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Author Physics of brakes
Hamish
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Registered: 4th Apr 05
Location: Ashtead, Surrey Drives: 100bhp Mint with Hole
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18th Jul 07 at 21:45   View User's Profile U2U Member Reply With Quote
Right following of from a discussion in Dan295 project thread. Im now confused about brakes.

I always thought that the bigger the brakes the better. Now provideing the setup on each corsa is the same the only difference is the caliper and the size of disk

gsi discs are 256x20
2ltr setup is 256x24
and a V6 setup is 288x24

Now the wider the disk causes more ventitation. however this cannnot cause anymore braking force as such...it will just stop brake fade.
So that means the only difference is the size of the slave cylinder, which as we have established is bigger and therefore exerts a smaller force for the same amount of input provided.

But yet these brakes apprently apply more force, but how can this be. Am i missing sometihng basic here
Kurt
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18th Jul 07 at 21:46   View User's Profile U2U Member Reply With Quote
greater surface area ie pads on disc
Robin
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18th Jul 07 at 21:47   View Garage View User's Profile U2U Member Reply With Quote
pad contact area.
Hamish
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18th Jul 07 at 21:48   View User's Profile U2U Member Reply With Quote
ok but that doesnt explain the difference in performance betwween the gsi setup and the 2 ltr setup. Or are the pads bigger on the xe setup?
Dan295
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18th Jul 07 at 21:48   View User's Profile U2U Member Reply With Quote
seems like this will turn out to be an extension of ed & hamish's argument then... personally i dont have a clue about the brakes i just didnt want to use a 2ltr setup because i wanted something different
Dan295
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18th Jul 07 at 21:49   View User's Profile U2U Member Reply With Quote
quote:
Originally posted by Hamish
ok but that doesnt explain the difference in performance betwween the gsi setup and the 2 ltr setup. Or are the pads bigger on the xe setup?


its not a gsi setup cos its red dot discs and pads
Hamish
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18th Jul 07 at 21:49   View User's Profile U2U Member Reply With Quote
like i said im not arguing im genuinly interested...like i told ed via u2u
Robin
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18th Jul 07 at 21:50   View Garage View User's Profile U2U Member Reply With Quote
quote:
Originally posted by Hamish
ok but that doesnt explain the difference in performance betwween the gsi setup and the 2 ltr setup. Or are the pads bigger on the xe setup?


Yep.

Remember that the larger surface area of the piston will exert a larger force on the pad too, regardless of the size of the master cylinder, due to the volume of fluid.
Hamish
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18th Jul 07 at 21:50   View User's Profile U2U Member Reply With Quote
quote:
Originally posted by Dan295
quote:
Originally posted by Hamish
ok but that doesnt explain the difference in performance betwween the gsi setup and the 2 ltr setup. Or are the pads bigger on the xe setup?


its not a gsi setup cos its red dot discs and pads

i didnt say anything about the type of pad and disk used
Hamish
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18th Jul 07 at 21:51   View User's Profile U2U Member Reply With Quote
Thanks robin...helpful as ever
Robin
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18th Jul 07 at 21:52   View Garage View User's Profile U2U Member Reply With Quote
Type of disc will make next to no difference anyway TBH, the pad will, but the disc is generally better if it's plain, not drilled and/or grooved, in my experience.
Dan295
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18th Jul 07 at 21:53   View User's Profile U2U Member Reply With Quote
quote:
Originally posted by Robin
quote:
Originally posted by Hamish
ok but that doesnt explain the difference in performance betwween the gsi setup and the 2 ltr setup. Or are the pads bigger on the xe setup?


Yep.

Remember that the larger surface area of the piston will exert a larger force on the pad too, regardless of the size of the master cylinder, due to the volume of fluid.


oops wrong formula

[Edited on 18-07-2007 by Dan295]
Kurt
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18th Jul 07 at 21:53   View User's Profile U2U Member Reply With Quote
http://en.wikipedia.org/wiki/Brake_caliper#Calipers

edit: even better

http://www.familycar.com/brakes.htm

[Edited on 18-07-2007 by Kurt]
CorsAsh
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18th Jul 07 at 22:24   View User's Profile U2U Member Reply With Quote
XE brakes use a larger caliper and have more ventilation, which gives the difference.

Just to reiterate the above.
ed
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18th Jul 07 at 22:33   View User's Profile U2U Member Reply With Quote
What you are doing by using hydraulics is amplifying the force by using a large master cylinder which displaces a large ammount of fluid into a small slave cylinder in the calipers. If you increase the size of the slave cylinder then you reduce the ammount of amplification you achieve.

That's the point I was getting at.
Hamish
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18th Jul 07 at 22:39   View User's Profile U2U Member Reply With Quote
i now understand that ed, but if you reduce the amount of aplification how are the brakes more effective?
ed
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18th Jul 07 at 22:41   View User's Profile U2U Member Reply With Quote
The reductions are probably minimal and the size of the pads are significantly larger than the standard solid disk brake setup on a Corsa.

You often hear about people saying they feel a soft brake pedal after upgrading, this is because of the mis-matched master cylinder.
Hamish
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18th Jul 07 at 22:43   View User's Profile U2U Member Reply With Quote
right, makes more sence now

 
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