[Fot] Pedal ratio correction

[Shane Ingate]

Kas Kastner wrote:

> Jimmy Coan just called me and reminded me that when I did that pedal box
and
> worked out the pedal ratio that it was WRONG and that I had to increase the
> ratio to 7 to 1 as we could only get about 700 pounds pressure with the
other
> ratio of 4.5.  With the corrected ratio the pressure went right up to 1500
> pounds. My excuse is: I FORGOT.

When I built my brake system, I computed the numbers for a stock TR6 brake
system without the servo and a pedal ratio of 4.36 (rather than the paltry
stock 3.5).  110 lbs of foot pressure (appropriate for "emergency" braking)
on this pedal gives a theoretical pressure at the pads of 1259 pounds.  700
pounds at the pads requires around 60 lbs of foot pressure.  But this is all
theoretical and the real world does include a lot of losses.

I stayed with a ratio of 4.36 because I am running Wilwood 4-pots on 11"-13"
vented rotors all round.  Unsprung weight for this (and Southwick hubs) is
the same as the stock brakes.

For a good treatise on modern and racing brake technology, I use Mavrigian
and Carley's "Brake Systems", published by HP Books.  Dated 1998 so it is a
bit
old, but non-computerized off-the-shelf systems have not changed much since
then.

Shane Ingate at 7,500' in NM.

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