Double versus compact chainring ?

ben@31
ben@31 Posts: 2,327
edited September 2014 in Road beginners
Hi,

I'm getting a bit confused about what the difference is between a double and compact.

For example... standard 53/39, semi-compact 52/36 or compact 50/34-tooth chainrings.

What are the pros and cons?

Thanks for your help.
"The Prince of Wales is now the King of France" - Calton Kirby

Comments

  • jibberjim
    jibberjim Posts: 2,810
    There's no pros or cons, they're just different, you want the one appropriate to the speeds and cadences you like to ride (and the rear cassette also matters)

    Unless you're fit and riding in fast groups, it's unlikely that anything but 50x34 will be appropriate for a new rider unless you live in a very flat location when 52x44 or something might be appropriate.
    Jibbering Sports Stuff: http://jibbering.com/sports/
  • ben@31
    ben@31 Posts: 2,327
    I am fit, live on a flat area on the coast and like to maintain a high cadence of 90 - 100 rpm. I much prefer spinning away in a low gear. I'm not a new rider.
    "The Prince of Wales is now the King of France" - Calton Kirby
  • danlikesbikes
    danlikesbikes Posts: 3,898
    BR's own take on the issue http://www.bikeradar.com/road/gear/arti ... ank-38845/
    Pain hurts much less if its topped off with beating your mates to top of a climb.
  • jgsi
    jgsi Posts: 5,062
    ben@31 wrote:
    I am fit, live on a flat area on the coast and like to maintain a high cadence of 90 - 100 rpm. I much prefer spinning away in a low gear. I'm not a new rider.
    so the point of your post is?
    Are you looking at a new bike with a standard double?
  • ForumNewbie
    ForumNewbie Posts: 1,664
    Looking in bike shops these days, you hardly see any standard doubles, its mostly compacts. I have a compact on a carbon road bike but find the drop from the 50 to 34 front ring quite big, and you immediately have to move up one or two gears at the back to stop spinning. I actually prefer the triple gearing on my Audax and hybrid bikes.
  • JayKosta
    JayKosta Posts: 635
    The differences are all about the overall highest and lowest gear ratios, AND about the choices of intermediate ratios between the high and low.

    For a majority of people doing recreational / exercise / social riding a 50-34 compact works very well. The 50 ring with a 12 or 13 tooth on the cassette is fine unless you want to be going 40+ mph. The 34 ring with a 28 (and larger) on the cassette will be fine for most any hills.
    A slight 'con' is that there might not be a gear setting that provides the exact rpm that you want - perhaps you have to spin a tad faster, or slower, but it won't be far off.

    The standard double of 53(or 52)-39 lacks the lowest gear ratio, so more leg power can be needed on hills. But is does provide more intermediate gear choices to find that perfect rpm.
    A nice option with a standard double is basically just using it as a 2-speed. With the large chainring, choose the rear gear that is comfortable for flat riding. When a rise or small hill occurs, just change to the small chainring. That way you don't need to be doing a lot of multiple shifts of both the front and rear.

    The compact gearing has enabled more people to be able to use their bikes because of the wider range of gear ratios. And less annoyance for dealers of customers coming back and complaining that the bike is too hard to pedal.

    Jay Kosta
    Endwell NY USA
  • imposter2.0
    imposter2.0 Posts: 12,028
    'Compact' refers to the 110mm BCD of the chainset/chainrings - nothing more. 'Standard' chainsets typically use a larger BCD of 130mm. There is no such thing as 'compact gearing' - just compact cranks. It's perfectly possible to run 53/39, or 52/42 on a 110mm 'compact' chainset.

    Any chainset is a 'double' if it has two chain rings. The difference being compact double or standard double. This sort of things comes up a lot and the same old misunderstandings keep coming up...
  • ai_1
    ai_1 Posts: 3,060
    ben@31 wrote:
    I am fit, live on a flat area on the coast and like to maintain a high cadence of 90 - 100 rpm. I much prefer spinning away in a low gear. I'm not a new rider.
    53/39 gives you bigger gears than 52/36 which is bigger than 50/34.
    If you're an experienced rider then you'll know whether you find yourself needing smaller gears to get up hills, wanting bigger gears on descents or with a tailwind or if you would like to trade either end of the range for smaller gaps between gears. Choose your gearing accordingly.
  • ben@31
    ben@31 Posts: 2,327
    JGSI wrote:
    ben@31 wrote:
    I am fit, live on a flat area on the coast and like to maintain a high cadence of 90 - 100 rpm. I much prefer spinning away in a low gear. I'm not a new rider.
    so the point of your post is?
    Are you looking at a new bike with a standard double?

    I'm looking to buy a new bike or upgrade the groupset.

    Looking at group sets for sale, a few sellers offer options for the chain-ring. One seller had a compact or a double. I was trying to work out the difference.

    Is it wise to have a wide range between the smallest and biggest gear at the sacrifice of big gaps between the gears?
    "The Prince of Wales is now the King of France" - Calton Kirby
  • imposter2.0
    imposter2.0 Posts: 12,028
    ben@31 wrote:
    One seller had a compact or a double. I was trying to work out the difference.

