I'm upgrading wheels on a cross bike. My new wheels are centerlock disc whereas current ones are iso 6-bolt, so I have to buy some new centerlock rotors. I'm confused about the lock rings. Shimano centerlock rotors seem to ship with some kind of lock ring, whereas SRAM centerline rotors don't. What are these lock rings and do I need to buy them separately if I go with the SRAM rotors?
SRAM discs also come with lock rings. Standard lock rings get screwed on with an cassette tool. If you have a 15 mm thru axle on the front wheel, you will need an special lock ring, because the tool wont fit between axle and ring, and the right tool (probably an bottom bracket tool). If your old discs are still in good shape you could use centerlock adapters. Lock rings and adapters are sometimes included in new wheel sets. Check that, so you don't buy them twice.