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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 12-25-06, 03:27 AM   #1
Briareos
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Should Road-Conversions Utilize Road Cranks?

I have been building up a 130mm rear spacing road bike for fixed-gear, and was simply planning on getting an IRO drivetrain to start with. But I forgot to consider chainline and things like that and now I'm not so sure about my choice. Chain-line and BB size are things I have trouble understanding, I can't visualize it in my head so it's difficult.

With 130mm rear-spacing, what sort of things should I be thinking about? Should I use road cranks with one chainring to achieve a better chainline? I've read some threads using the search function but like I said, it's mind-bending. The BB is a standard 68mm English thread (It's a GT Strike road bike).

Anyone have any ideas on how I can get a nice balance of chainline with either track or road parts?
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Old 12-25-06, 12:31 PM   #2
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What hub do you want to use? Flipflop or not?
Chances are that it will have a 42 mm chainline. See if your chainstay allows you to go 42mm with the chainring you want. If it does, go 42 for simplicity. Track bb and track crank.
However, getting a road crank and a shortish bb will prolly be cheaper. 45ish chainline, which is a bit trickier to match with your hub.
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Old 12-25-06, 12:55 PM   #3
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Sometimes a track crank will hit the chainstay on road frames with a short BB.
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Old 12-25-06, 12:58 PM   #4
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There's aways flipping the bracket over so the left side (shorter) is on the right...that often works, though it's often easier if you have an old-school spindle bracket and a box full of other ones to try.

Trial and error are integral parts of bike mechanics.
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Old 12-25-06, 01:01 PM   #5
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Quote:
Originally Posted by thurstonboise
Sometimes a track crank will hit the chainstay on road frames with a short BB.
Hence:"See if your chainstay allows you to go 42mm with the chainring you want"
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Old 12-25-06, 02:18 PM   #6
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what road crank do you plan on using? There are online databases for cranks and chainline. That should help you deterine what BB will give you a 42mm chainline.
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Old 12-27-06, 01:28 AM   #7
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Quote:
Originally Posted by mihlbach
what road crank do you plan on using? There are online databases for cranks and chainline. That should help you deterine what BB will give you a 42mm chainline.
Well, I can use a set of C-Record cranks a friend has no use of, and neither of us knows what BB length they use and what parts to use with it.

The other option is a Centaur Ultra-Torque crankset (one-ring obviously). I hear the difference between those cranks and regular ones is quite noticeable and I'd like to try it with a fixed gear or singlespeed.

If those two options turn out to be too much of a hassle, I'll probably get an IRO drivetrain.
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Old 12-27-06, 03:29 PM   #8
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It's a lot easier to mess with spacers on your chainring bolts than to switch out the crank or BB, so try that first.
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Old 12-27-06, 07:01 PM   #9
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The bottom bracket will probably be quite low so you want to go for 165 mm long to avoid pedal strike in corners. Not sure but you may have better luck finding that length with track gear? most road cranks are 170-175. Not sure what is available to you.

I have 165's on my road conversion and no worries until I tried racing, which was very scary in the bends!

I think Sheldon Brown has some measurements regarding sprockets, rings, and chainline. I just ordered my stuff and was lucky.
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Old 12-27-06, 07:15 PM   #10
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save yourself some money and just get a shorter bb
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Old 12-27-06, 07:17 PM   #11
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IMO, road cranks are far superior to track cranks in every way.
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Old 12-27-06, 08:45 PM   #12
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Quote:
Originally Posted by BostonFixed
IMO, road cranks are far superior to track cranks in every way.
Could you be more specific?

How many ways are there for a crank to be "superior?" They're not lighter, they're not stiffer, they're not stronger... May be prettier...

They also commonly use the semi-obsolete 144 mm bolt circle, for which chainring selection is rather poor and the rings available tend to be unreasonably expensive due to their rarity.

Sheldon "Cranks Don't Really Know Where They're Being Ridden" Brown
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Old 12-27-06, 09:00 PM   #13
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Quote:
Originally Posted by Sheldon Brown
Could you be more specific?

How many ways are there for a crank to be "superior?" They're not lighter, they're not stiffer, they're not stronger... May be prettier...

They also commonly use the semi-obsolete 144 mm bolt circle, for which chainring selection is rather poor and the rings available tend to be unreasonably expensive due to their rarity.

Sheldon "Cranks Don't Really Know Where They're Being Ridden" Brown
I think you read my statement backwards.
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Old 12-27-06, 09:01 PM   #14
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hey wait I have old school road cranks that are 144bcd what should I do??? hehehh
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Old 12-27-06, 09:18 PM   #15
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Quote:
Originally Posted by BostonFixed
I think you read my statement backwards.
!did I sseug I seY

yrroS

nodlehS
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