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MG MGA - Disc brake conversion on MGA 1500

I am interested in converting my front drum brakes to disc brakes on my MGA 1500. Is the possible and can will the disc brakes on the 1600 fit this car? Who has a kit or parts available?
I have new wire wheels.
For anyone who has made this conversion, does it really improve braking?
Many thanks.
Bill Chandler
Ann Arbor, Michigan
W Chandler

Bill

Moss do a complete conversion kit. I believe they also have a pdf instruction document on their site.

I did the exact same conversion. I am convinced it improved braking power and reduced fade. It also gave me that feeling of comfort that that my braking system was similar to all the modern vehicles around me; useful for judging spacing with the car in front.

I actually did my conversion piecemeal using an assortment of their parts about 12 years ago. This is what I wrote up on my website. Moss subsequently 'borrowed' my photos when they put their package together - since amicably sorted. http://www.mgaroadster.co.uk/mga_1500_disc_brake_conversion.htm


Steve
Steve Gyles

Steve, Many thanks for the reference to your description. This looks very straight forward. Do you know who is the best supplier of parts for this? Moss?
Bill
W Chandler

Bill,

I just completed the conversion with a mix of parts I collected over the years, a kit would be easier. It was very straightforward. I spent more time cleaning things up than most anything. I did my initial test run yesterday (car was also down for a new exhaust, a tune-up, misc other things).

Too early for me to tell, but the pedal feel is much firmer and the car now stops straight (both really good). Everything was worn out on mine so it liked to pull to the left. Found that one of the right side adjusters was broken....again.

All things considered, the drum brakes were fine and in Japan we never really get going fast enough to really worry about things. If I was not in a situation where I basically had to completely rebuild the front brakes and replace most everything I would have stuck with drums. With that said, I am glad I did the conversion.

Good luck!
Tommy Baker

Bill,

Sorry, but I forgot to mention...I did have one minor issue with the brake lines and re-routed the hard lines 180 degrees and hooked the flexible line so it comes from the top. Literally a 5 minute job. All is well now.

Tommy
Tommy Baker

Bill

I have been thinking about it for years but not done it although I have discussed with a number of people with experience of all 3 braking systems used on As.

Overall the views is any improvement is marginal as long as drum system is well maintained so they don't pull. There is also a view that drums probably have a better feel. In summary they all said it isn't worth the even relatively low effort unless the drums are 'broken' as in Tommy's case.

I was told by staff at THE leading MGA restorers that there are some issues with the adaptor plate which can make it very difficult to set up correctly. Their suggestion was that if you are going to do it just rebuild to standard 1600 set up as MGA calipers are now available. I believe there is a specific issue with disc wheeled 1500s as you need to get 1600 hubs which are unavailable new although getting secondhand may be easy. This problem does not apply to wire wheeled cars.

As an aside a guy who has As with all 3 brake systems says if he was in my situation he would add a servo to the drums setup which seemingly is a rather nice combination. Another aside one of my so called experts has a ex works rally car with drums and still rallies and he says it is almost impossible to get A drums to fade even when descending alpine passes at rally speeds, so don't do it for this reason.

Here endeth my brain dump.

Would I do it? Probably if my drum system required major work or if I was changing to wires. In the end it's up to you as both systems are fine, but don't expect a wonderful improvement.

Paul
Paul Dean

A sensible summary by Paul. I am guessing that the leading restorer Paul refers to is the same one who supplied all my bits. At the time I did my conversion (March 2003) the caliper adapter in question was a very new item . I never had any issues with it and still don't although I heard stories of the problems Paul refers to. Also, at that time, MGA calipers were a bit like rocking horse ****. so I went the MGB route, for which that adapter had been designed. I noticed a very significant improvement in braking, but I guess it depends on your starting point. Memory fades a bit but I seem to recall I was having issues with pulling etc. The drums were probably untouched originals so were likely approaching end of life (the speedo on my barn find car in 1996 showed 82000 and the car had been laid up for 22 years).

Disc brakes probably require far less maintenance than drums so if you are not heavily into doing your own maintenance then discs are a good option. That said, many of you will recall that I had braking issues for some time more recently and it turned out to be the pair of calipers I had bought for the conversion were poorly manufactored/restored - the seal metal retainer rings had been distorted on insertion, restricting piston retraction after braking. This caused overheating of the discs, calipers and fluid, plus squeal to name just a few issues. The MGOC calipers I installed last winter are excellent and life is now wonderful.

