I am building a new bike and want to take advantage of the 11 speed system. Can you combine a 14-25 ultegra cassette with a 11 speed dura-ace cassette. If anyone has another idea, it would be greatly appreciated.

I know this doesn't answer your question, but why not go for 45x12t? That way if you ever get a flat in a race and need to take a wheel you don't have to worry about getting a wheel with a 14t small cog.

Colin: I want to run a 52x14 since I have my own spare wheels and a 45 is a track chainring a the shifting is not smooth with 10speed let alone 11 speed.

I'm a junior and i've used 45x12t for two seasons now. There is one company that makes actual road 45t outer rings. Specialites TA, and its the zephyr model. You can buy it on probikekit, its the only place ive found so far. Also, 45x12 gives you 4" extra for a max of exactly 26' rollout, so somewhat of an advantage. You do lose some efficiency though.

No. The cog spacing between 10spd and 11spd is different.
Your best bet is to look some company that makes aftermarket cassettes and have them make one. Although I don't see much benefits going to 11spd. You are only gaining one lower gear. Just use traditional 45/39 in front, because I think you won't climb all hills on 45 front ring anyway.

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Scott Foil Di2 2012
Scott Scale 35 2010

I apologise for the bluntness.

What's wrong with 10 speed?

You're still junior, don't stress? Your advantage will come from power output. You aren't going to win an U19 race with one extra cog.

Otherwise the suggestions are good. If you want 11 speed. Find someone that will make a 45t front ring.

Here's another tip. What are the neutral spare wheels? If they're 10 speed. Run 10 speed.

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BMC SLC01

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