Advertise on Bikeforums.net



User Tag List

Page 1 of 2 12 LastLast
Results 1 to 25 of 26
  1. #1
    bac
    bac is offline
    Senior Member bac's Avatar
    Join Date
    Jun 2002
    Location
    Pennsylvania
    My Bikes
    Too many to list!
    Posts
    7,487
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Same ratio, different sized rings cogs, which to choose?

    Are there any advantages, or disadvantages to running a large (53) vs a smaller (39) chainring given the same overall gear ratio? In other words, what's the difference between say a 53/20 vs. a 39/15 with all other variables being equal? You'd get more chainwrap with the larger ring, but I don't know if that's good, or bad.

    Any help is GREATLY appreciated. ThanX!

  2. #2
    Iguana Subsystem dolface's Avatar
    Join Date
    Nov 2004
    Location
    san francisco
    Posts
    4,016
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    afaik there is no real difference. some folks say that smaller cogs == less weight, which is true, but i don't think it makes any difference in practical terms.

    others say that larger cogs == less wear, again, in real terms i'm not sure it makes a difference.

    my $0.02

  3. #3
    Mo' Senior SSSasky's Avatar
    Join Date
    Oct 2004
    Location
    Ottawa, ON
    My Bikes
    1984 Norco Monterey SL (Ishwata 3X butted), matte black, 42-15 fixed
    Posts
    371
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I've heard that you;re also less likely to get chain skip or jump on bigger cogs/rings because there's more chain wrap, and you're less likely to break teeth off because there is less force on each tooth.

    As well, the smaller cogs and rings force the chain to bend / wrap more tightly, which supposedly increases friction in the drivetrain, although i would imagine that's not very noticeable.

  4. #4
    loser
    Join Date
    Jan 2005
    Location
    portland, or
    My Bikes
    steyr, lejeune, schwinn, sears, crescent, blah blah blah.
    Posts
    386
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    you don't have to roll your pant leg up as far with the smaller chainring. I don't know about you but I think this is important.

  5. #5
    troglodyte ryan_c's Avatar
    Join Date
    Jul 2004
    Location
    the tunnels
    My Bikes
    Surly Pacer, Surly Steamroller, Fuji S-12S, Murray fixed-gear, Iverson 3-speed
    Posts
    1,284
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    whichever is cheaper.

  6. #6
    Senior Member
    Join Date
    May 2003
    Location
    Chicago, IL
    My Bikes
    Bianchi Pista, Miyata track, Schwinn Le Tour fixie
    Posts
    373
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I don't know whether it makes a difference to you, but I think that bigger chainrings look cooler..

  7. #7
    cxmagazine dot com pitboss's Avatar
    Join Date
    Jun 2003
    Location
    WI
    My Bikes
    Titus road, Fort CX
    Posts
    8,270
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Cogs are cheaper than chainrings - unless your budget is unlimited...
    Deathlap - cyclocross, training, beer,...escape hatch

  8. #8
    bac
    bac is offline
    Senior Member bac's Avatar
    Join Date
    Jun 2002
    Location
    Pennsylvania
    My Bikes
    Too many to list!
    Posts
    7,487
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    ThanX for the replies! I'll probably go with the 53, but it's good to know that there is no real difference between set-ups.

  9. #9
    Listen to me powers2b's Avatar
    Join Date
    Nov 2004
    Location
    Lexus Texas
    Posts
    2,791
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Large chainring = less wear on chainring (lower number of revolutions to turn a given length of chain).
    Chainrings are more expensive.
    Enjoy

  10. #10
    Rebel Thousandaire Ya Tu Sabes's Avatar
    Join Date
    Sep 2004
    Location
    Hartford, CT
    My Bikes
    Public D8, Yuba Mundo (cargo), Novara Buzz (1-speed, soon to be 2-speed w/ a kickback hub), Xootr 1-speed folder
    Posts
    733
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jasonyates
    I don't know whether it makes a difference to you, but I think that bigger chainrings look cooler..
    Definitely! When you look at a bike, it's hard to tell what size cog is on there (unless it's really enormous) because the cog is mostly hidden by the frame. But the chainring is quite visible. When you rock a bigger chainring, people with think you are tougher, and that's good.

