Weight Weenies

Hi the problem i have is compact isnt small enough for where i am (south spain) i currently have 50/34 ultegra chainset, and i want to go smaller would a Mountain bike chainset fit or work? What's my options?

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http://praxiscycles.com/pages/cx-rings
These won't look as good as the Ultegra rings, but it will work just fine.

Thanks for that but (currently have 50/36) which is to big Im after more of a mounting bike gear ratio?

Rotor does 46/34 rings if that is enough. You could always install a 2 ring MTB crank, but that may require some custom work.

What range does your cassette have? There might be some more inches lost there.

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Many compact cranks can take 33t rings. On some the crank arms are too long and interfere with the chain side plates. Harris Cyclery sells 33t rings in the US.

As mentioned above you can also get larger cassettes. With the popularity of wide range road cassettes there are plenty of options. You may need a different derailleur if you go over 30t. With Shimano, you can use a 9sp MTB rear derailleur to shift 32t and 34t cogs. The Sram 11-32 looks like a good wide range cassette for road use.

You can fit many MTB cranks if the BB you use has provision (usually spacers) to work on a 68mm BB. But the Q factor will be higher and it may be difficult to find large chainrings that are large enough for enough gear inches on the descent.