On Monday, March 13, 2017 at 9:27:24 PM UTC-7, ERSHC wrote:

If it has 89mm clearance with 175s then you can ride it with 175s. If
it has only 90 mm clearance with 165s then you can't ride it with
175s. You don't measure a frame, you measure a complete bike. Legal
with 165 mm cranks and not legal with 175s is possible. One might
question the sanity of some of the UCI rules, and of course they don't
apply to non-racers, but thems the rules none the less. So if you
spring for a custom bike with the intent to race it, and are not
allowed to race, you might reasonably want your money back. Assuming,
of course, the builder knew your intent and crank size.

A little while ago I measured my 62 cm Eddy Merckx Corsa Extra - I have less than an 1/8th inch clearance with 23 mm tires. That means that I would hit with 25mm's.

Not that I would pay any attention to that because of the way I ride but that is so near an overlap that the commonly used 25 mm tires today would strike.