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Does anyone out there know what difference the gear ratio makes for a rear cassette? I'm looking at buying a new one as i'm experiancing serious slippage. They have a range of options from 11-28/11-30/11-32 ?????

Any idea's i.e help please


  • risris Posts: 1,002
    do you know what the current cassette is?

    the ones you identify have increasingly large cogs at the 'top' of the cassette which would make them more suited to going uphill.
  • No idea what the current set up is, i'm just looking for a day to day affair with the ability to climb big hills when i need to. I've just started tri and been doing flat ones but i need it to cope with anything.

    This is what i'm looking at http://www.wiggle.co.uk/p/cycle/7/SRAM_ ... 0/#buyitem just not sure what ratio i need and if it'll make a massive difference??

    Ta for the help!
  • risris Posts: 1,002
    it really helps to know what you've got before wondering what to go to! lots of dull but hopefully useful questions...

    the cassette cogs have the number of teeth printed on them really small (if the cassette is worn/dirty then you might not be able to find it easily). alternatively, count the teeth of the smallest and biggest cogs - smallest cog is likely to be 11-12, top one 25-28 (possbily).

    do you know what your chanrings are at the front? 2 cogs or 3? if you feel like counting the teeth on those too that would be tops.

    are you happy with the gear range you currently have?

    if you aren't, do you find that a) you tend to spin out (run out of the smaller cogs at the back when travelling fast) or are you b) often changing onto a different front chainring to get to bigger gears (climbing hills, getting tired etc).

    when you want to cope with anything are you planning to widen the tri training and races to hill climbs and sportives?

    sorry if this seems a bit daft and overly detailed... i suspect i need to get out more and stop worrying about gearing... welcome to the forum btw.
  • ZacniciZacnici Posts: 1,385
    I rather think they are MTB cassettes with those spreads - 11-23, 11-26 and even 11-28 but 11-32! Crikey that would haul you up Blackpool tower - ah looked at link - should have done that first - they are 8 speeds

    What are you front chainrings (the size - number of teeth on each ring) what gear shifters do you have, and what are you running a road bike, hybrid, MTB?
  • Right after counting and then realising that the information was written on the cassette as mentioned I have the info:

    It has three cogs at the front and are 52 42 30
    On the back it says 21T-24T-32H

    All goobledy gook to me but hopefully that will help - i would like to maybe change it as i am spinning out and never use the granny cog and rarely use the very top ring when climbing. Probably would want to go up only one level (does that even make sense???)

    Really appreciate the help guys

    Oh yeah the bike is a Specialized Allez roadbike if this helps?!?!
  • ZacniciZacnici Posts: 1,385
    OK if it is the factory spec then the rear cassette should be 12-25.

    You don't use the granny ring and also rarely use the top ring when climbing by that do you mean the biggest cog in the cassette i.e. 25T and is that with the middle chainring at the front the 42T? If so you are doing well which begs the question if you rarely use a 25 then why are you looking at a cassette with 28, 31 or 32?

    Effectively, if I get this right, you are using the 52T and 42T chainrings on the front have occassional use for the biggest cog on the rear cassette, 25T and are spinning out on descents. In essence then you are running 'Standard' ratios.

    The only 'upgrade' that I can see is to swap out your triple for a standard 53/39 and maybe an 11-25 cassette, I personally would not be concerned about spinning out on a descent as you spend more time going up and that is where you want to save time and energy.

    Have a look at this posting which may be of use:

    But the question then needs to be asked why spend this money on upgrading when it may be simpler and cheaper to sell the existing bike and buy another?

    Hope that helps
  • Thanks for the advice, i think i'm just gonna change the rear cassette use the bike over the winter and upgrade for next season to a better rig.

    Is there any major difference, in your opinion, to using a 12-26 or 12-25 or 12 - 23????
  • ZacniciZacnici Posts: 1,385
    Well according to the specs - correct me if I'm wrong - but your bike should have a 12-25 already. You are a bit limited in choice owing to the 8 speed shifters as IMHO an 11-23 or 11-25 would be your best option.

    From what you told us you are only using the 52T and 42T front chainrings and rarely use the 25T on the cassette. I would suggest IMHO that you should look at a bike with 53/39 chainrings and an 11-25 cassette for challenging i.e. hilly courses and also get an 11-23 for flattish courses as the ratios will be closer together.

    A 42/25 according to Sheldon Browns gear calculator is pretty much the same as a a 39/23 and a 39/25 would give you that little bit of an 'oomph' going uphill.

    The 53 theoretically will give you an extra 5Kph using 53/11 as opposed to 52/12

    If you are 'well hard' then a 53/42 combo might be right for you as you are using 52/42 already, you would lose out on bottom end 'oomph' though compared to the 39.
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