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Overkill brake setup question

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Roy Grand Master

Roy

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Does anyone out there know for a fact the point where you should be looking at an aftermarket master cylinder etc because of bigger brakes.

Say if you were to run big ass 6 pots on the front, with big ass 4 pots in the rears (std Nissan 4 pots - possibly aftermarket 4 pots) with something like 355 front rotors and 324 rears.

Im expecting for such an over engineered braking setup you would need to do somthething about the std Nissan mater cylinder, perhaps bigger piston AP type setup or equiv? Std Brake booster ????

I know in a RWD car that weighs 1400kg this sort of system isnt warranted but im askign all the same. :D

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BHDave Grand Master

BHDave

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I have friends who have done an r33 front brake swap onto a silvia/180 and found that by using the original master cylinder thay have a very spongy feeling pedal but the car stops ok. They have then installed an s14 master cylinder and booster as the s14 has 4 pot fronts and similar rears and the pedal feel improved, probably improved the bias too.

In all honesty i'd think that if you are changing one component in the system so dramatically then the others should be changed as well to make the most of it, otherwise you won't get the most of the new calipers. Bias is something important in all of this too.

Roy Grand Master

Roy

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Yeh i expect to have to play with bias, and i seem to recall the R32 has a 32mm diam piston in master cylinder.

Whilst that std 32mm piston does a fine job at moving the std brakes 12 pistons within the std calipers (2 x 4pot fronts and 2 x 2 pot rears) i would expect it to run into trouble when expected to displace 20 pistons, may of which are a larger diam then std caliper pistons (ie 2 x6 pot fronts and 2 x 4pot rears)

Looking at some engine bays of Jap cars with massive brake upgrades (time attack or whatever they call them), many still seem to run std master cylinder setups etc, doesnt seem right to me... just wondering where the limits are, especiually since you look under the bonnet at circuits around the traps on circuit cars, and some/many run aftermarket setups when the calipers themsleves may not be dramatically different to std, ie a late model WRX with AP 6 piston fronts and std 2 pot rears?

Steve Grand Master

Steve

Posted
Posted

this sounds reasonable, but in my limited understanding of physics, isnt pressure distributed evenly over all area in fluid? so the number of pots would not be so relevant as the size of the piston itself, the pressure exerted on the pistons would be the same? does this make sense?

Then again, theory and the real world often seem to clash:)

I have seen vacuum bottles fitted to brake boosters - this was mainly because of the lack of vacuum at low revs due to large cams, but I suppose theoretically extra vacuum would be beneficial?

sorry for the red herring.

Roy Grand Master

Roy

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??? I dont know, as for the pressure being equal you are right, but thing to remember is if you increase the volume of fluid in the brake lines, then only have the same displacement of the piston in the master cylinder, then the overall pressure applied will be reduced due to the increased volume of fluid in the system, you may need a 40mm piston to get the same percentage in volume change... make sense? (Actually its not really a volume change, more a displacement of volume...as the brake fluid isnt compressible.)

Targa Tom Proficient

Targa Tom

Posted
Posted

a drip under pressure!!!

???  I dont know, as for the pressure being equal you are right, but thing to remember is if you increase the volume of fluid in the brake lines, then only have the same displacement of the piston in the master cylinder, then the overall pressure applied will be reduced due to the increased volume of fluid in the system, you may need a 40mm piston to get the same percentage in volume change... make sense?  (Actually its not really a volume change, more a displacement of volume...as the brake fluid isnt compressible.)

You need help Roy, and unfortunately the people who know enough to stop you slamming into a wall will want to charge you for it...

Find out your nearest brake guru, and you will find your answer. What you pay in quality advise, deduct from your T & E bill and you'll more than likely brake(sic) square.

TT

Roy Grand Master

Roy

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a drip under pressure!!!

You need help Roy, and unfortunately the people who know enough to stop you slamming into a wall will want to charge you for it...

Find out your nearest brake guru, and you will find your answer. What you pay in quality advise, deduct from your T & E bill and you'll more than likely brake(sic) square.

TT

The brake kit i was looking at getting ended up selling for a grand more then i was willing to pay, so for the moment brakes are fine...will have to see how they handle the big stops at Sandown at the end of the month, sonce now i have a bit more power then before and no speed limiter.

Targa Tom Proficient

Targa Tom

Posted
Posted
The brake kit i was looking at getting ended up selling for a grand more then i was willing to pay, so for the moment brakes are fine...will have to see how they handle the big stops at Sandown at the end of the month, sonce now i have a bit more power then before and no speed limiter.

What is the event Roy? I have 200litres of elf I need to use...

TT

Roy Grand Master

Roy

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MSCA Multiclub Sprint on 30th May @ Sandown www.cm510.com/msca/

OR

PIARC are holding a sprint weekend at the Phillip Island on the 29th/30th. www.piarc.com.au

Im thinking Sandown, because its closer, a few other Vic guys ive met are going, and i want to scare myself stupid on the back straight kink.

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