Care and feeding of your RL's tires.

[steveberger]

OK, so I’m not quite as fanatical as some when it comes to my RL. Winter in New England is just not the place to try and keep it showroom polished like the California and Arizona photos I’ve seen. The truck is filthy. The inside is a little better, but there is some sand (on and off) of the floor mats. I don’t change the oil every 3,000 miles. I’ve decided to trust the Honda engineers, and go with the maintenance minder for my oil changes. The stock stereo sounds great to my tin ear and the headlights and interior lighting seem more than adequate to me and will remain OEM.

So what am I fanatical about? TIRE PRESSURE!

I have a totally unproven theory that tire pressure is especially important to gas mileage and tire life on All Wheel Drive vehicles. The simple explanation of my theory goes like this… If one tire is significantly softer or harder than the others, it is effectively a different size. Therefore, it will want to rotate at different RPMs than the others. The AWD system will constantly be fighting to even them out. The differentials and transfer case will be continuously working the three identical tires against the one different one. The result will be excessive wear on all the tires; most noticeable on the unique one, and greatly reduced gas mileage. Anyone strongly agree or disagree with this theory?

I am in the business of transporting radioactive materials. Due to the sensitive nature of this business, I spend a lot of time inspecting safety equipment and tires on 18-wheelers. Commercial drivers are not as particular about this as you might think. Most of the ones I contract with are driving someone else’s equipment and they don’t pay for the tires, which can cost $250-400 dollars a piece. It is not uncommon to see an eclectic assortment of tires in different conditions on the same tractor-trailer rig.

The tools I use are an inexpensive tread depth gauge, and a good quality tire pressure gauge.

I have used them on my private vehicles for years. Here are the results of my most recent inspection on the Ridge that has 13,500 miles on it. The tires have been rotated twice, first at 5,858 miles when the Maintenance Minder said to change the oil and rotate the tires, and again at 12,759 when the B6 warning came up.


Tire ...............Pressure psi ........Tread Depth in 1/32” (Outside to Inside)

Right Front .....31.5...................... 9.5 .....9.5 .....9.5 .....10.0
Left Front ........32.0 ....................10.0 .....9.5.... 10.0 ....10.0
Left Rear .........32.0 .....................9.0...... 8.5..... 8.5...... 8.5
Right Rear...... 32.0...................... 8.5...... 8.5..... 9.0...... 8.5


I’m pretty happy with these results. I have the best tires on the front. These do most of the breaking, all of the steering, and I suspect this results in most of the wear. I have even wear across each tire. I will stop at the service station as soon as possible for a squirt of air to get that one up to the others. I say “up to the others” rather than 32 psi because this is cold tire pressure. They will warm up on the way to the station and will be a little higher. I will measure the others again and make sure they are all the same.

If this inspection reveals that your tires are wearing more in the middle you are probably running the tires too hard.

If they are wearing more on the outsides you are probably running too soft.

If they are wearing on the inside you probably have an alignment problem.

If one tire is wearing more rapidly than the others it can be any of the above or a bent rim.

Inspect your tires frequently, keep the tire pressures as even as possible and investigate any uneven tread wear immediately. Never wait for the TPMS to tell you it’s time to add air.

There was a post a while back about folks who thought their RLs didn’t coast as well as other vehicles. Check your tires. A low one will have the AWD working like crazy. This will slow you down and burn lots of gas.

There you have it! Steve Berger’s theory of tire inspection and maintenance. If any one has a personal story, anecdote, or imperical evidence that proves or disproves any of this, I would love to hear it.

[farmguy]

Interesting info, steveberger! A couple comments/questions:

I'm surprised you're not using a dial-type pressure gauge. My sense is they are more accurate, but I don't know that for sure, it's just that you can see the increments more easily.

How do you explain that your currently rear tires have more wear? It looks to me like the tires are back in their original position front/rear, and that the mileage in each position is nearly equal, (6901 vs. 6599 miles each). If they have lived about equally in front and rear postitions, why wouldn't the wear be more even? (Not that a 32nd difference is much!)

Do you cross the tires side to side when you rotate? Yes or no, why?

Do you know what tread depth was when new?

Just trying to obsess right along with you...!


P.S. I have been toying with the idea of a matching spare and a 5 wheel rotation, but it's probably too late now since I have already rotated. Any thoughts on that subject?

[hiPSI]

A few things I consider about over/underinflated tires and the AWD system.
While an underinflated tire will have a much different loaded diameter than a properly inflated tire, the loaded circumference will be close to the same. To check this measure across the tire parallel with the ground. I don't remember the exact difference between a unmounted radial tire and a mounted inflated radial tire, but I think it is about 3% difference in circumference unloaded. A tire has to travel around its complete circumference to make one revolution. In the case of an underinflated tire the circumference is about the same but the contact patch is longer. So, while there may be a little difference in the circumference, I don't think it is enough to engage the AWD. If the AWD was designed to engage with any variance in circumference, think about: A worn tire vs. a new tire of the same size or; A vehicle making a turn (outside tire travels farther than the inside tire). So, I would like to think Honda has some room for error before the AWD engages. If it didn't, it would engage everytime you went around a corner or everytime you had one tire worn more than the other. I think the real bad thing about underinflated tires most people tend to forget is the increased rolling resistance they cause. I have read many posts on here about gas milage and they don't realize a few pounds of pressure loss can account for up to 7% loss in gas milage. I would like to know from Honda (the real numbers) what has to happen before the AWD engages.

[shortspark]

Good information Steve. I use the dial air gauges and like them much better than the traditional pop-ups. However, both can be fairly accurate. I also rotate my own tires. I've only done it once as my second service due notice has not come on yet. I have my tires inflated to 34lbs and check this regularly. I believe that is a couple pounds over the recommended inflation but I would rather have a couple pounds more than less. I have found the extra pressure provides for no difference in ride, handling or gas mileage for that matter. I suspect the extra air will have some effect on the tires longevity but don't know that for sure.

I do not plan on having my tires balanced unless I encounter a problem such as shaking or wear pattern that is not related to allignment or rim damage. Of course, I will have to have them balanced if they ever loose their weights.

I believe there is a chalk or powder kind of test that can be used that will indicate any unusual wear problem fairly early on and before you can detect it with the eye. I think you put the chalk down and ride over it, then examine the tire and see where the chalk covers the tire. Ideally, the powder will cover the entire tread area. I have never tried this and I am not sure if this is exactly how you do it however.

I use a good stiff brush to clean my tires and then dress them with Meguire's Hot Shine. It lasts a long time and has more of a deep, black matte finish than a real wet finish. Unlike some poducts, this one has never turned a tire "brown" and I've used it on lots of tires, including those on my golf cart. I put Klasse All-In-One polish on the wheels.

[RTLofatruck]

Not long after reading your post, this showed up on my home page.http://www.motortrend.com/features/n...s52/index.html