Advertise on Bikeforums.net



User Tag List

Results 1 to 12 of 12
  1. #1
    Senior Member
    Join Date
    Jun 2014
    Posts
    108
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)

    One toothe = 1/2 link?

    Hi there.

    I just built a weird single speed with parts I had on hand that were left over from other projects.

    The frame is a mid-1980s MTB with semi-vertical dropouts and it has a Suntour roller-cam brake under the chainstays and a Deore cantilever brake up front. The stem has this really weird size of 21.?mm diameter. I wanted to swap out that stem so I could use a drop bar but wasn't able to find a stem that'd fit. It'd be easier and cheaper to swap the 1" threaded fork for one with a larger inner diameter steerer tube fork that'd take a common drop bar quill stem.

    In the meanrime and to use the Tecktro inline drop bar brake levers I have, I to cut a drop bar really narrow ass the cuts had to be made just where the curve from the top of the bar starts from the straight portion so thast I could get the bar through the stem.

    I've used an old Exage crank with a 39 ring on it. That's coupled to the 16 teeth cog of a three cog freewheel. I removed the other two larger cogs and the spacers.

    A small problem is that with this chainring and cog combination the chain is a bit slacker than I'd like. The gear does run well and doesn't bounce off even on rough terrain because the chainline is pretty good. I have three options to snug up the chain which is 3/32 by 1/2 inch.

    #1 . is use a 40 teeth chainring. That will only work if ONE tooth = 1/2 a chain link. Does it?

    #2 . is replace the solid nutted axle with a hollow one with a quick-release and grind/file the axle so that it fits tightly between the dropouts but does NOT rest in the dropout itself.

    #3 . is to order a 3/32 link online.

    The easiest and cheapest is option #1 . Does one tooth bigger on a chainring equal a 1/2 link increase in the chain length? If not is there another way to take up that 1/2 link of slack?

    Thanks and cheers from Miele Man

  2. #2
    Senior Member mihlbach's Avatar
    Join Date
    Dec 2005
    Location
    Long Island, NY
    Posts
    6,375
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    We need pictures.

  3. #3
    Senior Member
    Join Date
    Jun 2014
    Posts
    108
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Hi there.

    We need a picture in order to tell id increasing a chainring by one tooth will shorten the chain by 1/2 of a link?

    I'm confused, how would an image show that? I already know that the slack in the chain would go away if I was able to shorten the chain by only 1/2 a link. Unfortunately I don't have any 1/2 links here. That is why I asked if increasing the size of the chainring by one tooth would take an extra 1/2 link of chain. Would it?

    Or, is it that you want to see some images of the build itself?

    Thanks and cheers ffrom Miele Man

  4. #4
    Senior Member mihlbach's Avatar
    Join Date
    Dec 2005
    Location
    Long Island, NY
    Posts
    6,375
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    We need a picture. It's hard to visualize what you are attempting to explain. There may be more going on than what you are describing. Your English isn't so good either, which makes is difficult to understand.

    Adding one tooth will move your axle forward ~1/8".

  5. #5
    Grumpy Old Bugga europa's Avatar
    Join Date
    Oct 2006
    Location
    Adelaide, AUSTRALIA
    My Bikes
    Europa, Hillbrick, Road Chief, Repco Superlite (Ol' Rusty)
    Posts
    3,222
    Mentioned
    12 Post(s)
    Tagged
    0 Thread(s)
    Remove links until your tensioner can handle it. If one link is too short and the next too long (which is what I think you're trying to tell us), just get a half link.
    I had a good bike ... so I FIXED it

  6. #6
    Senior Member Steev's Avatar
    Join Date
    Jul 2005
    Location
    Backwoods of Ontario
    Posts
    2,139
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Miele Man View Post
    Hi there.

    We need a picture in order to tell id increasing a chainring by one tooth will shorten the chain by 1/2 of a link?

    I'm confused, how would an image show that? I already know that the slack in the chain would go away if I was able to shorten the chain by only 1/2 a link. Unfortunately I don't have any 1/2 links here. That is why I asked if increasing the size of the chainring by one tooth would take an extra 1/2 link of chain. Would it?

    Or, is it that you want to see some images of the build itself?

    Thanks and cheers ffrom Miele Man
    I think you need two teeth to equal a 1/2 link, because the chain only goes around half the chainring. Mind this is an estimate because it's not exactly half the chain ring that the chain sits on.

  7. #7
    Senior Member SquidPuppet's Avatar
    Join Date
    Dec 2013
    Location
    Coeur d'Alene
    Posts
    915
    Mentioned
    7 Post(s)
    Tagged
    0 Thread(s)
    Four teeth per link.

    For each tooth added or subtracted, the axle moves 1/8 inch.

