compact to double

Phekdra
Phekdra Posts: 137
edited May 2008 in Road beginners
Hi all, my bike came with a 50/34 compact chainset and a 12/25 10-speed cassette. I find the bottom gear okay (although as some people have said I think the very bottom couple of gears tend to blend together), although I could do with a higher top gear for pedalling downhill. I'm thinking of changing to a 53/39 double and a 12/27 cassette to give me a similar bottom, a higher top, a little more space between the gears and smaller jump between rings. I'm having doubts, though, as if it was such a brilliant idea then cheaper bikes would come with this setup rather than compacts. Does anyone have any advice whether this is such a smart thing to do or not, and whether it's even possible?

Phekdra

Comments

  • gavintc
    gavintc Posts: 3,009
    Yes, it is possible to do. The reason that the compact has become so popular is that you do not need to be a strong cyclist to ride a compact. Moving to 53/39 will give you quite a big step up in top gear. You might also want to consider fitting a 11-25 cassette as this might be a cheaper option, and would achieve one of your aims - a higher top.
  • fizz
    fizz Posts: 483
    I ride a 52/39 with 12 x 27 I only really really struggle nasty hills.

    Personally I seem to spend alot of time on the inner 39 and I dont use the big 52 ring unless its flat with the wind behind me or downhill. But even downhill there comes a point where I spin out of gears.

    I'm more of a spinner than a grinder so it does depend on your riding style and whether you like to push big gears or not
  • Phekdra
    Phekdra Posts: 137
    Thanks for the replies. I was thinking about it yesterday whilst out for a ride - some flat bits with quite a few sharpish hills. I spent most of the ride on the 50 ring, standing up for short climbs and switching down for some of the very steep hills or extended runs. It seems to me that a 53/39 with a 12-27 cassette has a lower usable gear on the big ring and higher usable on the small ring, which sounds very handy indeed.

    I suspect I'll need to raise the front deraileur a tiny bit to get it out of the way so I might wait until the cassette needs changing and then make a decision. In the kind of terrain around here I very rarely find myself just switching one gear, it's usually a couple, which suggests I could use with a bit more spacing.

    To Gavintc - I have considered a 11/25 cassette, which would give me a bigger top gear, and would be cheaper. I'll have to get my calculator out and work out which option would give a better spread.

    Phekdra
  • dennisn
    dennisn Posts: 10,601
    If you want a big top gear on your compact just put an 11 on the back. A 50-11 is
    a taller gear than a 53-12 and not a lot of people out there can use a 53-12 with
    any kind of regularity except downhill. I run a 50-34 and an 11-21 and have no problems.
    When in the mountains I switch out to 50-33 and 12-27. Once again no problems. I am
    thinking of going to a 35 or 36 tooth small ring as the 34 seems a bit low but it's not that big of a deal. Note that I spend most of my time riding on some of the flattest terrain
    around. Just happens to be where I live.

    Dennis Noward
  • redddraggon
    redddraggon Posts: 10,862
    Rather than change to a 53/39 and 12-27, I'd go for 50-36 and 11-28 (an SRAM cassette) - higher top gear and lower climbing gear.
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  • Phekdra
    Phekdra Posts: 137
    redddraggon wrote:
    Rather than change to a 53/39 and 12-27, I'd go for 50-36 and 11-28 (an SRAM cassette) - higher top gear and lower climbing gear.

    Thanks folks - I've discovered that I'm going to need a new chainset if I want to fit different sized rings as my current crank spider has a 110m bolt diameter, and virtually nothing apart from compacts is available in that form. Perhaps a 50/36 would fit, but I don't want to make it too easy! :D I might save up for a new chainset anyway as I've been wondering how to change a bottom bracket and this would be a good opportunity to find out! Besides, the logo's nearly rubbed off so it must be about time to change it... 8)

    Phekdra
  • redddraggon
    redddraggon Posts: 10,862
    Phekdra wrote:
    Thanks folks - I've discovered that I'm going to need a new chainset if I want to fit different sized rings as my current crank spider has a 110m bolt diameter, and virtually nothing apart from compacts is available in that form.

    As I posted in your other thread:

    53T chainring to fit on Compact

    Inner chainring

    The chainrings aren't too hard to find if you know where to look.
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  • dennisn
    dennisn Posts: 10,601
    Phekdra wrote:
    redddraggon wrote:
    Rather than change to a 53/39 and 12-27, I'd go for 50-36 and 11-28 (an SRAM cassette) - higher top gear and lower climbing gear.

