Front sprockets. I dunno?

gerroffandmilkit
gerroffandmilkit Posts: 160
edited October 2012 in Road general
Could someone please explain the differences between compact front chainsets, triples etc? Bamboozles the hell outta me.
Starting out and a lot to learn. :D

Comments

  • Kerguelen
    Kerguelen Posts: 248
    Could someone please explain the differences between compact front chainsets, triples etc? Bamboozles the hell outta me.
    Starting out and a lot to learn. :D

    Er, roughly...

    A compact chainset (also known as a compact double) has 2 chainrings, usually 34T and 50T although this is not set in stone. In combination with a wide range cassette (eg 11-28 or 11-32) can give you a nice wide range of gear rations.

    A racing (or standard) double has 39T and 52T (although these can vary a bit as well). Usually used with a close-range cassette (eg 12-25) by hard blokes who don't mind ruining their knees.

    A triple is 3 chainrings, somewhere in the range 30T-40T-50T for road bikes, much smaller for MTBs.

    You'll usually find people recommending a compact double in combination with a wide-range cassette as an alternative to a triple with a more close-range cassette.
  • Ok

    Standard chainset is a double sprocket on the front usually with 52 or 53 teeth on the big ring and 39 teeth on the smaller ring. You can have various cassettes on the back.

    Compact chainset is a double sprocket on the front usually with 50 teeth on the big ring and 34 on the smaller ring. Again various cassette ratios can be used on the back.

    Triple chainset has 3 sprockets on the front. On my old scott speedster I had 53 on the big ring, 42 on the middle ring and 30 on the smallest or "Granny" ring. this chainset is ideal for beginners or very hilly alp type riding.

    Also you have 8,9,10 and 11 speed groupsets. this corresponds to the number of sprockets on the rear cassette. Usualy the 8spd sets are at the lower end of the price range and 11 are your top end.

    Hope this helps.
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  • And if you're feeling a bit mathematical...

    If you divide the number of teeth on the chainring gear by the number of teeth on the cassette gear, the lower the number the lower the gear ratio, and vice versa.

    So, for example, my road bike's got a compact chainset (50 teeth on the big ring, 34 on the small), and an 11-28 ten speed cassette, so 11 teeth on the smallest cog and 28 on the biggest. Consequently, the highest gear ratio I have on offer is 50/11 = 4.54 (for serious gravity assisted moments only!), and the lowest is 34/28 = 1.21.

    Contrast that with my mountain bike. That's got a 44-32-22 triple chainset, and an 11-32 cassette. That gives me a highest gear of 44/11 = 4, and a lowest gear of 22/32 = 0.69 (which is bloody low, but magnificent if you're of the mindset that says you refuse to push unless utterly forced to).
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  • diy
    diy Posts: 6,473
    Interesting, I have a 50/34 on the front and 12/25 on the rear. When I first started road riding I felt I could have done with a 28 on the rear, now I hardly go in to the first 3. I do feel I am missing something at the other end and will look for maybe a 11/26 or 11/25 next time. Though its probably the front that is "wrong".
  • farrina
    farrina Posts: 360
    Kerguelen wrote:

    Er,

    A racing (or standard) double has 39T and 52T (although these can vary a bit as well). Usually used with a close-range cassette (eg 12-25) by hard blokes who don't mind ruining their knees.

    Well I road a 42/52 with a 12-21 for many years and my knees (even though I run 20 miles a week as well) are fine. :D

    That said I have to confess that as my 50 birthday is rapidly approaching I have switched to a 39/53 with a a 12-23 and this will get me up a 1:5 fine

    Regards

    Alan


    Ps I am not a hard bloke and appreciate my crossbar as it stops my knees knocking together in the cold
    Regards
    Alan
  • I am 56 and I am by no means a hard man but I have a 53-42 with a 12-25 and being stubborn I won't get off and walk. Saying that though there are a few hills I would not like to go back to at the tail end of a ride.

