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MG MGB GT V8 Factory Originals Technical - Rear disc brake conversion

I have already converted my 1974 GT to a V8 and the car has been fitted with a narrowed SD1 rear axle. However it retains the rear drums, converted to 4 stud fixing. I would like to try a conversion to discs and would appreciate help from anyone with experience in this area (not necessarily with the SD1 axle). Many Thanks
David Daw


I have carried out a disc brake conversion which you can see on the V8 conversions site:

I think that one problem you may have is half shaft end float/runout. It is a problem with the B halfshaft and even more so with the taper roller bearings used in the SD1 axle. I got that info from Nick Law at what used to be Rovercraft-now Progress Engineering-he's been involved in a few rear disc conversions on hot SD1s. The use of floating calipers is essential here.


John Bourke
John Bourke


I am just wondering ... why do you want discs in the back? Not as though you don't have every right to do it, don't get me wrong.

My MGB V8 is getting a Currie Enterprises Ford 8 inch rear 3.00 gears and rear disk set up complete with calipers. It is being ordered on Monday and is supposed to be a bolt in affair. Total cost is about $2500 with shipping, expensive but...when price is no object you get the best. I'm keeping the 4 lug set up (my conversion/renovation included the purchase of 5 new 15 inch Mini Lite wheels and 50 series Dunlops tires).
Currie's web site is:
check them out. I'll let everyone know how it all works out. I still have the stock MGB 4 speed transmission. That will be the final (?) upgrade to my conversion (other than engine rebuilding to obtain more HP).
Michael S. Domanowski

Michael, Currie is clearly exceedingly competent, but I'm wondering

1. ... how do you know the swept area of the discs they sold you is the same as that of the MGB drums you cast aside? If not, for the love of G-d man, install a proportioning valve!

2. ... an MGB/C rear end is more robust than a Ford 8" -- it contains more bearings. Or such is my firm understanding.

3. ... what is done about an emergency brake? Are you just going to install a line lock, or is there a way to rig it with the discs?

Would be really interested to see pics of your car. It's about time somebody around here did a cost-is-no-object conversion!

I have used the rear disc conversion many years ago on a stock B axle and they worked ok.

Ford 8" rear axle is plenty strong for any Rover engine
Don't forget other possibilities that may be cheaper.
I am building a GT V6 with about 230 lbs of torque in the 3K-rpm area with a 3:73 final drive and .79 5 gear final ratio. I am using a 1985 Pontiac Trans Am Posi traction GM 10 bolt with rear disc brakes cut and fitted with the springs pads ready to install.
This rear axle is cheap due to there believe that is not strong enough. They are partially right. No is not strong enough for 600 lbs of torque on a built 350 Chevy for drag racing duty. But strong enough for 300 plus lbs of torque on a stock V8 Chevy. The point is picking your parts for the torque you are going to be using. Cost? Complete ready to install with brakes and parking brake, $550. Keep the 5-lug 43/4-bolt pattern; change the front, now you have several possibilities for wheel combination choices.
An 8" is an excellent choice you will never break it.
I have used it in several swaps including some well-built V8 Chevy’s. And you don't have to do anything other than install it.
Just wanted to share other possibilities
Bill Guzman

Looking at the archieves, Roger mentions Granada calipers and Rover 800 discs. Has anyone tried this route. Roger also mentions complete kits to bolt on: has anyone a contact or recommendation.


Saab rear rotors bolted to MGB hubs w/machined bracket to hang midget calipers!!! Proportioning valve in line to adjust rear disc brakes!!! Now, can anyone tell me how to hook up emergency brake?
Tony Barnhill

A common setup for parking brakes is to use a small mechanical spot caliper like the one wilwood makes. You can see it and get dimensions here:

Michael Hartwig

Well, looks like my link doesn't work. Goto
click on the Wilwood disc brake link, then the disc caliper link, and finally the single piston caliper link

Michael Hartwig

1)Of course a proportioning valve and new master (dual) cylinder will also be installed. I havent selected the manufacture of the new master yet but I've been given a few tips and will price these out.

2)According to Currie the 8 inch (and this is his castings not Fords so they are even beefier)is good for 300 HP.

3)I'm going to double check on the emergency brake but I believe in my conversation with them it was mentioned that it is included.

4)I could always go to the Ford (All Currie parts) 9 inch for only slightly more $$$ but it is my understanding that it is physically much larger than the 8 inch and may cause some additionl problems.

I'll be happy to e-mail photos to anyone who would like. I can be contacted at:
Michael S. Domanowski

This thread was discussed between 04/12/2000 and 08/12/2000

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