Topic: 2X10 Crankset question

[johnny.louis]

Bike: 2010 Cannondale RZ 120 3
Front Derailleur Shimano Deore
Rear Derailleur   Shimano XT
Rear Cogs 9-speed, 11 - 34 teeth
Crankset   Shimano FC-M542, 44/32/22 teeth

I'm thinking about switching up to a 2X10 Crankset from the 3X9 after what I've read and seeing a lot of people riding this setup.

A. If starting off by just adding a bashguard -or- if switching out the crankset and rear cassette for a 2X10 would the front and
rear derailleurs also need to be changed? 

I don't assume if they are made to shift 3 and 9 that they can be adjusted to shift 2 and 10?  If that is the case I assume it's
quite an expensive switch as you have to replace the crankset, rear cassette, chain, and derailleurs to make it work, correct?

Again, is there a cheap and simple way to start, again by maybe just adding a bashguard to this bike? Or could I get a new
2x10 crankset and keep the 9 cassette and shifter?

Any info or advice is appreciated!

[dcluley]

Quick answer is yes, you will need to buy new shifters, derailleurs, and chain if you buy a 2x10 cassette and crankset combination. 

I believe you COULD temporarily buy a 2x10 Crankset and run a 9 speed rear cassette, derailluer, and chain on it for a temporary 2x9 depending on your setup or maybe a 10 speed cassette, rear derailleur, rear shifter, and chain, and play with the chainrings up front for 3x10 or 2x10 with bash.  (this could be temporary until you have the cash to finish it up.)

People with more experience feel free to correct me if I am incorrect on these temp setups.

Also, be careful on the BB setup you need for your cranks, the cage size you need for rear derailleur, and the front mount/cable pull setup you need for the FD.  There are dozens of mindboggling combinations of specs for the switch.

I personally switched to 2x10, and found i didn't need the whole range for our local trails, so just ended up doing 1x10.  This would be a lot cheaper overall, as you have one less derailleur, shifter, and CR to worry about.

[dcluley]

Here's a helpful thread on MTBR on how to cheaply convert to 2x9 temporarily with a 2x crankset:
http://forums.mtbr.com/drivetrain-shifters-derailleurs-cranks/2x10-crank-9-speed-setup-666457.html

with an 11-34, rear cassette, that could be a good low cost option for you right now, then you can switch some stuff out on the back if you like it and after your cassette and chain wear down.  I'm not making any guarantees that would work foolproof, but poke around on some threads on those forums to see if you find a combo that somebody has had proven success with.

[Alan]

I ran 2 rings on some Shimano crankset without an issue. Just adjust the fd and you don't need a new shifter. Chain line prob wasn't optimal for one of them but it worked well without spending a stupid amount of money.

[bjdraw]

I don't assume if they are made to shift 3 and 9 that they can be adjusted to shift 2 and 10?  If that is the case I assume it's
quite an expensive switch as you have to replace the crankset, rear cassette, chain, and derailleurs to make it work, correct?

Again, is there a cheap and simple way to start, again by maybe just adding a bashguard to this bike? Or could I get a new
2x10 crankset and keep the 9 cassette and shifter?

You might be able to reuse the front shifter, but just have an extra click that doesn't do anything. The rear shifter and derailleur for a 9 speed is def not compatible with a 10-speed (in either direction, as the indexing is completely different).

Just taking off the large chain ring up front isn't going to really help much. A middle ring up front on a 3x9 has less teeth than a 2x10 setup (say 38 vs 32). And the large ring on a 3x9 has more teeth than the large ring on a 2x10 (say 42 vs 38).

If you want to try it inexpensively, then I'd hit up eBay for take offs. If you don't mind midlevel components, you can get them very inexpensively. People often buy new bikes and upgrade the components before even riding it once. I recently got a brand new x5 crankset with bb for $65, compared to $135 new. It had more wear on it after one ride then it had when I received it.

The other option would be to buy a new rear shifter, rear derailleur, chain and cassette and run 3x10. The crank isn't optimized for the smaller chain, so you'll want to research the specific combo in advanced else risk problems shifting.

[johnny.louis]

Thank you!!!!!!!

Exactly the info I was looking for....