Join Date: Mar 2007
Bikes: Surly Pacer, Trek 520 & gaspipe fixed gear beater
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chainline & cottered cranks
Hello all...I'm pretty new to the forums and I'm brand new to fixed gear. I just got my conversion into a rideable condition and I'm trying to sort out a chainline/gearing issue with my old-fashioned cottered cranks. Here's what I'm working with:
Right now, I am using the 40 tooth inner chainring with a 16 tooth cog, and my chainline is off by 4mm. I've already ridden it and it doesn't seem to be that big of a deal. However, I would rather use the 48 tooth outer chainring. If I do this, my chainline will be off by 11mm!
Ultimately, I would like to step up my gearing to 70 inches. To do this I can either run 40x15 and my chainline is only off by 4mm but I have to keep the unused outer chainring, or I can run 48x18 and only have one chainring up front but my chainline is off by an enormous 11mm.
Because the outer chainring is attached directly to the cottered cranks, I can't remove it and use only the inner ring...basically, if I use the inner ring, I'm forced to leave both chainrings on. I plan on swapping the BB, chainring and crankarms later this summer for something that will work better. Since it's temporary, is it OK to run a horrendously bad chainline and quickly wear out my parts until I get a new BB? Or should I just ride on the inside ring and not worry about the stupidity of having two chainrings on a bike with one gear? If I have to stick with the inside ring, I suppose I could saw off the outside ring just past the 3 bolts holding on the inner ring.