rear brake upgrade

Nad

Active Member
Just to throw a spanner in the work, after a lot of testing rally cars are now running same size discs front and back with similar calipers to give equal braking all round. This may have something to do with the weight distribution and firmness of suspension, and also overall balance of the car.

Who knows, but I will be upgrading mine anyway to a larger disc and running a hydraulic handbrake but one that allows a cable to be used also. Most cars require a mechanical backup braking system as well but seeing that all the ones i have used are crap and never work would rather used a hydraulic one anyway. The handbrake also comes with a lockout so it can be used for parking on hills.

Nad
 
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Edd

Guest
Well i plan to run 304mm 6 pots on the front and 304mm 4 pots on the rear. Also the 4 pot calipers im running are the same physical size as the 6 pots.
It may be overkill, well it is overkill but end of they day 500-550bhp in a Nissan Sunny is overkill so may aswell make the rest of the car mental aswell :wink:
 

skiddusmarkus

Active Member
I've had my brakes fail twice and it's not a nice feeling.Once on track and once on the road coming up to a roundabout at about 70mph in traffic.The only thing that saved me and any other cars in my path was the mechanical handbrake which did a good job of hauling me in(and sending me sideways :lol: ).The cause was a hold in the brake line and even though brake systems are usually diagonally opposed the loss of pressure meant that I may as well have tried grabbing the armco to slow me down.
There's no way I'd remove that safety feature(and MOT requirement,although apperently hydraulics with a ratchet will pass)for anything now.
Can the viscous centre diff even cope with a hydraulic handbrake as we have AWD and locking the rear wheels while the fronts are still turning doesn't seem like a good idea to me?Rally cars have active diffs so don't have that worry(plus a rebuild between stages :lol: ).
 

Nad

Active Member
skiddusmarkus said:
Can the viscous centre diff even cope with a hydraulic handbrake as we have AWD and locking the rear wheels while the fronts are still turning doesn't seem like a good idea to me?Rally cars have active diffs so don't have that worry(plus a rebuild between stages :lol: ).
No, the clutch needs to be dipped when pulling the handbrake. The cable will still be there so i can just grab that.

Nad
 

campbellju

Moderators
Staff member
Interesting thread.

My own experience is large 4 pot system on the front and near standard on the back. I run on 16" 205's and found on the track the brake balance was too front biased and when pushed the fronts would lock up even at +60mph in the dry!!

The fronts are doing all the work but they are doing too much in my instance as the backs are not even close to lock up.

Maximum braking is when all 4 wheels are on the verge of locking, not just the two fornts.

IMO, a balance of about 60/40 is my aim so you get stability without fear of the back becoming the front halfway round a corner.

I like the sound of the 300ZX or uprated rear calipers and maybe a brake bias valve for tweaking.

BTW, I don't have ABS for more of a driving thrill but it does mean I can't just overate everything and rely on electronics to sort out an overspecced sytem. I don't fancy locking all 4 wheels at 100mph :shock:
 
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Odin

Guest
I also found that my Ap 4 pot's where doing to much of the work and the back was becomeing unstable, But after fitting the pagid disc's and pads it was a lot better :) more stable under heavy brakeing and I feel the back's working now which I didn't before....

I can't see the point of fitting bigger brakes on the rear as the R has most of it's weight over the front axle and under brakeing even more so, I very happy with the set up I now have :wink: .

As for the hand brake my mate tryed a hydraulic handbrake and all it did for him was get him in to a court room and 6 point's on his licence :cry: .

rob
 

campbellju

Moderators
Staff member
Nad said:
Just to throw a spanner in the work, after a lot of testing rally cars are now running same size discs front and back with similar calipers to give equal braking all round.
Rally drivers hate understeer, they much prefer to get the back end out under braking rather than plough straight on into a tree. I'm not surprised the cars are setup like this.

They also have brake bias valves to tune the brake distribution as well.
 
Talking about rear converts it would be interesting to know if anyone done a 300zx/ skyline rear caliper conversion?
Coz i noticed all my bunch of 180sx and Silvia friends converted the rears to that so that they can use the rear drum hand brakes to lock the rears.
Any idea?
My car aint out of the workshop yet so i havent gone about checking if it's a simple bolt on.
 
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Odin

Guest
campbellju said:
Are the Pagid discs any larger than OE?
No there not mate they fit strait on :wink: But they do seem to work very well with the matching pads, I had mintex pads on before with a drilled and grooved disc which I replaced with the pagid set up ant it's
soooooooooo much better 8) :D .


rob
 

skiddusmarkus

Active Member
I think 4 pots on the back is total overkill for any power GTiR unless it's being used for circuit racing where heat will be an issue and standard caliper can't cope.
 

Nad

Active Member
campbellju said:
Nad said:
Just to throw a spanner in the work, after a lot of testing rally cars are now running same size discs front and back with similar calipers to give equal braking all round.
Rally drivers hate understeer, they much prefer to get the back end out under braking rather than plough straight on into a tree. I'm not surprised the cars are setup like this.

They also have brake bias valves to tune the brake distribution as well.
I dont think it is suitable to heavily upgrade the front brakes and not fit a bias valve to reset up the braking system on the car. I certanly will be fiting one to mine.

Nad
 
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