Tires: tire, tire placard, bf goodrich

Question
QUESTION: is a load range c tire safe on my 2003 dodge ram3500. it is a bf goodrich m/t. the weight rating is 2400 at 50 psi. it was a mix up they should have been range d

ANSWER: Kyle,

On every vehicle sold in the US, 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.

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.

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.

So what does your vehicle's tire placard say for size and pressure.  I tried to look up your vehicle, but there are so many different configurations - and different tire size, that I can't tell what your placard may say.

So post a followup with that info - plus what the new tire size is.

(I'm expecting, that even if the new tire size is HUGE, a Load Range C would have much less load carrying capacity than the original tire at the placard pressure - and that is just plain dangerous.)

---------- FOLLOW-UP ----------

QUESTION: the placard says a 235/80/17 E at 2359 lbs at 65 psi. i went to a 255/75/17 C rated at 2400 lbs at 50 psi. i was also wandering can i put more than 50 psi in tire

Answer
Kyle,

Well, there are a couple of problems.  At 65 psi an LT235/80R17 has the load carrying capacity of 2680# - and your LT255/75R17 only carry 2400#!  You've lost a considerable amount of load carrying capacity - and that's not good from a safety point of view.

Also, LT255/70R17's have a minimum rim width requirement of 6 1/2", and according to Tire Guides, if you truck came with LT235/80r17's, the rims are 6".

So you have a couple of things to fix.