    Like I said - a compact is a double. I'm guessing they meant 'standard'.
  • JayKosta
    JayKosta Posts: 635
    ben@31 wrote:
    ...
    Is it wise to have a wide range between the smallest and biggest gear at the sacrifice of big gaps between the gears?
    ======================================
    It certainly is wise to have gearing low enough for riding on fairly steep hills.
    You might not use the lowest gearing on your regular routes, but it is very likely that you'll need it occasionally.
    For the high gears, I doubt there is much real need for gears higher than 50-13, or 53-14. Maybe for very strong riders, or fearless types who like to scream downhill.

    As for the gaps between gears, I doubt you'll encounter a situation where a useable intermediate gear isn't available - it might be a little high or low for you preference, but still useable none the less.

    Jay Kosta
    Endwell NY USA
  • paul2718
    paul2718 Posts: 471
    ben@31 wrote:
    JGSI wrote:
    ben@31 wrote:
    I am fit, live on a flat area on the coast and like to maintain a high cadence of 90 - 100 rpm. I much prefer spinning away in a low gear. I'm not a new rider.
    so the point of your post is?
    Are you looking at a new bike with a standard double?

    I'm looking to buy a new bike or upgrade the groupset.

    Looking at group sets for sale, a few sellers offer options for the chain-ring. One seller had a compact or a double. I was trying to work out the difference.

    Is it wise to have a wide range between the smallest and biggest gear at the sacrifice of big gaps between the gears?
    It's worth going back to basics here.

    A 'standard' crank set has the bolts that attach the rings spaced around a circle with a diameter of 130mm. This means that the smallest ring that will physically fit is 38 teeth. A 'compact' crank has a 110mm diameter for the bolts, so 34 teeth. The greatest gap between the front rings that can reliably be shifted in both directions is 16 teeth.

    (I realise Campagnolo are a bit different...)

    The modern traditional ring combinations are 53/39 on a standard crank and 50/34 on a compact. Recently 52/36 is becoming popular, again requiring a compact crank.

    New 11 speed Shimano has only one bolt spacing, so the distinction between cranks has disappeared for those models.

    So your decision is really about what rings you want now and might want in the future. I like 53/39 for most usages, but would change for an event that involved very steep and/or long climbs. If you don't pedal when the wind is behind and the road drops slightly (see Jay's comment above) then there is no reason to go above a 50 ring.

    Paul
  • mattsccm
    mattsccm Posts: 409
    check the chainset BCD. As said some newer stuff is coming 110 (compact size) with "normal" double chain rings or the newer variations.
    That would allow you to play around with ring sizes for the cost of rings which don't have to be too expensive.
    Despite the semantics almost everyone uses the word double to mean the traditional sizes of 42/52 or the newer 39/53.
    130 or 135 (Campag only) BCD 5bolts
  • iPete
    iPete Posts: 6,076
    I'm trying out 52/36 at the moment (from 53/39) and do like it. With a 12-28 on the back I don't fear much in those there Surrey Hills although 52/12 was a bit lacking at the London Ride 100. Depends on where you live, what you ride and how you ride but I think 52/36 offers a good balance on both ends.
  • ai_1
    ai_1 Posts: 3,060
    iPete wrote:
    I'm trying out 52/36 at the moment (from 53/39) and do like it. With a 12-28 on the back I don't fear much in those there Surrey Hills although 52/12 was a bit lacking at the London Ride 100. Depends on where you live, what you ride and how you ride but I think 52/36 offers a good balance on both ends.
    What brand/model is the 12-28 cassette?
    I find it odd that the Shimano Ultegra 11 speed cassettes don't come in that size since plenty people would rather drop the 11t on a wide range cassette to keep the small gear and keep the gaps smaller.
    I like having the 11t but I'd consider giving it up for another sprocket in the middle of the range.
  • iPete
    iPete Posts: 6,076
    I'm using a 6800 chainring on a 10 speed setup, it is likely a 5700 105 cassette, the Ultegra ranges didn't suit me. From memory they used either a 27 or 30 and had gaps in the mid range that I use a lot, I'd rather have a 16t than 11t.
  • drlodge
    drlodge Posts: 4,826
    For me the choice is a simple one...decide on the lowest gear you want and go from there.

    34x28/29 is what I want as a lowest gear, and therefore a 50/34 is the answer, combined with a 12-29 (Campag) or 12-28 (Shimano) cassette. The 16tooth difference between the chainrings doesn't cause an issue, just that when changing chainrings I also need to change a couple of gears at the back too...easily done.

    Very rarely do I use the top gear of 50x12 and evern more rarely am I spinning out...in fact on my the Condor the top gear is 50x13 with a 7 speed cassette 13-14-16-18-21-24-28. More speeds (10/11) just give closer ratios, its a nice to have. I agree with iPete that a 16 or 17T on the back is much more useful that a 11T.
    WyndyMilla Massive Attack | Rourke 953 | Condor Italia 531 Pro | Boardman CX Pro | DT Swiss RR440 Tubeless Wheels
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