Cyclocross rules allow the use of tyres up to 33 mm in width. This is a tool for  race organizers to check compliance. I made two versions, a slimmer and a beefier one. The slimmer one easily flexes by 0.5 mm just from finger pressure, but is probably adequate for the job.

I'm quite proud of the handle where a torus touches a sphere. The trig required some schoolboy puzzle solving, as this is modeled in OpenSCAD.

Print with support.