Changing Cassettes

Discussion in 'Bicycle Mechanics and Repairs' started by DHC, 3 Apr 2008.

  1. DHC

    DHC New Member

    I am new to road bikes and finding the gear ratios different from my hybrid and moutain bikes. Basically, hills that I can climb with ease on my hybrid, I struggle up on my road bike. Question is, can I change the cassette to one that would normally be fitted to a mountain bike/hybrid. Current setup is as follows:

    Shifters – Shimano Tiagra 9 speed STI
    Rear Mech – Shimano 105
    Front Mech – Shimano Tiagra
    Cassette – Shimano HG 50 9 speed 12-25
    Chain – Shimano HG73 narrow
    Chainset – Truvativ Elita 2.1 Compact 50/36T
    Bottom Bracket – Truvativ GXP

    Hope is that I can change the cassette to either of the following:

    11-32 or even 11-34.

    Any comments or advice would be appreciated.
  2. Mister Paul

    Mister Paul Legendary Member

    Yours comes in 11-32. HG50 9 Speed Cassette

    That should make things a fair bit easier for you.

    Though someone with more knowledge will have to advise on how this would match your compact on the front.
  3. MichaelM

    MichaelM Veteran

    That's a fair range for a 105 rear mech to handle, depends on whether or not it's a long cage or not. Try Sheldon Brown for info - though someone more knowledgeable may be along to clarify.........
  4. OP

    DHC New Member

    Thanks for the reply.
  5. fosmaal

    fosmaal New Member

    The max rear sprocket capacity of a 105 rear mech is 27 teeth, so you will need to get a rear mech with a long cage, which wold mean getting a MTB one (I'm not sure if you can get a long cage road specific mech, unless somebody tells me different) this should allow you to go upto 34 on the rear. Luckly a MTB mech will work with you index shifters, unlike MTB front mechs.

    Some of you questions are answered here.
  6. bonj2

    bonj2 Guest

    whack an 11-23 on there you girl. And use a triple chainset. Doubles are no good if you are having to grind up hills, and putting a MTB cassette on is not the answer! The main (only?) reason for having a double is to look hard. It kind of ruins it a bit if you then whack a dirty great 34 toother on the back
  7. bianco

    bianco New Member

    Why don't you use smaller tyres?

    The decreased diameter will give you a lower gear!
  8. OP

    DHC New Member


    I was informed that changing to a triple chainset would also involved changing the gear shifters and this was rasing the cost to an unacceptable level.

    Perhaps the answer is get fit, save money.
  9. Chris James

    Chris James Über Member

    I think you have been misinformed. As far as I am aware Tiagra STIs work for both double and triples and have done so for some years.
  10. fossyant

    fossyant Ride It Like You Stole It!

    South Manchester
    That's the cheapest option.

    Problem with having a wide ratio 11-27/32 or what ever, is you have big jumps between sprockets, so you'll not have the smoothest of transition between gears. I.e. spinning in one gear, then grinding a bit in the next.

    My cassettes are always close ratio - either 1 tooth or two teeth at the bigger sprockets, I don't like any bigger jumps.
  11. Danny

    Danny Legendary Member

    Personally I would go a wider range of gears, particularly if you cycle somewhere that is reasonably hilly. If you are struggling to get up hills you are not going to enjoy your cycling, and may even be deterred from going out regularly and thus getting fitter.

    You can always go back to closer ratio gears in the future.
  12. OP

    DHC New Member

    Thanks for all the valuable input. If I am correct, I can summarise it as follows:

    OPTION 1 - change cassette to 11-32 or 11-34.
    • Requires a longer MTB read derailleur/mech.
    • Existing Shimano Tiagra 9 speed STI shifters can be used.
    • Downside is bigger jump, not as smooth transition between gears.

    OPTION 2 - Change to a triple chainset.
    • May require a longer MTB read derailleur/mech.
    • Requires a new front derailleur, such as FD4503.
    • Existing Shimano Tiagra 9 speed STI shifters can be used.
    If the above is correct, then next step is to estimate likely costs of both options.
  13. DEWY

    DEWY New Member

    hi DHC

    it seems i'min excactly the same predicament as you. i have a boardman road comp with the same spec as your bike.

    i'm very interested what you did in the end, cost, are you happy with it???
  14. Globalti

    Globalti Legendary Member

    I have fitted this bike with a Compact 34-50 front and a Shimano 11-32 8 speed rear, (not in the picture) using the old 105 short cage derailleur. It works fine, the gears change fine, the gaps between ratios are big but as somebody else wrote above, it being freehub I can easily change the cassette for something with a shallower slope.

    If I was doing it again now from a fresh start I think I would go for a closer ratio cassette and a triple though.

  15. John the Monkey

    John the Monkey Frivolous Cyclist

    Sorry to sidetrack the thread a bit, but that really is a lovely looking bike RR, top job.
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