9/8 speed shifter compatibility

[citizenthom]

I've bought a flat bar road bike, the ridgeback flight 01.
I'm considering replacing the flat bar with a drop bar which means i must replace the brakes/shifters.

Currently the bike has an shimano 8 speed cassette. Can i replace the shifter with a 9 speed shifter and only use 8 of the speeds, as these can be bough for around half the price of an shimano 8 speed?

 

[Bigtwin]

Different spacing. Need to re-space the cassette, or live with horrible shifting, unless you get get a J-Tek Shiftmate adaptor.

 

[andy_wrx]

No, it won't work, as above.

But if you can get Shimano 9sp shifters so much cheaper than 8sp, all you need to do is also buy a 9sp cassette and chain. Your front & rear derailleurs, brakes, etc will work fine.