You want a good wide range and a really low granny gear. This is critical when buying a bike you plan to load for extended travel. You’ll want to be able to climb steadily at just above walking speed, and have your feet still turning at a comfortable cadence.
We find climbing at any cadences much below 60 rpm an excessive strain on the old legs.
Bicycle gearing is explained by Sheldon Brown, and he also provides an online calculator for examining the gearing for any bicycle.
Look carefully at the lowest gear on any bike you are considering for touring. If you are comparing two bikes with the same size wheels, look at how big the smallest chainring is compared to the biggest cog on the cassette. The front one should be at least as small as the rear one. If it isn’t, don’t even consider buying it! Often the smallest front one has 30 teeth, and the biggest rear one has 32, or better yet 34. That is OK, but an even smaller chainring is better.
If you are comparing two bikes that have the same numbers of teeth on cogs, but one bike has 26” wheels and the other has 700c, the one the 26” wheels will have slightly (6%) lower gearing.
We used the online calculator to examine the lowest gear on our Surlys, asking for the result to be expressed in km/h at a 60 rpm cadence. This shows how fast we’ll be travelling in a given gear when our feet are turning 60 revolutions per minute.
The Surly lowest gear (For specifications: 26” wheels, 1.75 inch tires, 24 tooth chainring, 34 tooth cassette) has us travelling at 5.3 km/h at 60 rpm as shown in the chart at left. As a long hill gets steeper – or Margo gets more tired – we’re still moving just above walking speed and turning at a comfortable cadence just before we need to get off and push the bikes.
Note: We’ve changed the chainrings on our Surlys from the original 48-36-26 chainrings to 46-34-24 teeth. Also, we now run 2″ wide tires on new wheels.
The Devinci Caribou lowest gear (700c wheels, 35 mm tires, 30 tooth chainring, 32 tooth cassette) puts us at 7.3 km/h at 60 rpm. This gearing isn’t suitable for fully loaded touring on rough steep roads – especially when the rider is well past 60.