Hello all,

Please bear with me on this post. This morning I had a small problem on my fixed wheel bike which ended up in a bent chain ring. It was only a tempory job. It was one of those all in one RHS cranks and chainrings that I slapped on in theory for a days ride but has ended up on there for several months. Not to worry as I have a crank in my parts box but just need a bottom bracket. This is what I am here to ask you about. Now I need to achive a 50 mm chainline for my fixed wheel.
I have a pair of these cranks FC-3301

http://bike.shimano.com/catalog/cycl...=1152542816672

Which I do not know if they have Octalink ® V1 Spline or Octalink ® V2 Spline. Less important as the documentation tells me which bottom braket to use (but if anyone knows it would be nice to know). The documentation tells me to get a ES30 Bottom Bracket which comes in spindle length 113 118 121 mm. My bottom braket is standard euro 68 mm shell if that is important.

http://www.wiggle.co.uk/Default.aspx...ycle%20Touring

As stated above I need a 50 mm chainline. The documentation that comes with the crank states that a 113 mm bottom braket will give me a 43.5 mm chainline. Now my measuments put the distance betweeen the two chainrings as 7 mm peek to peek. I could not measure very accuratly though as I only have a metal rule and no calipers or vernier gauge. With this is mind this gives me a 47 mm chainline on the outer ring and 40 mm chain line on the inner ring. Correct?
The next length up spindle length on the bottom braket is 118 mm. So my question is whether this increase in length is symetric around the bottom braket or not? i.e will as increase of 5 mm bottom braket spindel length move my outer chain line to 49.5 mm (which should be good enough) and my inner cahin line to 42.5 or is extra length all on one side giving me an increase to 45 mm on the inner and 52 mm on the outer chainline. Or am I stuffed short of a hack with washers on the stack bolts?

Thank you in advance.