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Old 01-05-2018, 03:08 PM   #16
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Join Date: Feb 2010
Location: Tasmania
Posts: 229
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CC: 1600
Make: Honda
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Originally Posted by AGoaty View Post
I think the issue is not pressure, but flow. If you want to move the 4 pot caliper pistons, this will take more fluid movement than a single pot caliper. Having a large bore rear needs quite a bit of fluid to move it. Reducing the cylinder size will increase the amount the piston comes out? Am I wrong?

I said earlier that there was a 2 tablespoon difference in fluid displacement. Im revising that comment after more measuring and research.
4 pot metro caliper piston diameter 1.414 Area = pi*0.707^2 * 8 = 12.56 sq inches
2 pot 8.4 disc mini caliper piston 2.00 diameter. Area =-pi*1^2*4 = 12.56 sq inches
Fluid displacements are exactly the same.
Also Minisport & KAD 4 pot calipers pistons are exactly the same dimensions as Metro calipers.
This info sort of debunks the idea that the rears cylinders move before the front calipers
If a small diameter piston is completely free to move without any restriction, it will move more for any given pedal travel than a larger diameter one. However it is restricted by the drum and because of its size produces less pressure
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