[Go Horns!]

I did some back-of-the-envelope calculations last night on some BBK kits I am considering to see how they would effect brake bias.

Based on 25mm piston for the front and 22mm for the rear, I calculated that stock setup has approximately a 57% front bias.

The first BBK setup would be about $3000 and would change the brake bias to about 65%.

The second setup would be about $4200 and would change the brake bias to about 61%.

I would rather not say who the manufactures are because my calculations may be off. I think I am close, but I am not an expert.

Car is a 2013 335is coupe. Right now it is a DD, but once CPO is done, I plan to track the car. I wasn't planning to buy a BBK right away, but if I can get front and rear for $3k. I figured I would go for it. Is changing the bias by 8% too much? Will I increase stopping distance? Or is it close enough to not matter?

[feuer]

There is a thread for brake system coding. BMW's with factory Performace brakes have different coding that introduces more front bias. I assume when these BBK were "design" for this platform, those manufacturers weren't aware that different coding is available so they opted different route to achieve more front bias.
http://www.e90post.com/forums/showthread.php?t=1317220
http://www.onelapx1.com/blog/how-to-...w-actually-fun

[Go Horns!]

Did some more research. Looks like I had bad info on stock piston sizes. Read that 335i calipers and M3 calipers are same size. M3 pistons are 60 for the front and 46 for the back. Rough calculation is a 63.5% front bias for the 335i.

[feuer]

No, 335i and M3 calipers aren't the same. They use same pad but pistons are different, I think is 57 vs 60. Also master cylindersuite are different.