QuestionI purchased the Definity Dakota P265 70 R17 for my 2003 Dodge Ram 2500 diesel at Pep Boys recommendation. 2 tires have completely de-laminated causing major body damage to my truck. I was told by another tire shop that these tires weren't even rated for my truck! Can you give me some info on this to take to Pep Boys?
Thank you,
Dave
AnswerDave,
To start off with, here is what I normally say about the vehicle tire placard:
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On every vehicle sold in the US - and I understand this is a worldwide practice as well - there is a sticker – commonly called the tire placard - that lists the original tire size and the proper pressure for that size. The placard is usually located on a doorpost or in the glove box – but sometimes it is located in the trunk or on the fuel filler door.
Personally, I like a car that handles crisply. So I use 3 to 5 psi above the placard pressure. I also get better fuel economy, better wet traction, better snow traction, better tire durability, better tire wear, but I do have a degradation in ride harshness (but I am willing to put up with it.)
BTW, it doesn't matter who makes the tire or what pressure is listed on the tire's sidewall, if the tire size is the same as the placard, then the pressure listed on placard is also appropriate.
One word of caution: Some trucks use tires with the letters "LT" in front of the tire size - and some trucks use tires with the letter "P" in front of the tire size - and some trucks use tires with the letter "C" after the tire size. You should not use "P"'s in place of "LT"'s and vice versa.
For this situation, you should be sure the pressure on the sidewall equals or exceeds that pressure on the placard. If you do this the issue about the letter "C" in the sidewall will take care of itself (which is not true with "LT"'s vs "P"'s.)
If you are using a tire size that is different than what is listed on the placard, then the pressure has to be recalculated. The calculation is not difficult, but it requires tire load tables which are not allowed to be published in the Internet because of copyright laws. However, I have a copy and would be glad to do the calculation, but the starting point is the vehicle placard: Tire size and inflation pressure. I will also need to know the new tire size.
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In your case, it is obvious that Pep Boys used "P" type tires in place of "LT" type tires - and that is what the second tire shop was referring to. So show pep Boys the vehicle tire placard, and then refer them to the above statement.
One little quirk that I am sure they didn't know about - since they did what they did - is that P metric tire have to be derated 10% if used on a pickup truck. making the P metric tire of the same dimensions carry less load than an "LT".
