Alright, sounds like a dumb question but what is the difference between the "p" designation and the "lt" desigantion. Looking to upgrade my weak stock Goodyear RTS to BF's AT/KO's. I have the P265/70R/17. BF's have the LT 265/70/17. Thanks.

 

"P" is for passenger, LT is for Light truck. The LT's are designed for towing and hauling, the P's are not. The standard load rating on a P tire has to be reduced by 10% for truck use whereas an LT can be run at its rated load.

The biggest difference is in the sidewall construction - LT's have more plies (generally) and can withstand higer pressure.

On the flipside P's offer better ride than LT's, so they are best for soccer moms.

Ian

 

I don't know about the load being reduced by 10% of it rating for P-rated tires, but generally the load rating is less on a P-rated vs. LT. The max load capacity for LT tires is had at a higher air pressure, like 50psi vs. about 35psi for P-rated tires. As mentioned, the sidewalls have more plys which means stiffer.

For an LT tire, the BFG AT KO is rather soft riding. Credit the tread, not the sidewall.

 

...and Raoul.

I've had my truck long enough now to know it has all the towing/hauling capabilities I need and it came with the 'P' tires. When it comes time to replace, I'll get the 'P' tires again because I want to maintain the current ride rather than increasing my macho image with the teeth rattling 'LTs' and an empty bed.

 

The P tires would have a max PSI cold of 35psi. The LT tires in that size would have a Load C rating and 50 PSI max cold. With the amount of sidewall on that tire, you may only gain a couple hundred pounds of extra load range per tire. The real gains would be in improved handling under load from a stiffer sidewall.

Switching to a LT tire would give you the flexability of a greater range of tire pressure, and load handling adjustment. You could reduce tire pressure to 35psi for a good ride empty, or raise it up to 50psi for much better handling while hauling and under load. I'm very glad I switched.

 

How does the 'P' tire know whether it is riding under a truck, an SUV or a car? Does the 10% reduction apply to truck based SUV's like the Expedition? Where did you get this info?

FWIW, Ford put P tires on my 2wd truck and wanted me to inflate them to some low amount like 28 psi. Presumably, the truck can carry its GCVR as delivered.

IMO, better quality, higher load rated P tires with proper inflation (32-35 psi) can only be an improvement over the rim protectors Ford put on at the factory.

 

I tow a #5500 fith wheel. When I went to LT's I noticed much better handling when towing. The wimpy factory P rated squished down pretty bad at axle weight of #3200. I only run 50psi but mine are rated to 80psi. I believe it rides better with a couple of hundred pounds in the bed rather than empty.

I have heard to derate P rated tires when used in a towing applications.

 

I did a little search, and the Bridgestone page suggest you should reduce the max load rating by 9% when using a P rated tires on a truck or SUV.

No explanation is given, though they do mention that trucks are more likely to be overloaded than passenger cars, which could damage the tires.

Essentially, the Bridgestone page says if you use your truck or SUV for hauling, you should use LT tires, even if the vehicle came with P tires.

Bridgestone claims the manufacturers use P tires on trucks to save money and reduce rolling resistance (increasing rated fuel economy).

 

I really hadn't considered my 'P' rated tires when contemplating why I get 18.5 mpg with my 5.4L.

 

I've been digging a little more. Another tire page suggests you only need to reduce the load carrying rating of the P tire by 9% if you are installing it on a vehicle that was originally equipped with LT tires.

The truck's door sticker will give the gross axle weight rating and with what tires. If the door sticker says LT, then reduce a P rated tire's max weight rating by 9% for use on that truck. If the door sticker is for a P rated tire, the weight rating is already reduced.

I checked my truck - it is rated at 3,100 pounds for the front axle and 3,200 for the rear, on P tires at 29/32 psi. Combined, both axles are not supposed to exceed 6,000 pounds per the manual.

My P rated Michelin tires are rated at 2,405 pounds each at 35 psi (what I use). This is 4,810 per axle, or more than 50% greater than the axle ratings on the door sticker. Clearly, quality P rated tires are not the limiting factor on my particular truck.

 

I was looking at some Michelin Pilot LTX's (185/60-18XL). On Tire Rack's web page they are rated for about 3000#, but on Michelin Canada's website the are rated for about 2800# (all numbers by memory). Looks like Michelin Canada already derates by 10%.

The Michelin site says "Tires derated by 9.1% for Light Truck/SUV application. This will differ from maximum load branded on the sidewall." Note that it doesn't say anything about whether LT's or P's were factory fitted. This is where I got the numbers. This often quoted on the RV boards as well.

I have also noticed that although I am under my axle rating when towing my trailer, the POS RT/S's really get chewed when towing.

Ian

 

I was happy to go to LT's for the added assurance they provide while towing. However, I never could figure out what the factory rims were rated to pressure and load. I don't know if it is possible but I don't want a rim to fly apart because of high pressure. I read somewhere here where a guy's rims like mine leaked from the factory.

Makes you wonder.

 

I too switched from P to LT rated tires. While I agree the P rated tires are "strong" enough to carry the rated load of the truck, I can say that with a load in the bed or towing, the LT tires do not flex as much when switching lanes or turning. The LT rated tires are also typically more resistant to road hazards.

 

LT tires typically have 1-2/32" deeper of tread than P tires. It aint much but the LT's should last a little longer.

 

My new Bridgestone Dueler A/T Revo's are "P" rating. They did not make a Revo in my size with an "LT" rating. 265/70R17