There are two key factors to keep in mind when dealing with TPMS systems. This results in light truck vehicle manufacturers selecting proportionately larger P-metric sized tires for their vehicles to help offset the forces and loads resulting from a light truck’s higher center of gravity and increased possibility of being occasionally “overloaded.” P-metric load ranges and maximum load pressures are Light Load (35 psi), Standard Load (35 psi) and Extra Load (41 psi). However, if the same P-metric tires are used on light trucks, their carrying capacity is reduced to 91% of the load indicated on the tire’s sidewall. P-metric tires used on passenger cars are rated to carry 100% of the load indicated on the tire’s sidewall (or listed for the tire in industry load/inflation charts). This is why the tires you’ve installed have a load range of E, but a max load pressure of just 65 psi. You’ve unfortunately discovered a loophole in these ratings, as industry standards specify that selected light truck (LT) tires be designed with reduced maximum load pressures.
The maximum pressure for load range B is 35 psi, for C it’s 50 psi, for D it’s 65 psi, for E it’s 80 psi and for F it’s 95 psi. Light truck tires are rated in load ranges from B to F. Higher load ranges are used to identify tires that have a stronger internal construction, and therefore can hold more air pressure and carry more weight.Įach load range has an assigned air pres- sure identified in pounds per square inch (psi) at which the tire’s maximum load is rated. Additionally, load ranges are used to separate tires that share the same physical size but differ in strength due to their internal construction. Since a tire’s load-carrying capacity is related to its size and how much inflation pressure is actually used, maximum loads are rated with the tire inflated to an industry-assigned inflation pressure. A tire’s maximum load is the most weight the tire is designed to carry. Let’s consider tire load ratings for a moment. But what will happen if one of them fails catastrophically and it’s later determined that your shop had changed the value? Who’s going to be on the hook and held liable for the damage then? So while it may be possible to reduce the placard value, the question is, should you really do that? You may believe the tires you’ve in- stalled will handle the truck’s GVW at the new, reduced pressure. Downgrading the placard value to the lower psi requirement of a lower- load-rated tire would not be recommended, for what should be obvious reasons. In most cases, a placard value would be increased when a tire with a higher load range is installed. Selecting a new pressure effectively reprograms the PCM, giving it a new range of acceptable pressures, above which the TPMS warning light will not be triggered. The tool accesses the vehicle’s PCM, which then presents you with the available tire pressure choices for the vehicle. You are correct the tire pressure placard value is adjustable on some vehicles, provided you have a TPMS tool that will allow you to access this feature. Are we going to have to replace the tires with others that have a higher pressure rating, to satisfy the TPMS? The new tires will easily carry the GVW of the truck. Is the vehicle’s recommended tire pressure value (shown on the tire placard) adjustable? I’ve heard that it is on some trucks, but I can’t find a way to do it on this truck. The maximum pressure rating of the new tires is 65 psi. We installed tires that were the same size and load rating, and now the TPMS light is staying on.
The customer asked us to replace the load range E (10-ply) tires that were on the vehicle. We have a 20 with the 6.4L Hemi engine in the shop.
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