Singlespeed & Fixed Gear - Sugino RD2R final word

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dtour
07-14-09, 11:32 PM
OK, so I've been scouring the internet, a past time I'm sure everyone here is familiar with, and I can't come up with a definitive answer on this...

I have a pair of Sugino RD2R TL cranks (with the old crown logo, doesn't say Sugino anywhere), 46t chainring, rear formula ff hub and am in need of a new BB. I have seen people say the 103mm works because it gives a 42mm chainline, but I have also seen complaints about the RD2R having a 45mm chainline with the 103mm.

The Sugino website says: Chain Line Single: 45.0mm(CBB-103)
Harris via Sheldon Brown: 103mm gives a 42mm chainline

I've seen suggestions of getting a 107mm BB and running the chainring on the inside, but I've also seen complaints with this too.


Does anyone have any proven insight as to whether a 103mm BB will work or if I need to try the 107mm. I'm at a loss, please help.

erichsia
07-14-09, 11:45 PM
Nope. Use the 107mm bb if you want to put the chainring inside the spider. Otherwise, go 103, and don't worry about it. Plenty of people (including me) have no problems with 45mm chainline.
Andy_K
07-15-09, 11:06 AM
Does anyone have any proven insight as to whether a 103mm BB will work or if I need to try the 107mm. I'm at a loss, please help.

Since you have the cranks, this is easy.

1. Mount the crank on a bottom bracket of any known width.
2. Measure the chainline.
3. Subtract half the difference between the bottom bracket you used and the bottom bracket you are considering. That will be your (potential) new chainline.

For instance, if you mount the cranks on a 115mm bottom bracket and measure a chainline of 51mm, then the chainline with a 103mm bottom bracket would be (51 - ((115-103)/2)) = 45mm.

Given the disagreement between two normally reliable sources, I wonder if it has changed over time from older production years to the current. If so, measurement is your best bet. Or live with an imperfect chainline. :)

dtour
07-18-09, 03:34 PM
Just in case anyone is still reading this I ended up buying a shimano 68x107 bottom bracket and mounted the chainring on the inside of the sugino rd2r cranks and it works like a charm, finally