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View Full Version : pedal force? / boost or no?


dannyho
10-06-2006, 07:48 AM
I'm plannign the brake system of my car and ran into a snag because the damn thing is so heavy. the brake brake force becomes really high to get any impressive performance out of the thing.
what would you say the braking force of your cars is at maximum decelleration? right at the point of lockup. Also please mention the weight of that car and anything else pertinent.

second question is a little more technical. my car weighs 4000 pounds, I'm not a weak guy so it wont be that much of burden, but am I just sootig for something that's impossible without a boosted setup , hydro or vacuum. I'm aiming high, but I definately like the 60-0 in around 100 feet. that's roughly 1.24g average. pipe dream, but is it possible?

I've been using the attatched spreadsheet to figure this out, but It doesnt have anything if i wanted to do a single master cylinder or boosted.
paul67
10-06-2006, 11:49 AM
In the old days it used to be 9 to 1 nonservo ,7to1 servo ratio thats the 9" length of pedal to pin, pin to the master cyl 1" arm side .
dannyho
10-07-2006, 06:56 AM
right but what i wanted to know how much force i should be aiming for in maximum stopping, not the pedal ratio, thanks though
paul67
10-07-2006, 07:08 AM
I would think its also to do with calipers 2-4-6 piston, rotor dia 11" 12" 13", pads , road ,road-track, track only , wheel dia , tire width, master cyl bore.
dannyho
10-07-2006, 07:17 AM
I came acros this set of data from some DOT tests. Maybe someone can help me make sense of it. it's saying that under maximum braking they used between 150 and 200 lb force, which seems like a lot, but i guess i could be wrong.
http://www.nhtsa.dot.gov/cars/problems/studies/brakes/Phase2/apph.html
they tested 4 vehicles, a chevy astro, blazer, f150 and a malibu
here's the page for the introduction to the tests
http://www.nhtsa.dot.gov/cars/problems/studies/brakes/Phase2/COVER.html

If this is the case I see no reason I can't go with a dual master cylinder and no power brakes.

this isnt a question of how much force i'm going to need, but rather, how much is acceptable. if its too high it'll feel like a completely solid pedal which is not good. But i dont have any feel for what is too much.
i know how to match sizes and everything, look at the spreadsheet it's all in there