Quote:
Originally Posted by Captain Caveman
I have been doing lots of research into doing a properly matched BBK retrofit, with calipers that have as close to stock piston area and front/rear bias as possible.
My first consideration was the F8X setup as it would seem a no brainer, however despite the relatively simple fitment, I've realised that the M4 has a 10% smaller total piston area than the E92 M3, which means a 10% firmer pedal with 10% less modulation, and 10% less torque at the piston.
Here are the caliper stats side by side:
E92 M3 calipers
Stock M3 piston area front 60mm - 2826 x 2
Stock M3 piston area rear 46mm - 1661 x 2
Stock M3 total area 4487
Stock front bias 63%
M4 calipers
F8X M3/M4 front BB-43 (40/40x30mm) - 2512 x 2
F8X M3/M4 rear BB-22 (44x24mm) - 1520 x 2
Total 4032 - 10% firmer - Stock bias 62%
Ideally you want to find calipers that maintain the total piston area to match the capacity of the master cylinder. If you compare the E92 specs with even the Stoptech setup, we can see that even they deliberately only differ total piston area by 1% and shift the bias slightly rearward:
Stoptech BBK
Stoptech non Trophy st60 front = 36/36/30 - 2741 x2
Stoptech Trophy ST60 32/34/36mm = 2729 x 2
Stoptech st40 355 back = 34mm 32mm - 1711 x 2
Total 4452 or 4440 x2 / 1% harder 61.5 front bias
To keep as close to stock piston area, ideally you need to find a combination of front and rear that are RADIAL mount to allow for easy bracket fabrication, NOT lug mount. Ideally with the following piston configurations, :
Front 6 Pot
32/34/38mm - 2845 x 2
30/34/38mm - 2748 x 2
30/36/36mm - 2741 x 2
32/34/36mm - 2729 x 2
Rear 4 Pot
34/32mm - 1711 x 2
30/34mm - 1614 x 2
32/32mm - 1608 x 2
Hope that's useful.
Mart.
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Really good info here.. Thank you.
Just a few questions,
Quote:
Originally Posted by Captain Caveman
E92 M3 calipers
Stock M3 piston area front 60mm - 2826 x 2
Stock M3 piston area rear 46mm - 1661 x 2
Stock M3 total area 4487
Stock front bias 63%
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Stock M3 piston area front is 2826 x 2 calipers, right? one piston each caliper and each side.
Quote:
Originally Posted by Captain Caveman
Front 6 Pot
32/34/38mm - 2845 x 2
30/34/38mm - 2748 x 2
30/36/36mm - 2741 x 2
32/34/36mm - 2729 x 2
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And these for example, 6 pistons with 32/34/38 is 2845 x2 also per caliper?
1 caliper OEM is 60mm which is 2826
vs
1 caliper 6 pistons is 32/34/38 at 3 pistons each side is 2845, so 1 caliper is 2845 x 2 which is 5690 per caliper?
Just curious.