The length of the BB is dependent on the cranks: two different cranks can achieve the same chainline, with different length BB.
You need to break out the internet to find what size BB is recommended as OE.
You'll then want to bring the cranks in a little to sit the chain in the middle of the cassette (assuming you use the outer ring position).
Found it, 110mm recommended with double, so 107mm to bring the line in a bit?
Assuming your cranks are Shimano standard, then the chainline measured between the two rings is 43.5mm and 46mm for the outer ring.
So in an ideal world you'd want a 105mm BB, but 107mm is probably as close as you'll get and will certainly be an improvement.
@jontea started
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The length of the BB is dependent on the cranks: two different cranks can achieve the same chainline, with different length BB.
You need to break out the internet to find what size BB is recommended as OE.
You'll then want to bring the cranks in a little to sit the chain in the middle of the cassette (assuming you use the outer ring position).