Everytime you pull on your motorcycle’s brake lever, a lot of mechanical wizardry goes on behind the scenes to slow your beloved steed down. The moment the lever is pulled in even a fraction of a millimeter, hydraulic fluid travels from your master cylinder, through your brake lines, ABS pump (if your bike has one), and into your caliper. From there, it pushes the pistons of your caliper out, where in turn, they push on the brake pads, which squeeze on the rotor, slowing you down.
Technically speaking, brakes work by converting kinetic energy into heat—exactly what happens when you slow down. This is where even more technology comes into play, particularly with your brake rotors. If you head over to your garage right now and take a look at your motorcycle’s brake rotors, you’ll probably notice one out of two things. If you have a performance-oriented machine, say, a Yamaha XSR700, you’ll notice that your front discs are composed of two main components—the rotor itself, and a centerpiece to which it’s riveted.
This construction is referred to as a floating rotor, because the rotor is technically floating from where it’s mounted to the wheel of the motorcycle. If you watch the video above from Revzilla’s The Shop Manual, Ari Henning does an excellent job of going into great detail about why floating rotors are ideal for performance-oriented machines. At the end of the day, it’s all about heat dissipation and pad contact. Floating rotors are better equipped to handle sudden changes in temperature thanks to the fact that they can move around their mounting point, as opposed to solid discs which are more prone to warping from excessive heat.
As the name suggests, solid rotors are, well, solid. As solid as this may seem, they’re actually more prone to warping as opposed to their floating counterparts. This is because their one-piece assembly means that the likelihood of the rotor warping close to the mounting points or “spokes” is much greater, as this is typically the weakest area of the component. This is also why floating rotors are called as such, because there’s a tiny air gap between the rotor and the center where it’s riveted.
Now, solid rotors do have one major advantage, and it’s cost. Given that they can be stamped from a solid piece of steel means that they’re incredibly cheap to produce. This is why you’ll most commonly find solid rotors on small bikes such as scooters, underbones, and commuters. Nevertheless, under nearly all road-oriented situations, solid rotors should be more than capable of surviving high temperatures generated by braking. As such, you probably don’t need to worry too much if your motorcycle is equipped with solid discs. On big bikes, however, solid discs are usually found on entry level models like the KTM 390 Duke and Royal Enfield Himalayan, as well as the rear brakes of other premium models.
Is it worth upgrading to floating discs?
If you ride your motorcycle primarily on the street for commuting or touring purposes, chances are you’ll do just fine on solid discs. I even rode my KTM 390 Duke, equipped with stock solid rotors, on the race track a couple of times, and never had any issues with braking performance. Nevertheless, you can’t deny that floating discs look much cooler than solid discs, so if you have the spare cash lying around, sure, why not? Now, if you plan on racing, or taking your bike on frequent track days, then absolutely. Upgrading to floating discs will certainly provide better braking feel, longevity, and overall performance.