Rupert

One of the many new bikes I am looking at is the Orbea Gavia. I'm about 6'1" and rode an older 58cm Specialized Allez but noticed that Orbea's sizing jumps from 57cm to 60cm, and all sizes are in 3cm increments. One website said I should be riding a 54cm at my heigh - https://www.wayfarerbike.com/id28.html - which sounds pretty small! Of course, I'll get a better feel after a solid test ride, but I'd like to get a feel for what people ride before I talk to the sales people.

DaveSSS 

Those general guidelines are worthless. To figure out the setup on a new Orbea you need to compare the head tube length (with the headset), the TT length and the seat tube angle.

Your Allez should have a 58.2cm TT, 73 degree STA and 205mm head tube length.

The 57cm Orbea has a 30mm shorter head tube, and it will require one size longer stem.

The 60cm has a nearly identical 204mm head tube, but a longer reach that will require one size shorter stem.

Rupert

I didn't even think about factoring in the head tube, thanks! Hopefully i'll get in a test ride on Saturday.