Change to 4 pots: do I need to change master cylinder?
Discussion
Looking to upgrade the brakes on my 71 Camaro over the winter.
At present has 11" front disks with single pot (75mm) callipers and 9.5" rear drums
Obv there's a few companies that will, in exchange for half the value of the car, kit me out with humongous disks all round etc.
What I'm hoping, is to fit much more reasonable (read cheap) 13" front disks with twin piston callipers (52mm) (PBR15 I think) and keep the rear drums until funds allow to change these as well.
Would this work, maybe with a brake balancer plumbed in?
Any hints/tips/advice/abuse greatfully recieved, ta.
At present has 11" front disks with single pot (75mm) callipers and 9.5" rear drums
Obv there's a few companies that will, in exchange for half the value of the car, kit me out with humongous disks all round etc.
What I'm hoping, is to fit much more reasonable (read cheap) 13" front disks with twin piston callipers (52mm) (PBR15 I think) and keep the rear drums until funds allow to change these as well.
Would this work, maybe with a brake balancer plumbed in?
Any hints/tips/advice/abuse greatfully recieved, ta.
I assume you're changing from a single piston floating caliper to a four piston caliper.
The new calipers have a slightly smaller total effective area but are around 96% of the originals which is not enough difference to argue over. The disc diameter change is slightly more significant. If the outer diameter is changing from 11" to 13" and supposing the center of effort of the pad is about 1.5" in for the old discs and 1" in for the new ones, that's an increase of about 26%.
Combining the effects of these two changes you get roughly a 20% increase in braking effort for a given pedal pressure.
That's going to tend to make the fronts more inclined to push on under braking and lock up earlier, but you would need to know what the original brake balance is like to know whether that's likely to be a problem.
Incidentally, if you only changed up to 12" then that would be a 16% increase in leverage, combining with the 4% loss in piston area that's a more manageable 11% increase in braking at the front for a given pedal pressure.
While you're here it would be worth looking at the thermal balance. If the rears are still drums, will you be able to push hard enough to take advantage of those dustbin lids at the front? The fronts usually do more work than the rears (typically twice as much) but the rears do still do some work.
The new calipers have a slightly smaller total effective area but are around 96% of the originals which is not enough difference to argue over. The disc diameter change is slightly more significant. If the outer diameter is changing from 11" to 13" and supposing the center of effort of the pad is about 1.5" in for the old discs and 1" in for the new ones, that's an increase of about 26%.
Combining the effects of these two changes you get roughly a 20% increase in braking effort for a given pedal pressure.
That's going to tend to make the fronts more inclined to push on under braking and lock up earlier, but you would need to know what the original brake balance is like to know whether that's likely to be a problem.
Incidentally, if you only changed up to 12" then that would be a 16% increase in leverage, combining with the 4% loss in piston area that's a more manageable 11% increase in braking at the front for a given pedal pressure.
While you're here it would be worth looking at the thermal balance. If the rears are still drums, will you be able to push hard enough to take advantage of those dustbin lids at the front? The fronts usually do more work than the rears (typically twice as much) but the rears do still do some work.
Thanks for the reply. Just getting my CSE grade 1 maths round it 
The PBR callipers (same as Z06 C5 Corvettes) are actually twin pot sliding types.
At the moment one of the rears is more likely to lock up so may just suck it and see.
Same company also do rear disk (with handbrake) conversion for earlier Camaros and hopefully will do one for mine soon. Just paid off my credit card too
The PBR callipers (same as Z06 C5 Corvettes) are actually twin pot sliding types.
At the moment one of the rears is more likely to lock up so may just suck it and see.
Same company also do rear disk (with handbrake) conversion for earlier Camaros and hopefully will do one for mine soon. Just paid off my credit card too
Paul Drawmer said:
Motown Junk said:
Looking to upgrade the brakes on my 71 Camaro over the winter.
What change do you want to make to the braking system?What braking problems do you have?
Tried different pads and braided lines, better but with planned further engine and chassis mods...
Not going to track day it (Had a Skyline previousley with bigger brakes for that) but would eventually
like to trundle over the Alps or round the 'Ring without rearranging the landscape.
Oh, and they'll look a lot better behind my pimped alloys
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