[Healeys] Reducing pedal pressure for clutch

PG britishcars at shaw.ca
Fri Jun 18 00:03:24 MDT 2010

Hi David,

What do you mean "drilled .5" higher"?


-----Original Message-----
From: healeys-bounces at autox.team.net [mailto:healeys-bounces at autox.team.net]
On Behalf Of David Nock
Sent: Tuesday, June 15, 2010 10:05 AM
To: Healey List List
Subject: [Healeys] Reducing pedal pressure for clutch

We had a car here in the shop that had a problem after a brake
rebuild. The pedal was always soft and no matter what we could not
get a hard pedal. The owner was crippled in one leg and was very
weak. What we found was the flex hoses were swelling when you pressed
on the pedal. The cause of the swelling was that the attachment point
of the master cylinder push rod had been re drilled about 1/2 higher.

Now the original pedal has a ratio of 4.89:1. So assuming 50lbs of
pedal pressure at this ratio your actually on the master cylinder
push rod is 245 lbs.  So if you move the attachment point up by 1/2
inch the ratio is now 6.3:1. Now with 50 lbs of pedal pressure the
applied pressure at the cylinder is 315 lbs.

So to get the same amount of applied pressure at the master cylinder
with a ratio of 6.3:1 you will only need to apply 38 lbs at the pedal.

Now to move the attachment point you would need to remove the pedal
and re drill a hole for the clevis attachment.

David Nock
British Car Specialists
Stockton Ca 95205

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