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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Brake overhaul

Is there a quality difference between the TRW and the Moss master cylinder?
I have had an AP Lockheed for 20 years that has started to sweat. I drive summer and winter, so the inside rusts. Overhauling the rubbers did not help. Honing helps for several years.

How long do the rubbers of the slave cylinders last? It is a single braking system.
Flip Brühl

Flip-Have you thought about having your cylinder reco'd with a stainless steel sleeve
William Revit

Flip
I think the Moss m/c IS a TRW, at least mine was when I bought it a few years ago (no alternative choice). After getting it I discovered several threads on here warning me about leaks with the TRW but so far, so good! I think the AP Lockheed is considered better. I was converting the Frogeye to front discs and 3/4" dual piston rear slaves for which I bought new Pagid slaves. OK so far with silicon fluid.
Bill Bretherton

I bought the AP one from David Manners , had no problem bleeding it and works as it should. It was a bit more expensive than the TRW . It has only been in about 6 months however so can’t comment on longevity.
Mike Fairclough

I believe the MGA boys recommend the AP over the TRW.
Dave O'Neill 2

Flip

There has been some people report quality issues with the TRW version of the 3/4 inch bore dual combined brake and clutch master cylinder for front disc braked cars up to about 1964/1965? Unipart part number: GMC112, AP part number: 4222-804P.

If you want a genuine AP Caparo (was AP, AP Lockheed, Lockheed - now known as 920 Engineering) as Mike says you can get this from David Manners: https://www.abingdonmgparts.co.uk/product/category/2270/ap-brake-master-cylinder-tandem-disc-brakes%3a---sprite---midget/gmc112 Powertrack Braking may also be a source of such AP master cylinders: https://www.powertrackbrakes.co.uk/

As Willy has said you can get master cylinders rebuilt including re sleeved. In the UK try Past Parts https://www.pastparts.co.uk/ or Coasting Ltd: http://www.coastings.co.uk/

Another alternative is to convert to a Sebring Sprite pedal box that fits the standard pedal box aperature and use either use two genuine Girling integral master cylinders (used on many older racing cars such as classic Formula Fords) - from Merlin Motorsport or Burton Power - and the Sebring Sprite replica pedal box from Pete Moore of Brook Fab in Northern Ireland: https://brookfab.co.uk/products/sebring-sprite-pedal-box

Some useful background info on differences between the disc braked and drum braked master cylinders including pushrod length and internal valve types: http://gerardsgarage.com/Garage/Tech/DbrakeUg.htm & http://gerardsgarage.com/Garage/Tech/DBrake/TandemMC_Part1e.htm

Cheers
Mike
M Wood

I just bought one from David Manners via ebay which was the last one on that multi-item listing. No idea if they have a separate stash for sale through their website.
This is the second AP I have bought, the first in 2014 when I converted our Frogeye to discs and it has only needed one set of seals so far (3 years ago on the clutch side). I've used silicone throughout.
Get AP if you can.
Robert
MG Moneypit

Thank you for all the advice and referrals!

Yes
I am looking to see if I can find someone here in the Netherlands who can put 3/4 stainless steel cylinders in it. The first few years I had silicone DOT 5. Then I had no rust problems. Because of the days on the track, I have been driving Dot 4 for years now.
Interestingly, in the original Worshop manual a Boot(19)is drawn with other Push Rod's (21)

Flip


Flip Brühl

Definitely avoid the TRW offering. I had one a few years back and it leaked straight out of the box. Was replaced without any quibble but had to adjust pushed length to stop brakes binding. It is now weeping again. I will only use AP in future.

Trev
T Mason

The brake fluid level dropped very slowly. That's why I decided to innovate. When taking it apart, almost all cylinders, including the clutch working cylinder, appeared to be sweating a bit. The brake calipers did not sweat and were intact. I expected the cause to be rust or worn/too hard rubber, but that was not the case. There were scratches in the cylinder walls and hardly any in the piston walls. The dust seal rubbers were intact, but dirt and sand could still pass through there. I always install all dust sealing rubbers with red rubber grease. Do you have a better idea?

Flip
Flip Brühl

This thread was discussed between 13/11/2023 and 26/11/2023

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.