Yes, that is weird.
Weirder is that my early 944 M/C has 23 cast in into the M/C housing for front and 19 cast in for the rear. This would 'suggest' a 'perfect' 23,00 mm and a exact 19,00 mm. :confused:
I haven't taken it apart to verify this tho (and its on the car now)
Maybe there are more different sizes made to suit different countries...who knows?

Best regards,
Walter

Hello,

I have lent (sp?) my aluminum 944 Turbo MC to a friend but I hope to get it back one of these days.
Not sure anymore what it said on the outside but as soon as I get it back I'll take it apart and measure the pistons.

Cheers,
Richard

my 85 944na m/c is 23mm/19mm.why would the bores be 12/16" when origenaly from germany and would be metric.
the bias realy is a presonal thing , i run 85 na brakes all round and have the 23 to the rear and 19 to the front with 7x16 205/55/16 front and 8x16 225/50/16 back.works spot on for me.
cheers rob

just fitted an audi a80 coupe one to the fasty..
 

pics

20.65mm dia. bore to run my setup comprising front audi coupe calipers and rear mk4 alloy calipers - cheap e-bay bargain new genuine ATE item ! - not bled them yet - hope it works ! straight bolt on fitment NO mods needed to mast cyl. only rod off brake pedal had to be lengthened 15mm. WHAT A FIT THOUGH ! :laugh:

comparison pic..
 

:cool: amazing 30 years difference !

Yeah, 30 years on and still imperial!

I bet the SAE are to blame for that :rolleyes:

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!

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?

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?

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

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

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

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.

Well i have been running my early N/A 944 setup (from and rear stock) with the stock M/C (19 front 23 rear) and have to say thay it is front bias (to much really, as i lock up to early due to the very little weight transfer of a 1303 under breaking). i have done 6 Autocross sessions with this set up, and have found adding weight (60 lbs) to the front of the car HELPs A LOT with breaking AND turning (no more scrunbbing in mid turn). anyways im going to swap the front to rear lines Ex: 23mm front and 19mm rear. this should give me more of the rear bias that im looking for. If i get time this week to do it i will post back. Im going to do another Autocross session this weekend.

i am right in thinking the 23mm front circuit is the end nearest the driver, 19mm rear is furthest?