Calculating key dimensions for custom brake systems

by Steve Strain

Brakes excel file

Hi all,
To the left is a copy of the spreadsheet tool I spoke about at clubnight Jul 12th 2016 for your info.
There were two versions presented. The “Original” modeled the Fiat/Lancia brake combination as recommended by my cars manufacturer, the second “Wilwood” models the cars current brake configuration. I suggest club members use the tool to model their cars current brake configuration.
Note that the objective of the tool was not to calculate the absolute result (i.e. braking force to 100% accuracy) but to model the effect of mixing and matching various components to arrive at a component mix that achieved my desired 60/40 brake force distribution withsome adjustability.
What I wanted to do was avoid the risk of buying something that did not suit mine and the Strato’s unique mix of requirements i.e. differing wheel diameters front to rear, 40/60 weight distribution, and my desired 60/40 brake bias with the front wheels locking just before the rears etc.
The Wilwood set up I have is not the best quality by any means as it was built to a budget using their cheaper components. The reason I chose Wilwood at the time was because they have a catalogue that I could choose components from with all the detailed dimensions.
My only tip if doing this again would be to buy radial mounted calipers because of easy adjustment (i.e. not the side mounted) and only buy calipers with assembly bolts that straddle either side of the pistons centre line. This avoids any flexing and a soft pedal.
The calculations are in lbs and inches as is the Wilwood catalogue.
To model your own system a good starting point is to determine your approximate input brake force. My 19-23kg’s or 50lbs input was determined by sitting on the floor and pushing the bathroom scales into the wall. I determined that 19-20kg would be a modest stop whereas 23-25kg would be a hard stop. The rest of the measurements can be made with a set of digital Vernier Calliper’s (mine has both inches and mm).

Because braking performance depends on so many other factors such as tyre choice, pads used, weather and road conditions, suspension design and its condition and your budget, NO responsibility for any errors or omissions is implied or accepted. Use the tool at your own risk.

The full article was published in the August 2011 Spare Parts Magazine ... see Page 18