Morris Minor Owners Club

G'Day All

I am in the process of switching over to marina disc brakes on my 57 Minor and I saw an artical in the new Prctical Classics "guide to the Morris Minor " on page 98 that says "Disc brake conversion requires modification to the MC internals,top hat blanking caps and rear caps" This was news to me .Is it required and what are top hats and caps?
Thanks
Michael

Welcome to the forum! As ever Pratical Classics have made a mess of it..... But they are half -right - you do need to remove the little top hat shaped 'pressure retaining' seal in the master cylinder.. So all the joys of removing the master cylinder lie ahead for you.... You may want to consider fitting a new set of seals while it is out - or even a new master cylinder.

The reference to 'blanking and rear caps' is if you want to fit a remote brake fluid reservoir under the bonnet.

Disc brake systems need a larger reservoir as the movement of the pistons is one way as the pads wear, unlike a drum braked system that returns the pistons to their start positions after the brakes are released.

It is possible to top up the under-floor master cylinder as the pads wear, but when you replace the pads and push the pistons back into the caliper, you will have to remove the excess fluid - much easier to have a reservoir with enough capacity to allow the drop in fluid as the pads wear, and then allow the fluid back when the pads are replaced.

Other than changing the fluid every couple of years, and checking it regularly, I have never had to top up the remote reservoir with our disc system between changes in 16 years. If I did it would mean a leak!

Thanks for the information.I just bought a new Master and installed it acouple of weeks ago! However taking it out the second time should be easier .That reservoir sounds like a good idea.

Michael

If fitting disc brakes - it IS !

Michael,

Are you planning to fit a servo with the discs? If you are you will also need to reroute the feed to the rear brakes, to a new 'T' piece at the front so that the servo works on both front and rear brakes.

No .No booster but I will fit the reservoir
Thanks All
Michael

Michael,

A 1957 Minor would have originally had the larger master cylinder bore of 7/8" and larger rear brake cylinder diameter of 7/8" as well. Do you know what is fitted now?

The 1098 engined cars had a smaller bore m/c of 0.8175" and smaller rear cylinders of 0.75" diameter. Combined with the bigger front brakes of 8", the result was almost 20% less pedal pressure for the same braking effort and a much better front/rear brake balance (the 948 is 63/37% and the 1098 is 74/26%).

37% rear balance is too high, so fitting the later rear cylinders is a good idea, but increases the required pedal pressure, so should not be done without using the later m/c as well.

Fitting Marina discs to the original 948 system will need the same pedal effort, but in comparison to the 1098 set up, Marina discs will need about 15% more pedal pressure for the same effort. Discs also do not have the same 'bite' as the standard front drums, that by design have a certain amount of 'self servo', so I would suggest to fit a servo as well as the discs, or you may be quite disappointed with the end result.

Or - fit a set of 9" Wolseley drums on the front and have great brakes without any need for servo/remote res/mastercylinder modifications....

Not sure what Master is in car .I just bought it new from GS jones about 2 months ago and the same goes for the the new rear wheel cylnders .I will try to find invoice and sort that out but I thought only one type was availble Thanks for the info
Michael

bmcecosse wrote:Or - fit a set of 9" Wolseley drums on the front and have great brakes without any need for servo/remote res/mastercylinder modifications....

That's nearly 2 whole days Mr BMC, I admire your restraint but you finally gave in.