Re:GTV Master Cylinders

["jkb83" <jkb83@domain.elided>]

Dan,

If everything else (calipers and linkages) are the same, the larger the MC 
diameter, the higher the pedal effort.  The increase is proportional to the area 
of the piston (or square of the diameter).

So, this means that
  (22/19)^2 = 1.34  ---> 22 mm needs 34% more pedal effort than 19 mm
  (23/19)^2 = 1.47  ---> 23 mm needs 47% more pedal effort than 19 mm
  (23/22)^2 = 1.09  ---> 23 mm needs  9% more pedal effort than 22 mm

Another thing to think about is how it will compare to the stock setup.  If you 
increase both the caliper piston area (over stock) and the MC piston area (over 
stock) by the same percentage, then you will have the same pedal effort and the 
same pedal travel as before.  If you increase the caliper area by a higher 
percentage than the MC, then you will have less pedal effort and more pedal 
travel than before.

You need to make sure the MC diameter is large enough so that you dont run out 
of pedal travel!

John Basel

On Mon, 03 Feb 2003 Dan Walker wrote:

>I am putting 4-pot BMW front calipers on my 74 GTV ( thanks Dean ) and I 
>bought a new 22mm brake master cylinder to replace the old 20mm unit since 
>it would move more fluid.  I just found out that Bruce's parts bin has 23mm 
>m/c's now.  Would that give any more advantage ?  What is the relationship 
>between m/c size and braking force or ease of use ?
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