We've got really steep hills where I live. Up to a 30% grade. I've built several pedal only riders bikes which can climb them. On twist shifters they are two directional. The 3 on the left goes down to go higher. The 8 on the right goes up to go higher. What I did was put the 8 on the left so you go down to go higher. I switched out the guts on the 3 (a 10 click Sram shifter) with a Sram 8 shifter then put the 3 on the right. This way the 3 still shifts down to go higher. Now both shifters are one directional. Down for higher; up for lower. Much like a twist throttle. There also color zones to coordinate the shifters. This is how it works: red (uphill (1,2,3)1); yellow (level ground (3,4,5,6)2); green (downhill (6,7,8)3. What I'm putting on these bikes are a DNP Epoch 8 speed 34-11 freewheel. The front chainrings are 22,38,48. I also put a bicycle computer with a cadence meter on it. Then tell them to be in a gear where they can comfortably maintain a crank rpm of 70-90. The bikes also use Kendra 838 slicks. For as long as I've lived here only the pedal only bikes I've built have I seen going up the really steep hills.
I helped a fireman friend of mine build 21 speed bike using this same style of twist shifters. He uses a thumb throttle. It's uphill (red (1,2,3)1); level ground (yellow (3,4,5); downhill (green (5,6,7)3). I custom built the 7 speed rear freewheel (34,28,24,21,18,15,13). The front 3 chainrings are 28,36,44. The Honda 35 engine max hp is at 7000 rpm. I told him to be in a gear where the tach is there. If he can't get 7000 rpm then the gear is to high so down shift. If its 300 or more rpm above that then the gear is to low so up shift.
