Tag on truck indicates 30 psi front 35 psi rear. Just put Load E tires on that max load is at 80. So pretty sizable differences, I want tires to last but don't want rock hard ride either, so wondering what folks suggest ?

 

This is for the 2001 Quad Cap f150 not the truck shown in my profile ....

 

Put 50 psi in and drive it a few days and see what you think... 80 psi is for MAX LOAD .... if your driving empty or average load, somewhere around 50 psi should be fine.

 

The MAX PRESSURE number is the inflation safety limit for the tires, it is not a recommendation of inflation pressure. It has nothing to do with the RECOMMENDED tire pressure which would have been selected as the best compromise of fuel economy, handling, and comfort for the originally specified tires.

 

Ok thanks guys ....

 

Google 'tire chalk test'.

 

I ran 45psi in my max 80psi tires on my F-150. I found the factory recommendation was a little soft, plus I prefer better mileage.

 

Read this from the tire people about tires and all that:
They did not get into the speed markings on a tire (these are the ones if you go over that can cause a blowout running just 5 minutes over top speed as the tires will start coming undone) which is different from tire type, etc.

On the chalk test, it is up to the size of the tire and tire type if you are going to get the layout of the tire. Now say you hook a trailer up you just changed that layout and load-carrying weight with the chalk test.

Now from the so-called experts:

Listed inside the driver's side doorjamb of your vehicle there will be the originally installed tire size, load rating, and tire pressure for the front and rear tires. The size and pressure have been engineered specifically by the manufacturer for correct load capacity and will typically render the best results for tire wear and ride quality. Tire load capacity is directly related to air pressure in the tires. As tire pressure goes up or down, so does the load capacity of the tire. Too much air can wear the tires unevenly in the center and can create a wondering effect on the vehicle's handling. Too little air can wear the tires unevenly on the outer edges and will reduce the tires' load capacity below the engineered level.

Each tire is rated with a load range, load index number, and max pressure rating. Passenger tires will be rated Light Load (LL), Standard Load (SL), or Extra Load (XL). Extra Load tires of the same size will typically have the same load capacity at the same pressure as the Standard Load tire. However, they have added load capacity above certain pressures. Light and Standard Load tires have a maximum capacity pressure rating of 35-36 psi and Extra load tires have a maximum capacity pressure rating of 41-42 psi. The maximum allowed pressure listed on a tire's sidewall can be higher, however. Some tires list 44 psi and much higher speed tires will list 50-51 psi. This added pressure does nothing for load capacity. Pressures above 35-36 psi for SL tires and 41-42 psi for XL tires will not increase the load capacity of the tire. Even if you put 50 psi in an SL tire the load capacity will remain what it is at 36 psi for the higher pressure levels. Adding tire pressure above maximum load capacity is used mostly for high-speed situations. A tire's air pressure is increased to reduce tire deflection for the increase in rotations per second compared to typically city/highway use.

Light Truck (LT) tires are rated using a tread ply system. (B) 4-ply, (C) 6-ply, (D) 8-ply, (E) 10-ply, (F) 10-ply, and so on. An LT tire size can have multiple Load Rating variants. Similar to Passenger load ratings, multiple Load Ratings will carry the same weight at the same pressure up to the lower rating max pressure. The higher-rated tire will then have added load capacity up to its maximum pressure rating.

When calculating a new tire's pressure to match an OEM tire's load capacity it's important to be very accurate. With metric passenger tires, there are actually two types, Metric and P-Metric. You've probably seen a 'P' in front of some of the tire sizes you've looked at. This actually designates a different size than the same tire size without the 'P' designation. They are very similar and typically interchangeable. However, they do have different load rating charts and should be assessed as different tires when calculating a new tire pressure. LT tires also come in two types, LT-Metric and LT High Flotation. Metric LT tires will look like metric sizes but will have an LT in the front of the size (LT285/70R17). High Flotation LT tires are your standard 'American' light truck tire sizes with inch measurements and the 'LT' usually at the end (35X12.50R20LT). When calculating, you should be looking at your vehicle's placard in the door and finding the exact size. If it's metric, does it have a 'P'? Does it have an 'LT'?

In the case of Light Trucks, there are most commonly 1/2, 3/4, and 1-ton variations. Most 1/2 ton trucks such as Ford F150, Chevy/GMC 1500, Ram 1500, Toyota Tundra, etc. actually come equipped with Passenger rated tires on them. As opposed to an LT265/70R17, it will usually be either a P265/70R17 or just 265/70R16. This is because not only are they lighter weight and provide a softer ride, but their load carrying and towing limiters such as suspension ability, don't exceed the capability of the comparable Passenger rated tire. Also despite what many might think, Passenger rated tires can actually have higher load carrying capacities at the same pressure as the LT version in the same tire size. The LT tire will generally have a higher maximum load capacity, but it takes a higher pressure to achieve the same load capacity.

 

Obviously, the chalk test will give you the results for the load at the time of the test only.

What's not so obvious is that if the tire is too wide for the wheel or has a very rounded tread you won't achieve full contact until the pressure is way too low for good handling. I find chalking to usually give a very good pressure, but sometimes you'll have to tweak up or down to achieve the ride or handling characteristics you desire. E rated tires on an F-150 is going to create a challenge in trying to get a good ride, it's just a bad mix. Not just because of the stiffness of the tire, but it's also a heavier tire which adds to the problem. I know a few people who've put E tires on light duty vehicles and regretted it.

 

oops, duplicate

 

Ok, thanks guys for the thoughts, discussion. I am starting with 50 and will go from there ...

 

Way overkill, but over is usually safer than under.

 

I have dropped recently to 40 psi and it definitely is less harsh on regular road bumps ...