Radial brakes offer specific benefits for motorcycle riders, but when people talk about them, they are often unclear about whether they’re talking about the calipers or the master cylinders. Since the caliper is really a hot button issue right now in the motorcycle world, this breakdown will help to determine the best usage of radial vs axial brake calipers for people trying to decide whether the radial caliper is right for them.
The difference between radial and axial brake calipers is actually very simple, and it lies in the words radial and axial. Picture the caliper mounting bolts: On an axial caliper, the mounting bolts run parallel to the wheel axle. This means that the braking force will be distributed around the same axis that the wheel rotates around, hence the name axial. As the rotational mass of the wheel comes in contact with the brake pads inside of the caliper, there is a transfer of energy from the brake rotor into the caliper. This energy then continues through the caliper bolts into the fork tubes, and ends up in your steering head bearing, where you perceive it in your handlebars and seat. This shearing force on the caliper mounting bolts can cause a lateral movement that is known as torsional flex. This is often felt in two forms, a mushy brake lever and a slight turn/wobble in your front end.
Both the former and the latter can, however, be attributed to other problems as well, such as improperly bled brake systems or warped rotors. But if everything is within spec on your bike and you still experience these things, you will know it. Until recently, this is how every brake caliper functioned, and it will get the job done. I will repeat that again, just in case you missed it; axial brake calipers will get the job done. They always have.
Now, think back to the caliper bolts we discussed before. In a radial caliper, the mounting bolts are perpendicular to the wheel axle, as opposed to be parallel. This slight change offers a number of benefits to the way that your bike feels and performs. First and foremost, it changes the transfer of energy to the rest of your bike. As the spinning rotor transfers it kinetic energy to the caliper, it is distributed along the same axis as the wheel is rotating. Since it doesn’t rotate around the axle like the wheel is, there is no shearing force on the bolts, and no torsional flex. This translates into a much tighter brake feel and improved brake feedback. This increased feedback and better brake feel is the main benefit of using radial brake calipers.As a nice bonus, mounting calipers radially allows for them to placed farther away from the axle so that a larger rotor can be used, which is a massive improvement in its own right. We will discuss the advantages of larger rotors in an upcoming article.
So, with all other things being equal (rotor size, especially), radial brakes do not offer more braking power, but a better braking experience with more usable feedback. This allows for easier threshold braking and trail braking, ultimately shaving seconds off of your track times. And if you aren’t racing, if gives you a more substantial brake feel and improved braking feedback. In part two, we will discuss the differences in radial and axial brake master cylinders. Until then, keep it between the ditches.