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MG MGB Technical - Rear Disc Kit

Does anyone know a UK company that sells a rear disc kit for the std Tube MGB axle please?
Regards
Dave
D M Tetlow

Hi Dave,

I've been looking into a rear disk conversion for some time now, you won't find much information out there, as this is not a frequent modification.

You will find some US company selling a 'Heath Robinson' set-up but it doesn't look much in my opinion.

Following my own investigations, so far, I believe that the rear disks from a rover 820 will fit on the MG rear hubs, and the callipers from a Rover 218 are about the right piston size to provide sufficient braking for the rear. They will also fit the 820 disks. The only task is to manufacture a calliper mounting bracket (easy) and a handbrake cable/mechanism (difficult).
All that said, the only reason to change would be one of preferring disks over drums, as the B's rear drums are well up to the job (if not too much) of providing sufficient braking. To be honest, there's little to gain for a road car.
I was only looking again yesterday on ebay for cheep callipers, when I do find some cheep ones, I will have a go. However, I don’t think the braking efficiency will improve, I just won't have to deal with manual adjustment and god awful drum brakes. Disks look nicer too!
MG Mike

Check the thread on rear discs on the mgb engine conversion forum. But I don't know if any of them will work on the early axle. At least you will find most of the kits available.

http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&mode=thread&access=&subject=36&source=T&thread=2007010718401926388

Richard
Richard Morris

Folks, Braking is not my bag, but what advantage would this give unless you are racing?. In most general cars the rear brakes are not used unless you really stand on them.

I have replaced a couple of rear disk brake systems because the froze from non-use.
BEC Cunha

I think it's mostly the wow factor.

I thought about the 4 piston fronts and the rear discs, but as it is, my 80 B LE can lock up the tires. What I would be more apt to put in would be an antilock brake system.

Unless you are using a lot of brakes and experience fade (from overusage), I can't see why anyone would need the big front brake kits or rear disc brakes. The down side to the big brakes is most all the conversions require you to go to 15" or bigger wheels for clearance. Another issue is with bigger brakes, you are simply going to lock up the wheels quicker.

Ok, you say, but then you ask, Richard, why do you know all those links to the big brakes and the rear disc conversions(see my message above for the other thread I started)? Well, I like the wow factor also.

Shot myself in the foot,
Richard
Richard Morris

About 25 years ago I was preparing a 1963 B for racing that had had the mga twin cam rear brake setup fitted. We had endless problems with overbraking at the rear even after fitting a brake balance valve. The car had been gutted out and a f/glass boot lid fitted. We tried all grades of pads but in the gave up and fitted the MGB drums again. We drilled 1" vent holes and used 3/4 cylinders and VG95 linings. We had no more problems and used the balance valve to change it for wet or dry cond's and different tracks. I have been involved in many B's since & have never found the drum setup wanting. So - why change to discs.
Garth Bagnall.
Garth Bagnall

Thanks for the comments Gents.

I agree that the B does not need rear discs. I have 185 15" MGC wires and I am sure that these wheels will lock up at even low brake pressures.

BUT

I have spent a fortune on new wires, limited slip diff, power steering, c locking, elec windows, heated seats etc... and I think rear discs look great.
Oh yeah, I have a V8 in the front.

I have looked at some options and they do look a bit Heath Robinson but from the outside they will look great and I think we all agree that they will not be overworked!!!

Regards

Dave
D M Tetlow

Dave,
How did you do the power steering? What components did you use? Got pictures available? Heated seats? now I am jealous (I already have a V8 in mine).

Richard
Richard Morris

Richard - Check this out: http://www.mgocaccessories.co.uk/acatalog/MGOC_Accessories__MGB_Power_Steering_200.html

R.
Rick Stevens

Richard
Rick's link is where I bought it.(£1500)
I am pleased with it but the turning circle is reduced and the engine had to be raised.
The heated seats are in the form of a kit I bought from your neck of the woods. (HeatedSeatKits.com) I have not fitted them yet but they look very professional.
If you want any pic's email me .
Regards
Dave
D M Tetlow

Garth-
I agree that the drum rear brakes on the MGB are quite adequate for the vast majority of uses. If brake fade becomes a problem, a set of brake shoes shod with Carbon Kevlar (no outgassing up to F 1,050) should fill the bill. I used them until I found that my brake drums were becoming frighteningly hot when driving hard in the nearby mountains of West Virginia. I switched to a TwinCam rear disk system and fitted a proportioning valve, but have had no problems. Why? My car is heavier than a racer, and tires have improved tremendously over what was available a quarter of a century ago. I must admit that they look great behind the 15" wire wheels!
Steve S.

I drive "The Silver Lady" which is a B roadster with a 4.0 ltr V8 under the hood. The front disc's are 12" vented cross drilled and grooved with Honda Zetec calipers, and at first I drove with standard drums on the back. With this set up it was obvious that I needed to do something with the back so I replaced the drums with 10 1/2" Saab discs with zetec calipers, Wow what a differance so much better. I think that rear disc's are really "horses for courses" on a standard B as someone mentioned you may not need the rear brakes anyway, how many actually work properly. I have seen many brake tests where only one rear side works and leaves a single skid mark, not safe in the wet?
Mike Cook

Mike - What sort of fabrication was needed to install the Saab discs?

