Changing From a Triple to Double Crank - Spindle/Chainline??
 

My Salsa Casseroll has a triple crankset on the bike. I am upgrading it to 10 speed. If I replace the triple with a "adventure" double, like the Velo Orange 46/30 crankset with a stated chainline of 43.5mm and a 144mm Q Factor. Will i need to shim the 46/30 crank to get a good chainline or is 43.5mm good to go? (FYI: I am changing everything to 10sp - f/r derailleurs, chain, crank, shifters).

Also, the VO website recommends a 118mm Spindle length BB for the 46/30 crankset (JIS square taper). Is that going to work correctly on my Casseroll?

get the crankset and the BB specified for it, and you should be good.

Chain line center was the middle chainring, on a triple, now the spider between the 2 of them is the chain line center Measure the difference ..


IDK, do it and report back ..

After you calculate your theoretical ideal chainline, what are you going to do about it?

Chainline
 

Gotta agree. As long as the two chainrings aren't out of alignment with the inner and outer of the original triple you should be better than fine.

The Casseroll appears to be a normal road bike, so 118 mm should be good if VO have done their homework. Check your rear dropout spacing. If 130 mm, go with a 118 mm BB. If 135 mm, 122 mm would be correct.

In practice, there is wiggle room and ability to fudge chainline, With a compact double, you will almost live on the big ring and only use the small ring on climbs. Given that, you may want to centre the big ring on the cassette and let the small ring fall inboard of nominal, using a BB a few mm shorter than calculated. This way the lowest gears will be smooth, but the small/small cross-over gears may be rattly. The main thing is to make sure you keep a couple of mm clearance between the small ring and the chainstay, and also to make sure the small/small combination is not so crossed that the shift pins on the 46 will want to grab the chain as it comes off the bottom of the 30.

On of the several great things about square taper is the ease with which you can tune chainline.