[Healeys] Reducing pedal pressure for clutch

[David Nock]

By changing the ratio of the pedal you can increase the amount of  
pressure that is applied to the master cylinder. So if you raise the  
attaching location of the master cylinder push rod my 1.2 and inch  
you increase the pedal ratio from 4.89:1 to 6.3:1. This increase in  
ratio will reduce the required pressure to operate the pedal.

So assuming that it requires 50 lbs of pressure to depress the  
original clutch pedal now it will only require 38 lbs pressure to  
depress the pedal and still have the same amount applied to the  
master cylinder pushrod.

DO NOT DO THIS TO THE BRAKE MASTER CYLINDER. This is how we  
discovered this



David Nock
British Car Specialists
Stockton Ca 95205
209-948-8767

www.britishcarspecialists.com
.
.

On Jun 17, 2010, at 11:03 PM, PG wrote:

> Hi David,
>
> What do you mean "drilled .5" higher"?
>
> Paul
>
> -----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
> 209-948-8767
>
> www.britishcarspecialists.com
> .
> .
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