29er.
Canal towpath/dissused railway type route…

Obviuosly spinning like a rampant hamster on usual 33/18.

36/16…?
42/16…?
48/18…?

CRC do some Black Sheep branded ones at £9.
Any good ?

Cheers.

48/17 (35c and 45c) on some slightly hilly mainly smooth and flat London roads. S’alright. Gurn up steeper stuff and spin on the open flats, but it works. might go a sneak lower for canal path stuff if it’s a bit slower than open road, though.

But would you use it on hills or open roads too? I reckon singlespeed gear choosing is as much about how much of the extremes you still want to be able to ride as what’s best suited for the majority of the riding.

34-16 and 39-18 on a 42C tyred SS CX bike for loaded overnighters, gets up most non-techy hills ok and 18-19mph on flat roads. 42-18 for town and towpath use on the 28C pop-to-shops hack SS. 46-18 on my Flyer that goes up easy gradients ok but is harder work on hills generally. 34 oval-18 on my SS 29er for reference.

first, get aquainted with a gear inch calculator.
http://sheldonbrown.com/gears/

then buy yourself…
a. 16t sprocket
b. 42t chainring

if having tried your current 33/18(54″) then 33/16 (60″) 42/18(68″) and 42/16(77″) and you still havnt found what you want you will have a pretty good idea what will work for you.

ps. your 42/16 vs 48/18 choices would be a waste of the cash splashed on the 48t ring.

As soobalias says get used to using gear inches as this allows you to compare different ratios easily
I’m running 44×17 at the moment and have run 48×18 in the past.

34-20 on my flat commute at the moment, embrace the spin 🙂

But would you use it on hills or open roads too? I reckon singlespeed gear choosing is as much about how much of the extremes you still want to be able to ride as what’s best suited for the majority of the riding.

This +1, 34-20 is just enough to keep up on a group ride at a sociable pace on a flat road, so that’s the extream it need to do. So on the usual more technical off road riding it’s acceptable.

Certainly beats running a high ratio that you can only just get up a hill, but rarely spin out.

Thanks chaps.
I already have a 48t I can play with. (Ready to go on a geared commuter for the winter.)
I’ve ordered a couple of these Black Sheep jobbies at £9 each. At that price I can play around a bit, see what works etc.