Overlapping frame sizes - go larger or smaller?
Hi all....am thinking of buying my first road bike since having a racer about 20 years ago.
Have settled on a Giant defy 1 (alloy) or composite 2 (carbon) but am now trying to decide what size frame to go for. I'm 5ft 11 1/2 inches tall so the Giant size guides suggest I can either go for a medium or medium large frame.
Yesterday I tested a defy 1 in both sizes, riding them both twice on a loop that was about a mile long and included a short hill that I went down, turned around and came back up again.
I'm still not sure which frame to go for though. The medium felt more nimble and went up hill easier, though I'm not sure if I'm just imagining that on the basis that its a bit lighter. Coming downhill though, it felt almost a bit twitchy and I definitely felt a more stable and confident when descending on the medium large frame. But, while the medium large felt more stable, it seemed noticeably heavier going up hill.
In terms of riding position, I didn't really prefer one over the other. It might be worth mentioning that I had a spine op on two slipped discs a few years back and struggle with my lower back if hunched over, so I'm maybe thinking that the medium frame would be better for me as it'll promote a more upright position.
If I was simply saying which I felt more comfortable on, it would be the medium large by a whisker, just because if felt more solid, but I'm wondering if that's maybe just down to the fact that I haven't really ridden a bike for 20 years and would I maybe get used to the more nimble (but slightly twitchy) medium frame?
Also, I haven't managed to test the composite 2 yet but am wondering whether I'm likely to experience the same thoughts or is the carbon frame likely to give me a significantly different feeling?
Thanks for any advice.