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Old 11-10-04, 11:56 AM   #1
HoboRandy
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I'm new to cycling and bike maintenance, etc. I have an old bike that I'd like to make into a fixed gear and I have one question that I haven't managed to wrap my brain around (some of you will probably think the answer is painfully obvious!).

I went to the LBS today and ordered a pre-built rear wheel with suzue (sp?) hub from my LBS (at their recommendation), and I was planning to use one of the chainrings already on the bike (it has a double chainring right now)...how will I get the cog and chainring to line up? Or do I need to buy a special chainring (or whole new drivetrain)? I didn't even think to ask while I was there...now I'm trying to get some work done and all I can think about is how on earth those are supposed to line up!

Thanks!
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Old 11-10-04, 12:49 PM   #2
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Most road bike to fixed conversions require you to use the smaller inner chainring mounted in the same inner position of your stock double crank to achieve a reasonably good chainline. Just make sure upon removal of your big chainring that you replace all chainring bolts with the shorter BMX bolts.
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Old 11-10-04, 12:51 PM   #3
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Chains are flexible and unless the angle exceeds that seen with derailleur multispeed chain angles
it should not be a problem. www.sheldonbrown.com has a series of essays in fixed speed conversions
and there is also a forum on this site devoted to "Single and fixed gear bikes". Prebuilt wheel should
be appropriately dished and spaced but "might be off" for fixed usage. You do have a choice with
standard road cranks of putting the chainwheel on the inside or outside of the spider. Steve
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Old 11-11-04, 01:56 AM   #4
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Hi,
When setting up a fixed gear you should get it in line within about 3mm either way.
The chain runs so much better when its not scuffing on the sides of the chainring.
Its best to use a stiffer 1/8th chain even if you still use the thin ring / sprocket.
I've found that frame offset, wheel dish, BBaxle offset, and crank fitting position all interact to make it impossible to predict the outcome.

Best is to fit up all your bits, sight along the chainring back to the sprocket, and decide...........
Also sight along the rear tyre to down tube, and rear tyre to toptube to check that the wheel is sitting straight in the frame.

is it all OK ? .................. you're very lucky!!!!
is it fixed by putting the chainring on the other side of the spider ?
is it possible that your chainring is dished and can be turned inside out?
is it possible your sprocket is dished and can be turned around ?
is it possible to reduce the frame offset and increase the wheel dish? Or vise versa ?
is it possible to change the BB axle to a shorter / less offset one ? Or longer one ?

If none of these help, there are a few more "crude" methods available.

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Old 11-11-04, 02:13 AM   #5
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Quote:
Originally Posted by The Fixer
Most road bike to fixed conversions require you to use the smaller inner chainring mounted in the same inner position of your stock double crank to achieve a reasonably good chainline. Just make sure upon removal of your big chainring that you replace all chainring bolts with the shorter BMX bolts.
Or the large chainring.....
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Old 11-11-04, 08:51 AM   #6
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You can do several things to improve the chainline on a fixed conversion. Generally, you will need to move the rear outward and/or the front inward. Looking at these two separately:

Front:

1. Choose the smaller or inner chainring.
2. If using the largest chainring, you can move it to the inside of the crank spider where the smaller chainring is installed.
3. Use some 2 or 3 mm spacers between the crank spider and the chainring.
4. Install a shorter BB axle or, if using a non-sealed unit, swap the axle around to use the shorter left side on the right.
5. Purchase a single speed crank that may be positioned further inboard.

Be careful in moving the front chainring that you don't get closer than about 2 mm to the chainstay or you risk rubbing the chainring.

Rear:

1. If you are going fixed only (not a flip-flop) you can usually adjust the position of the rear cog outward by changing spacers on the rear axle. Afterward, you need to redish the wheel to center the rim between the dropouts.

2. If you are using a flip-flop hub with a freewheel on the other side, you can probably move the fixed cog outward a couple mm because the freewheel cog will probably be further outboard to begin with. You can also make minor adjustments without redishing the wheel by moving washers inside and outside of the dropouts depending on which way you install the wheel.
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Old 11-11-04, 02:12 PM   #7
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Quote:
Originally Posted by sch
Chains are flexible and unless the angle exceeds that seen with derailleur multispeed chain angles it should not be a problem.
An improperly aligned chain will lead to excessive noise, premature wear and the increased likelyhood of throwing the chain, something you don't want happening on a fixed gear ride.
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Old 11-11-04, 07:48 PM   #8
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Sometimes I tweak the alignment by shifting the hub using spacers. You will need to add spacers to the hub anyway to get a good fit(Suzue is 120mm, your bike will be 126mm or 130mm) You can squeeze your frame down but the Suzue axle is plenty long enough to add a couple of mm of spacers to fit or to adjust chainline. If you use this method the wheel will probably need to be dished a little(Dishing shifts the rim back to center)
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Old 11-12-04, 01:24 PM   #9
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Quote:
Originally Posted by Rev.Chuck
If you use this method the wheel will probably need to be dished a little(Dishing shifts the rim back to center)
Or not. If you aren't going to run a rear brake, having your rim slightly off center won't do any harm and you won't hardly be able to tell by looking at it (if aesthetics is an issue). I'm not saying that redishing isn't the right thing to do; it definitely is, as my esteemed colleagues have said. But if you're so anxious to be start plying the streets with your new rig that you can't bear the thought of taking spoke wrench in hand, well, don't worry about it, at least for now.
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Old 11-12-04, 03:16 PM   #10
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go to the forums on the fixed gear gallery site for additional assistance.
http://www.fixedgeargallery.com/
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