Disc brake alignment- intermittent brake rub

I have 2 unicycles that both have a bit of brake rub with the rotor to the caliper. It’s not continuous as I hear it with each wheel rotation, not continuously. It seems like something is slightly misaligned, but I don’t know how or what to adjust. Can you give me any pointers? Is there a way to widen the caliper a bit? I suppose this is not preferred as it doesn’t really address the alignment, but maybe it is good enough?

I do not have much experience with these brakes. I’m used to the old cable side pull brakes on bicycles. Discs are new to me.

One brake is a Tektro Auriga Sub on a Nimbus, and the other is a Shimano on a KH27.5 (can’t see the brake model info on this one).

I’ve not done this on a unicycle, but on my bicycle, there are curved/nested spacers. I slackened the bolts just enough. applied the brake, tightened the bolt, and released the brake. Hey presto! Callipers now aligned with the disc.

That is always step one for me when mounting a brake, as it is the easiest way to align it. If your disk isn’t bent too badly, and the pistons are able to fully retract, this will fix rubbing.

You can check if your disk is bent visually, by looking at the disk through the slot in the brake caliper, and turning the wheel. If it is bent, you can either buy a fancy tool to bend it into shape, or (which has worked for me) use your hands.

I had one set of brakes that required a good clean of the pistons to get them to retract fully again, and that did fix the rubbing issue I was chasing. If the pistons don’t move quite freely, any tiny amount of a bent disk will rub.

If you need to straighten the disk you can use your hands as finnspin suggests, just make sure to wear gloves to avoid transferring oil from your fingers to the disk. Also if it’s a well used disk the outer edge may be sharp!

You can make the fancy tool easily enough with a chunk of wood and a saw, or even use a crescent wrench if you are really careful.

Just watch the rotor inside the caliper while spinning it slowly to see where it’s bent.

Very minor intermittent rubbing is normal on many models of break, but it shouldn’t be every rotation.

Thanks for the advice. I found this from Park Tool that also has helpful information and let me see what to look for: https://www.youtube.com/watch?v=uk_nC9anQcM Hopefully the rotor is not bent. I’ll try the re-centering first.

The fancy tool can be replaced by an adjustable spanner. You adjust it to the thickness of the disc and voilà. Then it’s all about truing the disc gently, not over bending it.