>>1944191for 7 speed its fine but 8 to 10 speed is a bit iffy as the lever has to cover an arc closer to 180 degrees, and the lever movement between each gear is allot smaller
most important is that the cables are roughed properly, and kept free of kinks rust and dust,
cheep friction levers tend to be excessively draggy and their tension screws come loose over time,
clean and lightly lubricate the friction washers and keep the tension bolts just tight enough that hitting a bump on the road will not change gears.
the best friction shifters to use are so fiendishly complex and fragile I would advise against them unless you have spare parts and manuals on hand.
you may have to get used to over travel, shifting the derailleur far enough to shift to the next gear, then pulling it backwards slightly to better centre on the gear your now in.
indexed shifters have this motion built in into them, as do some farely obscure rear derailleur
