New bike.. going from M, to S to X-S, how can I fit all these sizes?
 

I've been thinking of a purchasing a new bike recently, years ago I had my eyes set on a nice Canyon but after their sizing sounded weird, I went for a better value Planet X RT-80 offering instead in size small/50. Before this I rode a Cube Peloton M/53) which I am actually in the process of rebuilding. Now I find myself looking again, and seeing a few good deals on the Canyons again, but I just can't figure out how a 5'7" rider with 80cm inseam (I need to confirm this one) is supposed to fit an XS Canyon, Small Planet-X, and Med Cube.

Ok so maybe the Cube felt a little stretched out for me but it is comfortable enough to ride. When I went to the Planet X I noticed that it felt more snappy and racier. the position feels a bit more compact than the cube, the drop is slammed, shorted head tube, with a fair, not excessive amount of seatpost showing, and the BB is lower and frame stiffer - I assume this could contribute to what I am describing in terms of how the bike feels?

I am trying to understand geometry I little better but I can't get my head around it too much. I understand a bike fit is a good idea, but I've always winged it, kept my saddle height between bikes and I've been alright and able to do full days putting in the effort without any problems. Would an extra small Aeroad really fit me? it just doesn't sound right! From a look at these charts, would it slam the position even more on a size XS Canyon? And Small Canyon seems to be larger than my planet X?

Cube: https://geometrygeeks.bike/bike/cube-peloton-race-2014/
PX: https://geometrygeeks.bike/bike/planet-x-rt-80-2017/
Canyon: https://www.canyon.com/en-gb/road-bi...accordions=0_1

the sizing nomenclature throws people off since it's not your typical 48-58, but it aligns up pretty similar to other brands when you match up the geometry charts. There was some backlash against Canyon's size calculator early on but they seemed to have adjusted it, but a good way to start is just look up your height on their chart. 5'7" is 170CM which put you in the XS category now you say your SOH is 80CM which is really long for someone 5'7" since that is 31.5". With that being said if you truly have a 31.5" SOH than you either will have a massive 2" of clearance so you could try a Small but then you have to be very careful about reach being too long. Point being you might have to order a Small and work with Canyon about swapping out the stem to a 80mm instead of 90mm but even then sizing might be wonky.

How can you fit all these sizes?

The short answer is because the frame geometry it totally fudged on all smaller sizes of 700c wheeled bike and has been for a LONG time. So long in fact that its accepted as "normal".
In truth, you really can't make a 700c wheeled bike properly in anything under a "medium". Small and extra small frames are really just medium frames with seriously fudged/flawed geometry.

Take a look at the geometry for the Cube, https://geometrygeeks.bike/bike/cube-peloton-race-2014/

The Reach number for the 50cm is 379mm, 53cm is 380mm and the 56cm is 381mm.
Really!:rolleyes:

It hasn't changed. The difference is nothing and only there so they can quote a different number on a spec sheet.
Where are the real changes? Stack changed but that's easy, so how did they change the top tube length?
They steepened the seat tube angle which moves the seat forwards.
Is this a good thing for small riders? No its not.

It's going to be a compromise without going custom. In your case I recommend you using the largest frame you feel comfortable on and just fit a shorter stem.

When these things come up, I always advise putting one's measurements into this calculator: https://www.competitivecyclist.com/S...ulatorBike.jsp
then go mostly by ETT (effective top tube) length and stack. The way bikes are designed now makes ST measurement somewhat meaningless.

Taller seat post and stem.

https://cimg1.ibsrv.net/gimg/bikefor...7a05b1a67.jpeg