Front brake upgrades - a techincal look.


I've never understood that, I see race cars (extreme example) use say 8 pot fronts and 6 pot rears? Is it because of the whole fwd v rwd scenario?

Genuinely not sure as I've been told by a few to ditch the idea but never fully explained why.

Handbrake can be made up as a secondary.
 
The number of pistons is irrelevant, the overal piston area is what matters and a single front pot will be massive in area compared to several tiny ones on a rear caliper. :nice:
 
Kozy said:
The results are not absolute, but a good representation of the differences when absolutely everything else is held artificially constant.

Yep, 298s are on 32mm thick discs.

Using a better rear pad would certainly bring the bias back quite well, but woud still require you to use a weak pad up front, which would be a bit counter productive...
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Yeah not ideal is it , probably have to run different sets of pads too for road use..

Id love to know how the DC5 brembos fair out in your calculations !
 
boro_andy said:
I've never understood that, I see race cars (extreme example) use say 8 pot fronts and 6 pot rears? Is it because of the whole fwd v rwd scenario?

Genuinely not sure as I've been told by a few to ditch the idea but never fully explained why.

Handbrake can be made up as a secondary.
Click to expand...

rwd do need a lot more braking on the rear wheels too. they essetially have to brake all the rotating mass of the driveshafts, flywheel, clutch and so on. Thats why you setups on the back of rear drivers only marginally smaller than the fronts.
Rear brakes don't have to deal with all that extra momentum on fwd cars which is why they tend to be a bit weedy in comparison to the fronts (which do).
 
Darragh_K said:
Yeah not ideal is it , probably have to run different sets of pads too for road use..

Id love to know how the DC5 brembos fair out in your calculations !
Click to expand...

Bit more powerful than ATRs IIRC.

clockwoRk said:
rwd do need a lot more braking on the rear wheels too. they essetially have to brake all the rotating mass of the driveshafts, flywheel, clutch and so on. Thats why you setups on the back of rear drivers only marginally smaller than the fronts.
Rear brakes don't have to deal with all that extra momentum on fwd cars which is why they tend to be a bit weedy in comparison to the fronts (which do).
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Yep, more weight and more drivetrain mass does mean bigger components for RWD cars. The S2000 uses the same front brakes as the EP3, but with 280mm rear discs instead of 260s, with comparatively huge pistons. I still wouldn't be considering running front calipers on the rear even here.

You can get away with doing this in rear engined Porsches as the static weight distribution and load transfer effects often mean there is virtually no proportioning between the front and rear brakes. I am aware of people that have fitted GT3 front brakes to lower spec 911s and fitted the stock fronts to the back, but the extreme difference in vehicle setup should give you an idea of what makes this possible.
 
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Darragh_K said:
For the wilwood 298mm did you factor in the 32mm width discs ?
Click to expand...

Just checked this, I had it as a 28mm disc. Updated the rotor temp chart for a 32mm disc.

Found some interesting results for front vs rear rotor temps...
 
So what happens when using the same pedal force on all brake setups? Why is it your using different pedal force on the setups? Surely if using the same driver all setups would use the same force? Or am i totally not understanding? Is that the maximum amount of force the setup will allow you to use? Because from what i can see the less force that is used the further the stopping distance, which is understandable. Obviously its not just about stopping distance but would just like to understand better. If you could explain this to me or put me in the right direction i would greatly appreciate it, as im sure you know what your on about, thanks
 
Yes that could use some better explanantion. What that is, is the pedal input required to lock the front wheels, to make the brake force at the front wheels equal the available traction. The more powerful the brakes, the less pressure it takes to lock them, but at the same time the rear brakes get less pressure, so the overall traction used goes down and the stopping distances go up.

I have another column on the spreadsheet that will do a constant pressure comparison, but it doesn't give you the same results as it cannot determine the limit, effectively you could make the brakes as powerful as possible and it would always show as being better, though this is clearly not the case when you are driving on the limit.

As usual with my witterings, all of this is really concerns racing more than road use.
 
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