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8 spd cassette on 7 spd hub(2 posts)

8 spd cassette on 7 spd hubDan
Sep 22, 2001 4:00 PM
I have several 7 speed Ultegra hubs. I would like to build at least one into a 8 speed wheel. The 8 spd casette is too wide to fit the last gear on the splines. How is it done? If the answer involves taking off the ratcheting free hub part (splines), please be specific as to the tool needed and how it is done. I see that there is an inner spline that would allow a 12 sided?? tool to reach in and turn, but which way and ???? I assume a wider axle is needed. Finally, are some hubs 7 and 8 compatible or not?
THANKS
Can't be done, but...Robert
Sep 23, 2001 2:14 AM
An 8 speed cluster won't go on a 7 speed hub, it is 3.5mm too wide. You will need a new freehub. It can be switched, if you want to spend the money and take the time.

I believe the tool you ask about is the lockring tool. There are a couple on the market, either a Shimano HG15, or Park FR5. The Park costs about 1/2 as much as the Shimano. You will also need a 10mm hex wrench to remove the bolt holding the freehub to the hub. These all have normal threads. You can get a new freehub from Loose Screws (www.loosescrews.com), and they might be able to get you the tools. If not, most bike shops can get the lockring tool and the hex wrench is available almost anywhere they sell metric tools.

If the axel locknut spacing is 130mm (most road bikes made from about 85 on are 130), you can use the old axel, but you might need new non-drive side spacers, depending on the bearing placement in the two freehubs. If your bike has 126 spacing, you will need a new axel (140) as well as new spacers, and the dropouts widened (if your bike is steel, if it's not you can't widen them safely).

The only catch is, after you get a freehub, 10mm hex wrench, and axel spacers, it might cost you as much, or almost as much, as a new hub. If you are doing this to keep older wheels going, then the cost really isn't a problem because you will have the added cost of a wheel build, etc., if you change the hub.

But there is a cheap way to do this if you are just trying to keep old 7 speed wheels going for an 8 speed system. You can use 8 speed spacers on the 7 speed hub, but only 7 cogs, not all 8. You will need a freewheel/bottom bracket spacer to put on the freehub before you put the cogs on. I think a 1.5mm spacer would work. If you decide to do this, the lockring tool is about $10 (and you should have one of those regardless) and the 1.5mm spacer is less than $1 (US). If the cluster is rivited together, just drill out the rivets and keep all the parts. The Loose Screws is a good place to get just one cog at a time, instead of a whole cluster, which not only saves money but keeps you from wasting good cogs. I order a few cogs at a time, the one's I wear out fastest, or order just one or two cogs with other little parts like bearings, etc.. Loose Screws is a great place for all the little hard to find parts, and carries most high wear parts too.