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How-To/Mechanics: Is flipping a cog OK?

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    quick ? to all you fixed gear mechanics:
    is there anything wrong with flipping a cog over in search of a better chainline? I've heard of people doing this but I don't know if its bad for the bike (aka the cog was only designed to be put on one way).

    If needed, here's info about my bike.
    The chainline isn't horribly off, it actually feels pretty smooth, but it makes a fair amount of noise when I pedal. I've used this set-up for over ~100 miles now and I still hear noise, So I don't think it's a case of just letting the chain get used to the gears.

    I have a CNC machined 19T no name cog (got it from nashbar's website). The gears on the cog are offset to one side, and I have that geared side closest to the wheel. It's a pretty significant offset, might move the rear chainline out as much as 5mm if I flip it around. this should give me a new C/line that is close to ideal.

    I cannot do anything to the chainring because it is an "aero" chainring that can only go on the outside. I've cleaned and greased the chain but it still makes some noise (from both the cog and C/ring ends). I'd prefer not to by another, shorter BB unless there are no other options.

    Oh yeah one more bit of info, it's a 3/32 C/ring, a 1/8 chain, and a 1/8th cog. According to my measurements, the chainlines are 40mm for the C/ring and 32, maybe 33mm for the cog (rear seems too low). any other questions about my set up just click on my profile, I only have one bike.

    THANKS A TON!
  2.  
    All cogs are offset to one side, but the way you describe yours, it could definitely be flipped because the standard for cogs is to have the teeth on the outside. Either way the threads are the same, you can flip it either way you want. If you have a track hub and single speed cranks, they should hopefully be set up for the same chainline and you would have to use it with the teeth to the outside. Checking both directions was standard when I used to build more conversions with road hubs and had to find the right chainline. having a 3/32 cog and 1/8th chain makes it a little easier to get a straight chainline as well, because it's that much more play in the cogs position while it is still within the chains straight line. I think the only time you might have trouble flipping a cog is if it's one of the cheaper ones that isn't actually flat on both sides. Some of them are flat on the side with the threads, but the actual tooth side is curved under to where the threads start. They appear to have been cut from a flat piece of steel and bent in where the cog threads onto the hub, or else they started with a round pipe and flared out one end where the teeth are. You might have a hard time actually tightening up the cogs against the edge of the hub without the flat surface. It doesn't usually effect the lock ring much because it's wide enough to get past the curved part.
    • CommentAuthorthe rabbi
    • CommentTimeApr 23rd 2009
     
    yeah, you have the cog on backwards already.
    • CommentAuthormrymeski
    • CommentTimeApr 23rd 2009
     
    sometimes I wonder why some people even own chainwhips. You should just take your bike to a shop from now on
    • CommentAuthormuckymucky
    • CommentTimeApr 23rd 2009
     
    bad chainline = premature wear of your teeth right?
    and perhaps chain falls off?
  7.  
    Posted By: mrymeskisometimes I wonder why some people even own chainwhips. You should just take your bike to a shop from now on


    Well if I ever want to change cogs I don't want to have to ride down to a shop, have them do it, and then charge me. plus a lot of bike stores probably don't have 1/8 " chain whip on hand. it's only 12 bucks

    anywho, flipped it around no problem, chainline moved out to ~40mm in the rear! seems like it's only a chain link's width off, or .125 inches (~3mm). good enough for me.

    thanks for your help!

    still makes a little noise but it's not bad at all.
  8.  
    but apparently you don't know how to install a cog, thus you should not own the tool to install one. and it never hurts to make friends with the homies at your lbs.
    • CommentAuthorMaxThrash
    • CommentTimeApr 23rd 2009
     
    Cause if you don't get something right the first time, you should probably just give up.
  10.  
    You people don't think things through sometimes. If you flip the cog your wheel is gonna spin backwards. Unless your in Australia. And there headset crown nuts spin on the other way.
  11.  
    Posted By: hardsole5280You people don't think things through sometimes. If you flip the cog your wheel is gonna spin backwards. Unless your in Australia. And there headset crown nuts spin on the other way.


    Now that is lulz.
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    Yeah! and all those kids who put their chainring on the inside position of road cranks for a better chainline on their conversion shouldn't be allowed to own chainring bolt tools, or crank arm removers, or 14mm sockets, or pedal wrenches, or a crank arms bolt wrench! .......... right?

    Did you ever see someone take a stem that was meant to be angled up, but they flip it so their bars are lower? they've got the stickers upside down and everything. Who's passing out these 5mm hex keys?? it's like they're passing out classified tools to anyone who wants one!
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    Oh no I made a mistake, guess I'm not allowed to own a wrench anymore. what are some of you guys smoking?. Maybe you guys should get wider saddles, cause those ones you got now seem to be wedged pretty far up your asses.

    You know, I know none of you would like to admit it, but at one point y'all were new to this stuff too.

    Posted By: roadkillrossbut apparently you don't know how to install a cog, thus you should not own the tool to install one. and it never hurts to make friends with the homies at your lbs.


    so now that I've figured it out, am I allowed to have one? it's a fvcking $12 chainwhip that someone bought for me. relax dude.

    Oh yeah, and I did take it to two bike shops, wondering if there was some kind of spacer I could put on the rear. they took a good look at my set-up and suggested everything but flipping my cog around. when I got home, I thought of the idea of it ON MY OWN and was just trying to research it to figure out if it was safe.

