For the Harder Driver and motorsport, we also make our own 2 piece grooved discs and alloy anodised bells. We make discs as direct replacements for many cars to fit with the standard factory fitted calipers. We can also offer replacement for AP or Alcon Kits etc.
A two piece disc is far better than the heavier factory fitted one piece disc. A lighter disc will reduce the unsprung weight so will give the suspention an easier time.
As the centre bell is made from billet alluminium, alloy dissipates heat quicker than an all iron steel disc so will run cooler and you will have less heat transfer through to the bearings
As the discs and bells are bolted together, when they heat up and cool down (expand and contract) the discs can move very slightly on the bell which stops the disc and bell warping or going out of shape
As the bells are bolted in place, when the discs wear down and need replacing you only have to replace the outer rotor so works out much cheaper