I don't really know, but I ride road bike with50, 34 compact crank, 12-27rear, and I find that adequate for all occasions. I ride sagged. However, loaded touring is different. Wonder if 12,14,16,18,21,24,28,32,36 rear would be acceptable by the OP. I know OP has only 8 cog rear. The bottom cog would yield 25.3 gear inch against 24"minimum required by OP. BTW, I find that road bike is quite light to start with, and bare bike makes a better climber against heavier MTB. If you put just enough pressure on the pedal to keep moving, steep climbs can be tolerated. Don't try to pump watt like you're on Power Tap.