    Like I've said before, bikes are awesome, but some of the people that ride them are just total pricks
  14.  
    Posted By: Crank Pedaler
    Like I've said before, bikes are awesome, but some of the people that ride them are just total pricks


    amen.

    if you're still concerned about noise, you might want to try running all 3/32" parts. some people seem to get away with mixing and matching, but as an engineer i would never do it on one of my bikes; i couldn't sleep at night. i used to have a 1/8" setup on my commuting bike, but when i needed to replace the cranks the 130bcd option was far more economical, and rather than hunt around for 1/8" 130bcd chainrings i just went with the 3/32" that came with, and grabbed a matching cog from the box in the garage. it was time for a new chain anyway, and this drive train is perfectly quiet.
    • CommentAuthorAaron C
    • CommentTimeApr 24th 2009
     
    Posted By: upthemaidenYeah! and all those kids who put their chainring on the inside position of road cranks for a better chainline on their conversion shouldn't be allowed to own chainring bolt tools, or crank arm removers, or 14mm sockets, or pedal wrenches, or a crank arms bolt wrench! .......... right?

    Did you ever see someone take a stem that was meant to be angled up, but they flip it so their bars are lower? they've got the stickers upside down and everything. Who's passing out these 5mm hex keys?? it's like they're passing out classified tools to anyone who wants one!


    i about cried laughing!
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    Oh fuck. Don't get me started on choped upsidedown handle bars. Who on earth does all this shit? Wait.... I just realized I have done everything discussed so far on this form. I surrender my tool box.
  17.  
    Some drivetrains just make noise, there's no way around that, aside from spending money on expensive parts, but sometimes a little noise is worth the money you save. I built my wife a bike with a brand new miche drivetrain and a kmc chain and it makes noise and doesn't feel nice, her other bike has campy road cranks with a miche chainring, a cheap as could be 3/32 cog and a 1/8 kmc chain and it's so smooth you wouldn't believe.

    check to make sure your chain isn't excessively tight, and that you've got some lube on the chain, both of those can make your bike noisy. A 3/32 cog on a 1/8 chain might make things wear faster, but there's no reason that this alone should make your bike louder.

    And yes, I've done just about everything I can think of that I look at people weird for doing now, it just comes down to people forgetting what it was like when they were first getting into something new, this was already discussed in detail in another thread on here a couple weeks ago, I think it was called "Why all the hate?"
    • CommentAuthorthe rabbi
    • CommentTimeApr 24th 2009
     
    i have an izumi super toughness chain, 75 chainring, and an eai cog. my drivetrain still makes noise. but if you've ever been to a velodrome and hear how loud those bikes are, you'd probably be okay with a bit of noise.
    • CommentAuthorsfbee
    • CommentTimeApr 24th 2009
     
    Posted By: the rabbii have an izumi super toughness chain, 75 chainring, and an eai cog. my drivetrain still makes noise. but if you've ever been to a velodrome and hear how loud those bikes are, you'd probably be okay with a bit of noise.


    I run a similar setup with a 75 chain ring, izumi ESH chain, and dura-ace cog.

    I get a little bit of noise when the chain and cog are connecting. It's not really overwhelming, and I only really notice it at slower speeds... so I guess it's a plus in the fact that it gives me that extra incentive to keep hauling ass
  20.  
    Posted By: sfbee
    I get a little bit of noise when the chain and cog are connecting. It's not really overwhelming, and I only really notice it at slower speeds... so I guess it's a plus in the fact that it gives me that extra incentive to keep hauling ass


    fvck yeah, it does kinda motivate you to keep pushing it when you start to slow down!
    ----------------------
    fyi My chain practically too loose now I'm actually going to tighten it today before I ride. it barely makes any noise now, once I get past 15mph, it's hard to hear it over the wind.

    Posted By: cicadashell
    if you're still concerned about noise, you might want to try running all 3/32" parts. some people seem to get away with mixing and matching, but as an engineer i would never do it on one of my bikes; i couldn't sleep at night. i used to have a 1/8" setup on my commuting bike, but when i needed to replace the cranks the 130bcd option was far more economical, and rather than hunt around for 1/8" 130bcd chainrings i just went with the 3/32" that came with, and grabbed a matching cog from the box in the garage. it was time for a new chain anyway, and this drive train is perfectly quiet.


    Some one told me 1/8 are slightly stronger than 3/32 drivetrains. I don't really understand why that would be true though. maybe because the chain doesn't have to bend as much to comply with a chainline offset (because it's wider)? whatever, when this chain wears out, I'm probably going to give an all 3/32 drivetrain a try too.
  21.  
    alright man. glad you got it figured.
    • CommentAuthorSkidMark
    • CommentTimeApr 26th 2009 edited
     
    Yeah the cog was on backwards the first time.

    The only reason there are narrow chains is because geared bikes need them for smooth shifts. I think that on a fixed/singlespeed bike you should get the beefiest chain you can get. Stronger is always better.
  23.  
    Just because it is wider does not mean its stronger. I think a chain should fit the sprockets.
  24.  
    Posted By: Crank Pedaler
    Some one told me 1/8 are slightly stronger than 3/32 drivetrains. I don't really understand why that would be true though. maybe because the chain doesn't have to bend as much to comply with a chainline offset (because it's wider)? whatever, when this chain wears out, I'm probably going to give an all 3/32 drivetrain a try too.


    wider alone would not mean stronger. wider rollers on wider chainring teeth would mean less deformation of the teeth for a given pedal force. in track racing, a wider chain/teeth spec would mean less wear and better power transfer. but if you made that wider chain from of lower tensile strength then it wouldn't be "stronger".

    maybe someone who knows more about this can chime in. i assume that 1/8" chain links are a little thicker, so IF THEY WERE MADE OF THE SAME STEEL as a 3/32" chain, they would be "stronger"; or at least they would stretch less. anyway, my suggestion was just that all the parts match, and it would cost less to get a new cog and chain than it would to replace the chainring, especially to replace the cranks with 144 bcd types to give you the most choice in chainrings, bla bla bla. have fun on your bike!

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