Originally Posted by Dave Mayer

A spindle designed for a double will usually be shorter than one for a triple. The ideal outcome is where the chainrings lands (after tightening the crankarm bolts down hard) about 5mm from the right chainstay and the crankarm does about the same. A larger gap will result in a higher Q-factor for less pedaling efficiency, and a wide separation between the rings and the frame will lead to poor chainlines and front shifting.

Recommendation: seek out your local bike co-op and sift through their bin of old spindles. Find something that has the same specs as your old spindle, but a few mm shorter on the drive side.

Other recommendation: do not ride wheels with steel rims. At our local Co-op, we chop these up and recycle as soon as they land, as being a risk to life and limb.