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Gear Ratios for a relative newbie ….

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  • April 1, 2011 at 1:53 pm #13276
    phax71

    Hello all,

    Ok I need some more help.

    After recently mashing up a nice wheelset (rear anyway), I’m taking the opportunity to replace my totally unrealistic 11-23 cassette with something a little more “real”. I only did four rides and 11-23 was very tough on me (not done much riding these past 18 months).

    I’m new to the roadbike, having ridden MTB and commuters for years now, both on 12-27 cassettes and standard MTB rings … – more than comfortable with these ratios.

    My question is, as I don’t understand the workings of the ratios ….

    My roadie is running a 53, 39 upfront, in order to achieve a ratio similar to my MTB and commuter what cassette would I need to run?

    I’m not changing to a compact or triple as I spent good money on my crank so even if I cannot match the ratio, something a smidgeon tougher than my 12-27 wont hurt too much.

    Any links to charts, tables, info on gear ratios would be a great help also.

    Oh, may have a super lightweight 11-23 Recon cassette for grabs soon also, it weights just 87g and has only done around 60 clean, dry miles.

    Cheers all!!

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  • April 2, 2011 at 7:46 am #642157
    0
    dave atkinson

    technically i thing the 7900
    technically i thing the 7900 rear mech tops out at 27T on the rear, although i know people that have run a 28T with no bother, and i’ve seen threads elsewhere where people have run up to a 32T, although the mech would certainly struggle with that as the cage is too short.

    April 1, 2011 at 2:28 pm #642155
    0
    phax71

    Cheers all..
    I’m running a
    Cheers all..

    I’m running a Dura Ace 7900 Rear Mech:

    http://www.planet-x-bikes.co.uk/i/q/RMSHDA7900/shimano-dura-ace-7900-rear-mech

    if that helps.

    Will study those links and try and figure it all out this w/e

    Cheers!

    April 1, 2011 at 2:26 pm #642153
    0
    Fringe

    i was just about to suggest
    i was just about to suggest sheldon browns gear page myself, if you do find you need a bigger cluster of gears shimano do a ‘junior’ range in the ultegra sl dept (on their website) 13-25, 14-27 etc.. lose a bit in the higher end but good for hills, esp. with a 39 on the front.

    April 1, 2011 at 2:20 pm #642151
    0
    robert.brady

    Road chainsets give much
    Road chainsets give much bigger gears than MTB cahinsets, so if you’re sticking with 53/39 you’ll need a much bigger cassette.

    You may be limited by the capacity of your rear mech. Depends on what you’re using, but I think most short cage road mechs can’t cope with anything bigger than a 28T sprocket. I’m sure you can use Shimano MTB mechs and cassettes with their road STI to open up your options.

    If you use SRAM, Apex allows for bigger rear sprockets, up to 32T I think. Unless you’ve already got SRAM though, that’ll probably be more costly than a new chainset.

    If you use Campag, I think your only option is bigger legs.

    Sheldon Brown’s gear calculator is a good tool for finding different ratios that will give you the same gear:

    http://sheldonbrown.com/gears/

    Hope that helps.

    Rob

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