R.
Rick Stevens

Hi Rick
No work was done to the disc's they just slipped over the studs.
I notice that you are in California,it may be a bit early but I have aready decided to drive from Atlanta to MG2007 next July in the "Silver Lady", Mapquest mileage is 2,946 miles the way that my wife Sue and I will be going. will you be attending?
Mike
Mike Cook

Okay, next question(s): How 'bout the slave cylinders and parking brake? I can maybe see the slave fittings being okay, but how did you do the e-brake?

Long story (for me) on MG2007. I'm in the Army Reserve and going to school right now to learn Arabic. MG2007 is scheduled for the same week we're supposed to take what's known as the DLPT - basically, our final-final exam. In other words, alas, no - I won't be there. Which sucks, 'cause the following week we graduate and I'm free from this place. Sigh. :(

If all goes as planned, my wife - who is still at home in Virginia - will be coming out to drive back with me in the B. That will be sweet, if we can make it happen.

R.
Rick Stevens

This thing won't let me edit the post, and I forgot to ask: What make/model/year Saab was the donor for the disc?

R.
Rick Stevens

I did my own rear disc conversion about 4 yrs ago.
My car is a 4.6L V8 GT which weighs in at 1000kg and is used as a fun car and also for a lot of track days.
The rover 800 rear discs have the correct PCD but wont quite fit over the centre of the hub. To make the caliper bracket fall in the right place I fitted a 10mm spacer between the hub and disc. This made the caliper bracket easy, using some 5mm plate it fits to the two front bolts that retain the bearing.
I used Ford Sierra rear calipers but was never able to get the hand brake working well enough. In the end I went for a hydraulic handbrake which I must say is superb.

Front setup is 300mm vented discs with ally bells and Wilwood superlite 4 pot calipers and to balance the whole thing up I made a twin master cylinder pedal box with balance bar controlled from the dash.
The above setup has been tested to the extream and so far I have not had any brake fade. On track the rears can get quite hot and the pads dont last very long.

The best thing about my setup is the pedal feel (who needs anti lock brakes).

The standard setup is quite up to the job but a bespoke braking system looks cool.
In the future I will upgrade the rears to vented discs with small Wilwood 4 pot powerlite calipers, Then hopefully they will stay cooler and the pads last a lot longer.

Mark
Mark

Rick, pending a reply from Mike, this might answer your question:-

http://www.theautoist.com/saab_disc_brakes.htm

And these might help, too:-

http://www.scarebird.com/12802/19335.html
http://www.mgcars.org.uk/v8_conversions/files/brake/rdisc.html

Derek Nicholson

Rick,
I submitted a reply but for some reason it has not posted.
The calipers have a built in E brake that I just spliced into the b handbrake.
The m/c I used is a Willwood 1".
Whatever people say about the need for rear disc's the system works great on the Silver Lady.
Regards
Mike
Mike Cook

Mark,
Could you give some more information about your system? A link to a photo or two would be excellent. As far as I know you are only the second owner to have an inside adjustable balance bar and I'm curious how you did it. Flex cable perhaps?

Also what is the piston area of your front and rear calipers? I'd like to know for comparison. Lastly, where in the adjustment range of your balance bar do you usually run?

I still have the stock rear brakes and Mach-I Mustang front brakes but I'll have to look up the piston size. I believe it has a bit more area than the stock caliper, and my balance bar is very much shifted to the rear which is something I need to address when I upgrade the axle.

Jim
Jim Blackwood

MG Mike in Lancs and Mark in Wilts,

If you use Rover 800 rear discs why not use the Rover rear calipers? They have a built in handbrake. If they are too powerful would a proportioning valve fix it?

David
David Witham

David
I used the sierra calipers hoping for a greater range of pads available as there used on 2wd cosworth models.
Jim
Front M/C is .625 and rear is .75
Not sure of caliper piston sizes. I know the wilwoods have the smaller pistons and the fords are standard spec.
Mine run just rear of centre on the bias adjustment.
I use yellow stuff pads on the rear and poly 'E' up front.

Most production cars are heavily biased to the front for safety and you get the nose diving on heavy braking.
I can set mine so that the whole car squats and it makes a huge difference to stopping distances in the dry. However some adjustment is needed for wet conditions.
Hope this link works to the pics.
http://s76.photobucket.com/albums/j30/V8bloke/?action=viewwidgets

Mark
Mark

Try these
http://s76.photobucket.com/albums/j30/V8bloke/?action=view¤t=RIMG0006.jpg
http://s76.photobucket.com/albums/j30/V8bloke/?action=view¤t=RIMG0003.jpg
http://s76.photobucket.com/albums/j30/V8bloke/?action=view¤t=RIMG0002.jpg
http://s76.photobucket.com/albums/j30/V8bloke/?action=view¤t=RIMG0004.jpg

Fingers crossed.
Mark

Here in the US the Ebrake cannot be hydraulic.
Mike
Mike Cook

Thanks Mark, nice work. I guess you are using the hydraulic brake light switch.

Jim
Jim Blackwood

Mark, that's a very cool set-up! Have you ever thought about putting together some "How It Was Done" info and photos for the "BritishV8" website? We'd love to showcase your car. The URL is http://www.britishv8.org/
Curtis Jacobson

There are other MGB brake photos in our gallery.
http://www.britishv8.org/MG/JimBlackwood/Brakebalance.jpg
http://www.britishv8.org/MG/WillHoloman/WillHoloman-B.jpg
http://www.britishv8.org/MG/GaryWalker/GaryWalker-U.jpg
http://www.britishv8.org/MG/GaryWalker/GaryWalker-X.jpg

Curtis Jacobson

This thread was discussed between 14/01/2007 and 19/01/2007

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.