I've recently started using my Cannondale M300 commuting bike for road riding (got skinnier tires on it). Problem is that on flat ground I run out of high gears. So I would like to switch out the crankset to a road crank (was thinking of Sora or Tiagra). But the kids at two local shops have suggested that this is not possible, but I get the feeling they just don't know. Plus they want to sell me a new road bike instead.
The bike has 8-speed MTB cassette and chain that I'd like to keep if possible. So, would a road crank fit on Cannondale mountain frame and work with other components? Do I need to stick with a 8-speed crank or would 9-speed work as well? And will there be problems with chainline when going from MTB to road crank?
Any other suggestions/words of caution would be appreciated.
Masiman, the crankset I have now has the some of the chainrings (don't remember which one) built together with the crank, and thereforeit can't be modified.
Al, Can i switch out just the cassette or do i need an entire new road wheel? Are the road and mountain cassettes the same width (assuming I'll stay with an 8-speed)? Will the the rear derailleur still work? I am not very worried about losing the front derailleur functionality because in the 8 years I have had the bike I never used the smaller chain rings, and even on the back only need the 5 highest gears.
I assumed your cassette is Shimano or Shimano-compatible (Sram, IRD, etc.) If so, any compatible cassette should work. "Mountain" cassettes have wider range of sprocket sizes but there should be no difference in putting one on a road or mountain freehub.
Check out the late, great Sheldon Brown's articles on the Harris Cyclery website. His discussion of gears, etc. is very informative for those of us who are new to this stuff.
Depending on what gearing you have now you may not be able to do much with the cassette alone. For example, if you have 678mm rims and your high combo is currently a 48x13, and assuming you only do a 12 sprocket you gain %8.33 (23.46mph vs 25.42mph at 80rpm). Not much of a jump but some. If you can get it to a 48x11 you gain 15.4% (27.7mph). This is a nice little gear calculator.
If you are only using the top 5 gears look for a cassette with a tighter range. You'll have more usable gears that way.
Since your chainrings and crank are one piece I am guessing your bike is not worth alot. If so, I would not spend alot of money trying to upgrade it. Fix a price to modify it, if you can't meet it you should look for something used. It may serve you anyway as you may find that changing the cassette will require a new chain and maybe even a chainring/crank. At that point, new may become more cost effective.
(I am working within Masiman's view that the components should be appropriate to the bike - no silk purse for a sow's ear)
A 50T will shift ok (not great but not too bad) with the Avilio derailleur and 50-12 is common set up for road bikes (20% faster than current). Installation requires a crank remover and a cresent wrench (I can't believe I said that - as the man with complete Snap-On tool box)
Who's putting a silk purse on a sow's ear with his daughter's Trail-a-bike....but it will be FAST!
Thank you all! You have been most helpful.
Masiman and Prairie*boy, I do know that there is a real road bike in my future, but as long as my current bike serves me well (which is has done for 8 years), I'll put the extra $$ to other uses.
I appreciate you sharing your experiences.