45x16
52x18

I run 48x15 and 17 on my flip flop fixie.

I run 46:17 on my fixie, soon to be 46:19 (moving somewhere hilly). 2:1 is rarely an appropriate ratio, on or off road. If you swing over to the MTBR SS board, you'll see most of them running 32:18/19/22 or something along those lines. They think 2:1 is steep. And most fixed gear road rides think it's way too small, which I agree with.

53x11.

All the way.

48x14

50 x 16 and 49 x 16

46 Chainring, I have 13 thru 20 tooth cogs depending on my mood & training intentions that week. I've been running an 18 & 20 lately to work on spinning & that's been a lot of fun. I haven't changed the speed of my training, just increased the spinning, up to 165 to 170 cadence on the flats.

42x16 on my fixie
32x18 on my mountain bike. Though I have never taken it on the trails since I have converted it. May drop down to a 16.

SS 52x20
Chicago is quite flat.

Presently 52X17 (81") in a rolling urban/suburban setting with a 800-1000' dynamic range.

I took a long time getting to 52X17, playing with 47t and 48t chainrings and 16t, 17t and 18t cogs on the way.

This winter I might go back down to 47X17 (72") for the control it offers.

40x13
Chicago may be flat, but I've forsaken my masher ways. Plus it is my first fixed so I kind of just took a shot in the dark on the gears.
Can we just make this thread sticky? seems like a common question

48x16 on 700c

42x14 right now. 700c. 175mm cranks. i only ever rode in one gear on my geared bike so i just picked whatever that ratio was when i built my fix.
but i'm thinking of making it 43x14 so i have more than 1 skid patch.

48x17.

42x16 on the 700c SS cyclocross commuter. (170mm cranks)
36x16 on the 24" wheel SS urban rig. (175mm cranks)
34x16 on the 26" wheel SS mountain bike. (175mm cranks)

48x15 for the track... but I want higher still
48x17 IMHO the perfect city gear.

48x16 on my urbanite now with a freewheel so SS, need a back brake still. not need really but the front is getting raggedy, may as well replace with a matched set since it's SS from now on

53 x 14 SS

48x18. 165mm, 700cc.

Old thread!

50 x 17 on my nice bike
42 x 15 on my "beater"

both are used on the street, without hand brakes.

46x17, 700 x 25 tires, 170 mm cranks

52 x 18, eats hills.

49x18, switching to 17. 165 cranks

46x18 down from 48x18. and lovin' it. 9 skid patches!

44x16 170 cranks