early 944 brakes, stock MC....dosent feel right

[Pillow]

This 23/20 versus 23/19 really pisses me off with 944 N/A brakes!

with a 23/20 (actual 23.81 / 20.64) = 1.69 bias (a little too high I think)

with a 23/19 (actual 23.81 / 19.05) = 1.44 bias (as staded before and a very good bias IMO!)

Arg!

[1303R]

i know this is an old thread but i'm trying to work out my brakes. i have n/a 944 fitted along with m/c. i find the brakes a lill front heavy. i work out the ratio to be 1.53. now if i changed the rear calipers to a 40mm piston the ratio would be 1.25. but what is the best set up for a street driven car? would i be better off having more rear brakes and maybe a proportioning limiter?

[1303R]

oh hang on. i get 1.44 ratio going off of 23.81 and 19.05 mm m/c sizes. is this deffiatly the right size bore?

[Eliasson]

Hi
I rememberd that I read some articles about brakes.
Here is something for all brake-a-holics....

http://www.stoptech.com/tech_info/te...e_papers.shtml

[speedy]

i have read the thread and done the mechanical advantage calculations , but am confussed , i understand the ratio of mc to caliper size but if we have a split bore mc and the front and back pistons move the same amount the 23 will displace more fluid in comparison to the 19 for the same amount of movement , the pressure that can be applied is regulated by the 23 piston because of its bigger size according to the formulea (lower ratio).does this make sense or am i missing something . i aggree the 19 can apply a higher ratio of hydralic pressure but cannot displace as much fluide when on the same shaft as a 23mm piston .Does the 944 front and back pistons work independantly , this is the only possible solution i can think of . Can somebody please clarify the answer or am i going nuts
cheers jon

[speedy]

been thinking about this all day and it is sending me nuts , i thought i would give an example and somebody could correct it if i am incorrect .
say if we using wallys calculations (54mm caliper cup diameter / 23 mm front m/c cup diameter)²= 5.51
944 rears:
(36mm rear caliper cup / 19.06 mm rear m/c cup diameter)²= 3.57
F/R ratio would then be 1.54
i understand this this is the ratio of mechanical advantage but and this is the thing i cannot get my head round area is pi r squared so half 23squared *3.1472=419
and half19squared *3.1472=284
so for 1 mm of movement the 23mm piston displaces 419mm of fluide and the 19mm piston 284 mm of fluid if they are on the same shaft then the limiting factor is the amount of force that can be applied to the 23mm piston , as far as ican see increasing the size of the front mc piston will decrease the mechanical ratio but increase the force on the front caliper pistons therefore increasing the bias because the rear cannot displace as much fluid for the same movement please help
jon

[1303R]

ahh. i see what you mean. have you tried contacting a brake specialist by email and see what they say? maybe worth trying a few different ones.