on the leading end of the pad to apply less pressure on that end like what that cutout does on your single piston caliper
Stay safe
willy
William Revit

Interesting on these aftermarket calipers...I've had two lots, and the castings are terrible!. I've had to grind small parts away just to get the pads in.
Gary Lock

Thanks Willy I will take your advice and turn them. I should be able to grip the central post with a snap-grip and twist.
Gary the quality is quite good - no problems with fitting - maybe I was lucky.
Barry.
Barry Gannon

Barry

Following input on this thread and a similar enquiry on Autoshrine, I just bought and received a new pair of calipers from MGOC.

The piston cut away is the same as yours and I have tried to twist them round without success, the snap grip wrench just twists off. The calipers are both dated 06/20/15 and there must be a tight joint between the piston and its seal.

Additionally, the dust seal retaining rings are installed backwards. The rounded inner side of the ring is visible but the visible part should be the rolled edge.

I have informed MGOC and await their response.

Before I noticed the retaining rings I was planning on putting compressed air on the bleeder, and a piece of wood between the pistons, to see if I could break the joint between piston and seal by pushing the piston out a bit.

I would be very interested to know if you manage to turn the piston (and how) and if you have the same problem with the dust seal retaining ring.

Does anyone else reading this have any solutions?

Cheers
Dave



Bolney Coupe

I bought a pair several years ago. Not long after I suffered a lot of squealing and binding. Stripped them both down and found they had assembly damage to the retaining ring with associated off centre rubbing damage to the pistons.

Steve


Steve Gyles

I have seen two types, one finished in silver, the others in gold. The silver ones were poor quality castings with non standard bleed nipples, and one of these had a incorrectly machined thread and spat the bleed nipple as soon as bleeding was attempted (luckily). Once I received a delivery from Moss of one of each as a "pair", so it seems that it would be difficult to predict what you will get from any supplier

I was always happy with the gold finished units and before I retired I normally called to ask what was in stock before ordering
Dominic Clancy

To close the loop. MGOC called and could offer no solution to the problem with the pistons. They said that there is one manufacturer of aftermarket calipers and that the retailers all buy and offer the same stuff.

They offered a full refund of cost and shipping which I gladly accepted.

Barney has a picture of an aftermarket caliper, his BT-140 dated 2016, which shows the same defects as the ones in my earlier post. Even in 2016 the piston had frozen on to its seal. There is also some technical advice from Moss on how to unfreeze the piston.

I will stick with changing the seals on my OEM calipers. It’s really easy to do once the calipers are split.

Cheers
Dave
Bolney Coupe

Interesting info Dave. Now I'm a bit worried as I'm not able to get my car on the road to check the brakes for a few weeks yet!
I need to do more maintenance work first.
I still have the old calipers and have re-built them in the past so that is my fall back plan.
Dave do you replace the large bolts once the calipers have been split? Manual says change! But ------ ??
Barry
Barry Gannon

Barry

Barney’s BT-104 talks about splitting and refurbing the calipers. The only new parts mentioned are seals and the O ring, and locking fluid on the long bolts.

I reused the Lockheed special bolts. I would rather put my faith in those than in aftermarket bolts of unknown origin and specification. Last time I made new tab washers to replace those removed but this time I will use locking fluid and plenty of torque.

I also switched to MGB pistons. I could not get enough grip on the central pins but found they are easy to break off using a piece of tube and bending them back forth until they work hardened and broke.

Cheers
Dave
Bolney Coupe

This thread was discussed between 13/10/2021 and 26/10/2021

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