AlterZgo

I honestly don't know what the big deal is. Heat/cold expansion and contraction is not going to be enough to make the caliper hit the rim. Once the test fit confirms there's no contact - even if there's 1 mm of space - they will NEVER touch each other unless you seriously bend the rim or the brake caliper assembly comes loose.

Think about all of the metal things that get hot - for example, say a turbocharger. They get so hot that they literally glow red. The turbo impeller is super close to the housing - I'd venture to guess much closer than the caliper to rim clearance of an 18" G37 rim to the 14" brake caliper. Does the high heat of the turbo cause the impeller to expand and hit the inner wall of the housing? Of course not!

As long as there's a few mm of clearance btw the brake caliper and the rim, it'll be absolutely fine. If you end up having rubbing issues, you have bigger problems to worry about - like a loose brake caliper or a bent spoke on your rim.