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1600 with FJ20 & Simmons. something different.

ok, i found out. it's for a 200B. 13/16, 20.64mm bore, nabco brand, 200b 10/77-05/81

But...i also have a JB 1133, which is a 240z (and others) MC.

that's 7/8 (22.22mm) bore.

is this the MC is should be using for a 1600 with 180B booster? i also have the mad dat RX7 front brakes and R31 rears.

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1600 with FJ20 & Simmons. something different.

I've been using the 13/16" 200B master with exactly the same brakes as you, but with a 200B booster, for years.
Brakes are fine
I plan to replace the booster with the smaller 180B can soon, the 200B one caused a lot of clearance issues.
I don't expect the booster change to affect the braking performance but it may give a harder pedal feel.

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Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

graeme, seeing as you have a lot more experience than me in this area, you would use the 13/16 MC? even though the 7/8 bore is larger?

this still involves removing the RPV as shown in your FAQ/tech thread?

Thanks mate.

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1600 with FJ20 & Simmons. something different.

I personally didn't experiment with M/C bore sizes.
I originally had 200B brakes on the front and when I upgraded the system to 4 wheel discs, retained the 200B M/C minus the RPV as mentioned.
You gotta start somewhere right?
Anyhoo, that combo worked fine for me, so I left well enough alone.
Others may have had experience with the 7/8" M/C, but unless their brake specs./system is identical to yours, you won't be comparing apples with apples.
The R31 used a 22.22mm M/C.
The Mazda RX7 2/79 - 85 all used a 20.64mm M/C.
86 - 88 went to a 22.22mm M/C.
You would have to determine if the R31 rears are the same diam. pistons as the RX7 rears but even then you have to take into account fluid displacement, stray gamma rays and such.
It is just a easy to use the SIAS method, Suck It And See
You can also fit a manual Brake Bias Valve to fine tune any problems.
I believe they are legal as long as the driver can't adjust it from the cabin, i.e. mount it in the engine bay.
Once set for the desired balance F-R, you never need to adjust it again anyway

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Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

If Graeme is using the 13/16" master and the rest the same as yours, I'd start there.

I'm using a 7/8" master with 240K twin spot fronts and stock rear drums. Gives a very firm pedal with short pedal travel. Ideally, I probably should drop down to 13/16" or smaller to get a bit more travel and "feel" (or take the wimp's way out and fit a booster ).

Generally, the larger the master cylinder, the shorter the "stroke" or "push down" is needed on the pedal, but it takes more effort to do the "pushing".

A smaller one will be easier to push (takes less leg effort) but the pedal will travel further for the same amount of "stop".

So long as you come up with a master cylinder that isn't either way too "heavy" (cylinder is too big) or takes too much pedal "travel" to stop (cylinder is too small), you should be right.

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1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

7/8 inch diameter (Datsun 180B/240k) is the go.
Its what the maddat kit is designed (engineered) to use.
I have this kit in my grey 1600 and the pedal feel is good.

R31 ear calipers are matched to a 7/8 master cyl.
Use the 7/8" with the booster.

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A little knowledge is a dangerous thing.
www.datsport.com

"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT

okie doakie. thanks a lot for replying.

btw graeme, i purchased a full 1600 hard brake line set from mad dat, before they actually started producing and advertsing on website. couple of years ago now. Scott also sold me a willwood bias valve and setup the lines so the valve will sit next to the drivers seat once i mount the lines

maybe an offcut piece of carpet will get me through engineering LOL

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1600 with FJ20 & Simmons. something different.

I agree with Baz I had too much travel for my liking with R31 rears and 240K twin pistons with a 180B 3/4 master. The upgrade to a 7/8 gave nice feel, less travel and more confidence in late braking on the circuit or spirited black spur driving.

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1928 Model A CC Pickup