Join Date: Jul 2005
Bikes: 1984 Trek 520; 1990s Peugeot (Canadian-made) rigid mountain bike; 2007 Bike Friday NWT; misc others
Mentioned: 27 Post(s)
Tagged: 0 Thread(s)
Quoted: 1288 Post(s)
The smaller front chain ring (22 vs 30 teeth) , marginally smaller outer tire circumference (approx 26" vs approx 27") , and possible slightly longer crank arms (175 mm vs 170 mm) on the mountain bike, all together give it about a 30% lower bottom gear, so it's not a surprise you can tell the difference. The store should be able to tell you if you can add a smaller front chain ring. Lots of people consider it if they plan loaded touring.
With a 24 tooth granny, you will still not equal the mountain bike but you will be closer.
Mountain bike lowest gear (in gear inches): 22/34*26 = 16.8 gi (lower is better for uphill hauling)
Sojourn with 24 tooth granny: 24/34*27 = 19 gi (that's still pretty good!)
Soujourn with 26 tooth granny:26/34*27 = 20.6 gi
Sojourn as is: 30/34*27 = 23.8 gi
The probably longer crank arms account for an additional 3% advantage for the mountain bike (equivalent to about 0.5 gi).
Last edited by cooker; 09-08-09 at 08:39 PM.