Dual rear wheel? What size tire? For vans such as the Promaster and the Sprinter, the Euro metric C (commercial/cargo)
tires are required in some instances. The have much higher
weight ratings than comparable LT
tires, and not every tire company makes them and they are only available in a couple of the common van sizes.
Goodyear, Michelin, Nexten, Continental, and a few others make them.
The following is from Goodyear
What’s the Difference Between C-Type and LT
Tires?
Both C-Type tires and LT (Light Truck) tires are generally rated for a higher
weight capacity than standard passenger tires. However, they are meant for two different specific vehicle applications. LT tires have a load range rating typically of C, D, or E. Though some LT tires have a C in their description denoting load range C, this is not the same as a C-Type tire and cannot be used interchangeably.
Both of LT and C-Type tire types are reinforced to carry a heavier load than a typical passenger car tire. However, the C-Type tire is meant to handle a heavier load than an LT tire in equivalent size, though generally rated for a lower speed.
LT tires specify a letter code to denote the load carrying capacity of the tire based on load and inflation tables from one of the standards organizations (Tire & Rim Association, ETRTO, JATMA, etc). Common LT load ranges include C, D, and E – as the load range increases, the load rating increases commensurately.
The C-Type tire, on the other hand, is specifically meant as a commercial-rated tire, with a higher load rating for a given size than many LT tires. These C-Type tires will show the letter “C” immediately after the wheel diameter in the tire code. Example: 225/75R16C
Why is Using the Proper Tire Important?
The tire size and service description contain important information:
Light Truck Cargo Type Load Index Speed Rating
LT Tire
(Size: LT225/75R16 115R LT 115 R
C-Type Tire
(Size: 225/75R16C 121R) C 121 R
Standard Passenger Car Tire
(Size: 225.5R16 1047) 104 T
Note: This table shows only size characteristics that vary between these tires. Section Width (225), Aspect Ratio (75), Radial Construction (R), and Wheel Diameter (16) are all common across these 3 tires.
Technically, all of these tires might “fit” on the same vehicle. However, they are all designed for different loads. The 104T load index on the passenger car tire corresponds to 1984 pounds per tire load rating. The 121R load index on the C-Type tire? 3195 pounds. Over 1,000lbs per tire more load carrying capacity than the passenger tire, and 696 more per tire than the LT tire (2680 pounds).