Rear Disc Brake Conversion

[Bubblemechanic]

Hi everyone hope you are all well. I was wondering if anyone has converted the rear brakes to discs while keeping the shoes for the handbrake
I have just converted the fronts to discs, but brakes feel totally different for one cannot seem to get the pedal as firm as original and the whole system has changed. You get a more spongy feel is this normal I have spent nearly a fortnite bleeding the brakes and there is no air in the system
Cheers Guy's and Gals

[paul 300358]

You need to fit a 10lb brake valve on the pipe to the rear. They keep the rear shoes in contact with the drum. You have to remember that you have removed the top hat seal from the master cylinder.

[paul 300358]

Try a https://www.mcgillmotorsport.com/brake- ... c-70-p-365

[Steve Phillips]

we fitted rear discs to a traveller for a ""specialist"" many years ago who couldnt do it him self.....
we used VW/Audi calipers so they had the hand brake in the caliper, speedy cables made up some bespoke cables for us.

the problem with rear discs on a Minor (if using the single circuit master cylinder) is you can upset the balence of the car under braking, effectivly giving the rear to much braking, this in turn can make the car unstable under heavey / high speed braking. so you end up either fitting a balance bar, a device to give more or less efficency to the front or the rear, or you fit tiny calipers with small pads to decrease the rear bias, if you can find such a thing.......

if you want rear discs you would be best to take the front and rear brakes and master cylinder/servo all from one donor vehicle, one that is of similar size and weight to a minor, at the end of the day a manufacturer will spend a lot of time, effort and money getting the balance of the brakes correct and safe on a car,

if you do want to lok at rear calipers some japaneese (I know Subaru is definately one) have rear discs with a drum in the center so you have drum parking brake and disc for driving / stopping, but I fear these will be way to big for a Morris, so back to a balance bar.

If you have removed the origional residual pressure valve (the top hat) from the master cylinder then what you probably have is piston retraction of the brake shoes, remember the calipers dont have any sort of spring to pull the piston/s back in where as the rear drum brakes have dirty great springs pulling the shoes away from the drum when your foot is not on the brake pedal, so you have to pump the wheel cylinders out with the first pump of the brake pedal every time, (sometimes if you pump the pedal hard and very fast three or four times youll find you have a hard brake pedal) or the easy way to prove this is carefully line clamp the flex hose that goes to the rear brakes using a line clamp or a pair of mole grips GENTLY.. your only trying to stop the flow of fluid to and from the rar drums you dont want to damage the rubber line, and remeber if you have sytainless braided brake lines do not under any circumstance clamp the lines as you will damage the ptfe liner.

wilwood make residual pressure valves that go inline, they are not expensive about £30ish and work very well, have a look on flee bay or a generall internet search

Hope that helps

Steve

[ManyMinors]

Unless your car has some huge, very powerful engine in it and/or you are racing or driving on a European tour, I cannot imagine why on earth you would need to consider such a modification as rear disc brakes. My own Minor 1000 stops perfectly well with completely standard brakes but I understand that some owners feel the need to improve on that and fit front discs. This alone should provide more than adequate brakes for any Morris Minor. They simply need to be working properly. I would think perhaps you have a master cylinder fault or a faulty servo if you have one fitted?

[philthehill]

I have Marina discs on the front and Wolseley 1500 8" drum brakes on the rear and without a servo. The car will stop on a sixpence.
I do not have a residual brake line pressure valve fitted either.
Whilst I have looked at the rear disc conversion I have never felt the need to spend several hundred pounds to replace a brake system that is more than adequate for my needs.
https://www.petermayengineering.com/pro ... nd-hosesa/

[kevin s]

we have corsa front brakes, std rear brakes a beetle dual circuit master cylinder and a 1.7 :1 servo on the front brakes only, works a treat with a firm pedal and the fronts locking up just before the rears, you shouldn't need a residual pressure device, just adjust the rears regularly.

I can't see any need for rear discs, most modern small cars (our brand new fiesta for one) have tiny drums on the rear and ridiculously powerfull brakes.

[Bill_qaz]

With the narrow tyres and light weight of a minor surely you are simply going to increase the chances of wheels locking. Mine came with Marina front discs and I have renewed pads and rear shoes for peace of mind. The brakes seem perfectly acceptable and you can lock the wheels which is all the braking you can have. I don't think a residual pressure valve is needed if the rears are kept adjusted and the majority of braking is on the front anyway.
Unless your doing it just because you want to what would be gained.
A duel circuit master cylinder would be a nice additional safety feature

[philthehill]

https://www.minormagic.com.au/products/ ... -instructi

[Bill_qaz]

Nice kit Phil but too expensive for me
A £30 cylinder and DIY would be my route .but not sure if I would bother unless doing a major rebuild.
Pays to keep an eye on brake pipes and a good working handbrake just in case
https://www.ebay.co.uk/itm/363078543820 ... media=COPY

[kevin s]

Here is the beetle cylinder in ours.

zBVtPC3.jpg (85.51 KiB) Viewed 5200 times

[don58van]

The dual circuit kit that PTH refers to above is based on a Mazda 323 master cylinder. So by putting a kit together yourself, it can be done economically.
Don

[philthehill]

What about the feed pipes from the reservoirs?
Do they not come above the floor.

[Bill_qaz]

Is it just the picture or have you ground the m/cyl body to clear the cross bolt? Could a front mounting plate be welded in so cross bolts eliminated and the holes used to route resevoir and brake pipes?

[philthehill]

I have asked MinorMagic if the mount bracket is available separately.
If it is then the cost of supply and shipping costs to UK.
Update: I have had a reply from Minor Magic. The mount is not available separately only as part of the conversion kit.

It looks as if I will have to make the mount bracket.

I would not fit a dual circuit master cylinder but a similar master cylinder to that already operating the hydraulic clutch on my Minor. The master cylinder can be supplied in different bore sizes which allows for varying mechanical ratios/advantages.

[kevin s]

Is it just the picture or have you ground the m/cyl body to clear the cross bolt? Could a front mounting plate be welded in so cross bolts eliminated and the holes used to route resevoir and brake pipes?

There is a 8mm front plate the cylinder bears on, this in turn is welded to two side plates which bolt on in the original points. The front bolt clears the master cylinder (I may have had to radius the corner of the reservoir boss a little) the rear is 2 nuts and bolts instead of the through bolt. The reservoir pipes are plastic coated copper pipes which go forward and up to a 3 port reservoir with a level switch in the engine compartment (3rd one for hydraulic clutch). the floor sits about 1/2" higher to give clearance, the plastic reservoir fittings in the picture were later changed for lower profile Lancia Montecarlo ones.

[Bill_qaz]

I have asked MinorMagic if the mount bracket is available separately.
If it is then the cost of supply and shipping costs to UK.
Update: I have had a reply from Minor Magic. The mount is not available separately only as part of the conversion kit.

It looks as if I will have to make the mount bracket.

I would not fit a dual circuit master cylinder but a similar master cylinder to that already operating the hydraulic clutch on my Minor. The master cylinder can be supplied in different bore sizes which allows for varying mechanical ratios/advantages.

I think it would easier to just weld a plate inside the chassis as the front of the kit bracket without the sides.

[kevin s]

Here is a picture of the assembly before it went in the car. At the time I wanted it to be reversible, so I bolted it in but yes you could just weld the front abutment plate in.

20170113_200404.jpg (2.08 MiB) Viewed 4881 times

I also narrowed the mounting flange and added the aluminium clamp plate, the all the joints are designed to be in compression so if anything comes loose it still gives braking.