Originally Posted by RainmanP
Yes, a 7sp cassette will work on an 8-9 sp freehub. You just need to put on a spacer before putting on the cassette to make up for the difference in width. The spacers are inexpensive.
If your frame is steel you don't really need to do anything about the spacing. You can just spread the dropouts a bit as you put wheels on. 4 mm is just over 1/8". It doesn't take much. I do this with an old 6 sp Bianchi that I am now running 9sp cassettes on. If the frame is aluminum or carbon stick with the current spacing. You can buy a 7sp freehub body and shorter axle to replace the 8-9 and keep the spacing the same. Talk to your lbs or call Harris Cyclery and tell them what you are doing. They have what you need whether it is the spacer or new freehub and axle whichever you decide on. If your frame is steel go ahead and use the 8-9 body and spacer since that will be the least expensive option.
I have been through this both ways. Feel free to ask for more info if you need it.
Regards,
Raymond
Another/related question: Can I fit a 130mm 8-speed hub in my aluminum frame, 128mm rear dropouts?
I have a 1989 Cannondale frame, and I measure a rear drop-out spacing of 128mm. Is that possible? Was a 1989 Cannondale originally 130mm, but I've bent the aluminum by always running old school 6-speed freewheel wheels all the time? Now I'm thinking of switching to and 8-speed SIS system, that I gather is 130mm, I'm wondering what is possible. Thanks to any/all for your input!