master cylinder

[tbone]

Push the pedal down to its fullest amout of travel then measure the stroke of the piston ( how far the rod moves in).
Disconnect the pedal and the pipe from the master cyl and work the piston by hand ( push the rod in ) and again measure the stroke.
Is it the same distance?
if yes, then reconnect pedal and pipe, remove the return springs from the brake shoes, bleed the system and depress the pedal. check for drum movement. release then press pedal, check for movement, repeat untill drums lock up. then unbolt the cylinder, throw it away and replace with a bike rear  cylinder cos it means your not gettin enough stroke thro the bore.
if no, unbolt the pedal and work the piston by hand, this will not be easy. again check for drums locking up,if this works, you need to look at relocating the cylinder nearer the pedal or extending the pedal lever.
If i remember correctly, slave cylinders are designed to cope with volume rather than pressure.

[tbone]

     "......master cylinder (which is a landrover clutch slave cylinder"

as a sort of side question, has anyone else done this, does it work ? having rebuilt more than my share of cylinders over the years it strikes me that there are far more bits, bobs and seals in a master than there are in a slave, could this have some bearing on it all ? Genuine question, I don't know the answer.

I read an article by Alik Windrush ( formaly 100% biker mag ) about this very subject. His conclusion was not to run a slave as a master , something to do with pedal/lever ratio, but i honestly cant remember why, which is why i feel daft mentioning it.

[BikerGran]

Not trying to hijack the thread but I've been watchinmg it with interest cos I have a somewhat similar problem.

On the GT, Reliant axle and original drum brakes, used to be great and would lock up the axle quite easily.  Then the master cylinder failed and had to be replaced which it was, with something that looks identical to the original Reliant one and has the same bore (but cheap and nasty) - but it just doesn't work as well!

Then on the new trike which has mini brakes (presumably mini front brakes) on the rear, handbrake worked beautifully but foot brake was rubbish - till they locked on so hard I had to wind them off to be able to move it!

Ok, keep working on it and I'll keep reading!!

[Donut]

resorting to drastic measures now got my 70 year old dad to come and fix it

stripped everything back - back plate slightly bent fixed and drums now sitting on even rubbed down shoes again
pumped the pedal and started to get good brakes with the wheels off ie I braked and dad turned the drums just - dad might be 70 but he has hands like shovels and worked on a farm all his days can still out run me on 100m dash, you get the idea

so we made up new lines and put back the residual valve back into the equation seem'd ok so put on the wheels and it is like there is no brakes at all - all bleeded with the pressure bleeder so no air and no leaks

going to get a smaller master cylinder tommorrow so will let you all know the outcome which will probably be I have been nicked for torching my own property!  is that a crime to torch your own stuff?

[Manky Monkey]

Disc brakes.

[peanut]

Bikergran:If your brakes locked-on and had to be wound off it could be that the drums are worn-out, allowing the shoes to move too far. You may well have a master-cylinder sizing issue. Early Mini fronts were Single leading shoes. superceded by twin leading shoe, but neither have a handbrake facility. You probably have sls rear backplates, which are very similar, if not identical to Reliant, bolted to your hubs. If you have the original mini master cylinder it was big enough to move twice the number of pistons that you are asking it to do (I don't recall the early minis having split-circuit brakes). That would give you lots of movement but  not so much pressure, with probably a very 'hard' pedal. As Mankey said earlier, he has used a particular size of Master cylinder with a reliant axle with success and so measure what you have (The bore size is often cast into the bottom of the m/cylinder which saves you taking it apart) and then compare. You might also want to build some facility for altering pivot points into your brake lever system as that can make a big difference to feel at the pedal.
Since brake fluid deteriorates with age it might be no bad thing to have to strip and bleed your brakes.
Brake drums are easy to find on E-bay, either in original iron, or finned alloy Minifins but be aware that you will lead longer studs if you buy those with a built-in spacer.

[Manky Monkey]

Early Reliants used Triumph Herald drums I believe, while later ones were fitted with Mini equipment.

[Manky Monkey]

Mr Toad's selling a pair of VW Golf brake calipers at the moment -disc brakes!

[toad]

i,ve just noticed this thread if you have no air in the system and the shoes are adjusted right i reckon your gonna have to swap the back plates round to make the shoes leading instead of trailing i had the same problem with my goldwing. one last thought you cylinders in the drums arn,t seized are they???

[Donut]

Mr Toad where have you been? I am crying like a big baby.

what happened today

Went and got 2 different master cylinders from local scrap man today and it made no difference. Gave a man a call who went through it and said the shoes were tariling but should be leading but we could not figure out how the shoes could fit to make this? Dad ( starting to think it is his trike) went and looked at his mates trike, similar setup were we realised his backplates had been turned 180deg - did this and hey presto brakes. Put back on original master and things seem to be ok but have damaged fittings cut pipes etc etc so will strip everything down to clean and make up fresh fittings etc - hopefully saga is at an end - time will tell but looking very hopeful at the moment.

Sorry to everyone for this dragging on so long but hopefully it will help someone else before they go through this.

One question ( maybe a new thread) but what is required to get the big nut off to swap the backplates around as this would be the correct way to do it to keep the cylinders upright and forward of the axle along with the handbrake lever?

thanks again to all

Donut

[tbone]

To remove the backplate from the flange on the end of the axle tube, you simply pull the whole shaft out of the tube. Make sure the backplate is unbolted first though. Sometimes turning the shaft as you pull helps to free it.
Maybe Mr M has some tips cos he`s always pullin them to pieces to fit discs lol

[lunatic]

Sometimes you just have to bash the axles out with an axe, eh mr Manky!

[peanut]

I'm glad that you seem to have found  a set-up that works but I don't understand why. You can (and I have) put Twin leading shoe brakes on  'backwards' but a single leading shoe backplate will always be a single leading shoe backplate which ever way you fit it.
Could someone enlighten me?

[tbone]

Bearing in mind that only 1 shoe per side is being directly pushed out by the wheel cylinder,and the second shoe relies on the sliding movement of the cylinder, the answer must lie in the "SELF APPLYING" characteristics of the whole mechanism, the way that the rotation of the drum can drag the shoe tighter into it, creating a harder bite on the drum.
Hence my earlier question in the post, as to whether or not the drums moved freely in either direction.

[BikerGran]

Cheers Peanut and others and sorry for hijacking the thread Donut!

Got stuff to work on now, get son-in-law along to do the spannering and I shall direct operations and try to sound as if I know what I'm talking about!