Single Speed Chainline Help!

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***Disclaimer: This is not a fixie. I am in no way a Hipster. No coffee shops, or dubstep, or glasses, or PBR. Though, I DON'T hate, I thought I'd get that outta the way...***

I guess my chain is a bit Hipster-esque... oh well, it was cheap


For the longest time, I've been building bicycles and riding the crap out of em. I rode BMX and eventually found cruisers, but in the last year or so, I've found that older road bikes really keep my interest. I scavanged my local dump for months, and finally found a gem. I pulled this bike outta the dump and immediately got to work. I got the complete bicycle, it was all there. The wheels were good, the tires seem new, I even saved a tube. So far, I only have about 90 bucks in this bike...

I replaced the crank with a "fixie" crankset. Tec9 to be exact, they're all over E-Bay. I still have the original spindle, and I think it's too long, my chainline is WAY off. I've been doing a bit of research, and believe I've got a 68mm BB width on my frame. I just need to figure out what spindle length I need. My rear wheel is a Shimano cassette hub, with the gears removed, and a single cog with spacers now takes up the space. I've got a bit of room to play with the rear chainline, but even with the cog slid all the way towards the outside of the hub, my chainline is still off.

Is there any way to measure my setup, do some math, and figure out what I need? I don't have a caliper, and there is no bike shop in my town. The closest is an hour away, and it's a heck of a walk without a car...

Any help would be awesome. I'll take pics and have em up later tonight or tomorrow.
Thanks in advance
-Greg
 
Checkout Sheldon's page

http://www.sheldonbrown.com/chainline.html

Also download the spocalc spreadsheet from his website, it contains center to flange info for just about any hub, you should be able to figure out where you are with that. If you kept the same spindle going to the fixie crank you're probably about 1cm out too far. You've probably got a spindle length in the 120-127mm range you likely need something in the 110-113mm range.
 
slap the old crank on there and measure out from teh seat mast, then do the fixie one, . then you'll know how much you are out...
 
I've read all of Sheldon's stuff, and can honestly say I learned ALOT

I'm a somewhat sketchy bike builder, and can look past the best possible option for what simply works. I don't have the original cranks to measure (They have been donated to a program at the prison. They refurbish bikes and sell em...) Since I have a freehub in the rear, and have a bit of adjustment, could I order a spindle (regardless of length), and just space the rear to the spindle? Should I order a super short spindle (110mm) or say a medium (113)?
 
all you need is long enough so the chainrings clear the frame I would think... :roll:
 
grob23 said:
I've read all of Sheldon's stuff, and can honestly say I learned ALOT

I'm a somewhat sketchy bike builder, and can look past the best possible option for what simply works. I don't have the original cranks to measure (They have been donated to a program at the prison. They refurbish bikes and sell em...) Since I have a freehub in the rear, and have a bit of adjustment, could I order a spindle (regardless of length), and just space the rear to the spindle? Should I order a super short spindle (110mm) or say a medium (113)?

What length is your current spindle? That will tell you really what length to get get although I think you'll need a whole new bottom bracket Shimano square taper can be had for $10 new. 110/113 isn't super short or medium just a different chainline. Difference between 100/113 is negligible pretty much, there spacers to deal with that, 120/110 not so much.
 
scrumblero said:
all you need is long enough so the chainrings clear the frame I would think... :roll:

Unfortunately it's not that simple when going single speed. If you have ramped and pinned rings up front they'll want to shift if you're not close on chainline.
 
Just to clear things up a bit. My front chainring is 1/8 SS specific, and my rear is a BMX cassette cog. I shouldn't have any real problem with the chain derailing as long as my chainline is as straight as I can get it...

In my crazy logic, it would make sense to order the 113mm. I'd have a better shot of clearing the frame, and there's no doubt that it'll bring that chainline in. So even if it's not perfect, it'll be tons better, and I've always got plenty of room in the rear to match the front. Anyone agree?
 

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