Originally Posted by mechanicalron

I think the BCd is 135mm on your crank so 39 tooth is the smallest you can go on it. You can put a Sram MTB cassette and a long cage derailer so you can go up to 39 in or so in the back but if you have a 10 speed now, the MTB cassettes only go up to 9 speed. That will make you have to chainge the chain. To do the tripple you need ALL new stuf!