Too often we spoke to drivers who were using what they believed to be an ideal pedal ratio, only to be let down by cylinder stroke and bore choice, or, the geometry of the pedal box itself. Like any racer or engineer worth their salt, we went back to the beginning and looked at the physics and what we found astonished us. Through redesigning the pedal linkage system and master cylinder integration, we were able to maximise the mechanical advantage available with a geometric ratio varying between 3.5:1 to 4.5:1
Pedal Ratio is the mechanical advantage, easiest described as being pedal lever length to pushrod actuation length ratio, which is your effective lever.
So that being said, there’s more to it right?
The pedal ratio is only one part of four main influencing factors, the second is master cylinder bore, third is master cylinder stroke and finally your calliper pistons area.
To put this into perspective, you have the mechanical advantage (pedal ratio) and you also have master cylinder hydraulic advantage (bore area and stroke) and calliper hydraulic advantage (bore areas & stroke).
These elements when combined will place a force (work out) at your brake pad which is equal to your pedal input (work in), there may be some losses due to friction etc., but for the purpose of this example, we are excluding system efficiency.
The PE Racing series pedal assemblies are designed to be more compact, thus a lower pedal ratio than normal, but a longer stroke master cylinder (approx. 30% longer stroke) to increase the hydraulic ratio as a result, thus still giving the same pressure & displacement outputs for equivalent pedal forces & pedal travel rates. Both the Fabricated series and Billet series are designed to accept Girling type universal Master Cylinders in a variety of cylinders bore sizes – 5/8″, 0.7″ and 3/4″ with a maximum stroke of 34.9mm (1.375″).