I was hoping someone could ensure my logic is sane before I splash 2k on a Canyon.

Currently running a medium planet x SL Pro Carbon with a HA of 72.5, SA of 73.3, reach of 385 and an effective top tube of 547. I’m running this with a layback post and 90mm stem.

New bike in small canyon Ultimate CF has same Head and seat tube angle, but has a effective tt of 537, and reach of 375

With the same layback post and by getting a 100m stem will the fit be pretty much exactly the same, or am I not taking something into consideration?

other option is the medium, but I’d rather size down than up and 56 seems like a big frame.

The “56” doesn’t seem to have any relevance to the sizing. The medium is only 2mm longer than your PX . If your buyi g the full bike, think about the crank length too – medium is 172.5 vs 170 for the small.

How tall are you?

What is the stack height?
Are you using the same bars?

Some spec on that Canyon!!!

The wheels & groupset alone are about £2k worth….. 😯

Slight hijack – can someone point me in the direction of the original thread (I’ve searched but cant find). After some DIY bike fit guidance 😀

Despite the often repeated idea that road bike fitting is amazingly important, you don’t have to exactly replicate your current position; you are adaptable and can cope with some changes.

Your position can and will change over time anyway.

Shirley what OP was referring to:
http://singletrackworld.com/forum/topic/short-road-bike-stems/page/2