Next we have Axial or 'Lug_mount' calipers and Radial calipers. Until about 2002 all calipers mounted to the fork legs through an axial or side mount design. After 2002 Brembo started to mount their top racing calipers with a radial on ‘In line’ mounting system. This was mainly to eradicate the additional flex of the original design but also has a side benefit of making it much easier to mount the calipers to different disc sizes.
Now you simply change the spacers. This started in racing but quickly became available for the major sports motorcycles and is now spreading across sports tourers and even custom cruisers. Although the performance benefit is of little use to less sporting bikes they also tend to be easier to work with and more commercially available so expect to see their use continue to spread in the future.
Then last we can examine the Two Piece and Monobloc designs. The two piece is easier and much cheaper to make and casts the caliper in two separate pieces which have a fluid seal between them and are then bolted together. The design works fine for everything other than ultra high performance but as you can imagine as you apply pressure to the opposing pistons they are effectively trying to push the two caliper halves away from each other or open them out. You can’t feel it but there is a tiny amount of movement here as the two pieces try to push away from each other.
A Monobloc caliper is forged or machined in just one piece so that it eradicates this movement and therefore ensures that all the fluid pressure is pushing on the pistons and therefore the brake pads. The most modern designs are Radial Monobloc calipers which eradicate both the flex from the lug mounts and the movement from the two pieces and are the most powerful brake calipers currently available.