BB spindle length question

[Forrest]

If I want to put an RBW Silver double crank (42/28) on a Rambouillet (with an Ultegra front derailer), do I need a 110 spindle bottom bracket? Thanks.

[Bill Lindsay]

I would expect a 107 would be the best choice.  I'm pretty sure I had a 107 on both of my recently parted out Silver-cranked bikes.  My Atlantis had a 38/24, and my wife's Yves Gomez had a triple.  

I just built up a Quickbeam with a 38/35 on the big and middle ring positions and I'm running a 103mm BB.  

[George Schick]

Agree with Bill.  I took a look at my Ram with a two-chainring crank and that's what it has.  But attached is a chart that you might find handy in making the decision.

George

[John Hawrylak]

I agree with Bill & George.  The chart George provided, shows a 107 gives the same front chain line and C/S clearances as a 110 since the JR dimension is the same for the 107 and the 110.   The 107 gives a 3mm lower Q.    I believe George's chart is for IRD BBs.

John Hawrylak

Woodstown NJ

[lconley]

Unfortunately, the arithmetic does not always add up. 

22.5 + 20.5 + 68 = 111, not 110. This means that the Q is 4mm less with the 107, not 3; this makes sense as the JL difference (22.5 - 18.4) is also 4mm.

Laing

[David Person]

FWIW, when the BB on my Hillborne needed replacement, I swapped out the Tange 107mm BB with a Shimano UN300 107mm BB and the inner chainring made contact with the chainstay.  I though, no problem, I'll install a 110mm.  However, the additional 3mm spindle length was all on the non-drive side.  I had to go with a 113mm.  Something to be aware of.  I had assumed that when going to a longer spindle, the extra length would be added to each end of the spindle equally.

BB-UN300 
 
68x113
 
Spindle Length
114mm
Body Width
62.9mm
Drive Side Taper Length
19.7mm
Left side Taper Length
31.4mm
 
 
  
68x110 
 
Spindle Length
111.5mm
Body Width
63.0mm
Drive Side Taper Length
17.1mm
Left side Taper Length
31.4mm
  
  
 
68x107 
 
Spindle Length
108.1mm
Body Width
63.0mm
Drive Side Taper Length
17.1mm
Left side Taper Length
28.0mm

[George Schick]

David - yeah, that's why I attached that chart.  For some reason the 107 and 110 have the same chain line (CL), but the 110 has a bit longer non-drive side length (JL).  Not sure what the application would be for the difference between those two.  The chain line (CL) doesn't jump another 3-4mm or so until the 113.  As a buddy of mine used to always say years ago, "why's it have to be so complicated?"  Beats me.  I happen to be in the possession of a discontinued Park CLG-2  chain line gauge and whenever I have to change BB's I attach one end of that to the middle cog (or either side of middle for even numbered cassettes or freewheel clusters), see where the middle of the seat tube (as measured with a caliper) divided by half, plus the distance to where the midst of a two chainrings or middle of a three chainring crank would be and order accordingly.

[Wesley]

You can adjust the alignment of your bottom bracket by using spacers on the drive side: https://www.universalcycles.com/search.php?q=bottom+bracket+spacer