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Cycling Forum: mountain cassette/ rear derailleur on a road bike..... anyone?

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    • CommentAuthorFree Memberruudyvandy
    • CommentTimeMay 11th 2008
     
    ruudyvandy

    I am just getting into cycling and purchased an older steel cannondale with decent components (dura-ace front derailleur and shifters, ultegra rear) but my rear cassette is inadequate for the climbs I frequently find myself on. 

    I've been to my LBS and they suggested either replacing my 12-23 rear casset with a 12-27, or throwing on a mountain cassette (such as a xtr 11-34) and rear derailleur.

    I know that I am sacrificing the weight on the back, but I am desperate for lower gearing.

    PS - Putting a triple on the front is out of the question due to budget constraints.

     

    Thoughts? 

    • CommentAuthorFree Membersjk
    • CommentTimeMay 11th 2008 edited
     
    sjk
    a 12-27 will give you some breathing room on steep hills, but if you really want to make sure you have the gearing that might come with a triple, you'll need the XTR. Whatever small number of grams it adds will easily be paid back in spades when you can turn a 39/34 instead of a 39/27. Caveat: While the added grams aren't much of a problem, the new spreads between cogs might be difficult. a 12/27 jumps 21-24-27 if i recall correctly, with everything below that pretty closely spaced. a 10 speed 12-34 would have some mighty big jumps at the big end, meaning a switch up or down on a long climb would make for a big change in pedal speed to keep the same pace.
    • CommentAuthorFree MemberRonsonic
    • CommentTimeMay 11th 2008 edited
     
    Ronsonic

     

    Cannondale made a steel bike?!?!

    SJK is on the money with his comments. You might also consider a compact crank up front, cheaper than going triple and it'll give you a 34-50 up front which should ease the pain and it will keep the gearing closer together than the MTB parts. Even off road those are big steps on the rear cassette.

    You don't say if you've got 8, 9 or 10 in back. I'm sorta guessing 9. The 12-27, will certainly help a lot. If you also go with a compact chainring setup it'll get you to a pretty small gear for the climbs.

    Just a comment on part selection, XTR is certainly lighter than the less expensive stuff, but doesn't shift all that better and is not more rugged. You can use Deore and above without hurting anything and make the switch less expensive. Not as sleek, but it all works well and unless you are in racer shape, your body will have far more excess weight than bike parts.

     Here's a gear calculator you can use to compare the potential changes: http://sheldonbrown.com/gears/ If you set it to give you gear inches you can compare the changes you'd get from each setup and see how they look relative to each other and what you're riding now. 

    Bottom line is going to a 12-27 gets you a 38" low instead of a 45 - that's a worthy step. Compact will take it to a 39, Compact and a 27 = 33. That'll get you over most anything. Keeping your crankset and using an 11-32 gets your lowest gear down to a 32. Almost too many options.

    You might also get a second opinion at a different shop. Some shops are better at selling expensive stuff than making you a happy rider. 

    • CommentAuthorFree Memberruudyvandy
    • CommentTimeMay 11th 2008
     
    ruudyvandy

    Thanks guys --

    It's a 9 speed - sorry.  

     

    The compact crank up front seems to be about the same price as buying the MTB cassette and rear derailleur.  If it were you - what is your choice and why?

    • CommentAuthorFree MemberRonsonic
    • CommentTimeMay 11th 2008
     
    Ronsonic

    Me, I live in a really flat place.

    I'd try the 12-27 and then go compact if that didn't do it. That's me and I do my own bike work which may change the economics. Also don't know how severe the climb is and how much potential you have as a rider to grow into it. 12-23 is a pretty harsh gearset, pretty much belongs only under the hardcore riders or us flatlanders.

    • CommentAuthorFree Membersjk
    • CommentTimeMay 11th 2008 edited
     
    sjk
    Ronsonic and I might be good comparisons - I live in a really hilly / mountainous place where every ride has a lot of rollers and many have long climbs. I ride a 12-27 and my only complaint is the big jumps on the top end. I would be really concerned about the jumps on a 12-34. If I could do it all over again, I'd *probably* go with an 11-23 and a compact crank. But the work involved in changing a cassette is minimal and you could try different setups much easier. I'm also pretty sure that if you buy compact rings for the front you also have to buy a whole new crankset. I'd be surprised if all of that costs the same as an XTR cassette, but I'm not a mechanic. It's a question worth asking before you start collecting parts. I would divide this post into easy-to-read paragraphs but I can't seem to get it to work!
    • CommentAuthorFree Memberruudyvandy
    • CommentTimeMay 12th 2008
     
    ruudyvandy
    I've spoken to a couple people now and they seem to highlight the fact that the 'jumps' are the biggest downfall in this setup. My thought process is this - if I don't need the low gears then I don't use them. But if I need them - then the jumps are worth it.
  8.  
    PeterBayliss
    I have on my touring bike a road triple on the front and a mountain bike rear mech and 11-32 cassette. I find it works fine with no problem changing gears buy I don't really use the lowest gears at the moment as its flat where I am. I have the lower gears for hills with weight on the bike.

    I think this is the gearing on the shimano MTB cassettes so you might find the 'jumps' big.

    11-32  11,12,14,16,18,21,24,28,32

    11-31 11,13,15,17,20,23,26,30,34

    If money is tight I wouldn't buy the XRT or Deore XT as they are a lot more expensive than the Deore which I have and works fine. The Deore LX is the middle of these two.

    I would say just changing the rear cassette to 12-27 would make a difference but it depends how steep the hills are and how hard you are finding them.

    • CommentAuthorFree Memberruudyvandy
    • CommentTimeMay 14th 2008
     
    ruudyvandy
    What I probably need to do is get on some other people's bikes and get a feel for what the different cassettes feel like.  I just know that I am out of my seat on way to many hills and I want to get a better set up...

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