Singlespeed & Fixed Gear - Chainline ??....
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07-10-03, 03:17 PM
I'm trying to use and old triple crankset for a fixed conversion. I have the chainring mounted inside with 3mm spacers. The measurement from the center of frame to the center of the ring is 45mm. The cog is about 40-41mm from center. I'm using a Shimano 109.5mm BB(octalink). There's only about 3mm between the crankset and the BB.
I can't move the crankset closer, there aren't any spacers on the hubs(Miche) to move around.
What are my options? I don't have a chain yet to test the chainline, is 4-5mm difference too much? Should I be looking for a double crankset? will that make any difference?
07-10-03, 03:26 PM
I'm nearly certain that the bottom bracket common with most triples is too long to give you a proper chainline for any road fixed or flip/flop hub. You probably need to get a shorter bottom bracket spindle.
07-10-03, 07:55 PM
I will second the above info regarding too long a BB spindle/triple crankset...but do not give up hope. Call Sheldon Brown/Harris Cyclery if you have just about lost all hope.
07-10-03, 10:08 PM
I'd go with the shorter spindle also......but make sure your chainring clears the chainstay. What size ring are you running?
Unless I miss my guess, the 109.5 is the shortest octalink bb made by Shimano. The 118.5 is the triple length. I don't think a double crank of the same type will solve your prob.
4-5 mm is roughly the distance between two cogs on a cassette, so you're only off by one cog of a perfect chainline.
If you want to space out the cog, use a bb/freewheel spacer available for $0.80 from <http://www.loosescrews.com>. Type spacer in the search engine and it will take you right to them. One or two of those should solve da prob. Just make sure that when you reinstall your lockring, it threads on for at least three(3) full threads. Tighten the cog down real tight against the spacer/s before you install the lockring.
07-11-03, 07:51 AM
You got all kinds of room between the ring and the stay.
I would try another crank arm if you have one. They do not all line up the same.
I would also try a shorter bb spindle.
07-11-03, 01:50 PM
i just bought a shimano bottom bracket with adjustable cups, which allowed me to place the crank to where i could put the chainring on the outer part of the spider (i see it on the inner part on most conversions--like in the pic above) and didn't have to use any chainring spacers...
there are about 3 mm of space between the chainring and my chainstay though :)
07-11-03, 03:19 PM
Oh yeah, there's lots of room between the ring and the stay But even if there was such a thing as a shorter octalink bb spindle, I could only move the crank about 3mm closer before it hit the cup.
I'm going to find a double crankset, install it and see how it works out with an adjustable cub bb. I should be able to make it work...it has to be better than what's on there now.
shrimpx - what length spindle did you use?
Originally posted by shrimpx
i just bought a shimano bottom bracket with adjustable cups
Is this bottom bracket made by Shimano? Or is it an aftermarket bb with adjustable cups that fits Shimano cranks? If it is made by Shimano, let us know what the Shimano part number is. I'd like to get one.
07-12-03, 06:43 AM
Dura Ace certainly used to be adjustable. I assume it still is.
Dura ace used to have an adjustable chainline? When? What part #?:confused: I know they're BB is a fixed BB now.
07-12-03, 01:31 PM
Try looking into the Dura Ace track BB's. The ones I'm familiar with were Italian threaded, though.
Track, road, it doesn't matter. I have followed shimano for 25 years now, and I have never seen a Bottom Bracket manufactured by them with an adjustable chainline(ala Phil Wood adj. cups, Race Face adj. cups, American Classic adj. cups). Please post the part # to this part. I'd really like to see it. Thx.:)
07-13-03, 09:08 AM
Sorry-my confusion-the one I used to have was a Phil, which replaced an older Dura-Ace.
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