Morris Minor Owners Club

In normal use a disc braked set up should NOT need to be topped up.

If you keep topping it up, as will be necessary with the original m/c

Why will it be necessary if it should not need topping up?

Pad wear.

With the standard m/c there is not enough fluid capacity to compensate for piston movement resulting from the full pad wear, without going too close to, or below the top-up level.

The BMC Workshop Manual says the the fluid should be maintained at 1/2" below the filler cap, and not higher. This leaves at most 3/4" of fluid above the transfer holes into the piston bore itself - that's not a lot of fluid! It was designed for a drum-based system that, assuming reasonable adjustment, does not have much piston movement, and so does not need a large reservoir.

I prefer the much greater margin of capacity offered by the combination of the existing reservoir plus the addition of the remote one as well. In normal use the fluid varies from 'full' immediately after a pad change, to about 1/2 full when the pads need a change.

The confusion lay in the sentence stating that in normal use a disc braked system should not need topping up. That being the case a remote would appear non essential.

It is non essential - as long as you don't use the brakes

The confusion lay in the sentence stating that in normal use a disc braked system should not need topping up. That being the case a remote would appear non essential.

To be clear:

Because a disk braked system usually has a large reservoir, it should not need topping up, as there is enough capacity in the reservoir to remove the need. Without this large capacity it could run short of fluid, probably will need topping up, and then there is the problem about what happens to the excess fluid when replacing the pads.

Conclusion - fit an additional reservoir when fitting disk brakes to a Minor!

Q.E.D...

and... er... *in very timid voice* can i ask whether the servo complicates the situation at all?

With reference to the m/c and headertank no, but you will need to redo some rigid brake pipes to make sure that both front and rears are servo'd, plus you need a vacuum feed from the inlet manifold to servo.You also need to blank the original feed from the m/c to rear brakes. I can send you a plumbing diagram if you need one.

No, but it could give you early warning if the servo started leaking brake
fluid into the servo casing. i.e. level dropping with no apparant leak.

*in very timid voice*

In a whisper, not at all in fluid reservoir terms, but there has been a bit of a debate on whether you apply the servo to front and rear brakes, or front only?

I have Midget discs and the servo is fitted to both and with harder front pads (Mintex 1155), I found that the rears, even with Mintex M20 linings, locked up under heavy braking, so have fitted a pressure limiting valve to the rear brakes (Mini rear valve, converted to adjustable).

With the bigger Marina discs, and lower brake line pressure, this may not be a problem - what are others' experience?

With the brake line layout in a Minor, it is much easier to fit the servo to the fronts only, but I don't know how effective it is. I would have thought that the front/rear balance would be too biased towards the front?

How are you intending to fit the servo wibble_puppy?

IslipMinor wrote: How are you intending to fit the servo wibble_puppy?

I dunno, and you've raised the exact same point I wanted to ask!! so thank you very much! *waits for knowledgeable replies*

I have fitted the servo to my front brakes only because,after reading a very comprehensive article on braking modification I came to the conclusion that the rears were likely to lock up first if all four wheels were servoed. Since I have never had to do any sort of emergency stop so far I don't know if I was correct or not! This arrangement was fitted to my drum system and I have now fitted a JLH Ford based disc brake
system and I have had no problems with the rears being unservoed in
either case. It would be interesting to hear from those with all four brakes servoed if they have suffered from rear wheel lock-up which,of
course, is a very dangerous condition.

With the brake line layout in a Minor, it is much easier to fit the servo to the fronts only, but I don't know how effective it is. I would have thought that the front/rear balance would be too biased towards the front?

The more braking you get from the front brakes, the less grip is available on the rears. Therefore as you increase the front braking ability you have to decrease the rear - that's the simple answer and therefore in 'oversimplistic' terms this justifys not adding the servo to the rears when using servoed disks.
The exact implications are not easy to work out, as the effect of lowering the car, altering the suspension rates, weight distribution (traveller, 4 door, 2 door etc...) all have some effect on how much rear brake is desirable.

A handful of people have gone down the route of adding rear disks on Minors, only to find that they have to limit the rear brake balance anyway as it just locks up.

Q.E.D...

Probably latin I expect, but what exactly does that mean?

quod erat demonstrandum literally "which was to be demonstrated"

It is to say that something is definately proven

...and used at the end of a mathematical proof. http://en.wikipedia.org/wiki/Q.E.D.

Yes, I read that somewhere too...

http://en.wikipedia.org/wiki/Q.E.D.

Quod Erat Demonstrandum; "which was to be demonstrated."

I understand it to mean something like "that was the proof."

Sad to say, I just knew. Doesn't stop me annoying myself by using it wrongly in the middle of sentences though.
Better say before it all starts again that no, I didn't go to university and only have 5 O levels, none of them in Latin...