Hi, everyone. I've got a 2004 F150 SuperCrew with Pacer Gellyn 22 x 9.5 wheels. Currently running Nitto NT420S 285/45 x 22 tires. They're at 30,000 + miles and considering some new rubber. I've been quite satisfied with the Nittos.

Nitto now offers some 285/40 x 22 tires in the same model. The lower profile would give me a slight increase in rear gear ratio, but would also come with a slightly lower load rating. My truck weighs ~5200 lbs empty, and I don't do any serious hauling or any trailer pulling. Are there any realistic concerns involved in going to the lower profile tire?

Thanks,

Lee

 

I assume the tire you are talking about, is a P series tire, not an LT tire. If so, subtract 10% from the load on the tire wall. I would NOT get anything that has a load rating less than 2200lbs on the sidewall. It will have too much stress on the tire if lower than that.

Just checked the Nitto site, per their table that tire handles 2337 at 50 psi. That should handle it okay, but you will have to run at or very near max pressure.

 

Thanks for the reply. I'll be looking at the math as I evaluate the options.

Lee

 

As a followup, is there some "standard" for the percentage of load vs. load rating on our trucks? The above example produced a safety margin of ~50% per tire more rating than load. Is there any reference for this amount, or was this just a ballpark figure?

Thanks,

Lee

 

The 10% is not a ballpark figure. If you look at just about any tire site they will state that a P series tire used on a light truck has a reduced load rating than what is on the tire. The 10% came from sites like Tirerack, Discount Tire, etc. Tirerack uses 9%. I rounded up fore the ease of calculation and a safety factor. I believe other sites use that 10% number.
As an example, most of the current F150s without the higher GVWR, (normal is around 7200lbs) have a rear GAWR (axle rating of around 4000 lbs. That means that each tire must handle at least 2000lbs. More is better. I would never select a P series tire that handles less than 2200lbs. Again more is better. Also, I do not like P series tires as they have sidewalls that are to me far to soft, allowing for too much lean in turns, a lot of flexing with loads, etc. P serioes will get slightly better mpg, but for me safety and handling is far more important. Also with it's weaker construction, if a tire losses some pressure, it will fail far quicker than a LT tire. Also far more likely to have flats with road debris.

That being said, you are unlikely to find an LT tire in a low profile size, at least not that I have found. Just make sure you get a P series with the highest load rating you can find. And nothing under 2200lbs.

 

Thanks for the followup on the reduced load rating for "P" tires on light trucks.

However, I was asking about the difference between the load rating of the tire and 1/4 of the GVWR + passengers/cargo. My quick math showed a 50% extra capacity over the actual load weight.

Lee

 

Can't go by GVWR, best to go by GAWR, as that will have a higher value than 1/4 of GVWR. As I mentioned, my truck has a GVWR of 7200lbs, but a GAWR in the rear of 4000lbs, well more than half the GVWR. As far as the front, on a day to day basis, that has more weight on it than the rear, so those tires get a heavier workout, except when loaded or towing.
The tires you mentioned have a load rating of 2337lbs, minus 10, gets you down to about 2100lbs per tire, which should be fine for your truck, but will need to be run near max pressure to handle it. This assumes your truck is not an 8200lb GVWR vehicle, in which case those tires are not adequate.

 

Thanks. I've certainly had zero problems with my current tires (rating ~2600+ lbs), so I had a hard time believing that a reduction of just over 10% would produce failure. I understand that there's no guarantees.

My truck GAWR:

Front: 3450
Rear: 3850

So, using the 2100# figure (2337- 10%), that would give a 125# "clearance" on each tire of the rear axle when loaded to recommended maximum. Since I never load the truck that heavy, it seems that you're comments are spot on!

Lee