  11. #11
    Senior Member gilby's Avatar
    Join Date
    Jun 2004
    My Bikes
    Bianchi Brava (fixed), Nishiki Prestige (fixed), Plum Vainqueur (track), Fuji Boulevard (Single-speed)
    Posts
    520
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by thechamp
    you don't have to roll your pant leg up as far with the smaller chainring. I don't know about you but I think this is important.
    Ha! I never thought about it, but that is a very good point.

  12. #12
    The Alternative Dressing
    Join Date
    Jan 2004
    Location
    In the condiments section of your local grocer
    Posts
    169
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Ya Tu Sabes
    When you rock a bigger chainring
    Too cool for school..........

  13. #13
    Chronic Tai Shan ofofhy's Avatar
    Join Date
    Oct 2004
    Location
    PHL
    My Bikes
    '74 Fuji SRS
    Posts
    1,115
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You bring a smaller chainring in closer to the chainstays for chainline purposes. Something I am dealing with on a 50T chainring that I have.
    From Craig's List: IF its a singlespeed that means----all the other parts are broken cut off and dumped...dont buy singlespeeds, the bikes will make your balls fall off

    * no -- it's NOT ok to contact this poster with services or other commercial interests

  14. #14
    bac
    bac is offline
    Senior Member bac's Avatar
    Join Date
    Jun 2002
    Location
    Pennsylvania
    My Bikes
    Too many to list!
    Posts
    7,487
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ofofhy
    You bring a smaller chainring in closer to the chainstays for chainline purposes. Something I am dealing with on a 50T chainring that I have.
    Good point! Has anyone else had a problem with proper chainline when using a big (more outside) chainring??? ThanX!

  15. #15
    Track Rat gotambushed's Avatar
    Join Date
    Dec 2004
    Location
    Pittsburgh, PA
    My Bikes
    To many
    Posts
    128
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    if you can space the ring, the problem lies in the frame, specifically the bend or crimp in the chainstays,
    i've had frames that i could'nt go bigger than a 48 tooth and keep a straight chainline on a flip flop, but if you space the hub uneven you can usually go 52 and up within reason on a problem frame
    Almost is only for horseshoes and hand grenades.

  16. #16
    Senior Member
    Join Date
    Dec 2004
    Location
    austin/san antonio corridor
    My Bikes
    a dozen or more at any given time. currently: pro concept pro, badd 24", hutch trickstar, looptail pk ripper, reynolds quad, 82 hutch pro racer, yamaha "a" model, matthews monoshock, and several more.
    Posts
    114
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by [165]
    Cogs are cheaper than chainrings - unless your budget is unlimited...
    not if you know where to look. ;D
    i paid 99cents for the last chainring i actually bought.

  17. #17
    troglodyte ryan_c's Avatar
    Join Date
    Jul 2004
    Location
    the tunnels
    My Bikes
    Surly Pacer, Surly Steamroller, Fuji S-12S, Murray fixed-gear, Iverson 3-speed
    Posts
    1,284
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I got my last chainring (47t, 110mm) for $4.99 from danscomp.com - they are $5-14 or something like that. Of course, those are cheap chainrings. If you are talking track chainrings, I would be blown away to see one for less than a decent cog.

  18. #18
    Tiocfáidh ár Lá jfmckenna's Avatar
    Join Date
    Dec 2003
    Location
    The edge of b#
    My Bikes
    A whole bunch-a bikes.
    Posts
    5,401
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by ofofhy
    You bring a smaller chainring in closer to the chainstays for chainline purposes. Something I am dealing with on a 50T chainring that I have.
    Yea, thats why I run a 40x15 on my road conversion. The chain ring is about .5 mm from the stay and the chain line is perfect. Prior to that I was ruinning a 46 on the outside of the road crank spider and the line was off. It really was too big a gear to push for a commuter anyway.

  19. #19
    Chronic Tai Shan ofofhy's Avatar
    Join Date
    Oct 2004
    Location
    PHL
    My Bikes
    '74 Fuji SRS
    Posts
    1,115
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jfmckenna
    Yea, thats why I run a 40x15 on my road conversion. The chain ring is about .5 mm from the stay and the chain line is perfect. Prior to that I was ruinning a 46 on the outside of the road crank spider and the line was off. It really was too big a gear to push for a commuter anyway.

