Chain alignment is probably the most crucial operation you will have to perform with #25 chain, along with maintaining good chain tensioning. If the chain becomes slightly loose, and you take a side hit from another robot, it can walk the chain off the sprocket. Tensioners in the middle of a chain run can help substantially to minimize this potential. 17 inch wheel spacing is a dimension we have used with a single tensioner, and with good sprocket alignment, we have lost only one chain in 14 years of competition. That happened in the days BB (before bumpers), and the chain took a direct hit from another robot frame.
