8 Speed Freewheels
After finishing my Hotrock 20 7-spd upgrade it's time to move on to my other son's 2009 24" Hotrock. I was going to replace his grip-shifters with a set of Shimano MC-40 trigger shifters. It would be nice to convert his 7x3 setup to an 8x3 setup while I was at it.
I noticed that you can still get 8-speed freewheels. Instead of relacing the rear wheel to accept a cassette hub, can I just install an 8 speed freewheel? Will it work with the rear wheel spacing I have now? Also, can I use a standard Shimano 8 derailleur and shifter?
My son an I are in the process of changing around his 24" Giant XTC. My thought process was the same as yours. In fact, we are going from a 3 x 7 to a 1 x 8.
I happen to find a nice set of quick release wheels on ebay. The rear had a hub setup. Because I can only work on my son's bike at night, or for 15 minutes during the day (he rides it constantly) I bought him a 7 speed cassette to use with the 8 speed hub. I use a spacer in the back so there isn't a problem using the 7 speed cassette.
The hub/ cassette combination is worlds better than the freewheel he had on the bike. Number 1 it's lighter. 2, it's quieter (no clinking noises), and 3, it shifts so much better with the stock derailleur.
I know this isn't what your plan was, but you might want to think about this route of buying a new rear wheel with hub. Just my $.02 from my experiences.
2013 Rocky Mountain Altitude 730
2013 Pipedream Sirius R853 - 650b Belt Drive
IBIS Tranney 29er
An 8s FW is about 5mm wider than a 7s. You cannot just directly swap the freewheel because the small cog would hit the dropout. You would need to move about 5mm of spacers from the non-drive side of the axel over to the drive side to give the 8s FW clearance. THis will necessitate re-dishing the rim/spokes by back over toward the drive side (tensioning the drive side spokes, decreasing tension on NDS) so that the rim is centered in the frame.
Instead of chaning the freewheel or swapping to a casette hub, if you are more concerned with getting the shifters working than actually having 8 gears it is possible to get 8-speed shifters working OK on a 7s freewheel. The cog spacing is not exactly identical for 7s and 8s but is close enough that you can adjust the cable anchor position to alter the derailler pull ratio if needed.
See explanation of B-position cable anchor;
Mixing Brands of Shifters, Rear Derailers and Cassettes
Originally Posted by chuckactor
Most any index compatable shimano RD will be compatible with any 7,8,9 or 10 speed freewheel/Casette (and matching speed # shifters). Noteable exceptions being pre-1997 dura ace and recent dyna-sys MTB RD's.
Shimano Dura-Ace Compatibility
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