Brake pedal ratio needed? 6-1 or 7-1

[Crosley.In.AZ]

I am looking around for brake pedals and ratios used.

I see brake pedal with cylinders complete unit  listed as 6-1 ratio in the pedals that mount on the floor.  If the pedals mount under the dash , they list the ratio as 7-1

I am looking at Wilwood stuff for information.  Dual master cylinders mounted on the bracket with pedal

The Wilwood calipers I have on the rearend need a 7/8" cylinder.

It appears a 7/8 cylinder will operate the front VW disc calipers too

[parklane]

Always been told 6 to 1, but haven't read up on that lately, so could be wrong.

[ragdol]

I would say that the 7:1 ratio is needed on swinging pedals because the rod is located below the pivot point 1/7th resulting in a 6:1 ratio.

[phat rat]

I would say that the 7:1 ratio is needed on swinging pedals because the rod is located below the pivot point 1/7th resulting in a 6:1 ratio.

Not quite the way you figure pedal ratio. Here's a diagram.

http://www.mpbrakes.com/uploads/documents/pedalratiopdf.pdf

A little more info here

http://www.piratejack.net/index.php?option=com_content&view=article&id=14&Itemid=21

[Warpspeed]

It depends on pedal stroke, and how high the pedal ends up off the floor.

You want the master cylinder to bottom out just as the pedal hits the floor, so pedal ratio ultimately determines pedal height.

A larger motion ratio creates more force, but if the pedal ends up too high, it becomes awkward to lift your foot that high quickly in an emergency.

Get the stroke right, then adjust fluid displacement with the master cylinder bore size, and force by selecting an appropriate vacuum booster.

[Hooley]

Crosley,
            We run the wilwood duel master cyl. with their floor mounted peddle on the Henry J.  It is 4 wheel disc non power brakes. It stops better than any thing else that I have built in the past.  
The Stude [974] I used 69 corvett master cyl with 4 wheel non power GM brakes.  It didn't stop very well but at Bonneville but there is lots of room to stop. When I got ready to do the Texas Mile I went over the brake system after talking with a Wilwood Tech guy. FOUND a 4:1 peddle ratio which had been the peddle assemble from a Camero. Changed the ratio to a 6:1 and have great brakes. Not as good as the Wilwood.
 I would think that the peddle ratio depends on if it is power brakes or not.

Just my thoughts
Good luck with it,
Hooley

[jaybee]

Exactly. Nonpower brakes use a higher pedal ratio than power brakes in order to increase mechanical advantage.