markboris
Well-Known Member
- First Name
- Mark
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Brian, do you have or know of a chart that has higher load ratings than 108?That's not compliantly accurate.
The way it works is tires have a load range the ones that fit the MME are:
225/60/18 104H XL
225/55/19 103H XL
245/45/20 103V XL
The load range is set by the Rubber Manufacturers Association and tires are made to fit the standard. For example, 225/55/19 99 is a standard load and 225/55/19 103 is an extra load. All MMEs use an XL or extra load tire.
The 104 or 103 is the load range and that tells the automobile manufacturer how much load the tire will support. Then they look at the load tables and adjust the pressure to maximize the contact patch. There are some other factors the automobile manufacturers look at like temperature range, passengers, cargo, towing ECT
An example of this in action is if you went from a 225/55/19 103H XL to a 245/50/19 105H XL you should technically lower the pressure from 39psi to 36psi.
How to use the chart, and how a car manufacturer sets the pressure
103 load index @ 39psi supports 1819lbs per tire
105 load index @ 36psi supports 1808lbs per tire
This is why it's either important to stick with the same as factory size so you keep the same load index or know what you're doing if your gonna make changes.