What's This Extra Piece With My Rotor?

If you purchased a TC Bros. floating brake rotor for your Harley, you might have noticed it came with a small ring. And you may be wondering what it is and where it goes. Here’s the scoop on that. 

TL;DR? If you're not building an off-the-wall custom, you probably don't need the ring; set it aside. For the full story, read on.

Most builders won’t need this piece, which is an adapter. Harley-Davidson used the same brake rotor bolt pattern on their wheels on early and late motorcycles. Nominally, our brake rotors are designed for recent wheels—model year 2000 and later. However, because that bolt pattern is the same, they’ll bolt up to earlier wheels, but the hubs on those wheels are a bit smaller. Brake rotors are hub-centric, meaning they register (center) on the hub. The adapter rings help our rotors locate correctly for those using them in non-stock applications. So if your bike falls into our application list, you can just set that ring aside; you won’t be using it.

If you’re one of those intrepid individuals chucking fitment information to the wind and grafting floating discs onto an earlier set of wheels? The adapter ring will be in play, but you should know the rotors aren’t compatible with the stock calipers that correspond to those motorcycles. You’ll probably choose more modern calipers for your custom anyway, but the information may help you as you’re selecting components for your bike.

So that’s the skinny on TC Bros. rotor adapters—now you know a little more about what fits what. While most people will be installing this on the listed apps, we wanted to help out the hardcore builders whipping up something a little more "out there."