Just curious if you guys notice that on the bi-turbo CL600's have small front calipers as compared to the SL600 which has the big 8-piston calipers similar to the 65/55 vehicles. Are the calipers a direct swap? Are the rotors different size? Hopefully someone can shed some light on this because the parts to switch over are cheaper than a Brembo upgrade. thanks

AFAIK (and that's generally not much) the SL55 brakes are the same as the SL600 brakes, albeit with a different logo on the calipher.

The CL600 brakes should then be related to some S-Class brakes one would think...

Could have to do with the size of the wheels? The SL55/SL600 brakes need an 18"+ wheel.