i was just having a gander through the Rally Design website and drooling away as usual when i cam across these two pedal boxes.

Pedal Box 1

Pedal Box 2

The first has a ratio of 5:1 & the second has a ratio of 6.25:1, but i don't understand what there ratio's are for?

Cheers

Can someone please explain what they are for?

Ratio of the stroke of the foot pedal in relation to piston travel, or cable pull.

so the piston moves 1 cm when the pedal moves 5 cm?

[Edited on 21/3/10 by omega0684]

Very difficult to get a decent pedal ratio in any Seven style car even with top hinged pedals.

Even if long pedals are used to get a high pedal leverage ratio the true mechanical advantage depends on where the drivers foot makes contact with the pedal pad.

[Edited on 21/3/10 by britishtrident]

So what would be best to go for the 5 or the 6.25?

Without knowing anything about the rest of the brake system (master cylinder piston sizes, caliper piston sizes and quantity, brake disc diameter) that's rather like asking how long a piece of string is!

However, without a servo most people are looking for the most braking they can get from a given pedal force. You should therefore go for the longer pedal (6.25); the compromise is you will end up with a bit more travel.

You need to check the dimensions first other wise you could find you are operating the pedals with your heels --- a rather over priced mistake.

you can find dimensioned drawings at the wilwood site.