List members,
For a given brake line pressure, the force acting on the pads is equal to the pressure
multiplied by the piston area.
Hence the larger the effective piston area the larger the force on the pads for the
same brake line pressure.
The friction caused by the pads being forced against the discs is equal to "mu" (the
coefficient of friction, depends on temperature, pad composition, etc...) multiplied
by the clamping force.
Technically speaking pad area shouldn't affect braking force, however the larger the
pad the less the pad will heat up - less prone to fade...
Friction is not as simple as it seems and other effects can come into play (Drag cars
can accelerate at over 2g's)
You have to consider the effective pad radius and the wheel diameter, 'leverage' comes
into play as Errol said.
Braking torque is equal to braking force (see above) divided by effective pad radius.
Braking force at the tyre is equal to torque multiplied by the tyre rolling radius.
Class dismissed, :)
Regards,
Nick
============================================================
From: "Errol Smith" <[EMAIL PROTECTED]>
Date: Mon, 11 Dec 2000 09:12:27 +1100
To: <[EMAIL PROTECTED]>
Subject: RE: Piston vs Pad area
Diarmud, et al,
Braking efficiency results from a combination of factors
For a constant applied brake pressure, piston area, over pad area, times
radius of effective pad centre on disc This gives brake torque in
newton/metres.
These results should then be normalised to account for varying minimum wheel
sizes applicable to the brake combination. Bigger wheel diameters result in
less effective braking effort for a constant applied force. Open to flames,
and healthy discussion,
Cheers
Feral Errol
mailto:[EMAIL PROTECTED]
<a href="http://www.datrats.com.au/">http://www.datrats.com.au/</a>
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Diarmuid Tyson
Sent: Sunday, December 10, 2000 21:12
To: [EMAIL PROTECTED]
Subject: Piston vs Pad area
It's been a long time since I've tried to get my head around these kind of
physics, and while the piston area is obvously important in calculations,
surely the pad area is a major factor too. Anyone tried different
pads/calipers with similar piston area? (Trev? 240K vs VT Comm? Pad area
would have to be almost double!)
Might have to get my Uni Dynamics texts out...
D.
At 12:28 PM 10/12/00 +1030, you wrote:
>While we're on the subject -
>
>Mazda RX7 series 4 - 3.25 33.16
>
>PL
>
>
>Continuing on from there Zac...
>Z32 - 3.75 44.18
>Wilwood - 4.45 62.21! Now there is a 4 pot guaranted to peal the ears of
>your head upon deceleration!
>
>
>
>and for the record:
>Nissan R33 4s - 3.5 38.49
>
>
>
>
>> Nick,
>>
>> I recon cheapest and easiest convesion would be to use twin piston
>> simitomo's from early 240K's. Consider the following caliper info.
>>
>> Each Piston diameter (cm) Total piston area (cm2) (ie
>> pi x r^2 x number of
>> pistons)
>> Simitomos 4.8 36.19
>> Hilux 3 28.27
>> 200B 5.4 22.9
>>
>> So if you apply the same amount of hydraulic pressure to the caliper then
>> the twin piston simitomos work better.
>>
>> Regards
>> Trev
>>
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