Discs (or rotors) for mountain bikes are of two categories: monobloc or two-piece (usually floating but not all two-piece discs are floating). The floating discs are made in two pieces and the track is free to move axially and in some cases also radially thanks to specific pawls. Why this feature? Because it allows, in case of slight deformation of the disc (due to heat), thanks to a slight play, to "self-align" and remain on axis.
In the motorbike world, floating brakes have many advantages, precisely by avoiding deformation of the brake (which leads to unwanted rubbing of the disc on the pad at each rotation) and the greater ability to dissipate heat. There are no real advantages in terms of braking power between fixed and floating discs.
DISADVANTAGES OF FLOATING DISCS
If you opt for floating discs, keep in mind that you will have to replace them more frequently because the connecting bushings (pawls) have deteriorated. Floating discs, in our opinion, are not the solution in MTB: many are misled by the fact that in the motorcycle sector floating discs are widely preferred to fixed ones due to the undoubted advantages of heat management and deformation.
However, in MTB, less thick discs are used compared to the motorcycle world (around 2mm compared to around 5mm in the motorcycle sector) and this may be due to the fact that a fixed MTB disc already flexes a minimum given the small thickness, while in the motorcycle world the fact of having a disc that flexes serves to avoid causing imbalances when braking, given that a 5mm disc doesn't flex at all. And, in the long run, floaters can generate inaccuracies at the plant level if they play too much.
But I admit my ignorance and, shortly, we will update the article with a record manufacturer that instead focuses heavily on floating. Stay connected.
BCA'S THOUGHT
PROJECTED IMPACT
For those looking for pure performance and precision of the braking system, (quality) fixed discs can still be a more than valid solution. Floating brakes can be useful for all those users who want to have a brake that requires less worry in terms of adjustment and remains aligned, even after long descents, but taking into consideration to keep them checked and replaced once they take on too much play.
I conclude by saying that it is important to evaluate the general quality of the disc (solid structure, quality of materials and suitable disc thickness) rather than focusing solely on whether or not it floats.
