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  1. #1
    McNightrider
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    51/20 v 42/16 Gearing ??

    Hey,

    Ok the question is....
    51/20 make up of 67 gear inches and 42/16 make up of 69 gear inches..they have similar gear inches.

    I am a newbie. I locate in Sydney I could not find a 42T chainring but I could find a 20T Philwood cog. I am just wondering the pros and cons using big chainring and big cog relatively to small CR and small cogs to achieve similar gear inches? Despite the weight factor.



    Cheer,
    Dub.

  2. #2
    Senior Member pirate's Avatar
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    Big chainring/cog combos have been said to wear slower, as the wear is spread out over more teeth.

    there are a ton of threads about this same topic, the search button is yer friend.

  3. #3
    Large Member urodacus's Avatar
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    That's not a bad ratio for sydney hills, unless you live on Carrington Road Bronte. Western suburbs can even happily go 53-16 most places. Eastern suburbs/northern beaches: that will make you strong.

    if you want more chainrings, i have been happy with the BlackSpire stuff from Canadia. all sizes BCD combos in 8/9 speed, no ramps: good for fixed on 3/32 chains. Make sure your chain fits the Phil cog!

    No practical difference at all, just a tad heavier and you have slightly less space around your BB for climbing kerbs etc. (Oh, you're going fixed... that's noice. keep a front brake on the bike at least till you don't feel you need it anymore)
    05 Giant TCR Composite; 83 Colnago Saronni: 81 San Rensho Katana Super Export track bike, #A116-56; 89 Zunow Pentaglia: SOLD; 85 Tommasini: SOLD; 83 Guerciotti: SOLD

  4. #4
    McNightrider
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    Thanks for all the help...
    Yep...i have 1/8 Chaing with superb pro cranks and 51 chainring and 16t cog.

    Running 51/16 at the moment my chain sits in the moddle of the track dropout if i got 51/20 would i need to extend the chain or get a new chain?

  5. #5
    aspiring dirtbag commuter max-a-mill's Avatar
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    if you don't have an extra link for your chain your gonna need a new one.

    new chains are nice and can be had cheaply.
    - the revolution will not be motorized -

  6. #6
    McNightrider
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    Yep I dont have extra link because I got the bike secondhand, the seller promised me will give me few cogs and lockrings..but end up he bailed out.
    Tried to msg him .. he wouldnt reply.

    Cheer,
    Dub.

  7. #7
    fix
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    Quote Originally Posted by pirate
    Big chainring/cog combos have been said to wear slower, as the wear is spread out over more teeth.

    there are a ton of threads about this same topic, the search button is yer friend.
    I always wondered if the fact that each rotation involves less angle for each chain link to turn helps chain stretch too.
    soh-CAh-T-oa-meter 0 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ X ~ ~ pi

  8. #8
    ť wot?
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    Big rings are more efficient.
    a life well lived is the best revenge

  9. #9
    out of shape
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    in my experience, finding big enough cogs to use a big ring and keep a reasonable gain ratio is the hardest part. If you've already got a 20t, then there isn't a good reason not to try out a 51 or 53 ring. Another advantage of bigger drivetrain that hasn't been mentioned is that adjustments are finer— adding or losing a tooth has a smaller effect (percent change) since there are more teeth involved.

  10. #10
    McNightrider
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    Okies dokies..thanks guys...
    Well I am currently running 51T chainring and 16T cog as i said.
    I want to run lower gear inch..so I guess I will get a 19 or 20T cogs..

    And would larger cogs easier to skid with rather than 51/16 I am having hard time to skid on pavement but able to skid on wet and on grass..

    Cheer,
    Dub.
    Last edited by vee_dub; 05-08-07 at 09:01 AM.

  11. #11
    mofo
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    Quote Originally Posted by chase.
    Another advantage of bigger drivetrain that hasn't been mentioned is that adjustments are fineró adding or losing a tooth has a smaller effect (percent change) since there are more teeth involved.
    isn't that in reverse?

    if I have 48-18 I get 70.1 g.i.; 48-14 I get 90.1 g.i.. A difference of 20 gear inches.
    if I have 52-18 I get 75.9 g.i.; 52-14 I get 97.6 g.i.. A difference of 21.7 gear inches.

    I've always thought the smaller drives power up fast, but yes, the larger feel more efficient at speed.

  12. #12
    McNightrider
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    51/19 and 42/16 Have same gear ratio...therefore they should be the same right? Like effort to pedal and effort to skid???
    I am really bad at mechanic and physic, hoping someone can enlighten me.

    Dub.

  13. #13
    cab horn
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    Quote Originally Posted by yairi
    Big rings are more efficient.
    WTF? Efficient how?
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  14. #14
    ť wot?
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    Less drivetrain loss.
    a life well lived is the best revenge

  15. #15
    out of shape
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    Quote Originally Posted by me thinkst
    isn't that in reverse?

    if I have 48-18 I get 70.1 g.i.; 48-14 I get 90.1 g.i.. A difference of 20 gear inches.
    if I have 52-18 I get 75.9 g.i.; 52-14 I get 97.6 g.i.. A difference of 21.7 gear inches.

    I've always thought the smaller drives power up fast, but yes, the larger feel more efficient at speed.
    I meant that a one-tooth difference from 51 to 52 is a smaller delta than 42 to 43, so if you're trying to dial in your cadence or overall gear inch measurement, it would be easier to get it right.

  16. #16
    mofo
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    Quote Originally Posted by vee_dub
    51/19 and 42/16 Have same gear ratio...therefore they should be the same right? Like effort to pedal and effort to skid???
    I am really bad at mechanic and physic, hoping someone can enlighten me.

    Dub.
    It will feel like the almost the gear at speed, difference of 1.6". I think the 42 will skid easier, as well as accelerate faster.

  17. #17
    mofo
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    Quote Originally Posted by chase.
    I meant that a one-tooth difference from 51 to 52 is a smaller delta than 42 to 43, so if you're trying to dial in your cadence or overall gear inch measurement, it would be easier to get it right.
    gotcha...

  18. #18
    Senior Member mrwhite's Avatar
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    51/20.

    Forget weight, its all about asthetics, and your drivetrain will last longer. as there is less stress on the the bigger wheels.

    Ride safe in razzle dazzle town.

  19. #19
    mofo
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    absolutely, the 51-20 will look better. 42t chainring will look like mountain bike gears.

  20. #20
    Packfodding 3 caloso's Avatar
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    A 42t is more aerodynamic. Duh!
    Cyclists of the world, unite! You have nothing to lube but your chains!

  21. #21
    McNightrider
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    Quote Originally Posted by me thinkst
    It will feel like the almost the gear at speed, difference of 1.6". I think the 42 will skid easier, as well as accelerate faster.
    Mmmh yer its 1.6" difference but the acceleration and skidability (my own stupid words) varies that much?????

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