Datsun Roadster Forum-311s.org

Hi Everyone,

I have front Volvo brakes with a 280z brake master.
Does anyone have a solution to connect the brake master plunger to the brake master?
I have been using a shim(thin washer) behind the brake master snap ring to hold the plunger but this engages the brakes.

Thanks

Paul

Pauljsouza@yahoo.com

Pics might help...

? 280 z is a powered/ boosted cylinder setup and a Roadster is not they , the engineers are thinking ahead of
A 75 280 push rod doesn't rock up and down like a 311s @ the piston

I used the plunger/rod from a roadster clutch master. Took a 1/4"x 3/4" diameter fender washer and fashioned an "arbor" by cutting off the head of a bolt. Sandwiched the washer between two nuts and chucked it up in my drill. Then I filed a bevel on the washer to match the bevel on the cylinder. Some pics of the process. Hope this helps. Pat

Hi Pat,

What is holding your washer setup in place so when you release the brakes it does not fall out? Can you possibly provide more Picts of it installed?

Thanks, Paul

Paul,
I only used the washer. The other pics of the "set up" was to show how I machined the angle on it using my drill and the arbor. Use only the beveled washer, toss the arbor away. Unscrew the yoke of the plunger and place the washer on the shaft to mate with the bevel on the master cylinder bore. The bottom left pic shows the washer installed on the clutch master rod being held in place by the circlip.
The upper right pic show the 280z master, on the left, with plunger rod and yoke attached compared to an OEM master. I adjusted the rod to the same length by using the jam nut and threading the yoke.
The clutch master has the correct domed head that mates with the concave in the master piston.

Hope this helps, Pat

redroadster wrote: Mon May 10, 2021 6:22 am ? 280 z is a powered/ boosted cylinder setup and a Roadster is not they , the engineers are thinking ahead of you

This is spot on. Paul you might want to consider a different approach all together. The 280 master is a very poor match for volvo calipers, if you do the math.

You would be MUCH better off running the stock master cylinder. If you can't afford an original Nissan cylinder from one of the vendors, you would be better off with one of the aftermarket cylinders-check with Brian Zana- or a 3/4" 510 master.

Will it stop with the Z master? yes, but your stopping distance will be inferior to the original brakes especially with volvo calipers, so certainly not an "upgrade".

Jim: Do you believe the 280z master is also a poor choice for the 300zx front/RX-7 rear disc setup. Why do I ask... because that's what I'm running. I will say that the larger cylinder does require quite a bit more pedal effort than the stock master.

Shannon

Yeah they have a stiff return spring To counteract the booster ...I'd bet ( it could be replaced )
If it happens to wreck & the investigators find the mods , it cancels coverage

It’s not about the return spring, it’s simply the math of the hydraulics.

Rather than get into a technical discussion and risking the thread getting locked, I’ll just say the 7/8master
paired with the Volvo calipers is just about worst case. The only thing worse would be a 1” or
larger master.

I’m not trying to sell you anything or bash anyone, strongly suggest you use a 3/4” master if you are using the Volvo calipers.
Cheers

I bench bleed all master cyl replacing
Those 280 / booster MCs are a 2 hand , hard to push deal , some to hard to do it , only with the pedal , they counter act the booster wanting to power it where as the no boost are easy

& Yeah I wouldn't recommend the 311 MC on a 280 , bet your better off in the long run with stock brakes in GC
It's hard to compress the return spring fully on a boosted cyl ,and almost no effert on a non boost
I wouldn't take the Pistons out of a boosted cyl it's frustrating to get it back together

Even if the spring is slightly stiffer, it’s nothing close to braking efforts. (Just open fully a bleed screw fully and press the pedal-that is the total return spring effort).

The issue is basic hydraulics. The surface area of the 7/8 master is about 30% larger than the 3/4. That means the psi is way down for the 7/8. Some real world numbers would be 1600 (7/8 master) psi vs. 2300(3/4 master) psi for equal leg effort. If you want to stop, you have to make it up with more pedal force.

Hi Everyone,

I installed the Volvo front brake calipers and 280z brake master to get improved braking.
I followed the instructions on our 311s site but they are no longer there. It was my understanding the 280z brake master was required since more brake fluid volume was needed. I am happy to install my stock brake master cylinder if it can handle the Volvo brake calipers.
Is anyone using the the stock brake master with Volvo front brakes that I can talk to?

Pat: can we talk offline about your solution? We could exchange phone numbers at Pauljsouza@yahoo.com.

Thanks for everyone support!
Paul

Paul, we ran Volvo calipers a decade ago, that is why we posted the information. Not sure exactly where you got your information.

The Volvo calipers do not warrant a bigger master. The total caliper piston area is noticeably smaller than the stock brakes (also by about 30% if you do the math). Reduced caliper piston area means reduced rotor clamping force.

Reduced caliper piston area and increased master cylinder bore is the worst case combination. That combination creates lower system pressure added to reduced clamping force. Clearly the Volvo calipers were also designed for fairly high pressure systems. (With Volvo power assisted masters)

An oversized master cylinder will "give the feel/illusion" of better brakes by providing a very hard pedal, but will not improve stopping distance over the original brakes.

The bidg problem is the boosted cyl has a pin / rod that only moves out and back ( on one plane )
The non boosted moves downward at rest thus needs a ball and socket @ the piston
And yes with a MC on the car there's no trouble bleeding it , bench bleeding is different
Put the stock or non boost cyl on and let us know
How braking is

I wonder if everyone knows the difference between cars 83 & up to older in wrecks
as 82, 83 with crumple zones 5 mph bumpers the new steel ( sheet steel formula was changed in 82 it bends easy ,at first then stiffens )

800 ft from my home in the 60s-70s was the most dangerous intersection in KC metro
so many wrecks we would hear them lot of fatalitys but many of the seriously injured died too from head , neck ,brain trama weeks later
It's why I opted out of driving my 311 overy zx t