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MG MGA - Disc Brake Conversion

Hi I'm considering converting the front brakes on my 1957 1500 to discs. I see Moss etc do a kit which seems to contain all parts needed. However is the original master cylinder OK to use or would I be better to fit the later 1600 type.
Thanks Paul
p anderton

Paul

I used the original quite satisfactorily for a few years although I did subsequently fit the extension because one came available. Bob West does the extensions. In fact he supplied me with all the conversion bits. This was my conversion: http://www.mgaroadster.co.uk/mga_1500_disc_brake_conversion.htm

Steve
Steve Gyles

Do you really need the bigger reservoir on the master cylinder Steve?
My master cylinder has the earlier flat cover and in use (some very hard use at times!), it has been fine.

Is the larger volume in the reservoir just needed for when you push the pistons back into the calipers when you replace the pads, to prevent the brake fluid from overflowing?

Colyn
c firth

Colyn

No. IMHO the flat top is adequate. As I said above it worked fine for a few years. I just put the extension on because I had one.

Steve
Steve Gyles

Thanks I guess as you have both done this conversion you feel it worth while? Can you tell the difference with discs fitted? reason for asking about the master cylinder is mine could do with a refub anyway so if I replace it I may as well get a larger one
p anderton

Paul

I have a 1500 and have considered and extensively researched this twice. The last in the autumn 2013 but I can't find it in the archive. Some times it is difficult to search as I might have added on to an existing thread that has wandered a long way from its title.

There are at least 4 options:-

1) There is the Moss kit As it says in their catalogue if you are on bolt on wheels you will have to obtain 1600 hubs that are only available secondhand. The other issue that I was told about by one of Bob West's assistants is that these kits are very difficult to set up correctly due to what I understand is the holes in the special plates being slightly oversize (a metric not imperial size I think). I also know someone local who had a problem with one fitted by a professional and was it taking back for fine tuning. Obviously once fitted correctly this is no longer a problem.

2)There is the MGOC approach that was around a couple of years ago that may be what they still list. This involves a rebuild of much of the front suspension/steering with MGB components at least one of which is not available new. Seemingly this approach can upset front geometry. I suspect it was the first approach but is now well past its sell by date.

3) I discussed the above 2 approaches with Bob West a couple of years ago. His view was then that while option 1 was useful when new A calipers weren't available, and all you could do was use B calipers, they were no longer the best approach. This was because A calipers were now available and you might as well get the bits and just convert to standard 1600 set up. Assuming you can locate all the bits the only remaining issue is that you have to weld a new support for the brake pipe/hose join. I nearly did this option, but he also added that it is a lot of effort for minimal if any adventage.

4)Stay with drums. Having discussed my plans with several very experienced A expert there is widely held view that is 'stay with drums'. The experts include one who owns 3 As that between them have all 3 front brake variants, one guys who has as an ex works rally 1500 that he still rallies in major international events, and a couple of well established restorers. The view is that there are 2 reasons quoted for changing. Firstly 'drums fade', well people who have rallied Alpine passes say they don't. Secondly drums can pull, this can be true but this can be solved by careful set up. Thirdly they all say that the A drum set up is excellent and also drums have a nicer progressive feel. To be fair if you read original roadtests of which I have several they all seem to like the move from drums to discs although the test figures only show marginally better braking, (Of course this move had to be done in late 1950s as any credible sports car had to have new fangled discs)

A general conclusion I came to is that if you are going to upgrade a 1500 bolt on wheeled car to discs, and if you have any interests in wires, you might as well go to wires at the same time as both jobs require a hub change.

I hope this isn't confusing but there are at least 3 real options (1, 3 and 4) all of which have issues. I am still on drums and just about to give them their annual set up check to avoid any pulling.

By the way I have no idea about the master cylinder extender question.

Good luck, I think this is about all I know on the subject.

Paul
P M Dean

Thanks Paul I can wee you have given this some serious thought.
My car is on wires and the brake pull in a straight line but the feeling is they slow you down rather than stop you. I expect a difference between a 1957 car and modern one. just thought if it made a big difference for 500ish it was a good improvement. I also own a 1972 Triumph TR6 with the disc/drum combination and it brakes much better than the MG, but it has got a servo.
Thanks Paul
p anderton

I have a 1500 (1800 3brg engine) with disc brakes - flat top mc, greenstuff EBC pads - that I used in super sprint competition for several years with no problems, for regular road use there wont be an issue. Check your fluid level regularly and use a bellows pipette to remove excess fluid when changing pads.
Mike
Mike Ellsmore

Paul

Can I suggest that your next step should be to try and get a drive of a 1600 style disc braked car.

Personally I have never driven a disc baked A.

Mind you the first A I ever drove in 1968 was a drum brakes 1500 with a servo. It was also the first servo car I ever drove. On my first low speed brake application I nearly went through the windscreen, no belts either!

In fairness one thing I didn't say is that in the end all say braking of discs is probably better but the general view has been not to an extent you will notice in even hard road driving.

Paul
P M Dean

Paul

Can I suggest that your next step should be to try and get a drive of a 1600 style disc braked car.

Personally I have never driven a disc baked A.

Mind you the first A I ever drove in 1968 was a drum brakes 1500 with a servo. It was also the first servo car I ever drove. On my first low speed brake application I nearly went through the windscreen, no belts either!

In fairness one thing I didn't say is that in the end all say braking of discs is probably better but the general view has been not to an extent you will notice in even hard road driving.

Paul
Paul Dean

Paul,
Although my car has disc brakes, I have been told that a well set up drum braked mga has superb stopping power. The only difference is that disc brakes are much more fade resistant but you would have to drive your car to extremes to get your drums to fade.
Dont forget that the le mans cars had drum brakes.
You will probably have to spend a bit more time adjusting your drum brakes than you would with discs but otherwise, they are fine.
Colyn
c firth

Thanks lads I've also been advised (but cant remember by who) that if I change the master cylinder to make sure its a Caparo make not TRW which had sticking problems. Any thoughts
Paul
p anderton

If your master is in good shape no need to change it. The only difference is the extended aluminium top which you can retro fit to yours
gary starr

This thread was discussed between 22/05/2014 and 23/05/2014

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