Triple to Double Groupset Advice

Secteur
Secteur Posts: 1,971
edited September 2011 in Road beginners
I love my 2010 Secteur Comp and I see no reason to change the whole bike (although I wished it would take full mud guards in the winter), but I do want to change 2 things with it;

1) I'd like routed cables on the handlebars - (purely an aesthetic thing)

2) I'd like a double as I never, ever use the 30 "granny" ring, and again aesthetically I find a double more pleasing

The best way to acheive this is to upgrade the groupset, which I can get for just over £400.

My current triple set up is full 105 (5600) groupset, and it's a triple (50/39/30). The cassette is 12-27.

My question is that despite lots of research, I still can't figure out what the best ratio would be in a double to give me the same range of gears as it is pretty hilly where I ride and I am still not yet super-fit, although I think I do pretty well on the hills.

I spend a lot of time in my 39-27 gear on the hills (middle chainring, large sprocket) and I can't afford to lose this gear as it is my hill gear.

I find that the 50 chainring sometimes means I spin out on descents, though I'd rather sacrifice this for a decent climbing gear (but both would be ideal).

So, how do I figure out what double/compact specification I need?

Cheers.

Comments

  • rafletcher
    rafletcher Posts: 1,235
    Most doubles are either 39/52 "standard" or 34/50 "compact". You should still be able to use a say 12-27 cassette with 39/53 double - that requires a rear mech capacity of 15 + 14 = 29. So as long as your rear mech has a 29 tooth or better capacity you'll have your 39/27 gear, and get a higher "top" gear - 53/12.
  • Thebigbee
    Thebigbee Posts: 570
    I am not sure you need to spend £400 to upgrade the groupset.

    £79 for this one http://www.chainreactioncycles.com/Mode ... elID=41435

    and this one http://www.chainreactioncycles.com/Mode ... elID=35739

    Ultegra from £143 http://www.chainreactioncycles.com/Mode ... elID=39017

    Or maybe just check out this link

    http://www.chainreactioncycles.com/Cate ... goryID=577

    If I had a spare £80 I would definitely get one of the doubles at that price. Unfortunately I don't and do use the granny ring!!

    HTH
  • Secteur
    Secteur Posts: 1,971
    rafletcher wrote:
    So as long as your rear mech has a 29 tooth or better capacity you'll have your 39/27 gear, and get a higher "top" gear - 53/12.

    If my cassette is 12-27 (i.e. biggest sprocket is 27 tooth), then why does the rear mech need to be have 29 tooth capacity?

    Anyway, thanks for the advice, it's clarified it a bit for me!
  • desweller
    desweller Posts: 5,175
    edited September 2011
    You only need a different chainset. The shifter and derailleur will already do it.

    Although, I'd suggest a few rides in the Peaks or the Lake District before you bin it off...

    EDIT: Gear ratios table, feel free to edit
    - - - - - - - - - -
    On Strava.{/url}
  • kayakerchris
    kayakerchris Posts: 361
    The rear derailleur has to swing forwards and backwards to maintain a constant chain tension whether you are in the 39 front and 12 back or the 53 front and 27 back and anything in between. The difference between the front chain rings in terms of teeth and the sprocket in terms of teeth added together is the capacity of the rear mech.
    Hope this helps.
    www.hand-surgery.co.uk
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  • mikeeye
    mikeeye Posts: 162
    I realise that this doesn't address your aesthetics issue, but have you considered changing your cassette to an 11-23? That keeps pretty much the same range of gears as you have with the 12-27 and restricting yourself to only the 39 and 50, but it improves things by making the ratios closer together. i.e. it allows you to fine tune the gear you're in better than you can now. It's a cheap option too - just the cost of the cassette.

    I have a bike with a triple and bike with a compact. The smaller gaps on the chain rings for the triple (9 or 11 teeth) make for better gear changes than the compact (15 teeth).

    Edit: I see you're considering a double rather than a compact. 11-50 isn't that much shorter than 12-53. You'll get your longer top gear and keep a low gear to get up the hills.
    If you still don't know what recursion is, read this sentence.
  • mrwibble
    mrwibble Posts: 980
    Why do you need to change everything with your bike? I get the feeling you just want to change things for changing things sake! Crank arms, group sets and so on. Stick with your bike for a while then save all your money on upgrades and buy a better bike a couple of years down the line

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