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Old January 1st 2005, 18:14
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MattKab MattKab is offline
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Join Date: Jul 2002
Location: NW UK
Posts: 371
First of all Happy new year to all!

Shad's formula is standard textbook mechanical advantage formula. As Shad mentioned in his post, we are fortunate, in that we can use the formula in it's stripped down, simplified version. We can ignore factors like friction, radial differences front to rear, pad area, etc. as these can be considered to be constants

Like Wally, I still have the 3/4" T1 m/c and 40/36mm & 30/28mm Brembos (~15,000miles)

I got to a value of 1.72 to the front and I had 1.23 as the bias of NA 944 rears/T1 front and a T1 m/c.

If we had the 1986 only 944T Front calipers with their 36/34mm pots, we would have a bias of 1.45

This compares very well to the stock NA 944 with the Ate calipers bias of 1.44

Now compare this to the very earliest 911 which had a bias of 1.88 for the first year. This was then changed to 1.6

By lengthy mathematic (plus assumptions) I get the T1 front/CB roto hub and stock m/c to have a bias of 1.38

I put Al B's gold custom Bug (with the cool 'flame' wheels and ALL new parts) on our Arex computer test lane and I recorded stock T1discs/drums and m/c to have a bias of 1.57

I have 'invented' an m/c that can be 'made' for our Brembo 4pot systems that will yield a bias of 1.47...

If I fitted the Kerscher split bore m/c my bias would be down to 1.3

m/c bore has no affect on bias, just the leverage ratio.

Feel free to challenge my values, I still have the pages of arithmetic I used. Plus many possible configurations, feel free to ask.

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