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Location:
qld
Registered:
May 2003
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Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 03:53
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hey guys at them moment i have a problem at the moment that my front brake arnt as good as my rear(in a ratio way) so my back locks up a long time before my front does.
My setup is a ta22
Front Ra60 front brakes, reconditioned
Rear Nissan pintara disk brakes, reconditioned
i have been given quite a few option already but as we all know there are a million opinions on everything
1) Upgrade front brakes, (to expensive thought for me atm)
2) Drill holes in the rear disks till the braking is equal
3) buy bias controller (have been told they arnt that great???)
thanks guys
Jason
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 03:58
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get a bias controller - cheapest and easiest way to do it. drilling holes in your rear discs until they're crap is a very silly option imho.
Obviously the front brake upgrade would be the best, but if you cant afford it, it's not really an option 
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Location:
Canberra
Registered:
February 2004
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 03:59
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Go to a decent brake joint and they will be able to measure properly your front/back brake bias. They will be able to put a proper bias valve inline before the back brakes and give you a proper braking distribution.
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Location:
Cabramatta, NSW
Registered:
May 2002
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 04:02
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I agree. Do the bias valve.
Drilling holse in brakes is bad, mkay...
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I supported Toymods
Location:
Australia
Registered:
November 2003
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 04:02
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Its pretty normal for the rear to lock up first, considering there is little weight back there when you stand on the anchors.
This is really bad if you have soft springs, and can be rectified by getting stiff springs.
If you already have soft springs, get a bias valve as suggested.
Brakes are designed to work in harmony with each other.
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Location:
Cabramatta, NSW
Registered:
May 2002
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 04:05
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Actually, brakes are tuned to lock up the fronts first. That way you can see what you're gonna hit, plus there's shitloads of metal between you and whatever you might hit.
Rear brakes locking up is bad, mkay...
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Location:
Campbelltown
Registered:
November 2003
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 04:11
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In my experience my car the front lock up first, but when at an advanced driver training course majority of the FWD cars/cars with rear drums had the rears lock up, generally they had fairly soft suspension bar a corolla which was lowered but still locked the rears.
This was generally more of a result of the fact that the front hits the deck and they almost start to lift the rear tyres off the ground, this in turn means theres is less friction/grip and the brakes will lock up easier. Maybe some new springs and shocks wouldn't go astray either.
My car has drum rears, but i have a feeling they don't work to well ie i can rip the handbrake up and they barely pull the car up, i think they need to be adjusted.
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Location:
c'town, NSW
Registered:
May 2002
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 04:19
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the lockup problem is common when going from drum to disk, talk to brake specialist they can set u up with the correct proportion valve.
i cant confirm but from what i remember being told in the drum circuit there is a one way bias spring (?) in the proportioning valve. Once you gut that out the disks on the rear should work fine.
since youve upgraded both front and back a specialist should be able to set it up tip top.
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Location:
Melbourne, Australia
Registered:
March 2005
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 05:12
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I think the common theme here you have to see is it's not that your front brakes are 'crap' and the rear brakes are 'better' but that you're not working them in the appropriate ratio.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 05:18
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nahh, the front brakes are crap 
what you need is either larger diameter front caliper pistons.... or smaller area rear caliper pistons..
it may be much easier to change rear calipers than to change the fronts..
the bias valve is good for small imbalances, but it's not the "best" way to correct it...
what are the diameters of the front and rear pistons, and what are the inner and outer diameters that the brake pads touch, front and rear?
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 05:20
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oh, what pads are you running???
you could run stickier pads in the front, and not so sticky in the back, and that can also correct the problems without having to do any major hardware changes..
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Location:
cambo
Registered:
May 2002
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 06:28
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yeah like others have said, upgrading to discs on the rear can cause them to lock up before the fronts. if i were you i would gut the factory proprtioning valve, and run an after market adjustable proportioning valve in line with the rears, this is what im going to do as soon as i put my rear discs on. i have a couple of brand new adjustable bias valves if your interested, pm me if you are.
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Location:
Canberra
Registered:
February 2004
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 06:33
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I dont think that your allowed to use an adjustable valve on a road car. Off road use only I think but i might be wrong.
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Location:
cambo
Registered:
May 2002
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 06:43
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i have never checked it with an engineer so cant say for sure, but afaik they are legal as long as the cannot be adjusted from inside the cabin ie they must be in the engine bay, under the car etc.
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Location:
brisbane
Registered:
October 2004
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Re: Rear Brakes are to good for my front brakes
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Mon, 22 August 2005 09:30
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drill holes?? 
you need to be more specific about the setup, you have only written half of it,
what:
- bias valve
- master / slave cylinders
i would say these components are affecting your setup,
bias valve:
what has happenend is that your factory bias valve was setup for rear drums which arent super good so they recieved a decent amount of force from the bias valve. now you have changed to disc, the discs are recieving the same force but are way more effective. im not sure exactly how the bias valve operates, it may have a constant bias or it may have some kind of pressure bypass circuitry... in the end it provides a bias, the proper factory bias for disc/drums and not the correct bias for disc/disc in your case.
you may get a bias valve setup properley for your car but cannot have an adjustable one from in cabin.
cylinders:
the master and slave cylinders may be the wrong size relatively, ie the wrong area.
if the master cylinder is a different area then when a force is applied a different pressure will result,
and visa-versa:
when pressure is recieved on a different area in the slave, a different force will result.
pressure = force / area.
the master and slave stroke can be wrong too and thats another issue.
also:
when you brake there is a front to rear weight transfer that weighs down the front and lightens up the rear, so the fronts are forced to roll and the rears are lightened with a small weight on them and can easily lock up if they are overpowered.
*some technicalities are in this post*
i hope you get it sorted
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