I've just bought a 10 speed shimano cassette and a 10 speed SRAM chain for my road bike when I currently have a 9 speed. Is it possible to adjust the rear derailler and shifters to accommodate a 10 speed cassette and chain?
You would probably have to look up your RD on the manufacturers site to see if the specs allow it. If you let us know what model you have maybe we can look it up for ya.
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
A 9 speed won't work 9 cogs of a 10 speed cassette.
The gaps between the cogs is different between 9 and 10 cassettes.
See for dimensions:-
There is 0.4 mm per cog difference so by the time you've shifted 8 clicks it will be 3.2 mm out.
You will need 10 speed shifters but you may be alright with the derailleurs?
[font=Trebuchet MS]Ride hard or ride home alone![/font]
derailers don't know how many cogs you have, and most road bikes use a long cage, so you should be fine (although you'll have to adjust the limit screws to be able to shift into that extra gear. it's simple and only takes minute or two.)
if you're not changing the front chainring setup, you can keep the front shifter, but you'll have to get a new shifter for the rear.