[Ron Sutton]

Hey Guys,

Rob & I already discussed this on the phone, but I figured I'd catch up the details for anyone following along.

Originally Posted by FETorino

Ron

You didn't expect a technical discussion with this crowd on this thread did you
No ... not in my wildest dreams.


Great seeing you at the Lat G party and at Optima. Sorry I missed Phx.
It was great meeting you and a lot of guys on from Lat G. The party was fun.
Even my racing buddy Randy that tagged along had fun.

Time for some brake tech


Previously on the forum you had run some brake calculations for me that are now slightly out the window. As I progressed on my engine setback project I abandoned my swing pedals and dual master setup. Buried a few post back under the ribbing you can see I posted about it.

I purchased a set of floor pedals but as with all floor pedals their ratio is limited. They are 5.75 to 1 at best so using the 100lbs std driver force there is an obvious loss in clamping force.

My floor pedals have a .875 and .813 master cylinders. Intuitively I would think with the lower pedal ratio of 5.75 maybe I should be running the .813 master for the front and a .750 for the rear to raise the line pressure and achieve a total braking force closer to 4000.

I also understand we could achieve more braking force through the use of a higher COF pad.

Intuitively doesn't make for much of a scientific discussion so plugging in the master sizes and new pedal ratio into your chart would be the best starting point for a discussion.

I also understand that setting my overall suspension parameters, either tweener or high travel, will also dictate what brake bias 65/35 or 70/30 we are targeting.

Based on the front suspension travel I think you'll end up with, you will probably need around 70% front braking.

The cool thing with adjustable bias in the pedals is you can fine tune the bias to perfection without giving up any total braking force. (Unlike a proportioning valve which reduces braking force).

Changing from the planned 6-1 pedal ratio to 5.75-1 is a small change. Only a 4% reduction in fact. That does not dictate a MC change, as that would produce a much larger increase, of about 16%.

As you can see from my calcs below, dropping 1 step on both M/Cs puts it over 4000# of braking force, which in my experience is too much braking force for a mid-to-high travel suspension strategy. I think you'll find 3562# is plenty of braking force.

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On another note, I do these calcs based on 100# of leg force at the pedal. In the racing world, we "tune & adjust" braking to fit the driver all the time. 100# is just a starting baseline #.

For smaller drivers ... I have raced cars with champion female drivers that weighed 100# and male drivers as young as 12 that weighed 72# ... I designed a brake package that decreased the amount of leg force required.

We don't want the pedal to be too hard to push, or you wear the driver out over long races ... and you don't want it to be too easy to push ... making it too easy to lock up the brakes. In then end, it's all about tailoring it to the driver.

For those of you who haven't met Rob, he's a big fella. So Rob, I'm thinking you pushing the brake pedal with 100# of force will be easy. I feel we need to be concerned that we don't make the brakes too easy for you to lock up.

Let's start with what I originally outlined but with the 5.75-1 pedals ... making 3562# total braking at 100# of leg pressure ... and see how the braking characteristics fit you. We'll "tune & adjust" to your tastes after you and the car get up to speed.