Originally Posted by
mstateglfr
I think this is why stack and reach exist.
Sure it'll fit, but will it feel the same? Compare bottom bracket drop, fork trail, head tube angle, and seat tube angle.
Typically, the smaller the bike the seat tube becomes more upright and the head tube slacks out. But with you comparing one size different, hopefully all these numbers are the same/similar.
Exactly. Even if we ignore feel, which also depends on frame material and construction in addition to the measurements, you need to consider at least seat tube angle in addition to just reach and stack to get an idea on fit.
Even a small difference in seat tube angle means the saddle may be so much further forward or backward that the change in distance cannot fully be compensated by the offset, depending on the existing offset of your seat post and saddle.