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Brake guys, check my math.

Started by flyinlow, July 02, 2012, 02:53:39 PM

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flyinlow

Stock Mopar floating caliper   2.75 inch piston  , 3.14 x R squared..... about 5.9 square inches


Wilwood  120-6815 4 piston fixed caliper  1.75 inch pistons  2 per side X 3.14 R squared.....9.6 square inches


So about 50% more clamping preasure?

John_Kunkel

When computing the clamping pressure of rigid multi-piston calipers you only use the area of one-half of the pistons on each wheel.....I know it's counterintuitive but that's the way it actually is, one set of pistons only acts as a backup for their opposites.

Floating calipers OTOH use the measured area minus a few percent for friction losses in the caliper-to-bracket interface.
Pardon me but my karma just ran over your dogma.

flyinlow

Yea , that's what I was wondering about.  

John_Kunkel


The surface area of two 1.75" pistons is 4.81 cu. in.

If you read caliper specs on Wilwood's website they only count two of the pistons surface area in their specs. IE, they call a 4 piston caliper with 1.75" pistons a 4.80" caliper.

Bottom line, the factory 2.75" floating caliper has more clamping force than the Wilwoods. Some would argue that the two pistons on each side give a more even application of force on the pads but even that is debatable.
Pardon me but my karma just ran over your dogma.

flyinlow

So I can only count 4.8 sq. in.

That means the stock Mopar caliper clamps harder than the Wilwood. Who would  of thought.

flyinlow

Thanks John,  I guess I need some Cordoba brakets to use the 11.75 rotors with stock floaters.