Play in rear brake caliper...

[interceptor44]

Was checking my rear brake pads (look ok) and noticed that the caliper has some play in it.
Was able to wiggle it and move up and down slightly...guessing not normal. What could it be?

 

[ST1100Y]

What could it be?

Normal part clearance to keep it functional...
The caliper bracket is hinged on the axle, rotation prevented by the stop-bolt at the forward end; as this is supposed to flex, some clearance there...
The caliper itself "floats" on the bracket, steel pins suited inside sealed rubber grommets, otherwise it couldn't compensate/adjust to pad wear (and transfer horribly vibrations into the undercarriage), hence more clearance points given, resulting in some movement while trying to wiggle it...

Pretty much every automotive disk brake (probably also aviation ones) are utilizing and rely on this designs/elements...

 

[Upt' North]

+1 @ST1100Y you may feel some normal movement......but.......with brakes I would check it out.
Look for pin and pivot wear and it'll be a good excuse to clean things up.
As an aside I've also had a rear disc crack around its mounts so you could give that a good look over too.
Good luck.
Upt'North.

 

[SMSW]

Was checking my rear brake pads (look ok) and noticed that the caliper has some play in it.
Was able to wiggle it and move up and down slightly...guessing not normal. What could it be?

Short answer is it could be wear. There have been other discussions of the stopper bolt (steel) wearing 'chatter marks' or the hole in the caliper (aluminum and softer) into an other than round hole. Inspect these and all contact surfaces for wear. What you are feeling could also be normal. Its hard to quantify these things by reading someone's description but from what I've seen, there has never been much play (aka wiggle) in these parts, only a little. (Yes, I know, you cannot quantify what I mean by 'not much' and 'only a little', sorry).