The original 11.00X20 bias ply tires on split ring wheels were later changed fleet-wide to Michelin radials on bolt-together wheels in 2002 due to safety concerns. Tank truck The M49 fuel tanker and M50 water tanker variants were initially based on the M44 chassis. The M49C series, however, were vehicles converted from C series drop-side cargo variants. M49s have 1,200-gallon tanks. Early models had triple compartments (200g front, 400g mid, baffled 600g rear), but most models have two 600-gallon baffled tanks. The M50 had a water tank, of which later variants had internal baffles to combat weight transfer during motion. In some areas the M35 is still used today as a wildland firefighting truck with a portable water supply and fully operational pump. Van A number of variants with van bodies, primarily for use as maintenance shop vans, were also created. The basic model was the M109, with a variant that could mount the PTO winch was designated M185. The M185 was a machine shop version of the M109 that carried a light duty crane, tools, other items. It often towed a M105 trailer. An expandable van variant with hydraulic lift gate was designated M292. Two variants of the M109 were specifically developed as service vehicles for the MGM-18 Lacrosse missile system, the XM411 for the Ground Guidance Electronic Equipment, and the XM412 with special tools and test equipment for the electronic guidance and control system. A medical van variant was designated M132. Wrecker and tractor A wrecker based on the M45 chassis was designated as the M60, while the similar M108 crane truck was used for many tasks, but primarily to handle guided missiles such as the Lacrosse. Two tractor variants for towing semi-trailers were developed, the M48 and M275. The M48 featured a full-length M45 chassis (178 inch wheelbase, identical to the M35 cargo), while the M275 featured a shortened M45 chassis (166 in wheelbase) for reduced weight and greater maneuverability. However, due to the smaller size and lower power of the -ton trucks, most heavier loads were handled by their respective 5-ton counterparts. As a result, few were produced. Construction A number of specialized construction variants were developed. The M47 and M59 dump trucks were developed, based on a shortened 166 inch wheelbase M44 and M45 chassis respectively. An improved dump truck based on the full length 178 inch wheelbase M45 chassis, designated the M342, was designed