Luc_D

Hello there,

I have a bewildering issue that I cannot solve.

I've installed a sugino impel crankset, the 94/58 bcd version.

According to my research, this crank should give a 47.5 mm chainline (measured at the middle ring, 52.5 mm external) with a 110 mm JIS spindle on a 68 mm shell.

Now, I have installed them on a 103 mm JIS bottom bracket to use it a compact double.

Imagine my surprise after measuring the (external) chainline at 58mm!!!!!!

How is that even possible?!

I've measured multiple times using a caliper I know being accurate, and I've tried to install a double derailleur: the cranks are waaaaaay off.

Any help is very much appreciated.

PS, I am 100% sure the bottom bracket is a 103 mm tange JIS

Thanks!

79pmooney

You've got me stumped. (I am guessing you have done the obvious, taken the cranks off and measured the length. Yes, you know but still .... (Or leave the cranks on, remove the bolts, measure down inside and use a little math.))

58 mm at the outer ring would be 53 at the middle ring or 55.5 midway (the "chainline" for doubles. 53 - 47.5 = 5.5. 5.5 + 103 = 108.5 This isn't 108 or 110 by any chance? Or: I don't know the Tange BBs but they may be asymmetric like the older Suginos, extending out further on the drive side. Do your cranks sit equal distances from the chainstays? (Or insides of the cranks to the BB shell.) Old Sugino BB'd cranks sat a lot closer on the non-drive-side. 5.5 mm asymmetry would put your crank where you see it.

Ben

Luc_D

Thanks Ben.

​​​​​​The bottom bracket is a sealed Tange, and it is symmetric. Cranks arms are not equally close to chainstays, but they sit equally close to the bottom bracket
I have a sugino messenger crankset installed, and the chainline is 43.5 mm as specced (with a 103mm spindle)

Even if it was a 110 mm, the middle ring should be a 47.5 or a 50; now it sits at 53 mm...
​​​​​​​

wesmamyke

My go to solution on the cheap is a 73mm BB. It will install too far in, but you can add spacers back to get it into a usable range. Sometimes requires messing with different non-drive side cups if you don't want it sticking out.

Luc_D

The 73 mm bottom bracket is not a viable solution unfortunately...

I will double check the spindle length and check how the two different crankset sit in the taper after torquing.

What a headache!