Oh, you know...
Join Date: May 2009
Bikes: '74 Schwinn Sports Tourer (Polo), S-Works E5 Team Festina (Chorus 11), Trek 2200 Bonded Carbon (Fixed), Trek 920 (7 speed IGH), Chesini Olimpiade SL (1x7)
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Originally Posted by Philasteve
Unfortunately what you're experiencing is one of the common pitfalls of converting a geared road bike frame to single speed. Because of the wider rear dropouts, the angle of the driveside chainstay relative to the centerline of the BB is greater, meaning that clearance for larger chainrings is reduced. This problem is compounded when using the shorter spindle required to achieve a proper chainline; while many geared frames have dimples in the driveside chainstay to allow clearance for the inner ring of a double, these dimples are often placed and sized to accommodate a 42 tooth chainring at most, while a typical fixed gear application uses 46T chainrings or larger.
One solution is to move the chainring to the outside of the crank arms and find a 130mm track hub to give you a more appropriate chainline. Alternatively (but less desirably), you could use spacers to move the 120mm hub more towards the drive side, and then re-dish the wheel.
Probably the cheapest solution is to use the largest chainring that will clear the stay, and then size a rear cog appropriately. After all, 40x14 is just about the same gearing as 46x16.
Hope this helps.