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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 07-11-05, 10:50 PM   #1
wetjett01
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Vertical Drops are a Drag

here's the prob... trying to make a bike with vertical drops out into a single speed. i have a 38 tooth ring up front and a 16 tooth cog in the back. i've tried it with some crappy singleator imitation that i got from Nashbar but it's not working because i can't change the spring tension in the singleator. i think the tensioner spring is broken or something. so, i've tried to remove a couple of links in the chain and not use the tensioner but that makes the chain too tight to insert the rear axle into the drop outs. i'm about ready to get the Dremel out and make my own horizontal drop outs and solve the problem real quick-like . but before i do that i was hoping someone else had run into the same issue and had a good solution. also, just to let everyone know i also have a 15 and a 13 tooth cog to try on the rear. would that possibly work without making the gearing too low? any thoughts or advise would be much appreciated

thanks much
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Old 07-11-05, 10:52 PM   #2
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half-link?
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Old 07-12-05, 12:24 AM   #3
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There is a reasonably good chance that the 15 will work, especially if the dropouts are not absolutely vertical and allow you to move the axle at least a millimetre or two. Remember, the 15 cog will only give a 6.7% bigger gear than the 16.
Try the halflink if you can: http://www.sheldonbrown.com/harris/chains.html
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Old 07-12-05, 04:32 AM   #4
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You have a few options. What you ideally need is a "magic gear". Dig around here. The section "How do I tension the chain" should be helpful.
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Old 07-12-05, 07:42 AM   #5
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Quote:
Originally Posted by wetjett01
here's the prob... trying to make a bike with vertical drops out into a single speed. i have a 38 tooth ring up front and a 16 tooth cog in the back. i've tried it with some crappy singleator imitation that i got from Nashbar but it's not working because i can't change the spring tension in the singleator. i think the tensioner spring is broken or something. so, i've tried to remove a couple of links in the chain and not use the tensioner but that makes the chain too tight to insert the rear axle into the drop outs. i'm about ready to get the Dremel out and make my own horizontal drop outs and solve the problem real quick-like . but before i do that i was hoping someone else had run into the same issue and had a good solution. also, just to let everyone know i also have a 15 and a 13 tooth cog to try on the rear. would that possibly work without making the gearing too low? any thoughts or advise would be much appreciated thanks much
Having trouble adjusting the spring tension in the "Singulator"? Have you tried using an 18mm cone wrench on the thin wrench flats on the back of the pivot bushing? (That's the ONLY way to set the internal speing tension!!) You need to thread the singulator's main pivot bolt onto the derailer hanger loosely, THEN hold the 18mm wrench flats in place with an 18mm cone wrench to set the desired amount of internal tension and THEN tighten the main pivot bolt tightly. If you simply thread the singulator's hex bolt onto your derailer hanger WITHOUT using an 18mm cone wrench to pull back on the singulator's wrench flat section to set the internal spring tension....well, there just won't be any spring tension inside the thing and your chain will be droopy.
Do you have an 18mm cone wrench? You need one to install singulators correctly.
They look like this:

If you still have trouble, pop off the clip on the back of the singulator and open it up. Check to make sure the ends of the internal spring are seated inside the little holes that keep it in place.
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Old 07-12-05, 07:52 AM   #6
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yeah.. i tried the cone wrench.... i think the spring is broken. there's no wire sticking in the hole that keeps the spring in place.
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Old 07-12-05, 07:56 AM   #7
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Oh, that's too bad.
I guess you could return it, or try to get lucky with the magic gear.
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Old 07-12-05, 10:08 AM   #8
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Try this:

http://www.teambigtime.com/software/ssConvert.htm

Or this:

http://www.peak.org/~fixin/personal/...p/tutorial.php

Helps you find the right gear combo for your bike without the need for a tensioner.
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Old 07-12-05, 11:14 AM   #9
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ok.. i did the FixMeUp thing and came up with a number of 47....is that the length of chain that will provide the proper chain tension w/out a tensioner?... i have a 38 tooth front ring running to either a 16,15,or 13 tooth rear cog(have the 16 on right now). the chainstay is 42.4 cm long if anyone wants to check my math
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Old 07-12-05, 12:26 PM   #10
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I assume you're using a road bike with 700c wheels? If so, then you plug in 38 as both the largest and smallest chain ring, and 16 as your largest cog, 13 as your smallest. You measured your chainstay length as 42.40 centimeters, and when you generate results you get:

Ring Cog Stay_length Chain_length Gear_inches
1 38 14 42.266 46.5 71.0
2 38 16 42.311 47.0 62.1
3 38 13 42.562 46.5 76.5
4 38 15 42.609 47.0 66.3

This means that none of your gear choices will *exactly* fit your chainstay measurement - note that the stay_length with 38 x 16 is 42.311 and with 38 x 13 and a half-link it's 42.562. 38 x 15 is longer still at 42.609.

Your best bet would be to:

A) Buy a 49t chainring and an 18t cog - that would give you a stay_length of 42.399 and a gear ratio of 71 inches (again assuming you have a 700 x 23c wheel).

B) Buy a 47t or 46t chainring - 47 x 16 would give you a 42.399 stay_length and a 77" gear, and 46 x 15 would also give you a 42.399 stay_length but an even bigger 80" gear (again assuming you have a 700c x blah blah blah).

C) Buy an Eno hub and rebuild your rear wheel or buy a new wheel built around an Eno hub - then use any of those chainrings and cogs you already have, or now have the option to use a lot of different ratios, buy some new chainrings and/or cogs, and find the ideal ratio for your riding style.

craig
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