[Tigers] Not Tiger Related-Brake Upgrade

[deiland1 at elp.rr.com]

Erich,

How do I factor in the area of the pistons into my calculations so I have a better idea as to how much pressure is actually being applied to the disc to stop the car. Do I multiply the psi times the area of the pistons in my calipers?

Dan


---- e.coiner at cox.net wrote: 
> Dan,
> Only one correction.  The area of the pads is irrelevant to force calculations.  You need to know the area of the pistons in the caliper. Only count the area of the pistons on one side of the disc. ie a 4 piston caliper only count the area of 2 pistons.
> Erich
> ---- deiland1 at elp.rr.com wrote: 
> > I've been doing more research on my brake upgrade and the following is what I 
> > have found so far. If more knowledgeable souls are out there, I welcome your 
> > input/criticism/outright yelling at me or what ever input you would like to 
> > give. 
> >  
> > I can't get to the pedal box very well since it is mounted to my car, but based 
> > on my crude measurements I think the pedal ratio is close to 4:1 if my 
> > measurements are correct. The formula for calculating Master Cylinder line 
> > pressure is: 
> > Pressure = (Leg force on the pedal) x (Pedal Ratio) divided by (Master Cylinder 
> > Piston Area). 
> > Just for comparison's sake I'm using 100 for the leg force on the pedal. Actual 
> > pressure may be more or less. 
> >  
> > 0.7500" bore MC = 0.4418 sq. in of piston area 
> > 1.0000" Bore MC = 0.7854 sq. in of piston area 
> >  
> > Therefore; OE MC with  .75" bore P= (100 * 4.33)/0.4418 = 980 psi 
> >            New MC with 1.0" bore P= (100 * 4.33)/0.7854 = 551 psi 
> >  
> > With the original 7" single diaphram booster you would gain about 494 psi of 
> > free boost on the OE MC and about 381 psi with the 1" bore MC. But with the dual 
> > diaphram MC this would increase to around 490 psi free boost. This means the 
> > total boost are as below: 
> >  
> > OE 0.75" bore with 7" SD booster 980psi + 494 psi = 1474 psi total 
> > New 1.0" bore with 7" DD booster 551psi + 490 psi = 1041 psi total 
> >  
> > Although this is about a 40% difference, when you consider the OE application 
> > was with a two piston caliper with about 3.3 sq/in of pad area compared to my 
> > new 4 piston caliper with 6.63 sq/in of pad area and slotted discs then the end 
> > result is actually improved braking over the OE even with the 1" bore MC. If I 
> > use a smaller bore MC with all my new parts I would really have a lot more force 
> > at the brake disc which may actually not be that great of an idea. 
> >  
> > I have thrown out my calculations for all to see (flawed or not) and now I wait 
> > the gunfire. 
> >  
> > Dan Eiland 
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