    Thanks folks - I've discovered that I'm going to need a new chainset if I want to fit different sized rings as my current crank spider has a 110m bolt diameter, and virtually nothing apart from compacts is available in that form. Perhaps a 50/36 would fit, but I don't want to make it too easy! :D I might save up for a new chainset anyway as I've been wondering how to change a bottom bracket and this would be a good opportunity to find out! Besides, the logo's nearly rubbed off so it must be about time to change it... 8)

    Phekdra

    To be honest you have lost me as to what you want to do. Buying a new crankset
    just to learn how to put it on seems a bit excessive. Whatever. Good luck.

    Dennis Noward
  • Phekdra
    Phekdra Posts: 137
    dennisn wrote:
    To be honest you have lost me as to what you want to do. Buying a new crankset
    just to learn how to put it on seems a bit excessive. Whatever. Good luck.

    Well, that was my attempt at humour - rather too heavily disguised, unfortunately! 8)

    To Redddragon - thanks for the chainring links, something I'd failed to uncover. As is apparent from the forum I'm very much a road beginner and trying to find the gearing that would suit me best. It's probably best if I have a go on a standard double setup and see if I prefer it. If not I'll fit a wider range cassette and keep the compact.

    Phekdra
  • jedster
    jedster Posts: 1,717
    I have a triple at the moment but think I would go with a compact double in future as I hardly use the granny ring. Seems to me that a compact double is ideal because with a change of cassette it gives you everything you could ever need (as others have suggested):

    50/34 and 11:21 or 23 - gives you just as big (or bigger) gears than a standard double set up.
    50/34 and 12:25 or 27 - gives you plenty of low gears for the mountains.

    What advantage does a std double have over 50/34 and 11:23? I could see that you might want to run very big gears for time-trialling if you were a grinder but for everyone else? Is it just image?

    J
  • CrookedCucumber
    CrookedCucumber Posts: 324
    Phekdra wrote:
    Hi all, my bike came with a 50/34 compact chainset and a 12/25 10-speed cassette. I find the bottom gear okay (although as some people have said I think the very bottom couple of gears tend to blend together), although I could do with a higher top gear for pedalling downhill.

    You could always just pedal a bit faster :)

    But, seriously, with your gear ratios you should be getting a speed of about 30mph in top gear at about 80 pedal revs per minute, and 40mph at 110.

    My point is that it may be less costly, and better for your knees in the long run, to change your pedalling rather than your gearing. I appreciate that some folks like to turn the pedals less frantically, of course.
  • Phekdra
    Phekdra Posts: 137
    CrookedCucumber wrote:
    My point is that it may be less costly, and better for your knees in the long run, to change your pedalling rather than your gearing. I appreciate that some folks like to turn the pedals less frantically, of course.

    I'm sure you're right - although I don't think that I pedal particularly slowly, at least compared to some people! I try and keep it around 80 on the flat, but I do tend to stand up on hills rather than change down. Anything much more than around 80 and I tend to feel unbalanced and uncomfortable, and even trying to pedal at 40mph doesn't bare thinking about!

    Phekdra

    P.S.
    Jedster wrote:
    Is it just image?

    I've been asking myself the same question. As I've mentioned I really don't like the big gap between rings and some wider spacing would be nice. Perhaps the disadvantages outweigh the advantages. As should have become clear by now I really don't have much experience with road bikes!
  • CrookedCucumber
    CrookedCucumber Posts: 324
    Phekdra wrote:
    I'm sure you're right - although I don't think that I pedal particularly slowly, at least compared to some people! I try and keep it around 80 on the flat, but I do tend to stand up on hills rather than change down. Anything much more than around 80 and I tend to feel unbalanced and uncomfortable, and even trying to pedal at 40mph doesn't bare thinking about!

    To be honest, I wouldn't even be pedalling at 30mph, let alone 40. I'd be hanging onto the break levers with my teeth gritted. So I suppose whether your existing gearing is tall enough does depend, to some extent, on how bold you are :)

    Maybe that's partly where the image thing comes from? Despite the remarks you sometimes read around here, and in the cycling press, the argument that bigger chainrings are for `fitter' or `stronger' cyclists is not one that can really be maintained. It just just doesn't stand up alongside the actual biophysics. But the idea that big chainrings are for bold cyclists, well, maybe there is some truth to that :)

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