Front Disc Run-out Checking - Spacer Suggestions?

[Randyjim]

Hi!

I'm planning on changing the front disc and pads on my ZT190 this weekend as I need to cure some brake judder. I will be checking the hubs and discs for run out of course, but I've found in the past that the wheel bolts are too long to hold the discs true to the hub without a spacer.

Does anybody have a suggestion for a handy bit of garage detritus that serves the purpose. I'm sure there must be something knocking around I can use, even if it's a left-field as a pair of bog roll tubes or some old spark plugs.