Quote: Thats the Japanese disc brake, so if this strut is from a 1976 Datsun 120Y it was either, built before July 1976 if it is from a sedan, or it is from
some other body style. These other 'non sedans' were all imported.

The bare strut body & the brakes are the same as 1200 coupe. The replacement shocks are the same too, but use your 1200 springs & top
pieces to make it work properly in a 1200.

Overhaul kits for these are cheap & recomended & about the only real problem that I found with mine was the need to replace one pitted
piston, & yes, new parts are still available.

Heres a pic of the brakes on the strut

Yeah your right. Have to change the springs and the tops of the strut over.




The 120Y one is on the left...

When I have my lowered spring out I might line them up and take a pic for comparison.

one thing i noticed when i swapped the 120y struts in, is that the springs on the 120y were longer and the strut top was higher. so i had to swap the springs over for my ute ones and put the ute strut top back on. might be different for 1200 coupe/sedan again....

nah they will think the whole responce is aimed at me and just skip to the next post

Yes, you are probably right, but the response will hopefully be of some use to other members with less experience.
Well, that's my excuse.

so a simple reply there being, sorry i wrote that wrong.....i meant that there is more pressure needed in an unboosted disc drum system than a drum drum system

could save yourself some typing next time

Pigdog

It's not the presence or absence of a booster that affects the line pressure in a 1200, it's the difference in the pedal pressure required between disc & drum models. The 1200 does not have a booster, so you need to push harder to create the requisite line pressure in the stock disc brake versions.

The original drum brakes are of the dual leading shoe type & this means that that they have a self servo action. The rotation of the drum actually tries to pull the brakes on harder. The actual effect is to need less pedal pressure than might otherwise be the case.

As an experiment, reverse a drum braked small Datsun at a modest clip [15kph] & apply the brakes. If it wasn't for the single leading shoe in the rears, the brakes would feel like a feather on a cannonball as there is no servo effect from the front brakes when the wheel/ drum is rotating in the reverse direction, so it will be seen that the drum brakes actually help themselves to apply when driven in the forward direction.

The front discs, on the other hand, simply clamp the rotor between the pads. There is no servo, or self applying function, & all of the effort must be provided via your right leg.
Keep in mind that the master cylinder is the same bore size as the drum brake one & it isn't too hard to see how it all works. This is why the coupes used a smaller bore rear wheel cylinder. The higher line pressure in the disc braked coupe was leading to rear wheel lockup, particularly in the wet, so a piston with a smaller surface area is used to reduce the braking effort at the rear at any given line pressure. Since the system now has more line pressure than in a drum brake system, the balance is restored.

A smaller bore master cylinder will supply more line pressure for a given pedal pressure, but the amount of piston [& pedal] travel will be greater for a given amount of fluid displacement. It's all a matter of balance & if the rear brakes are adjusted regularly, & properly, then the smaller bore cylinder will be a bonus.

right, dont worry about what the factory intended the size to be...as long as you dont go heaps smaller you will be right(not that you can really go heaps smaller than 11/16ths)
i ran an unboosted 11/16th master on brakes that the factory gave a booster and a 7/8th master....still had great pedal feel and pulled up really well

i really doubt that you will have the need for a booster or a bigger master on standard 120y brakes

Quote:

dodgeman, how is there more pressure needed in the brakes lines without a booster? after all a booster only makes for less effort pushing the pedal in(just coz your pressing harder without a booster doesnt mean your doing more).....same pressure is in the lines its just easier to make it

EDIT: you want to ask for a 1200 coupe disc drum master
or if you want a bigger master ask for a sunny disc drum master
or if you want bigger again ask for a 240k disc drum master( will make your pedal a rock)
but the 11/16th coupe one will be plenty for 120y brakes

You sure do know your stuff :) Its a 1973!

I'll grab that manual like you suggest. I'll grab a 1200 one while I'm at it too. I'm sure it will come in handy.

If i was to buy a replacement master cylinder what would i ask for? A 1200 coupe one? Or is it just a generic thing?

Cheers for your help. The link to ebay is above and beyond