Manual brakes on Z432R

[River City Speed]

I just learned that the Z432R's came with manual brakes. The MC appears to be a standard 7/8" Z part. Did they use a different unit that looks similar? Did they use the same one and adjust the pedal ratio to provide more leverage? Both?

The OEM manual brake offering intrigues me. I presume they did this because the race cars didn't produce enough vacuum to operate the booster.

[esprist]

I just learned that the Z432R's came with manual brakes. The MC appears to be a standard 7/8" Z part. Did they use a different unit that looks similar? Did they use the same one and adjust the pedal ratio to provide more leverage? Both?

The OEM manual brake offering intrigues me. I presume they did this because the race cars didn't produce enough vacuum to operate the booster.

Each Z432 R was built-to-order, so it all depends. It did not even come with bumpers, center console, glove box lid, clock, door armrest, rear hatch shock, or carpet.

I have few pictures of Z432 in Japan here, it seems to have vacuum hose from the booster.........It might have been added for street driving.....

http://jdm-car-parts.com/datsun-240z-original-detail/fairlady-z-432-r/

[preith]

Assuming it came with manual brakes, it's my guess they changed the ratio. Boosted cars are typically 5:1 (our Z's included), manual are 6:1. The tilton pedal sets are 6.2:1. My road racer is manual braked, the pedal ratio has been adjusted, and it doesn't feel too different from a typical car.

[HS30-H]

I just learned that the Z432R's came with manual brakes. The MC appears to be a standard 7/8" Z part. Did they use a different unit that looks similar? Did they use the same one and adjust the pedal ratio to provide more leverage? Both?

The normal 'production' spec of the PS30-SB 'Fairlady Z432-R had no Master Vac booster, but had a unique master cylinder ( 3/4" ) and brake pedal assembly. The brake pedal itself had a different operating leverage ratio, and a stronger clevis pin:

46520-E4100 PEDAL arse'Y BRAKE ( PZR )

46123-08700 PIN-CLEVIS ( PZR )

46010-E4101 CYL-arse'Y - tandem brake master ( PZR )

Of course, some people who bought a 432R new requested the Master Vac be fitted for 'normal' street driving, and this is why we sometimes see them fitted to surviving PZRs.

The OEM manual brake offering intrigues me. I presume they did this because the race cars didn't produce enough vacuum to operate the booster.

It was mainly done to save weight on the homologation of the PZR model for the JAF 'GTS' class. Nissan homologated the PZR for the 'Special GT' class at a weight of 855kg, which was not all that easy to get down to......

Factory 'works' and privateer / works-supported PZRs all used the Sumitomo MK63-20S four-pot front brake calipers with ventilated discs when racing, and first of all these were used without a Master Vac. This gave a very heavy pedal ( relieved a little by the brake pedal leverage ratio ) but it was reportedly more consistent in feel than the Master Vac-assisted setup.

Alan T.

[River City Speed]

As usual, great information Alan! I used to enjoy your posts on HybridZ, but the quality of tech and information has declined in the past few years so I haven't visited there for quite some time. Thanks to all who posted.

So, the special pedal and pin... I assume the pin was larger in diameter? I say this because I would also assume even the regular production Z pin would have been a hardened material. Alan, do you know what the pedal ratio would have been?

preith, thank you for that information. I do want to convert my car to manual brakes, but I want it to appear OEM. I am putting disc brakes on the rear and upgrading the fronts.

esprist, lot's of neat information on your website. Thanks.

Edited February 22, 2010 by River City Speed
spelling error

[HS30-H]

So, the special pedal and pin... I assume the pin was larger in diameter? I say this because I would also assume even the regular production Z pin would have been a hardened material. Alan, do you know what the pedal ratio would have been?

Glad if I can be of some practical use occasionally!

Here's a scan from a page in one of the Nissan Sports prep manuals from the early Seventies. I think It's fairly self-explanatory. If any questions, fire away:

[River City Speed]

Alan, thank you for the page. It shows two different sets of dimensions. Is one for manual brakes and the other for power assist? If so, which one is which? I don't read Jp.

Edited February 22, 2010 by River City Speed

[preith]

Alan, thank you for the page. It shows two different sets of dimensions. Is one for manual brakes and the other for power assist? If so, which one is which? I don't read Jp.

Understanding Japanese isn't required. The ratio is determined by dividing the overall length (in this case 340mm) by the distance from the pedal pivot to the clevis pin (L1 - 70mm or 80mm). The resulting pedal ratio is listed at the end, they are 4.8 and 4.2. I this find puzzling because both would be suited for a boosted application at best. If they (Nissan) used these with manual brakes it's no wonder the pedal was hard.

Simply shorten the L1 value to increase the ratio, again, 6:1 is optimal. Master cylinder diameter plays a role in pedal feel as well. A smaller diameter will give a softer feel.

[River City Speed]

Well, the reason I was saying I didn't understand Japanese was because exactly what you said. The ratio's were so close together and neither one appeared to be close enough to what I'd consider a manual ratio.

[jmortensen]

Phil, I think it's pretty common to find manual brakes with a 5:1 ratio. Here is a Wilwood setup with a 6:1 or 5:1 ratio: http://www.wilwood.com/products/005-PedalAssemblies/003-RSMP/rsmdmcbp/index.asp

Here is a Tilton with 5.5:1 or 6.2:1: http://www.tiltonracing.com/content.php?page=list2&id=13&m=b

Here is another Wilwood with a 7:1 ratio: http://www.wilwood.com/products/005-PedalAssemblies/002-FSMP/clutch/index.asp

[preith]

Phil, I think it's pretty common to find manual brakes with a 5:1 ratio. Here is a Wilwood setup with a 6:1 or 5:1 ratio:

You're right, I should have stated it differently. It's been my observation the majority of production based race cars use a 6:1 ratio. I'd like to see the circumstances under which 5:1 would be used.

[jmortensen]

You're right, I should have stated it differently. It's been my observation the majority of production based race cars use a 6:1 ratio. I'd like to see the circumstances under which 5:1 would be used.

How about because some dumbass modded his pedal box to 5:1 after looking at some of the aforementioned links... We'll see how it works out. If it's really horrible I'll just run a smaller master and have a squishier pedal I guess, or do it over...