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Sorry if this has already been covered, I did check.

I am gonna go for a 2 x 9 set up this year. I was just reading a thread on 'the other forum' about 2 x9 and somebody said they were using smaller rings (26/36) with a 12/27 Ultegra block.

This got me thinking, if people are using 1x9 now and managing, would a 2x9 with a road block be adequate for XC use, and what small ring/big cog combo would give similar to 27/34?
 

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rockyuphill said:
There's a bazillion 2x9 and 1x9 posts in the drivetrain forum.

Whether those gear choices will work depends on how big your hills and legs are.

Use Sheldon's gear calculator to work out what ratios you have and what you'll need.

http://sheldonbrown.com/gears/
correct - 1st step is to decide which low and which high gear you need and then choose the gearing accordingly.

Below you'll find a gearing chart which makes it pretty easy to see what you currently have...and which gear combination gives you the same or similar gearing. Often people don't need the full standard spread 22/32/44 paired to 11-32/11-34 gives. Many don't use 22/32 or 34 at all and at the same time very seldom ever use 44/11 on top speed...

Just a sidenote:
Road cogsets have a very narrow gearspread...very small steps from one gear to the next.This may be a welcomed feature on steady climbs as you will find a gear that perfectly suits your legpower. BUT on the other hand such cogsets make for much more front shifts. If you have up-and down situations you will have to shift on the front way too much. Just keep that in mind.

I for myself found my ideal setup using 27/40 chainrings up front paired to a 11-32 in the back. That's as low as i need and on top just as fast as i seldom go. It's really rare that i'm running out of gears and i can keep front shifting to an absolute minimum since the small chainring still allows me to go over 30 km/h (18,5 miles) while the big rings lets me do climbs up to 12% degrees....you can stay on the same ring for much more time than you would on a triple setup or if you would use a road cogset.

Look in the gear chart below and find a suitable combination!
I think it shows Meters per revelation of the cranks but i'm not sure if that's for 28" or 26"...but basically that doesn't matter. All that matters is to look for the actual gears you need and to find the same/similar numbers with the different gearing you're choosing.
 

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