I keep meaning to ask Marcel about that difference. It was not what he suggested would be the case when we discussed the proto. I wonder if its a typo for the med?
I would have expected it to be 600mm or 605mm for a med. much like the 29s.
I'm just under 5'11"/178cm and run 605mm TT with 50mm stem/800mm bars.
Dipper is running a 610, mine is 605, but both have 470mm seat tubes.
@pimpmessiah On the production Ion15 the ST is 0.5deg steeper and the CS 7mm shorter. You could get away with moving your saddle back the 5mm on the med to bring the effective ST angle back a touch without affecting the handling and run a 50mm stem.
I run 50mm as the Easton 35 only comes in 50mm (Cant go much shorter wihout rise as there's not much between the steerer and bar!) 605 was just right for me with an 800mm bar. I needed the TT 5-10mm longer when I was running a 750mm bar.
Its gonna sound weird but if you run a 160mm fork rather than the reference 150mm it also adds about 4mm to the effective TT after compensating for sag...I'd better scurry of to the 29 threads, sorry to derail a bit chaps, but its all Nicolai innit :-)