Would I do the conversion again. Yes, definitely.

Steve
Steve Gyles

Here's my $0.03 worth of opinion.

I like the front drum brakes for having slightly less unsprung weight. How's that for an endorsement? They do require occasional adjustment (two or three times during the tread life of tires). They do NOT pull to one side when working well and properly adjusted. I have been driving with all drum brakes for decades and hundreds of thousands of miles, and I have never had the yen to do the conversion. Even when autocrossing regularly, I found no deficiency in drum brakes. These 10-inch diameter drum brakes are similar to what was commonly used on American size station wagons in the 50's and 60's and 70's. They work very well on the MGA.

The primary advantage for disc brakes is fade resistance. The only time I have been able to produce brake fade was hustling down a mountain when towing a trailer. Unless you will be flat out racing regularly, performance difference is negligable.

Pedal force requirement cannot possibly be much different. If front disc brakes required more or less pedal force than front drum brakes, it would dramatically upset brake balance front to rear, making one end lock up prematurely (and it doesn't).

If you neglect to adjust drum brakes for a long time you get longer pedal travel, which may give the impression of slower braking. This is no problem when you get used to it, and the longer pedal travel is telling you when the brakes need adjustment. Longer travel of the hand brake lever will also tell you when the rear brakes need adjustment.

Back in the day, I suppose disc brakes was a new car sales enhancer, as some people may have found drum brakes on other model cars to be deficient. It is largely a matter of preconception. If you think disc brakes may be better, it may affect your purchase decision. Once you have spent the money, and the disc brakes work well, you may think it was money well spent. If you like to spend money on your pet project, it can be fun. For me, it is not cost effective. But then I'm so tight I squeak when I walk, and I haven't bought the 5-speed either, even when I'm driving 40K miles per year.




Barney Gaylord

Maybe replacing all the rubber lines with braided ones and an overall PM on the brake system contributed to a perception of a firmer pedal? Or I was just used to the characteristics after driving the car for the last 13 years....

I don't have this issue (yet) but wire wheels are bound to stay cleaner with the drum brakes perhaps?
Tommy Baker

I believe that disc brakes do require higher pedal pressures.
I have owned an MGA 1500 with four wheel drum brakes and a Twin Cam with four wheel disc brakes.
The disc brakes on the Twin Cam require much higher pedal pressures. This is because, unlike drum brakes, the disc brakes do not have a "self wrapping" effect such as the drum brakes do.
The reason that the higher pedal pressure of the front disc brakes on the MGA 1600 do not upset brake balance is because the design engineer chooses the correct slave cylinder diameter to match the rear drums.

Mick
M F Anderson

I've got a 1500 with drum brake with minilite wheels and a 1600 with disc brake wire wheels....the 1500 with drum brakes is always more dirty than the disc brake 1600.



The braking feels the same to me on both cars...but the drum brakes up front make for a little more maintenance as they usually need adjustment half way through the summer driving season.

.....where as the disc brakes just keep on trucking.

I specifically left my 1500 stock to see if there was a difference between the to setups on a street car.

I'm my opinion good drum brakes are as good as discs on an A. I just do the required maintenance and all is good.


S

Discs need less adjustment/fiddling, and pads can be sourced that minimize fade, but for tootling about on Sunday drives, there is nothing wrong with drums all around.

I currently run two cars with 4 wheel Dunlop discs and one on which I converted to MGB uprights and brakes (I'd run out of 1600 parts) and intentionally left the rear drums - better hand brake performance.
Bill Spohn

I agree with Bill. The handbrake on the four wheel disc brake mga twin cam is not very efficient.
This is especially noticeable when used after a fast run and the discs are very hot. The handbrake tends to come off when the discs cool.
Several attempts have been made to minimise this. The Jaguar E-Type has has Dunlop disc brakes like the Twin Cam but they self adjust with each application.
An extreme approach is with the Porsche 356C which has rear disc brakes with a drum handbrake designed into them (item 57).

See image.

Mick


M F Anderson

Just a follow up on the comments on the poor handbrake performance on the rear disc brakes of the MGA Twin Cam.
Attached is a better image of the solution on the Porsche 356C.
Note the difference between the front discs 1A and the rear discs 1B.
The rear discs have a drum brake incorporated for the handbrake (emergency brakes).

Mick


M F Anderson

This thread was discussed between 18/07/2016 and 27/07/2016

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