  8. #8
    Senior Member
    Join Date
    Jun 2014
    Posts
    108
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by SquidPuppet View Post
    Four teeth per link.

    For each tooth added or subtracted, the axle moves 1/8 inch.
    Thank you very m uch. Wow! I didn't realize that it'd take 4 teeth more on a chainring to move the chain 1/2 inch. 1/8 inch per ink is good though because i can replace the39 teeth ring with one that has 42 teeth which should take up the needed slack. 3/8 inch should do it and the 42 x 16 gear will still be very useable for what I want.

    Cheers from Miele Man

  9. #9
    Senior Member
    Join Date
    Jun 2014
    Posts
    108
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Interestingly enough todayI got a reply in my Inbox but that reply was posted nearly a week ago.

    The bicycle has vertical (or near vertcal dropouts) and does not have a chain tensioner.

    There is some slack in the chain and when I installed the chain that slak amounted to 1/2 of a link.

    The front ing is 3 teeth and the rear is 20 or 21 teeth. I forget off hand which. I thought that if i used a 42 teeth ring I'd get rid of the chain slck. That's 3 teeth more.

    Because of the dropouts I can't move tthe wheel forwards or rearwards to take up the chain slack.

    This is a single seed not a fixed gear and I don't want to bother with a chaitensioner.

    Befre i swap the chainring I'll see if the shop here in tow can get me a 3/32" half-link since that'd really solve thchain sack problem.

    The slack is a purely aesthetic issue since the bicycle runs fine and the chain doesn't come off even on very rough terrain.

    If it's not raining tomorrow I'll post some images of this beastie. It's a real hodge podge of arts but it rides very well.

    Cheers from Miele Man

  10. #10
    Senior Member
    Join Date
    Jun 2014
    Posts
    108
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Hi there.

    I haven't changed the chainring on this bike yet. I've been riding it a lot and all seems fine in operation. I finally got around to taking some images of it. Here are four images. IMG_2752 shows the chain sag I was thinking about getting rid of by swapping out the 39 teeth chainring for a 42 teeth one.


    IMG_2751 by Miele Man, on Flickr


    IMG_2752 by Miele Man, on Flickr


    IMG_2753 by Miele Man, on Flickr


    IMG_2756 by Miele Man, on Flickr


    Given that the bike runs well, do you think I need to remove that chain sag?


    BTW, the reason the handlebar is so narrow is because in order to get the drop bar through that 2-bolt stem, I had to cut the bar off where the bar starts the first curve from the straight section.

    This bike was put together from left over parts. It's a fun ride and surprisingly stable on dirt trails even with the narrow handlebar.

    Thanks and cheers from Miele Man
    Last edited by Miele Man; 08-23-14 at 06:26 PM. Reason: added info about handlebar

  11. #11
    Grumpy Old Bugga europa's Avatar
    Join Date
    Oct 2006
    Location
    Adelaide, AUSTRALIA
    My Bikes
    Europa, Hillbrick, Road Chief, Repco Superlite (Ol' Rusty)
    Posts
    3,222
    Mentioned
    12 Post(s)
    Tagged
    0 Thread(s)
    If the chain's not leaping off, I wouldn't worry about it. What's that old technique? Hold it over your head and shake it to see if the chain falls off?

    Had to laugh at your rear brake, it had me foxed for a bit trying to work out what it was. Those bars'd drive me mad. If you've got a bike co-op or similar nearby you should be able to buy new bars real cheap. Mind you, low end flat bars aren't expensive in the shops either - that's assuming you WANT wider bars, you might like what you've got.
    I had a good bike ... so I FIXED it

  12. #12
    Senior Member
    Join Date
    Jun 2014
    Posts
    108
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by europa View Post
    If the chain's not leaping off, I wouldn't worry about it. What's that old technique? Hold it over your head and shake it to see if the chain falls off?

    Had to laugh at your rear brake, it had me foxed for a bit trying to work out what it was. Those bars'd drive me mad. If you've got a bike co-op or similar nearby you should be able to buy new bars real cheap. Mind you, low end flat bars aren't expensive in the shops either - that's assuming you WANT wider bars, you might like what you've got.
    Thanks.

    I used the cut down drop bar so I could use the Tecktro In-line brake levers i had Here. The clamp is too big for an MTB bar and I didn't like the idea of shimming them. Turns out that I really do like those narrow bars.

    The rear brake is an old Suntour Roller-cam one that was on the bike when I bought it. The bike is from the 1980s and has Deore cantilevers on the front fork. The seat post is an American Classic one.

    Here's an image of the Suntour Roller-cam brake from under the chainstay. I didn't bother with the heavy Cordura nylon sleeve on it when I replaced the cable because that sleeve looked like a great place for stuff to collect.


    IMG_2757 by Miele Man, on Flickr

    Cheers from Miele Man

Posting Permissions

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