I use nitrogen. The reason why makes no sense but it works for me. Every truck I've ever owned has had one tire that would not keep pressure. On my GMC it was the right rear, on my F250 it's the left front. Even after rotating the tires, that left front would lose 5-6 psi in two weeks. I can't explain it but that's what happened. Since using nitrogen, all four tire have stayed at the same psi for over 6 months.

I don't have to know why, I just know it's working for me.

CedricR.

 

I'm going to get my wife's Accord done too. She's a nurse and drives a lot. The tires on that car are always losing air on ALL FOUR wheels. We've had the stock tires, replaced them with Kumhos, another brand I can't remember and are currently running Uniroyals. We've replaced the valve stems with every tire change.

I hope nitrogen can give us more consistant tire pressures.

CedricR.

 

Here's a tip that is worth sharing here:
All too often I've seen tire busters slam tires on to dirty rims. All those little particles provide a place for air to seep out around the rim.
The tires that I never had to check were on my old 75 Chevy 2500. I took those rims and cleaned them with a wire brush and then applied a thin coating of NAPA Sil-glide Part # 765-1351 silicone grease to the rim area. Then had the tires mounted.
They would hold air to the pound for months.

 

An under inflated tire wears more and will cause more blowouts than a tire with its psi set at what the tire states on the sidewall

 

First part of what you say is true but it has been my experience that my tires wear more in the middle when inflated to sidewall pressure and running without a load. Its a different story if you are loaded.

 

Yopur post got me to thinking about my daughter's car. Her tire pressure flucuates wildly and I am always on her about it. Maybe the nitrogen would be the way to go for her too. She drives up and down the interstate to college and back every day and then to work and puts a lot of miles on her little car.

 

Are you claiming that you've seen a compressor that can suck in ambient air, and compress it, and then put out pure nitrogen under 80 psig pressure?

 

I always watch my tires being mounted, and the professional shops (tire truck places) that I go to have always followed this procedure without my having to ask. To all those who've posted that their tires won't hold air, that's called a leak and it needs be fixed. If your tire won't hold pressure when inflated with plain old air, you've got a leak!

 

In addition to making sure the 55 psig in the front is adequate for carrying your weight (my front weighs 4400 lbs), you also need to adjust the tire pressure for speed. Here's a quote from the official tire and rim document...

"A) Load Adjustments for Increased Speed:

6. Find inflation pressure increase required for the speed range desired. (This is not additive, for example, if there is a +5 PSI for 66 thru 70 mph, and +5 PSI for 71 thru 75 mph, to go 75 mph, only add 5 PSI.)"

My theory as to why running your front tires at lower pressure improves MPG is as follows. Even though lower tire pressure INCREASES the HP LOST due to heating the tires, this HP loss is much less than the HP GAIN by reducing the aerodynamic drag because the front ride height is reduced with the lower tire pressures. Almost all the HP required to cruise on the flat is due to aerodynamic drag, and it's proportional to MPH^3.

 

Ain't that the truth. I can just watch the difference in my pyro when towing the travel trailer into a good head wind. Then I learn how much difference there is when I fill up!

 

Interesting. I was wondering how long it would take you to offer up another view on my post, and that's not saying that I was expecting an argument... just that I was expecting an additional good perspective from you on what I've observed and theorized.

I do know for a fact that I feel a LOT less jolt when I encounter bumps at highway speeds with the 10lbs less pressure, which is why I believe that there is at least some element of truth behind my theory. Perhaps, though, there is a combination of both our theories taking place together, because I also saw a barely noticeable change in tire height for that 10 psi reduction, which means that there was precious little "attitude" change with the vehicle, albeit possibly enough to impart some of the benefits (if not all) from your own theory.

Thanks for the input, Ernest.

 

Measuring from the time I actually see a post (and I don't catch all of them), the time it takes me to respond to a one is a complicated equation that involves many variables including my health status, sleeping and eating schedule, and performing my husbandly duties, which unfortunately are ever increasingly trending towards keeping the wife happy by doing chores and shopping and sightseeing trips, and not the kind of duties that I enjoyed when we were both younger.

Maybe we both need to sniff some of this pure nitrogen that seems to be all the rage here. Better yet, if I could get the 21% O2 that's left over from that magic Costco compressor that turns plain air into pure N2, I could sniff that pure O2 instead. Actually, if you could get one of those compressors and hook it up instead of the leaf blower, then you could put the pure O2 directly into the engine, and use the N2 for the tires!

Your observation about your front end bumping up and down more with higher tire pressures fits my aerodynamic drag theory, because every time it bumps UP the ride height and therefore the aerodynamic drag are increased. According to my computer model, when traveling on a 0% grade with no head or tail wind, you need 61 RWHP to overcome drag and rolling resistance at 64.6 MPH, and this increases to 80 RWHP at 71 MPH.

Every 1 HP that's required to overcome the rolling resistance must be dissipated as heat in the tires, shocks, air bags, and other suspension components. Each 1 HP that's absorbed this way dissipates 2545 Btu/hr=746 Watts of heat. As a reference to how much heat this is, it's half the amount of a standard 1500 Watt (12.5 Amp) heater, which is enough to heat my trailer for ambient temps down to 30F. At 80 MPH, this works out to about 3.4 HP being dissipated as waste heat, and the other 76.6 HP being required to overcome drag.

Most of this 3.4 HP=2536 Watts=8653 Btu/hr, which is about 25% of the heat output from my propane heater in the trailer, is dissipated in the tires. That's why your tires get hot, and their pressure goes up, and no matter how much pure nitrogen you fill them with, their pressure will still go up due to this heating just as much as it does when they're filled with plain dry air. I've made many of these tire temp and pressure measurements to help calibrate my computer model.

 

Interesting article on the science of using Nitrogen in your tires.

http://www.straightdope.com/columns/070216.html

 

Who knew there was such controversy to what psi to run in the tire, I think its great.

 

I agree drag a huge factor, but I was alway understood drag increases at square of speed, not cubed. nevertheless the faster you go the more drag you create and anything to reduce it a little will have a much greater affect at higher speeds.

As far as costco nitrogen, go to a tire equipment supplier. They have nitrogen generating compressors that somehow (i dont know all the details) supply a shop with nitrogen for inflating tires. Its not some special koolaid drinking compressor.