Certified Bike Brat
Join Date: Jan 2011
Location: Montreal, Quebec
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Sure sounds like a lot of trouble to go through to move from 9 to 10 speeds!
Originally Posted by Fleet59
Here are the specifics: Current bike is a Litespeed Sirius, 9 speed double, with a Shimano 105 (FC-5502) Octalink crank that has been professionally shortened to 148mm. New bike coming in soon is a 09 Look 566, 10sp double, with Ultegra SL crank and components. Assuming that the Look bottom bracket will accept the Octalink components, I want to replace the 10sp Ultegra crank with the shortened 105 crank. Shortening the Ultegra 10sp crank or any other 10sp crank is currently not viable and is not an option. The shop that shortened the crank said that I can purchase 9/10 sp compatible chainrings from FSA and they will make my FC-5502 10sp compatible. My LBS said that if I try that terrible things will happen like my frame will crack and the rear derailleur will buckle. Referencing Sheldon Brown's website, many cyclists have just changed to a 10sp chain and have not had any problems. Now it is my understanding that the inner ring is closer to the outer ring on a 10sp crank vs a 9sp crank. If that is really the case, why can't I just take my FC-5502 and mill the inner ring mounts to match the spacing on the 10sp Ultegra? I'd appreciate opinions on the FSA chainring option, is my LBS correct and is milling the proper path forward? Any other ideas?
Hi - read the posting a couple times to make sure I grasped what you want to do. Looks to me like you had a set of 9 speed crank arms shortened and want to use that with a 10 speed setup. The bike it would go on is pretty incidental.
So yup, there is apparently a difference in the front chainring spacing between the 9 speed and 10 speed cranksets. The chainrings are slightly closer together on the 10 speed setup.
Would that make your frame crack or other terrible things? It would give you some shifting issues with the front derailleur but unless the chain comes off and gets jammed in the rear wheel while you`re going downhill at speeds that should get you arrested - I personally think any danger is being a little exaggerated.
But would suggest you skip mixing in the FSA stuff and stick with a drive train that comes from ONE manufacturer. You can put Shimano 10 speed chainrings on that 105 crank/spider assembly and thats what I`d suggest.
Unless you plan on changing the entire drive chain over to another brand, which is possible since you`ll be using the 10speed cassette and chain from that other bike anyway.
Shouldn`t have to machine anything, but double check me. I`ve been known to be overly optimistic.