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MG TD TF 1500 - Disc brake question

Here's a question which probably has a simple and obvious answer, but I've never seen it anywhere... I see threads on disc brake mods and I believe that Moss sells a kit for disc brake modification, but these are only for the front wheels.
Why? What's the reason that people aren't putting disc brakes on all 4 wheels?
Thanks for your patience... :)
Geoffrey M Baker

I haven't looked lately but I believe Moss sells a retro fit kit to convert earlier MGA front drum brakes to the later MGA disc brakes. It Might and I emphasize the word might be able to be utilized for converting the TD/TF to front disc brakes. That said I don't believe they have anything available off the shelf to do so for a T car.

The MGB world has a few rear disc brake conversions on the market. Good ones are expensive. Getting a set up to the market is going to cost a good deal of money and I would imagine the liability insurance for the product would be enormous. So I would imagine profit would have a lot to with the lack of availability.

An enterprising individual could certainly engineer his own system with a great deal of time and unknown money spent.

A well engineered system...not just rear discs but a system engineered for the car would provide some impressive braking I'm sure. A poorly engineered system would be no better than the stock drum/drum arrangement and may be worse or even very dangerous.

For a good system to be put on the market there is going to have to be a demand for it...which with a T car is minimal at best and a price point that those who are interested are willing to pay. With the low volume I would expect a well engineered system would cost several thousand dollars and I think few would shell that money out for it.

Just my thoughts
MG LaVerne

It's probably because the added benefit isn't really worth the conversion cost. Typically, your front brakes provide at least 60% of the stopping power, if not more.

Consider the weight shift of the car as you are braking-- it moves toward the front and lifts off the back. While the rear brakes do provide some braking, it just isn't as much.

You'll note that modern cars with four wheel discs will wear out the front pads much more quickly than the rears, which reflects this phenomenon. My Dodge truck, which is also very front heavy with the diesel motor, has gone through three sets of front pads and I've yet to need to change the rears, for example.

That said, there are rear brake conversions available for some cars. There is a cottage industry providing them for vintage racers, as for my MG midget. Of course, they are largely illegal in vintage racing, because they aren't period, but the rules rarely stop anybody. They are legal in SCCA. Many of these cars also run with adjustable brake bias.

While I can see a front disk conversion being useful for a vintage street car like the TD, I can't see much, if any, benefit from doing the rears.

Of course, higher hp and performance cars like the mga twin cam and the E-Type got them out of the factory...
David Littlefield

I agree with David on front pads verses rear shoes. My Chevy truck will get three sets of front pads and the rear shoes get changed when the 4th set of pads are due. Now it does have the automatic skid control on it if that makes a difference. PJ

Well, I'm still surprised someone isn't offering rear discs if there isn't a specific engineering issue that makes it harder to do; after all, you mention liability and insurance issues in production, and it's hard to see how that would be any different for rear discs vs the currently available front disc brakes...
I just assumed there was something about the rear wheels that would make discs much harder to do...
Definitely there are many threads on converting TD front wheels to disc brakes.
I have no plans or funds to do any of this and my brakes work just fine anyway. I'm just curious why nobody is installing disc brakes all around (except for Jay Leno, naturally).
Here's one from ebay:
Geoffrey M Baker

I've looked at that kit and I've made up a parts list from the Moss catalog using MGA parts and come up with about $1,000 for parts.

When I get a chance I will price it out from an MGB which I understand will work also. Of course careful shopping for used parts will reduce it even more.
Mort 50 TD

Correct me if I'm wrong but one also needs to convert to wire wheels and that adds another $1000 USD/wheel in addition to any brake caliper, adapters, etc parts costs.
So a disc brake conversion starts at about $4000-$5000 for a TD!
R Biallas

That's correct Randy, the only disc conversions I've seen are for wire wheels. As I have steel wheels, I have no intention of doing disc brakes anytime soon :)
My question was rhetorical; I was just curious if anyone knew why there aren't shops selling disc brake kits for all 4 wheels.
So far, I have not gotten an answer. But I'm patient and, until I win the lottery, there's no hurry :)
Geoffrey M Baker

One thing is that disc brakes are a challenge for the parking brake because they are not self enforcing. Some cars use a drum brake setup inside the (rear) disc hub for the hand brake. Adds complexity.
I had an Alfa Romeo many (30) years ago that had 4 discs -very innovative af that time. Worked very well. Major advantage is that disc pads are easier to change.
But rear brakes do indeed not wear out much. My Suzuki is 25 years old and the rear brakes are as new. I check them every 2 years and the replacement shoes keep sitting on the shelf...

Rgds Mike
Mike Fritsch

I believe my DS-21 had a separate pair of cable operated calipers for the emergency brake.

Jim B.
Jim B in NJ

You are correct of course. My analysis started with my already having wire wheels.
Mort 50 TD

Well there was always the MGA Twin Cam and later Special Edition that had four wheel disc brakes. This system, however was not adopted for the MGB. Wheels were not wires, but I believe were splined disc wheels. Not likely you're going to find any of these parts lying around in a scrap yard.
John Quilter (TD8986)

Mike you hit the nail on the head, I think. Discs on the rear would leave the handbrake inoperable without major modifications. Guess nobody has thought of a way to do that with existing parts and wheels...
Geoffrey M Baker

This thread was discussed between 06/08/2015 and 12/08/2015

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