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I would like to buy a single-speed bike that happens to have 120mm hub spacing, and add the Shimano Alfine 8-speed hub. That hub, however, seems to have a 135mm spacing.

Can the 8-speed Alfine hub be modified (in less than two hours, with standard hand tools) to 120mm?

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You could easily spring a standard 120 steel frame to 126 or so without tools. Much beyond that, though, and the dropouts are no longer parallel (and, unfortunately, Sheldon doesn't describe how to realign the dropouts). However, a good frame person can bend you frame to 135. –  Daniel R Hicks May 28 '12 at 12:53
    
Actually Sheldon does describe how to align dropouts: sheldonbrown.com/forkend-alignment.html (A 120mm rear quite likely has track forkends which technically aren't dropouts, or aren't dropouts in its original stricter sense, depending how more generic use/misuse of "dropout" has become: sheldonbrown.com/gloss_dr-z.html#dropout sheldonbrown.com/gloss_e-f.html#forkend ) –  armb May 8 '13 at 13:45
    
The lower quality Nexus 8-speed hub has a lower limit of 127mm, which doesn't help you, but might be worth noting for someone with 7-speed spacing who doesn't want to reset their frame: sheldonbrown.com/nexus-mech.html#advice –  armb May 8 '13 at 13:49
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2 Answers 2

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No, with either the 8 or 11 speed Alfine hub, there is no possibility of using it on a 120mm frame. The hub shell itself is about 120mm wide, without the cable carriers for shifting, or any spacers at all.

If, as it appears from your 120mm reference, you are considering a fixed gear frame with that spacing, then you should reconsider. 120mm spaced dropouts are typical on track specific frames, or track frames from very traditional builders.

Frames like these will also have geometries which are not suited to use on the road, and I assume you don't want the bike for the velodrome, since you want gears.

There are plenty of fixie frames with 130m or or 135mm dropouts. If it is 130mm and steel, you will have no trouble adjusting the frame to fit a 135. Otherwise, you should use a 135mm spaced frame, which likely means a hybrid or mountain bike single speed frame, or a frame with a concentric bottom bracket.

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Judging from the picture, I would say no. The usual method for narrowing the over locknut distance of a hub is to use narrower locknuts. You can tell from the picture you posted that this is not possible. The locknut on the left is plenty wide, and it looks like you could probably shave off 5mm over there, but the drive side has no room to budge. It looks like you're out of luck.

But not entirely. From your 120mm reference, I'm guessing you have an older bike you want to install the hub into. These older frames are often quite amenable to being respaced, as they are generally steel frames with a lot of give. You should check out Sheldon Brown's article on frame respacing.

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