Good Day Sirs.

Have a 1990 F150 Longbed truck. Just use to haul trash or make trips to Home Depot, go camping...etc... Needs new tires. Found some cheap 215/75/15's..... My mindset has always been trucks have to have 235's.... I'm thinking the 215's would be fine.

Can anyone back me up on that?

 

They're a little shorter. Biggest thing is weight rating. They're not rated for max gawr of the rear axle. Load index of 100. It probably will be fine unless you're running heavy, which is easy to do. How cheap are they? 215's are cheap to begin with.

 

For this statement alone, I would go no less that a P235/75R15 XL.

A LT rated tire would be best.
Pretty nasty things can happen when you overload a tire and the failure does not always happen when they are loaded up, but the invisible damage does. The tire casing will start to deteriorate from the inside out.

 

I was 16, put a new set of LT tires on my truck. Not 5k miles later had a screw in the sidewall. Trying to save money, tire shop sold me a used P-rated version of the tire. Within 10k miles, it blew out at 70mph with essentially zero warning, on the front axle, driver side. 5 people in the truck. I went from the right to left lane faster than I thought possible, but was able to maintain control, and thankfully no one was in the left lane when it happened. No more used tires for me unless the truck won't go on a highway.

 

I've had excellent experiences with treadwrite recaps and remolds. Put almost 90k on the first set and I've got close to 35k on this set and still have probably a 1/3 of the life left. (Havent rotated and balanced as religiously as the last set).
for 31s and larger the prices cant be beat. But for 235s Wally worlds Goodyear Wrangler is about the best price you'll find for that size

 

Recently I have been looking at tires as well. I found passenger tires with hire load ratings than LT tires.

https://www.ntb.com/sku/sku1410158/optimo-h724
https://www.ntb.com/sku/sku5580051/open-country-atii

What am I missing?

 

It won't let me look at the links because there is no store near me, but I am assuming they are XL tires.

XL have a high weight rating, but also may have more sidewall flex. LT tires are more rigid.

 

P-rated tires get their load rating and that's it. LT tires are rated, then get derated by 10% to account for the fact truck owners overload their trucks regularly.

For the linked 235/75R15 tires, take that 2205 lbs, subtract 10% (220.5 lbs), and get 1984.5 lbs of the LT tire.

The XL construction of that P-rated tire is what makes it capable of withstanding the higher pressure, and therefore load. Both would be OK for a half ton, but I would pick the LT for durability.

Taking the above into consideration, the 215/75R15 tires discussed above with the load index of 100 (1764 lbs) should be derated by 10% for truck use, down to 1588 lbs. Makes the rear axle rated for all of 3175 lbs, instead of the factory rating of 3777 lbs. This pretty much cuts safe payload in half.

So, all of this to say it is not recommended for your intended use.

I attached the Toyo Tire application PDF. Its full of good load index tables and other useful tire information.

 

I have always thought that the 235 75 15 was too small for an F150, even though it was a factory size. Our old Ranger and our Moutaineers have that size and it is a good fit or them. Having said that 215 75 15 are going to be tiny on an F150. I would just get the 235s for your purposes and your speedometer won't read wrong either.

 

 

Thank you for the good information. Interesting what an XL load rating actually means. So, if I don't plan to carry loads a passenger tire would be fine otherwise a LT tire would be the better choice? Does that work as a rule of thumb?

 

As it was explained to me, "XL" is sort of between load range B and load range C.

 

What I find interesting is the correlation between load rating and tire pressure. From what I understand a passenger XL tire needs at least 41 psi where as LT tires use lower psi (please correct me if I am wrong). So the load rating of a XL tire is somewhat misleading because most people use the psi range off the door sticker. In my case it is 35 psi. Occasionally I will tow or carry loads and I am sure I will forget to increase the tire pressure. So if I get an LT tire I should be fine. I understand that an LT tire is more expensive but if you compare the $200 more for the set to a potential hospital visit the $200 are nothing.

 

This is a pretty decent chart that shows load carrying capacity per load range, load index and PSI.

https://static1.1.sqspcdn.com/static...+inflation.pdf

 

Thank you!!!