chain + chainrings for conversion problem
 

I was wondering if maybe someone here could lend some help to this wall i've run into. I am trying to convert my trusty old trek road frame that i've had forever, into a fixed gear. I purchased a phil hub that is spaced to 126 (the correct size for my trek), installed cog etc, and bolted on the rear wheel. I removed the outer chainring from the previous double that was on there because on sight it looks like the inner lines up pretty well.

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I was adjusting the chain length, as i have done in the past and realized that the chain is just too loose, it looks like removing one link will cause the hub to have to move too far forward, and apparently these horizontal droupouts arent really that long (at least not long enough to support that). So, first question is Is there someplace that i can get a half-link that will work with this type of chain? (Kool Chain). Or is there a manufacturer that makes a chain that has different chain link lengths, that might result in smaller, removable units?

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The second (related) wall is that i was hoping to run a larger chainring (46) that what is on there now (42) but it looks like running that inner chainring will not allow me to, leading to a situation where the chainring will rub against the right chainstay. any idea how to get around this? using the outer chainring will screw up the chainline. The phil wood hub has these fixed width axel caps that prevent any play in any direction, so i dont think there is much wiggle room there. Perhaps i will need to get a whole new bottom bracket? i dont know if that will work even.

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any input is greatly appreciated. Hope these photos help illustrate what i am talking about.

Perhaps you can get a chain tensioner?

That won't work for fixed.

Cru's Ghost: what you want is a half-link. I did a conversion on a trek that had the same dropouts, and it's necessary for some setups. Here is a picture of what it looks like:

http://harriscyclery.net/merchant/37.../half-link.jpg

You can get them in 3/32 or 1/8 widths.

Alternatively, you can get a chain that is all half-links.

http://www.ride-this.com/images/product/halfLink.jpg

KMC who makes the Kool Chain makes half links. I would contact them to see if the would be any issues with the half link and that chain. KMC also makes a complete half link chain. Shadow Conspiracy does too.

Well, the Phil hub probably has 42.5mm between the cog and the centerline of the hub/bike, so you want a chainring that is the same distance from the center of the bottom bracket. Unfortunately, your Trek frame has wide-ass chainstays that were designed to have a smaller inner ring. You'll never be able to fit a bigger ring there and maintain the chainline if you can't now. Your two options are to somehow respace the hub to the right and redish the wheel, which seems like a pretty terrible idea to me, or to just buy a smaller cog if you want a bigger gear ratio.
Welcome to the great and terrible world of road conversions.

Thanks, Aero + Fluff. that's good news. I have definitely seen half links before. Now i will go hunt one down. Any other ideas re: the chainring size and rubbing the chainstays? I guess my LBS might have a better idea how to pin down the straightest chainline when they can actually review it all.

Yeah, smaller cog was the only last resort i could think of. Somehow on previous conversions, the chainstays were always quite a bit more accomodating, or even have indentations on drive side to allow larger rings to fit. cant believe i didnt think to measure that **** first! Thanks, alex.

Chainline wise: I'd either go with a smaller cog and the smaller chainring (super-easy, kinda $), or else throw a BB spacer on the inside of the cog to push it out a little bit, and then put the chainring on the outside of the spider. That might not work depending on how straight you want your chainline, how much threading you have left on your hub, etc.

why don't you just buy a smaller rear cog? then you can remove a full link no problem.
both problems at the same time

it looks like with the current tension + where it is in the dropouts you should be able to remove a link just fine.. worst case get a half link, both are cheaper than a new cog...

shadow inter lock maybe? check albes.com

Get a cog with another tooth?

to answer a few more of the questions you asked - almost all bicycle chain has links that are a half-inch long. this is called "pitch." some very old gear is "inch-pitch," and for a hot minute in the (i think) 80s, shimano made dura-ace "10-pitch" - instead of a half inch, the links were 10mm long. however: if there were a chain with smaller removable units, it wouldn't fit on your cog and chainring. it's all made for half-inch pitch chains.

also, it never hurts to measure your chainline, to be right. that phil wood hub will put the cog at 43mm from the bike's centerline. use a ruler to measure from the center of the seattube to the center of the chainring. it should also measure 43mm. if not, you might want to consider moving the chainring, or getting a bottom bracket with a longer or shorter (as needed) spindle [if you need to move your chain 2mm outward, you'd need a spindle that's 4mm outward].

that trusty trek ought to make a lovely conversion.

It looks like you have enough dropout room to remove a full link. Removing a whole link from your chain will only move your axle ~1/4" forward.
It also looks like a 46T chainring might fit. if not, just have a your LBS or local framebuilder dent the chainstay for clearance.

46 wont fit. the 42 is almost hitting the stay as it is. I'm not sure how close to the end of the dropout the hub can bolt on and still be secure.

I have short horizontal dropouts on my mtb and so far have not had any problems at all with the axle and bolts this far forward. I use a halflink that I add/remove when switching cogs.
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