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I have a 50/34 chainring and 11-25 cassette. I don't yet feel strong enough to go to the big chainring and keep cadence at 95+. I can however push the 11 gear in the small ring for duration and hold cadence. ( now to the question) can I switch my #34 small ring to a 36 or 39? Will i need to make any adjustments?

thanks nickens,md

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Your statement 'I don't yet feel strong enough to go to the big chainring and keep cadence at 95+' doesn't really make sense, because there is significant overlap between the gear ratios available in the small and big rings.

Here are the ratios:

    50    34
11  4.5   3.1
12  4.2   2.8
13  3.8   2.6 
14  3.6   2.4
15  3.3   2.3
16  3.1   2.1
17  2.9   2.0
19  2.6   1.8
21  2.4   1.6
23  2.2   1.5
25  2.0   1.4

You can see that in the 50 tooth chainring you basically have the same ratios in the 16-15 tooth sprockets as you do on the 34 tooth chainring, 11-17 tooth sprockets.

If you want to ride in a higher ratio than 36/11 (and you should actually avoid cross-chaining from the small ring to the largest sprocket), just go to the big ring and work in the lower half of the cassette. If you need lower gears just pop back to the small ring.

You can swap the 34 ring for a 36 without having to change the chain or front derailleur settings, but you will be losing your lowest ratio. If you don't live in a hilly area that may be OK for you.

You can technically swap in a 39 ring also, but they tend to come with a mounting bolt circle diameter of 130mm rather than the 110mm that 52/36 and 50/34 cranks use.

  • can you share your resource for these ratio numbers? I'd like to use a master list in deciding my next upgrade to my drivetrain (from 3x8 to likely 2x11). However the favorable price point of 3x10 systems and my stubborn old school mentality still intrigues me. The compact, sub compact situation adds to my indecisiveness. At my next computer session perhaps I'll formalize this as a question, but any info I can scan on break would interest me. Thanks – Jeff Nov 28 '18 at 11:59
  • @jeff The ratios in the list above are just chainring teeth/sprocket teeth created in a spreadsheet. There are several online tools for bicycle gear calculations. Try bikecalc.com. – Argenti Apparatus Nov 28 '18 at 12:52

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