Touring bike build: chainline
1 Attachment(s)
I am building up a touring bike from a Velo Sport Alpin frame (very much like the one is this thread).
I have a 7 speed freewheel and a Sugino XD triple crank. The rear spacing is 126mm and the chainline (middle sprocket) is 42.5mm. Sugino recommends a 113mm (or larger) spindle length; this give me a front chainline (middle chainring) of 47.5mm. Does anyone think the chainline being off by 5mm is going to be a problem? I don't have much choice in the back, but I could try to see if the crank will mount on a smaller spindle as there is plenty of frame clearance. Right now I have a Shimano UN54 113mm that I could exchange for a 110mm or 108mm, but there may not be enough room as the Shimano bottom brackets seem to have a spacer or stop installed (see attached image). I assume the crank is not supposed to be touching this? If anyone has any thoughts, advice, or comments I would like to hear them. Thanks. |
Originally Posted by sfclearwater
(Post 9066291)
I have a 7 speed freewheel and a Sugino XD triple crank. The rear spacing is 126mm and the chainline (middle sprocket) is 42.5mm. Sugino recommends a 113mm (or larger) spindle length; this give me a front chainline (middle chainring) of 47.5mm. Does anyone think the chainline being off by 5mm is going to be a problem?
Sugino's recommendations are likely based on a 135mm spaced rear triangle common on touring frames. With your rear spacing, you will need a more narrow BB to get the correct (for your application) chainline.
Originally Posted by sfclearwater
(Post 9066291)
I don't have much choice in the back, but I could try to see if the crank will mount on a smaller spindle as there is plenty of frame clearance. Right now I have a Shimano UN54 113mm that I could exchange for a 110mm or 108mm, but there may not be enough room as the Shimano bottom brackets seem to have a spacer or stop installed (see attached image). I assume the crank is not supposed to be touching this?
If anyone has any thoughts, advice, or comments I would like to hear them. Thanks. The arrow in your picture is not pointing at a stop on the BB. Square taper BB's don't utilize a stop for the crankset. The spindle is designed so that the crank stops sliding down the spindle prior to contacting anything. Your crank will fit just fine on a 107mm BB. The only limiting factor with BB width is frame/chainring clearance and it sounds like you have plenty of room there. |
I have a Sugino XD2 crankset on an old road bike with 126mm spacing. I forced in a 130mm wheel and have a 110mm bb in there - chain line is great. The 113mm bb works for a mountain bike or something but 110 or 107 is probably going to be better on a road bike.
Also, I think the Shimano 107 bb is asymetrical - the non-drive side is shorter than the 110 to give a narrower q-factor but the drive side is the same so they both give the same chainline. |
Thanks for the info guys; I will take the 113mm back and try a 110mm or 107mm. I just went with the smallest recommended one, but I should have read Sheldon's crank page first as he confirms that a 107mm BB may work with some road bikes.
http://www.sheldonbrown.com/bbsize.html#sugino
Originally Posted by joejack951
(Post 9068174)
The arrow in your picture is not pointing at a stop on the BB. Square taper BB's don't utilize a stop for the crankset. The spindle is designed so that the crank stops sliding down the spindle prior to contacting anything. Your crank will fit just fine on a 107mm BB. The only limiting factor with BB width is frame/chainring clearance and it sounds like you have plenty of room there.
Originally Posted by Al Criner
(Post 9069505)
I have a Sugino XD2 crankset on an old road bike with 126mm spacing. I forced in a 130mm wheel and have a 110mm bb in there - chain line is great. The 113mm bb works for a mountain bike or something but 110 or 107 is probably going to be better on a road bike.
Also, I think the Shimano 107 bb is asymetrical - the non-drive side is shorter than the 110 to give a narrower q-factor but the drive side is the same so they both give the same chainline. |
1 Attachment(s)
In case anybody finds this thread in a search...
The shimano UN53/54 107mm and 110mm do indeed have the same length drive side. I ended up using a 107mm with the older touring frame, this resulted in a chainline of about 46mm (1mm off the standard road triple 45mm). As you can see from the picture it is pretty much as far inboard as it will go. |
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