QuestionIn a 11/18/2009 response to an AllExperts.com question entitled "Tire Inflation on BFG's" you stated the following:
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Let's do the math first.
According to Tire Guides, a 2002 Land Rover Discovery Series II came with 2 different tire sizes, and one of them was 255/65R16 105H inflated to 28 psi front / 46 psi rear. ... That means the load carrying capacity of the tires is: 825 kg (1819#) front / 1030 kg (2271#) rear.
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It does look like you did the math, but can you share what those formulas/calculations were that you used to get the load carrying capacity of the stock tires at the vehicle prescribed tire placard pressure? I would like to apply them to other situations. Also, how did you calculate the pressure needed in the new/different tire sizes using this data?
THANK YOU!
AnswerTony,
The load calculation is pretty complex. In order to make it simple, the tire standardizing organizations publish tables that have the values in them.
Unfortunately, those tables are covered by copyright laws and are not allowed to be published. They publish them in books that are pretty pricy. (It is, after all, that organization's only source of revenue.)
The good news is that you can find portions of the tables on the internet - especially through tire manufacturer's web sites.
Oh, and a caution: There's a reason why tire manufacturers refer to the vehicle tire placard for inflation pressure. It's because there needs to be a certain amount of unused load carrying capacity - good engineering practice. The vehicle manufacturer will have a handle on how much load transfer takes place in its vehicle and adjusted the inflation pressure accordingly. The tables only provide minimums without any consideration of the dynamics of the vehicle.
Personally, I would be very careful using the load tables - especially if a vehicle manufacturer has already provided an inflation pressure specification.
