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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 05-14-12, 08:37 AM   #1
zurikella
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Chainline woes

First time poster; so please pardon if I post in wrong forum.

I built fixed gear based or steel road frame from 80's (obscure brand Diamant from Belgium, but very nice steel with campy horizontal dropouts and Cinelly BB shell). The distance between droupouts 130mm. I bought a set of Vuelta Zerolite wheels for this project; with rear SS/FG flipflop wheel. The cog is 120mm. I am running it as a fixed gear. The crank is Sugino with single chainring. The problem I am having is that there is about 4-5 mm offset in chainline between the cog and chainring, with cog side being closer to the centerline than chainring side. I have bottom bracket with 107mm spindle. The chainring is bolted on inside of crank arm, and there is only 3mm clearence between it ands chainstay, so I can't bring it any closer to the centerline I guess. I really would not care about this, but at high speeds I hear what appears to be the chain rattle, as if is was multispeed bike with lousy shifting. So I don't know where to from this point. Sould I get longer hub that would yeld longer offset? I tried to offset entire wheel with offsets (I have several 10x1mm washers in place to accomodate 120mm axle) but than the tire comes in contact with upper part of chainstay. Thanks in advance for your help!

P.S. Not sure if this is related to chainline, but at sudden acceleration, or when backpedalling to brake; pedals have free movement before they "engage", just as if something was loose. The lockring appears to be tight.
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Old 05-14-12, 09:15 AM   #2
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Sounds like you're going to have to re-dish the wheel or use a different one.
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Old 05-14-12, 09:16 AM   #3
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1st still dont understand why they call regular long road dropouts horizontal when the track dropouts are horizontal as well.

2nd... add 5 mm of washers at each side of the hub to make it up for the 10 mm in difference with the bike rear end (130)

3rd... go to the lbs and ask the guys for BB shell spacers, grab one and put it between the hub and the cog (if you cant figure it out where to put then we a serious problem), that will bring the cog tiny out. Put the lock ring.

4th... that the lockring it tight doesnt mean the cog is, probably the cog is lose and u havent figure it out yet. Obviously if you have a fix gear you shouldnt have the problem you are having, besides the a lose cog i doubt you have more lose parts for that to happen.

5th... diamant is a well known brand between old people, is not obscure or anything. If unknown to you then thats another story , they sponsored pro teams back in the day. Very good bikes so I advice you to take care of it because probably you wont see another one in a while. People doesnt know what they have sometimes.

Good luck.
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Old 05-14-12, 12:32 PM   #4
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sounds like you have a couple of problems.

1) your rear wheel OLD does not match your rear dropouts. solution is to add spacers on both sides. i would get a number of washers so you can adjust it. then redish rear wheel.

2) your chainline is out of whack. solutions can be found by adjusting the chainring as follows: 1) mount chainring on inside or outside of sypder. 2) use washers between chainring and spyder. 3) change BB spindle length. 4) use spacers when mounting BB. 5) adjust hub on rear axles using spacers (previously mentioned). 6) mount cog (or SS freewheel) with spacers. this is not an exhaustive list.

one, or more, of these should be able to solve your problem. good luck.
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Old 05-14-12, 12:45 PM   #5
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Do you have all three drivetrain parts (cog, ring, chain) the same size- 1/8" or 3/32"? Some of the slop can be a chain that isn't tensioned ideally either.

I know I'll get jumped on for this, and have to explain it out, but I'm of the mind that if I can hammer up hills with weird chainlines on my geared bikes, what's 1/2" of fudge factor (other than extra chain wear) in my chainline on a single speed?

And yea, space that wheel out, I can't imagine the axle isn't long enough to do so. Just be sure to sandwich the spacers between the cones and locknuts.
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Old 05-14-12, 01:51 PM   #6
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Quote:
Originally Posted by IthaDan View Post
if I can hammer up hills with weird chainlines on my geared bikes, what's 1/2" of fudge factor (other than extra chain wear) in my chainline on a single speed?
A couple issues:
- On a geared bike, the derailleur guides the chain up onto the rear cog. On a fix/single, the chain goes directly to the rear cog under tension. So with a bad chainline, you're more likely to drop the chain on the rear cog.
- A front derailleur helps keep the chain on the front chainrings, so without, you are more likely to drop the chain in the front.
- Single speed chains aren't designed to flex as much as multispeed chains and bind up more at steep angles
- Your losing some of the improved efficiency of a single because steep chain lines introduce more friction
- Dropping a chain can be a lot more serious on a fix than on a freewheeled bike (depending on brake setup) so the stakes are higher

Of course, you can get away with some misaligned chainlines on a single, but get away with and not care about are two different things.
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Old 05-14-12, 06:38 PM   #7
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Quote:
Originally Posted by echo View Post
Sounds like you're going to have to re-dish the wheel or use a different one.
Dish problems (easily correctable) will simply be a symptom of the corrections that are made with spacing changes at the hub and bottom bracket and crankset - spacing alignment changes are the driving issues as already noted by others.

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