slcbob

I've noticed a trend of rigid forks intended for suspension fork replacement to be labeled as, e.g., "80mm suspension corrected" or "100mm suspension corrected."

Are those useful labels? In other words, is there enough standardization in 80 or 100 mm travel geometry for those labels to apply better than the more traditional axle to crown measurement?

I understand the need for a suspension corrected fork, as has been covered on many threads here. Getting a rigid fork with the same axle to crown measurement as the loaded (i.e. with sag) suspension fork is the key to maintaining the same frame geometry (with other impacts from rake, trail, etc.). It strikes me that the travel of the suspension fork only puts you in the ball park, whereas the axle to crown puts you on target.

dabac

Sure. Apart from the comparably rare parallelogram forks, all the fork legs do is to compress axially.

Well, getting the axle-to-crown right require the ability to do a reasonably accurate measurement, while getting the intended travel right only require the ability to read labels or perhaps catalogues.

but sag is an approximate value. You'll have one sag sedately seated, another when out of the saddle etc etc.

First off, bikes as a rule aren't that critical. The rider can easily adapt to quite hefty changes in fork length and design. Ball park will do fine.

But it's a moving target. One for seated coasting, one for standing coasting, one for honking, one for braced for braking ASO. No real reason why one of those should be significantly "better" than the others.