    When I got into road cycling about 4 years ago I did weigh 5 stones heavier (20 stone) so maybe my legs will give up soon???
  • fsd61b
    fsd61b Posts: 109
    Is it possible to change the front chain rings from std double to "compact" sizes without too much cost? I have seen a reduced price new road bike with a double chain ring & 11/ 23 cassette and im worried that I won't manage on hills and won't be in a financial position to alter the gears after buying the bike. If it is only a sase of buying a chain ring then I may risk it.
  • davidof
    davidof Posts: 3,036
    fsd61b wrote:
    Is it possible to change the front chain rings from std double to "compact" sizes without too much cost?
    No
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  • buckmulligan
    buckmulligan Posts: 1,031
    davidof wrote:
    fsd61b wrote:
    Is it possible to change the front chain rings from std double to "compact" sizes without too much cost?
    No
    Hah! That's not necessarily true, it's cheaper and easier than switching to a triple, that's for sure! You just need to find a compact chainset that's compatible with your existing set-up; you said you're just starting out, so presuming you're on a fairly entry level bike, could find a suitable second hand one on eBay or the classifieds section on here for £20-40 perhaps and you could recoup most of that by selling your existing one.

    You wouldn't have to change your front derailleur, rear derailleur, chain or shifters, which would all potentially be an issue when switching to a triple (which is your other major option for wider ratio gears). If you're doing the work yourself you'll need to move the front derailleur position and possibly take a couple of links out of the chain, because the big ring on a compact will likely be slightly smaller than a standard double (50 vs 53 teeth maybe). Not a hard job and more importantly, not too hard to mess up if you're willing to buy a couple of proper tools and teach yourself!

    As others have said, have a look at what cassette you're running. If it's a narrow range one like a 11-25, it might be cheaper and easier to switch to a wide ratio one (11-28T perhaps).

    EDIT: Woops, only just noticed the (unquoted) rest of your post! On a 'standard' chainset, the diameter of the chainring bolts is 130mm, which imposes a lower limit on the size of chainrings you can run; iirc you can get some 130BCD rings that are 38T, but more common is 39+. As stated above, it's not hard replacing the chainset, you might prefer a wider range cassette, but then you may need a new (longer) chain to compensate for the increase in largest rear sprocket from 23 to say 28T.
  • drlodge
    drlodge Posts: 4,826
    farrina wrote:
    Well I road a 42/52 with a 12-21 for many years and my knees (even though I run 20 miles a week as well) are fine. :D

    That said I have to confess that as my 50 birthday is rapidly approaching I have switched to a 39/53 with a a 12-23 and this will get me up a 1:5 fine

    Me too :-) Had my current bike in 1987, had a 42/52 with 13-14-15-17-19-21 cassette. Think I managed with those guys for 2 reasons (a) I was younger/stronger and (b) didn't really go up any steep hills, I can remember going up Box Hill and found that hard going at the time.

    I now have a compact 34/50 and 13-28 cassette which does me great due to (a) being older/weaker and (b) trying all the steep Surrey hills I can find (Barhatch/Whitedown etc)
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  • drlodge wrote:
    farrina wrote:
    Well I road a 42/52 with a 12-21 for many years and my knees (even though I run 20 miles a week as well) are fine. :D

    That said I have to confess that as my 50 birthday is rapidly approaching I have switched to a 39/53 with a a 12-23 and this will get me up a 1:5 fine

    Me too :-) Had my current bike in 1987, had a 42/52 with 13-14-15-17-19-21 cassette. Think I managed with those guys for 2 reasons (a) I was younger/stronger and (b) didn't really go up any steep hills, I can remember going up Box Hill and found that hard going at the time.

    I now have a compact 34/50 and 13-28 cassette which does me great due to (a) being older/weaker and (b) trying all the steep Surrey hills I can find (Barhatch/Whitedown etc)

    52/42 sounds like my old Raleigh. Blimey that was hard work at times!
    Just to further confuse the OP, many cyclocross bikes use a 48/36 or in my case a 46/36 up front. Within limits, it's usually fairly straightforward to change chainrings and cassettes to get the range best for you.
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