Upgraded To 34 Brembos And They Are Worse Than Stock

[unique1]

hi guys im just wondering why my upgrade to r34 front brembos from the stock 1 piston calipers is feeling so bad and hard to operate?

do all skylines and stageas use the same size brake booster?

i have some r34 brembos on my stagea and the brakes are dreadful. I think its because of the stageas tiny brake master cylinder, now do i need to just upgrade to a r33/34 master cylinder and will it fix the terrible pedal feel ? or do i need the master from a r33/34 as well?

I have bleed the thing to death on current master/booster and its still really bad and i cannot make the car pullup hard at all, the pedal is solid.

I dont run the vacuum tank that gtr's run either but im 99% sure thats only for the clutch anyway.

I have big big lift cams and my vacuum is about -7 and usually stock cammed cars are -21 or so, maybe this is an issue and i need a vacuum pump of somekind to help? The brakes feel like when u switch the engine off and try and stop on a regular car.

any thoughts and ideas much appreciated

thanks

[Scooby]

a small mcyl will give you a soft pedal with more travel (same pressure over a smaller area but you need to move it further to move the same amount of fluid), a big one will give a harder hard pedal with less travel. so a larger mcyl will give you a pedal that's harder still.

bleeding wll give you a harder pedal not a softer one, as you're not compressing air.

the GTR does have a vac tank for the clutch.

sounds like the booster might be faulty or disconnected, have you got the directional valve for the vac feed in the right way? brake boosters do develop leaks, i got mine reco'd for $200 and it made a big difference.

if the pads are race type this can sometimes give a similar feel, it's just that you are pushing so hard to get the thing to stop when they're cold that it feels like a hard pedal.

-7 to -21 is a big drop, have you checked for leaks elsewhere?

do you know what was like with other brakes or were they on the car already?

Edited March 14, 2008 by Scooby

[unique1]

a small mcyl will give you a soft pedal with more travel (same pressure over a smaller area but you need to move it further to move the same amount of fluid), a big one will give a harder hard pedal with less travel. so a larger mcyl will give you a pedal that's harder still.

bleeding wll give you a harder pedal not a softer one, as you're not compressing air.

the GTR does have a vac tank for the clutch.

sounds like the booster might be faulty or disconnected, have you got the directional valve for the vac feed in the right way? brake boosters do develop leaks, i got mine reco'd for $200 and it made a big difference.

if the pads are race type this can sometimes give a similar feel, it's just that you are pushing so hard to get the thing to stop when they're cold that it feels like a hard pedal.

-7 to -21 is a big drop, have you checked for leaks elsewhere?

do you know what was like with other brakes or were they on the car already?

Hi mate thanks for the reply, the pedal is harder and doesnt travel far at all, it honestly is exactly liek when car is switched off and u try and pump the brakes (no vacuum assistance). The more i try and pump it (with engine running), it gets harder and harder like when car is off on normal cars.

i have directional feed in the brake vac line correctly but i just went and moved it abit to try and pull the valve off the vac hoses and it made a hissing noise as i moved it (without actually pulling any hoses off) so maybe there is a leak somewhere.

the low vac is normal with the cams i have, they are drag specs only and not made for street use usually, its not the usual set of poncams or anything

the stock brakes were abit shitty but not the same as it is now, it just feels like the vacuum booster isnt workin at all, but i dont know if its the master cylinder being the wrong size or just the booster is stuffed all of a sudden?

[Scooby]

i'd look for the source of the hissing noise, then have the booster checked. i don't think it's the mcyl size for reasons already stated.

[R34GTFOUR]

^^ +1

if you dont have vac assist your going to have that hard pedal feeling, the brake booster is either leaking internally (which you should be able to hear), or the line itself is leaking. If you hearing that hissing noise, thats most likely your problem

Edited March 14, 2008 by R34GTFOUR

[unique1]

thanks fellas ill suss it out asap and let u know what happens

[Duncan]

the vacuum tank is for the brake booster, but that is only an issue if you don;t have vacuum when you use the brakes. and unless you are left foot braking while the throttle is still open it is not the problem.

non-assited brakes in these big cars feel like standing on a rock to try and stop it

[Scooby]

the vacuum tank is for the brake booster

apologies, indeed it is, jut like the one in the shed. that'll teach me to rely on memory.

[unique1]

thanks duncan, i took car down to local brake and clutch shop and he reckons its either the master is the wrong size and also possibly the vacuum tank needs to be put on as well. I have fairly low vacuum even on deacceleration, most vacuum i can get is -11 or so when slowing down off the throttle so its still twice as low as a factory setup car. I will purchase the correct size master asap and see what happens, any ideas where to buy one besides nissan? Nissan qouted $366 trade for me yesterday and i'll email RHD Japan soon and see what they want for one.

[Duncan]

yeah you should be fine to get an aftermarket one, talk to PBR once you know the number of outlets, diameter and plug on the master cylider warning ligth