Singlespeed & Fixed Gear - Anticipating Chainline before I order...

I'm looking at ordering an IRO wheelset and I'm looking for a set of cranks (Probably IRO but I'm still in research mode, any suggestions for cheaper cranksets also appreciated). I'm just curious as to how I can anticipate what my chainline will be with different cranks. Is the chainline in the front purely a result of the bottom bracket? If I measure the chainline on my existing cranks will this hold for any crank I put on there (the existing crank is not a track crank, just a road crank with chainring on inside spider)?

Please enlighten me on the issues surrounding chainlines... and how I might solve mine... I'm not opposed to getting a new bb if it means a perfect chainline.

Oh and for what it's worth I'm performing all of this on a converted Peugeot UO 6... Teiaperigosa posted a pic of the same bike a little while ago here (http://www.bikeforums.net/showthread.php?t=160171).

I'm not an expert in any way but 42mm i supposed to be the standard track chainline. Most track hubs have a 42mm chainline but there are some with a wider chainline (LeVel, Gaansari...). The IRO hubs have the standard 42mm chainline I'm sure.
When it comes to your cranks I would just get a standard track crank IF it fits the bottom bracket and go from there. Try to determine the width of your existing bb. If it's around 109, 110mm then it's good for a proper chainline with a track crank.
You can measure your existing chainline by measuring the distance between the center of the seattube and the center of the chainring which should be around 42mm.

You should be aware that the bb threading on a Peugeot can be non standard which therefore makes it a bit tricky to find a new bb for.

Like I said I'm not an expert, still learning also, but I thought I'd atleast try to answer your question. Search this forum and search Sheldon Brown's home page and you'll finally come to an understanding I hope.

I'm looking at ordering an IRO wheelset and I'm looking for a set of cranks (Probably IRO but I'm still in research mode, any suggestions for cheaper cranksets also appreciated). I'm just curious as to how I can anticipate what my chainline will be with different cranks. Is the chainline in the front purely a result of the bottom bracket? If I measure the chainline on my existing cranks will this hold for any crank I put on there (the existing crank is not a track crank, just a road crank with chainring on inside spider)?

Please enlighten me on the issues surrounding chainlines... and how I might solve mine... I'm not opposed to getting a new bb if it means a perfect chainline.



The simple answer is get an IRO crank and matching BB - Tony supplies the proper BB axle length so that the IRO crank will have a chainline that matches the IRO hubs, which, BTW, is at about 42mm, the standard track chainline.

What Tony has done is to sell hubs and crank/BB combos that adhere to the standard used on track bikes: a 42mm chain line. This standard exists so that parts can be interchangeable, so that they can work together. A Dura Ace track crankset will work with a Kogswell track hub, for example.

The answer above points to many of the variables or constituent dimensions that make up chainline:


the crank itself (each model is different)
the BB axle (different models and lengths and where they seat in the BB shell)
axle/crank interface (different cranks fit on a given axle differently)
hub thread dimensions (where the threads are relative to the hub's centerlne)
cog dimensions (they vary a little)


So if you have a track hub like the IRO, you can use any crank/BB combo as long as that crank/BB combo positions the chainring within a mm or so of 42mm AND it does not result in some kind of interference like the chain/crank/chainring rubbing the right chainstay.

So, if you use 'track' components chainline is more or less a science. And if you go off page and use other components, it becomes an artform.

Most of us just try different BBs until we find one that works. It isn't difficult, it just requires practice and access to a lot of BBs. Those of us who've been doing this for a while have both.

You've done the smart thing by asking for help. Asking questions here will bring you good answers that will save you lots of time.

If you find a crank that you'd like to use, post another question here and ask if anyone know a good BB to use that will render a 42mm chainline.

You may run into a crank that cannot be made to work w/ your frame. It's rare, but it happens.

this is probably the best explanation on the interw3bz on how to obtain proper chainline: http://sheldonbrown.com/chainline.html

if you're converting the peugeot, you most prob need a new bottom bracket

110m spindle IRO worked for me(on stock double stronglight cranks and 42.5 phil rear hub chainline)..my chainring is on the inside of the spider.... if I had the patience to wait tho, I prob would have gotten a phil BB (something around 110mm) because of the adjustable chainline

You should be aware that the bb threading on a Peugeot can be non standard which therefore makes it a bit tricky to find a new bb for.

Like I said I'm not an expert, still learning also, but I thought I'd atleast try to answer your question. Search this forum and search Sheldon Brown's home page and you'll finally come to an understanding I hope.

It's not on my home page, but see:

http://sheldonbrown.com/velos

and:

http://sheldonbrown.com/chainline

and:

http://sheldonbrown.com/bbsize

Sheldon "Over 2000 Pages And Growing..." Brown.com
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Wow, Kogswell and Sheldon Brown weighing in... guess I can't go wrong on the advice given :-) I think I'll just go with the whole IRO package if I can since it'll be for a winter ride, so I don't want to sink to much cash into it. Now to figure out what threading my bb shell is...