i am thinking about taking an old road bike and turning it into a commuter rig. right now it has old downtube shifters (6 speed) and biopace rings. last year a put on a new carbon fork, and i think i will keep that there. i would like to throw on a flat bar for comfort and "upgrade" to a shifting system that leaves my hands on the bar. (it looks like the commute will be 20-30 miles each way. i am doing a dry run this weekend). here are a few questions i have about component mixing:

1) i have an old 7 speed gripshift system i took off to make a SS. i don't think i can use the gripshift for the front, but could i keep the current crankset/rings on the front (use the downtube shifter for that) and use MTB shifters and derailluers in the back? i know it would be rear on the handelbars and front on the tube, but i am working with a very limted budget. can you even use a road crankset with an MTB rear drivetrain?

2) i have sora brakes on there now. i know cantis or v brakes would give better stopping power, but there are no bosses for that. if i switch to flat bars will i need to get a certain type of brake lever? i have an old set of canti and an old set of V levers.

any advice would be helpful.

There shouldn't be a problem using the canti levers with the Sora brakes; not a perfect match, but more than acceptable. There's no reason you can't use the GripShift shifter for the front; it's not indexed, and you can think of it as another type of friction shifter, like the existing downtube shifters you have. I've used GripShift with road derailleurs and cranksets on a couple of Frankenbike projects, with good results. There's no reason you can't use a road crankset with an MTB rear derailleur and cassette; look around at cyclocross bikes and you'll see probably half have XT mechs on the rear.

I'm assuming that all this 7sp stuff includes a cassette, because you won't be able to use the 7 sp shifter with the 6 sp cassette.

the 7sp stuff is 7 speed. i need to get a new cassette. will the chainrings be ok? they are from a 6 speed...

also, are you sure grip shift isnt indexed? it has been a while, but i thought they were indexed...not sure of the model number, but off a 1995 specialized...

...the rings will work with your setup. As for the indexing, yes, the right/rear shifter is indexed, but the left/front is not--it has numerous click stops, but those are for trimming the front derailleur. I haven't used GripShift in a few years, but I seem to remember taking three clicks to go from one chainring to another.