    So how close to the stay is too close?
    From Craig's List: IF its a singlespeed that means----all the other parts are broken cut off and dumped...dont buy singlespeeds, the bikes will make your balls fall off

    * no -- it's NOT ok to contact this poster with services or other commercial interests

  20. #20
    Tiocfáidh ár Lá jfmckenna's Avatar
    Join Date
    Dec 2003
    Location
    The edge of b#
    My Bikes
    A whole bunch-a bikes.
    Posts
    5,401
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by ofofhy
    So how close to the stay is too close?
    As long as it doesn't touch. I mean you could probably stick a credit card between mine but thats about it. It never hits the stay. I guess there could be some flex there but with the smaller chin ring it's marginal.

  21. #21
    cxmagazine dot com pitboss's Avatar
    Join Date
    Jun 2003
    Location
    WI
    My Bikes
    Titus road, Fort CX
    Posts
    8,270
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    show me a track chainring (sugino, etc - track specific) that is brand new and less expensive than a rear cog.
    I should have been more specific.
    Quote Originally Posted by pgringo69
    not if you know where to look. ;D
    i paid 99cents for the last chainring i actually bought.
    Deathlap - cyclocross, training, beer,...escape hatch

  22. #22
    Senior Member
    Join Date
    Dec 2004
    Location
    austin/san antonio corridor
    My Bikes
    a dozen or more at any given time. currently: pro concept pro, badd 24", hutch trickstar, looptail pk ripper, reynolds quad, 82 hutch pro racer, yamaha "a" model, matthews monoshock, and several more.
    Posts
    114
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by [165]
    show me a track chainring (sugino, etc - track specific) that is brand new and less expensive than a rear cog.
    I should have been more specific.
    who said anything about brand new? there is stuff out there that literally only has a touch of grease on it that can be had for cheap or free. imo, unless you bust a couple of high quality 3/32 chains (do your research), you're throwing your money away on 1/8 stuff and adding big rotating mass.

  23. #23
    The Alternative Dressing
    Join Date
    Jan 2004
    Location
    In the condiments section of your local grocer
    Posts
    169
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jfmckenna
    As long as it doesn't touch. I mean you could probably stick a credit card between mine but thats about it. It never hits the stay. I guess there could be some flex there but with the smaller chin ring it's marginal.
    Too close and the crap that accumulates on the ring and frame will act like an abrasive, slowly but methodically chewing away at the frame.

    Somebody posted some pic recently showing the result of running tires that were quite a tight fit. Did some nice damage to the frame over time.

  24. #24
    cyclist/gearhead/cycli... moxfyre's Avatar
    Join Date
    Oct 2004
    Location
    DC / Maryland suburbs
    My Bikes
    Homebuilt tourer/commuter, modified-beyond-recognition 1990 Trek 1100, reasonably stock 2002-ish Gary Fisher Hoo Koo E Koo
    Posts
    4,172
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I'm currently reading "Bicycling Science", and there's some research in it showing that the efficiency of a 53/15 drivetrain is about 93%, less than a 53/20 drivetrain, about 96%. I can find the exact figures and references if anyone's interested. This is including a rear derailer and non-straight chainline. The principle is that the chain has to bend more around smaller sprockets, causing greater frictional losses.

    All the mechanical research in the book fascinates me, it's a really good read.
    My bikes | Linux and Python stuff | Photo gallery

    Sheldon Brown, I miss you. Thanks for the advice, ideas, humor, and infectious enthusiasm for everything bikes...

  25. #25
    Banned.
    Join Date
    Oct 2004
    Posts
    4,418
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by moxfyre
    The principle is that the chain has to bend more around smaller sprockets, causing greater frictional losses.
    This 'principle' which you are talking about is the smoothness of a ratio that you feel. A ratio such as 44:22 will feel smoother than 30:15, due to the fact that the chain has to bend more, and engage less teeth at any certain time in the crank rotation.
    The derailleur and off chainline caused by derailleurs suck a lot of efficiency. You'd be surprised at how much efficiency a derailleur system loses over a SS/fixed system.
    I know, because when I converted my 80's touring bike to SS, and I could feel the difference immediatley.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •