Originally Posted by Grenade10

If it is on the left, non gear side it is probably the clamping hub. I had to machine mine, as it gets off square when you clamp it to the axle. Did not take much to clean it up on the lathe, just need a to have a shaft the same dia as your carbon axle (yes there are some tolerance in these) clamp it to the axle and then cut the mounting face until you just kiss all the surfaces. Red anodize is a good "Guide Coat".