Lowell reached over his head again and adjusted the trim control, a four-inch diameter wheel.

Smaller diameter wheels, all else being equal, have higher rolling resistance than larger wheels.

Smaller diameter wheels gave better traction, essential for a fast freight locomotive.

Minor evolutionary changes including new 18" diameter wheels and tires were introduced in the 1999 model.

It was also fitted with larger diameter wheels.

On most types of poor surfaces, large diameter wheels perform better than lower wider wheels.

The Victor had the engine further forward to increase interior room, the battery moved to the engine bay and smaller diameter wheels.

A 'plus zero' upgrade means changing to a wider tire size while using the same diameter wheel.

New, stiffer undercarriage struts were introduced, along with larger diameter wheels.

It had smaller diameter wheels (28") and a smaller truck frame.