7 to 9 speed ques
 

Anyone ever use a Shimano 7 speed rear der on a 9 speed? The 9 sp cassettes are only about 4.5 - 5mm wider than a 7 sp. I was going to set up a Deore 7 speed rig but 7 speed barcons are far and few between. Actually, they're getting as expensive as the 9 speed versions. So, I figured that if the Deore 7 sp der had enough range it might be easier to use it as a 9 speed. Then I could use the readily available 9 sp cassettes and barcons. Thanks

Tim

I asked almost the same question yesterday. It doesnt matter what speed the derailleur is. It will work regardless if its a 7 speed der on 9 speed cassette or vice versa. Check this post http://www.bikeforums.net/showthread.php?t=223685

I don't think that you'll have any trouble with the derailleur. Are you changing wheels or how are you planning to fit the 9-speed cassette?

An interesting concept that I've heard about is removing 1 cog from a 9-speed cassette and installing the remaining 8 on a 7-speed freehub body. You'll need 9-speed shifters, of course, if you want it to index but it sounds like a cool idea.

As others have mentioned, there's no problem using a 7-speed derailer on an 8/9/10 speed bike. The precise width of the cage and pulleys may have been tweaked over the years, but it'll work fine.

The 8-of-9-cogs-on-7-speed-freehub is a neat trick, but the results aren't so great. It requires 9-speed shifters and cassette, and you only end up with an 8-speed drivetrain. It's better to do the full upgrade correctly, by getting a new freehub body (~$20) and respacing the rear hub to 130 mm for 9-speed use. Someone will protest that it's a good solution if you have 126 mm dropouts and don't want to/can't spread your frame. But I personally have TWO 9-speed hubs in 126 mm frames right now (one steel, one aluminum) and I just squeeze the dropouts a little to take the wheel in and out... been doing it for a couple years with no ill effects!