Fixed Gear Chainline with Older Road Crank
 

I am hoping to use an older Dura-Ace Crankset for a fixed gear set-up (on a track bike.)

Budget fix for the first little and will upgrade parts as I have $.

Since the track hub and cog in the back will give a 42mm chainline, I will most likely need to run the chainring on the inside (of the double crank.)

I believe the spindle length for this crank set is a 109 for a 43mm chainline (on a road bike set-up.)

does anyone know where this would put the chainline of the inner chainring and the outer chainring? (assuming that the 43 is the center of the two double chainrings?)

If I wanted to run on the outer chainring, could i just get a smaller spindle length BB (107, 105?)

Will I run into problems with putting this crankset on a smaller BB?

I know the correct answer is to go to my LBS but I would just as soon build this on my own and learn some lessons...

Thoughts?

Sheldon says typical chainring spacing is 5 mm. That means the outer ring sits at 46 mm with a 109. You need to lose 4mm on the right to get it down to 42mm, I guess... Are you sure your cranks take a 109 when used as a road double?

FYI a 107 works with my 600 cranks to give 42mm-ish chain line on the outer ring. Probably more like 43. However I had to file 1.5 mm off each of the inner horizontal chainring tabs for clearance against the chainstays.

Sounds like it might be time to ebay or CL a new-to-you crank.

It is impossible to know for sure unless we know what your old crank is. The reason being different cranks have different offsets; meaning the chainline for crank X will probably not be the same for crank Y.

If you are confident on the 109mm spindle size you can use Sheldon Brown's Bottom Bracket Database to see what your chainline might be. It states that the Dura Ace doubles have a 43.5 mm chainline on a 109.5mm BB.

ASSUMING YOUR BB IS A 109: You can assume if you mounted that dura-ace crankset on your 109BB the double centerline would be 43mm. Since the standard distance between double cogs is 5mm you simply add 2.5 to find the outer chainring chainline or subtract 2.5 to find your inner chainring chainline. Which are 40.5 and 45.5, which, if this is the case, would be fine for running an inner chainring.

Exactly.. According to Sheldon Brown's database you'd need a 105.5mm BB to mount a chainring on the outside of a dura-ace crankset and get a perfect chainline. A quick look around turned up a 105mm Phil Wood BB(but it is like $120)

I am not sure what you are talking about; do you mean shorter spindle? if so, no, it is not a problem.

If the bike shop caters to SS or fixed gear then you could go that route. You'll have a lot more fun and enjoy the bike more if you build it yourself.

chry

Thanks for your help - good information.

crank, bb compatibility
 

Hey
Im in the same boat you are, I have a vintage shimano rd crank, and have yet to get the BB.
Mine is an EXAGE sport, with the original intended bb being a 113mm for double set up.
If you have the late 80's DA crank (7400) I used to race on this one back in the day, and it used a 112mm bb, so in your case, with a high end crank that already has a narrow Q factor, Id get a shimano 115mm BB, and run the ring on the INSIDE, because originally , with the stock BB, you'd get an inner ring chainline of about 41mm (too close), so the next size is 115mm.
Good luck, and tighten down cranks pretty hard, you can safely go up to 50 Nm in torque.clean taper and spindle before installing with cloth, no need to degrease so its a bone dry taper though, just a faint bit of skin oil should be fine, but dont grease spindle like its an Octalink.
Jack

your fixie conversion
 

You say you use 107mm bb withyour shimano 600 crank. Is that the 600 Ultegra model of the late 80's? Or the 600 EX crank of teh early, mid 80's?
I have an Exage Sport shimano road dble crank, with original BB being 113mm, you think that the 107mm BB unit should work for my track bike? I have a C-dale track bike, Miche rear hub.
Jack of CT

same here..
wondering what bb to use with a Shimano 105.
i was thinking a 107mm BB would be the closest to 42mm
i can get without the cranks hitting the chainstay.

Bolt the bits together and then see what you need. Once you've worked out what you've got, go to your lbs and ask them for something to give the difference (bit longer, bit shorter). Bottom brackets aren't expensive enough to make mucking about with mail order worth it and while charts might give you a start, a good mechanic will resort to experimentation anyway.

Richard

+1

I had the same scenario. I took it to the LBS and he gave me a BB that he thought would work. He told me to install and don't mess it up and if it was too long to bring it back and I could try another one. He knew what he was doing so I didn't have to go back.

With my FC6207 shimano 600 a 107mm BB gives about 43mm chainline with the ring on the outside. I run a 3/32 dura ace ring and dura ace cog and it is quiet enough and works fine.

With the same BB and shimano 105 (FC 1050) cranks I had to run the ring on the inside with about 41mm chainline.

So basically who knows!