Originally Posted by
BoraxKid
This seems like a good thread to explain my current situation and plans. My wife has an 1991(?) Trek aluminum frame road bike that I'm pretty sure is using a 126mm OLD hub, as measured with a crappy, plastic Fisher Scientific ruler. A few years back, I had our LBS lace up a new rear wheel with a HG freehub body for this bike, but I'm not sure if it will take more than 7 gears. I would like to upgrade this bike to use a 9 (or maybe 10) speed cassette, to allow a wider gear range. I did this exact thing to my old road bike, but that was a steel frame that I could cold-set. My plans for the Al frame bike at the moment:
- measure the rear dropouts and OLD using digital calipers that should have arrived today and confirm the 126 mm measurement
- attempt to fit a 9-speed cassette on the freehub body (cassette should arrive next week)
- if the cassette fits, move on to upgrading the derailleurs & cranks to modern 105 level equipment
- if the cassette does not fit:
- order a new freehub body that will accept an 8/9/10 speed cassette
- adjust the spacers on the rear axle to give adequate space for the new cassette (there is a large spacer on the left side of the axle; I'm pretty sure I will need only a few mm moved from the left side to the right side)
- assemble the wheel and adjust the dish to re-center the rim in the bike frame
The biggest potential issue I can see at the moment is that according to miamijim's work, 16-18 mm of dish on the right side of the back wheel is "normal", and anything outside that range should be avoided. I think my plans will require dishing to less than 16 mm on the right side, but I also cannot find any credible sources that show this will be an issue. There is a lot of speculation and lots of well-reasoned hypotheses out there, but I can't find anything that shows either a lab or real-world test that is relevant. In fact, plenty of 10+ speed wheels seem to be built with much less than 16 mm of right-side dish.
What do you people think? Will it work?
Before you do that, as with the OP if you have 128 spacing in the rear just get a 130 wheel and then you can use any cassette you want. 126 spacing may not fit a 9sp cassette. There's a reason they went to 130, the cassette is just wider with the freehub to match. The first cog will be against the dropout or the freehub will extend too far over the locknut. You may be able to use 8 of 9 on a 7sp freehub. I don't like the idea of moving spacers around on an old wheel. Re-dishing an old wheel sounds like it could go terribly wrong. And then too, what if the spacers are necessary for clearance on the other side?
So if you have 128 spacing on that frame, take advantage of it and use a 130 wheel. It'll be tight but it will work. If it is 126 you likely won't be able to use 9sp, or it will just fit without any room to spare. And there is barely any room to spare with a 130 wheel. And with the thinner cogs of 11sp they still needed to steal an extra mm, 11speed wheels are 131, but they didn't spec it for the frame, you just squeeze it into the 130 spacing on most road bikes. There's this 1mm cassette spacer that you need to use with 10sp cassettes on 11sp hubs.