A Question on BB spindle width.

[winjohn]

I have an M Steel touring frame with a 68mm BB shell that I am intending to put a Sugino triple crank on. I had an Ultegra Hollowtech set up on it but decided to go back to a more period correct set up with a wider range. I had a look in my BB box and slotted in a 68x103 since it was the only suitable one I had. With this installed with the Sugino cranks the inner ring just contacts the chainstay. So clearly I need a longer spindle length but what length would be best?
My simple brain says that adding 10mm and installing a 113mm BB would give me 5mm clearance but then I am wondering if I should be considering Q factor and chainline too. But will I need to fit the BB first and tighten down the cranks before I can check that?
Any thoughts or suggestions would be welcome.

 

[SteelNipple]

Triples usually use spindles from 113mm up, but it's hard to say without seeing the setup or the crankset. I would use maybe a 118mm or 122mm just to be safe. Did you use symmetrical BB to check the clearance?

 

[winjohn]

Triples usually use spindles from 113mm up, but it's hard to say without seeing the setup or the crankset. I would use maybe a 118mm or 122mm just to be safe. Did you use symmetrical BB to check the clearance?

I didn't know that there were asymmetrical BBs. Every day is a school day around here.

 

[Guinessisgoodforyou]

Bring it over John I have 110, 113 and 118mm you can try.

 

[SteelNipple]

You can calculate chainline if you measure from inside of the right dropout to the middle of the cog set and minus that from the over locknut distance. So for example 130mm/2 - 21mm = 44mm. Then to work out the spindle lenght place the crank on a flat surface outside up and measure from the top of the spindle hole down to the surface, the measure from the surface to the center of the middle chainring and then subtract that from the first measurement and maybe subtract about 3mm (because when tightened the spindle stops a few mm's below the end of the square taper hole) then add that number to the rear chainline number and multiply by 2, example 25mm(top of the hole to surface) - 8mm(surface to middle ring center) = 17mm then 17mm - 3mm = 14mm add that to the 44mm so 44mm + 14mm = 58mm x 2 = 116mm (in the example Campagnolo NR crankset with 130mm o.l.d and shimano 7spd cassette to get 0mm chainline)