Tire inflation and rolling resistance

[brainpause]

On our 1500 Silverado, I have E range tires (max PSI 80), and C range trailer tires (max PSI 50) on the camper.

 

For the past 3-4 years, I have generally run 65 PSI on steer axle, 74 on drive axle, and 50 on trailer tires. I was planning on replacing the trailer tires next spring (their 5th birthday), but they were starting to separate in the tread. I replaced them before my infamous trip to Florida for the roof repair.

 

I have always known that my tires were nowhere near their capacities, even though I run them close to or at max pressures.

 

A couple of weeks ago, we camp at a campground it is about 100 miles away. I decided to do an experiment. I put 44 pounds of air in all 8 tires. I arrived at these pressures using each tires' manufacturer recommendations. I measured temperatures at stops and they were really no higher than usual.

 

However, it seemed like the truck had a harder time towing the trailer for this trip. It downshifted a lot, but I'm not sure if it was more than usual. I didn't measure mpg for this trip, which might be the best indicator.

 

So, here's my question: Do you really think the rolling resistance was increased enough to really make a difference? Remember, I have a half ton pickup (5.3L engine) with less than ideal 3.42 gears.

[jlr860]

Can you see the tires squatting down?

 

MPG probably is the most sensitive inication of how much harder it was.

[Zembonez]

I can't imagine driving around on E rated tires at 65-75 pounds. They must feel like they are carved out of rock.

 

BUT

 

Higher pressure should reduce rolling resistance to some degree. Not sure if it would be "felt" though.

[brainpause]

Can you see the tires squatting down?

 

MPG probably is the most sensitive inication of how much harder it was.

 

 

No, not really. Maybe just a little.

[brainpause]

I can't imagine driving around on E rated tires at 65-75 pounds. They must feel like they are carved out of rock.

 

BUT

 

Higher pressure should reduce rolling resistance to some degree. Not sure if it would be "felt" though.

 

 

You are right. Running around empty with high pressures feels like I'm riding in a Flintstone Bedrock car. However, I don't. I lower the pressures to around 50 when unladen. This is mainly a tow vehicle, though.

 

Not very scientific, but took another camping trip this past weekend, and I put 50 PSI all around in the tires. It seems like the truck work less, but again it was a different route. Maybe I can do a 50 mile route with various pressures just for test purposes all on the same day so that the weather pressures and temperatures would be similar. I live near a non busy interstate, and could easily fill up and take a trip several times and check gas mileage, while maintaining the same speed because traffic is relatively light. maybe I'll do that. It might be an interesting test.

[Wintersun]

I get the best results by using the manufacturer's recommended load range tires at the recommended tire pressure and by manfacturer I am referring to the makers of the vehicle and not the makers of the tires. With a 1/2 ton pickup D tires are all that are needed and MPG is as much a function of the tire design as it is the tire pressure. In order of declining MPG performance (and tread life) there are highway tires, all terrain tires, off-road tires, and mud tires. I get 25% more tread life and 10-15% better fuel economy with a highway tread over a AT one.

 

Running a 10-ply rated tire at 50 PSI is not going to result in a big improvement in ride quality as compared to running it at 80 PSI. Change the shocks or add more weight in the bed (as with a truck cap or a tool box) if you want a less harsh ride but a 1/2 ton already has a pretty cushy ride if you stick with D rated LT tires. You are certainly not going to save money by spending at least 50% more to run E rated tires on your truck.

[brainpause]

E-rated tires might be too much for a half ton truck, but it is the only thing that fixed my trailer away, aside from buying a $2000 pivot point projection hitch such as the 3P ProPride. And yes, I changed shocks, trailer weight distribution, weight distribution hitch adjustments, speed adjustments, the whole gamut.

 

And I must respectfully disagree when you say there isn't much difference between E tires at 50psi vs. 80psi. There is a huge difference.

[AzDragonLord]

With lesser rolling resistance, does that mean less friction? When there is less friction, doesn't that then mean poorer grip?