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I have a Specialized Secteur with a Sora 3x 9-speed crankset and drivechain and am looking to upgrade to the Tiagra 2x 10-speed crankset 52/36t (as I need a bigger top gear and never use my smallest chainring).

I'd like to keep as much of my existing mechanical setup as possible (shifters, cassette, front & rear derailleurs, chain & BB), and am seeking advice on what I would need to complete this upgrade and what would you recommend I also upgrade - e.g. cassette and/or chain, etc

Thanks.

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  • Note that Tour de France riders aren't strong enough to need more than a 53t chainring in most races. If you think you "need" anything near that big a gear, chances are you're doing it wrong. If you really want to get faster, you need to work on the engine - which is you. In this case, probably learning to pedal at a higher cadence and generating more power (for longer periods of time...) that way. A 50/11 combination will get you 30 mph at a mere 80 rpm. Changing the gearing won't make you faster.
    – Andrew Henle
    Apr 27, 2020 at 16:53
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    Out of curioisity, what range cassette to you have in the rear?
    – Argenti Apparatus
    Apr 27, 2020 at 16:59
  • Thanks for the advice. I have a 11-32 cassette on the rear. My cadence when cycling is around 90 rpm and I try to keep that on long downhills but find I’m having to increase to around 100rpm doing around 80km/h. Any suggestions are welcome to get a bit more top end speed without spinning over 100 rpm.
    – Shaun
    Apr 28, 2020 at 11:18

2 Answers 2

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Shimano's compatibility documentation says there is no compatibility between components of groupsets of different 'speeds'. E.g., there is no compatibility between 3x9 or 2x9 Sora and 3x10 or 2x10 Tiagra. The specific reason a '10 speed' front crank is not compatible with 9 speed group is that chains get progressively narrower as the number of rear speeds goes up and the spacing between sprockets decreases. The chainring spacing on the crank is optimized for the chain width.

That said, the concensus on this site seems to be that you can get away with a 1 speed difference in the crank.

Rear shifters and derailleur do not need to be changed. You do of course need a double front shifter and derailleur, the triple front shifter and derailleur you have now won't work.

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    I think a 2x9 front derailleur might be a good switch though to match the 2-speed crankset.
    – Noah Sutherland
    Apr 27, 2020 at 16:49
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    @NoahSutherland. ahhh, I missed that the OP has a *3*x9 setup, not 2x9, stand by for update.
    – Argenti Apparatus
    Apr 27, 2020 at 16:52
  • Maybe the triple front derailleur works with a double chainring? Worth a try.
    – Michael
    Apr 28, 2020 at 5:46
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In my experience all you need to do is change the crankset. Triple front derailluers tend to work well with wide ranging front cranksets, you will need to set the limit screws and indexing carefully for reasonable shifting performance. The potential problems are two:

  1. The cage will not clear the lower ring when you shift onto the big chainring. If you do want that large a jump in front, I would recommend installing some kind of chain catcher to avoid dropping the chain when downshifting.

  2. The curvature of the old cage is too small to get the cage close enough to the larger new chainring. Generally this is only an issue when trying to use a MTB front derailluer with road sized chainrings.

I've used 10 and 11spd cranks with 9spd rear and chain with no real issues.

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  • I've successfully used a 5 speed triple crank/derailleur with a 9 speed deore rear end.
    – Criggie ♦
    Apr 27, 2020 at 21:05

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