max1iu

Currently, I'm riding a Kilo TT (55 cm) and the reach is a bit too big for me. I already shortened my stem but it still feels like a stretch. I believe the effective top tube is 560 mm.

I'm looking at the Big Block geo and am debating between a 49cm and a 52cm frame. The top tube for the 49cm is 535mm while the 52cm is 550mm. Is it better to go smaller and get a bigger stem if it the reach is too small?

A little bit about me: I'm about 5'9" - 5'10" and have an inseam of 30". I have slightly shorter arms (my wingspan is about 5'7"). If anyone could help I'd greatly appreciate it. Thanks!

psyphr

Personally Id recommend demoing a 52 and 55cm if you have a LBS who carries All City. Both Surly and AllCity’s low-and-long geometries are tricky to size up. I have a similar build to you and I ran a 52cm Surly Straggler with a 90mm stem and riser bars as a commuter for years. Converted to drop bar and rode a 350mi. bike tour, rode and fit like a dream!

Definitely try before you buy.
Id say the 49cm is sure to be too small. Keep in mind that with each size down, the headtube shrinks, thus giving a more low and aggressive handlebar position.

TugaDude

I own a Big Block and while I typically ride a 58cm, All City calls the size I have a 55cm and it fits similarly to my 58cm or 23" bikes. Based on your height, which is only one factor, but an important one, I'd say the 52cm should work for you.

My assessment of bike fit is not based on stand over height as much as top tube length. The reasoning is I care more about how it feels when I'm riding it, compared to how much clearance there is when astride it. I don't do that very often.

My experience with the Big Block is 100% positive. Good luck and I'm sure you'll love it!