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I currently have a focus road bike running on Ultegra group set. The rear wheel is currently 10SP.

I’m looking at purchasing new wheels, and most of the second hand ones come with fitted 11SP. Can I straight swap them?

2 Answers 2

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Actually, if all you meant is can you put a 10s cassette on that rear wheel, the answer is yes, but you'll need a spacer. Those are a stock Shimano thing. The 11s freehub is just a bit longer than the 10s freehub, hence the spacer. Now, your bike store should know where to get one. They're often supplied with Shimano cassettes or with wheels. Or a friend may have a spare - for example, I don't use mine.

If you meant can you put an 11s cassette in your 10s drivetrain and have it shift correctly, the answer is no. Your shifters have ratchets and other contraptions inside that pull a certain amount of cable. That moves the rear derailleur a certain amount. There's no way for the shifters to know that you now have 11 cogs. In theory, you could machine new internals for the shifter. In fact, SRAM shifters have much simpler internals than Shimano, and Ratio Components has done this. For Shimano, it's completely impractical.

If you have Di2, then in theory, Shimano could probably update the 10s firmware to tell it to move the motor accordingly. They haven't done this. None of the other manufacturers have. Perhaps someone could figure out how to hack the shifter firmware, but nobody has yet done so.

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Short answer: No, you can't.

For common road groupsets, the spacing between the cogs, the width of the cogs and the key dimensions of the chain are dependent of the number of speeds. So the derailleur won't be able to align itself correctly with the different sprockets.

That being said, cassettes are considered consumable. So if a second-hand wheel comes with a cassette, and nothing is said about the state of wear of the cassette, it can also be worn and could then need a replacement anyway.

EDIT: Weiven's answer adds a very relevant point, linked to the compatibility of the wheels coming with 11-speed cassettes, the wheel will be compatible (if the wheel has a Shimano freehub body), but the cassette not. A spacer is required for 10-speed cassettes.

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    Agreed. To give a little more detail, the amount of cable that the shifters pull is different between 10- and 11-speed Shimano groups, and the distance that the derailleur travels in response to cable pull (the "cable pull ratio") is also different between 10- and 11-speed Shimano groups. So you'd need to replace those parts.
    – Adam Rice
    Jan 5 at 14:28

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