Well as I ride a 2013 Kona unit , I have been experimenting with different gear combinations on my 29 inch MTB. Pretty much the standard gear combo that comes stock on any single speed MTB is a 32 T chain ring with a 18 T rear sprocket which is running 29 inch tyres gives you the following result.
29 inch wheels
Front chain ring 32 T
Rear sprocket 18 T
Gear inches 51.6
The above combination gives you a great all round gear for off road riding and it allows you to ride most sections spinning at a high cadence, this is fine if you only use your bike off road, but if you often commute to work on the same bicycle it will take you much longer in the above gear combination. In other words its slow on the flat.
What I did to my Kona unit was to remove the rear 18T cog which is the cassette type ( more on that later ) and replace it with a wider body single speed cassette cog in 13T with a 33 T ring up front. The result is the following gear combination.
29 inch wheels
Front chain ring 33T
Rear sprocket 13 T
Gear inches 73.6
The above gear combo lets you ride comfortably at 20 km per hour even fully loaded for touring, but you are limited to the hills you can ride in other words you will be doing some walking on a long tour that involves mountains. So what are the benefits of this type of setup as opposed to a full cluster and multiple chain rings
1. lighter bike - no extra gears, derailleurs , shifters or extra cables to worry about
2. Simple to maintain - especially in locations with bad weather , snow, road grit etc
3. Ease of use - you just get on and pedal, no need to change gears or worry about which gear you are in
4. Bullet proof - bikes with a multi speed drive train are delicate , single speeds are simple & strong
5. Perfect gearing - you can pick the perfect gear for the type of cycling you do
Before Oct I will try out another gear combination which I think will suit the style of touring I currently do which will evolve putting a slighter larger sprocket on the back such as a 16 T which coupled with the current front chain ring and cranks with give me 59.8 gear inches . Not quite as fast on the flat but better for tackling the hills.
My rear hub is a single speed disk hub with has a far narrower cassette body than a typical rear hub which allows great chain alignment with the use of spacers . Pictured below is the type of hub I currently use.
As mentioned before I use a single speed rear cog, my favorite type is made by Surly and has a wider body than a normal cassette cog and is made from stainless steel for extra durability . The benefit of a cassette type cog over a single speed freewheel is the cassette cog comes in a far greater range of sizes compared to a freewheel . Pictured below is a single speed cassette cog