My engineer wants to know if the 15/16th M/C has enough total dispacment to cover for the hilux 4 pots and R31 rear discs..

Does anyone know if it has..??

im up sh*t creek if it hasnt

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If in Doubt ... Call Datsport

If your engineer can't work that out himself he's a penis and you shouldn't be paying him any money

He should have all the dimensions already of the caliper pistons, displacement of the master , thickness of pads , pedal ratio

Hilux has a 15/16 master by the way

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1969 Datsun 1000 wagon (Daily)
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15/16th should be plenty

ive got a 7/8th with landcruiser front and r31 rears and the pedal only travels about an inch if its lucky

I agree, get another engineer.

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A little knowledge is a dangerous thing.
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"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

Are you serious?

I'm sure he can figure them out, it's just that it would probably cost you for him to figure it out. So what they do is ask you to figure it out, as your time is cheaper than theirs. (the guy i'm using charges $150 an hour...)

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

just say yes then!!

But what proof do you have?
If he's a good engineer he'll ask how you figured it out (appropriate dimensions/calculations etc.)

OR

If a similar car (such as a hilux) uses a similar displacement MC. That's enough.

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

time to pull out the calculator, pen, paper and some vernier calipers to measure sizes, unless you have them already

calculate the individual piston volume area of each one, and then against the resovoir

Consider that if the S13 master cylinders can still be fine when upgrading the S13 brakes to R33 front and rear - capacity wise (even though an R33 m/c should be used) indont think that this/ setup should cause too much of a hassle

It's a pain in the ass, but as you said, you can do it for free or let him do it for $150 an hour

Thinking and knowing are two different things. When it comes to brakes you don't wanna just think they will work ok, you wanna know.
The statement you made had better be made from fact, because every man and his dog may copy this, and may have sub-standard brakes. Pedal travel may be too large and not meet the ADR, pedal travel may be too small and not meet the ADR. etc... What this means to you or me is if we are driving the car, and all of a sudden there is an emergency, we apply the brakes but have to push 'harder than normal' to keep a certain stopping distance, which results in greater stopping distance, which results in an accident/fatality etc.

These systems are designed to work under a variety of conditions. As they are a system, if you change one small part of it, you may compromise the way the system works. Therefore by using 4 piston calipers from a hilux (for example) and single pistons on the rear, but using a MC (even if it is the right size) that is not suited to this system, you are jeopardising yours and others safety. So basically it is necessary to find this stuff out on paper first before the you know what hits the fan.

I would suggest you find out what the piston displacement is for the Hilux MC (from a known source) and the displacement is of the MC you are going to use, and if they are the same, you should be ok. Speak to your engineer to find out by how much they are allowed to differ. (I'd ask this first actually). The other thing is the leverage ratio of the Pedal acting on the MC. If this is different between the Hilux and the car you are putting your MC into, then the amount of travel the MC will go through is going to be different between cylinders.

The other thing you have to do is find out what size the piston is for the rear calipers you are using, and compare it to the Hilux.

An easier method may be to find out the amount of fluid displacement for the Hilux calipers, compare it to the 200SX/300ZX/GTR sumitomo 4 piston calipers and then say the MC that you are using is the same (or very similar) to the factory MC. That would be a good justification, and would keep the Engineer happy and keep you with safe brakes.

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

Sorry to go a little bit off topic, but is there one good answer to the pedal effort we should be aiming to use (in a race car situation). All the info I have seen in books generally talks about 35kg pedal effort for maximum decel ('emergency stop'). Now in a race car, alot of the time you want to be braking as hard as it is possible to do so (ie - in this situation 35kg's). So for repeated hard applications should the pedal effort be lowered, or is 35kg's not really pushing 'that' hard? And therefore do-able repeatedly over a long time. Is there any good way I can test how hard I would normally push on a pedal?

Usually what the Automotive engineer does is attach a strain gauge to your pedal to find out what the load is when he does the repeated emergency stops. I don't know of anyone that has access to this equipment, but the engineer I am using does.

To answer your question about 35Kg... I really don't know, what's comfortable for you?

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

i should've put a disclaimer at the top of my post, i dont mean to say i have proof and know exactly what i'm talking about abut i have seen S13's with a full brake upgrade and still relying on the standard M/C, it's not the way i'd do it at all, was just saying that it has been done and i've seen it

personally when i upgraded the front of my S13 N/A brakes to turbo, i still ran standard non turbo M/C, the pedal was softer but i liked it better as i knew more precisely when the brakes were gonna lock up, however if i was going to 4piston front brakes, then i'd have changed to a larger M/Ca

And yes, when it comes to the safety of passengers and fellow drivers, there should never be a reason to just "think" it's right, i agree whole heartedly.

It just sux when they charge $150 an hour

guys considering this is a very popular conversion..

someone out there should already have this information handy right..

its not like this conversion is a once off...

p.s i have already changed engineers..

_________________
If in Doubt ... Call Datsport

as said at the start, i have that setup with a 7/8th master and it is fine....no calculations to go with it though
i just figured seems as all the datsun modification places, maddat datsport and so on, seem to sell 7/8th ones to use with 4 spot front and r31 rear that i would give it a go

and it worked

you can tell the engineer anything you want, he is still required to check it, even if you show him a page of calculations it means nothing
if you tell him it is and it isnt, its still his fault if something goes wrong
the burdon of responsibility lies completly with him, and thats why you pay $150 an hour

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