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Friday, November 24, 2017

Are Nitrogen Molecules Really Larger Than Oxygen Molecules?

According to the "Get Nitrogen Institute" in their paper on N2 effusion

"The correct answer, with respect to 'permeation,' is yes."

So I imagine your question is why don't I support the effort to "sell" the idea of always inflating your tires with just Nitrogen. It comes down to effort and cost VS level of benefit.

Maybe one way to think of this would be to imagine dropping a penny as you walk away from making a small purchase at a store. If you dropped a number of coins you might stop, bend over and pick them all up. But what if you only dropped one penny and didn't discover the fact till you had walked to your car. Would you walk the 20' back to the store to look for the penny? I bet not.

There is no doubt that you would have more money if you picked up the penny but would you consider it worth the effort?

In general, tires lose about 1%  of their inflation pressure each month in laboratory testing. This is almost entirely Oxygen. It is also true that tire pressure changes about 2% for every change in temperature of 10F. This is true for Nitrogen or air.
I haven't tried to run a test but it is also true that every time you use a hand pressure gauge to check your air you let a little air out. How much air do you let out if you use a gauge to check your tires every day? Might it be 1% in a month's time? Might it be more?

Finally, what does it cost to inflate your tires with N2? Even if you have a deal with a dealer and can get your pressure "topped-off" for free, you still have to drive to the store location to get that "free" inflation.

Bottom Line:
IMO the small level of benefit of inflating with N2 just isn't worth the effort and cost. There is also the real negative of not checking your tire pressure simply because you believe that by inflating with N2 your tires will never lose pressure so you don't need to check. What about small punctures or leaking valves? If you don't check the pressure you will not learn about the leak till it is too late.

However, if you want to inflate your tires with N2 I see nothing wrong with doing that. After all, it's your time and money, not mine.

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Friday, November 17, 2017

When to replace tires? Can you drive on one "dual"?

Was reading a magazine aimed at motorhome owners and there was an item about a man that suffered a tire failure. It was one of his rear duals. The RV owner reported that he decided to drive to the nearest tire store where it was suggested that he replace all six tires. The tire dealer had to educate the RV owner about the life of tires in RV service being 10 years or less with many recommending that tires be replaced after six or seven years life.

The magazine did offer a brief explanation on how to "read" a tire DOT serial and learn it's age.

IMO the magazine missed an opportunity to further educate their readers with a warning of the damage that was probably being done to the mate of the tire that failed.

First off there is a good probability that the tire, being over 10 years old, failed from a belt/tread separation. We can't be sure, as the RV owner didn't have a TPMS, so we don't know if he could have avoided the problem of a "Blowout" or Run Low Flex Failure on the Interstate. We do know if there was a slow air loss, the tire that did not fail was being run with ever-increasing overload, for as the companion tire lost its air the load on that end of the axle was being transferred to the fully inflated tire.

In the tire industry, there are tables that provide information on how slow you need to drive as you increase the tire load above its normal load capacity.

Basically, you need to run no faster than 40 mph if you are running 107% of the rated load.
If you want to run 113% you can drive no faster than 30 and the max speed drops to 20 mph if the overload is +21%.

Since our RV owner was running at 200% load I would estimate that maximum speed he could travel without doing damage to the "good" tire to be no faster than 5 mph and even that is questionable as there are also distance limits for those conditions

If you have a tire failure, no matter the reason, you need to change out the failed tire and should not attempt to "limp" home on its companion. If you are concerned for your safety on the side of the road you need to be aware that driving over 5 mph means you need to have the companion tire also replaced. No matter its age. As always when changing tires in a dual position you must also match the pair as covered in THIS post.

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Friday, November 10, 2017

DId your RV company or dealer follow Federal law?

Been reading a number of posts on recalls, violations of federal safety standards in the RV industry and on tire and fire extinguisher recalls.
If you have been a reader of my blog you know that I am a strong proponent of filing complaints on failures of safety-related systems and of tires to NHTSA.

You can read a portion of the Federal Regulations on what RV companies are supposed to do HERE as far as the regulations relate to identifying who owns what tire in case there is a recall.
Obviously, if the S/N ( full DOT serial including the date numbers at the end) of a tire is not recorded when the tire is sold there is no reliable way for a tire company to contact owners of tires that are under a recall order.

Selling dealers have the following responsibility
"The National Highway Traffic Safety Administration (NHTSA) requires that tire dealers must provide every tire purchaser with a pre-addressed completed tire registration form OR complete the tire registration process electronically on behalf of the tire purchaser (49 CFR Part 574.8). This is not voluntary, tire dealers must do one or the other"

When a vehicle is sold (car, light truck, or RV) the tires are "sold" with the vehicle. The regulation says "tire dealer" but obviously just because a company sells vehicles and doesn't think of themselves as a "tire dealer" they are in fact selling tires.

However, I have found that few people have received the appropriate forms. Did you receive a form with the purchase of your last set of tires at the tire store, or with the tires that were shipped to you if you bought them online?  How about when you bought a new or used RV?

You say you bought your RV used so you don't think the tire ownership needs to be registered? Well, I know of nothing prohibiting a tire being covered under a recall just because ownership was transferred. The entire reason for this registration is simply to let either NHTSA or the tire company contact the owner of tires covered by a recall. The information is not used for any other purpose.

IMO the odds are that very few of you received the pre-addressed form or if you did you may not have bothered to complete the information.

Well HERE is a website that you can fill in the information and submit it online and don't even need a stamp.

I started this post and mentioned Fire Extinguishers. If you have following the blog you know about the recall and free replacement of potentially defective extinguishers. You may have discovered you have one or more of the covered units. Unlike tires, fire extinguisher ownership is not registered so there will be millions of extinguishers that are not replaced simply because people do not know about the recall and Kiddy company has no way of contacting the owners.

Do yourself a favor and register all your tires RV, Car or truck. Who knows you may just end up with a new set of tires if the ones you have are covered under a recall.

Friday, November 3, 2017

Summary for Newbies

This is a summary of a discussion I had on RV Forum on tire pressure that started with a question and some comments.

"I'll give my take on maybe why, we have ----- Travel Trailer owners ----- Motor Home owners that never had a TT ---- TT owners that moved up to a MH ----- MH owners that still act like they still own a TT -- maybe there is any other I can not think of right now.


I have friends that own MH's and suffer blow outs all the time and their tires look good at the pressure they are using and not a Run Low Flex Failure that will most likely cause a blowout.

Maybe Tireman9 will answer some of the differences between TP's of TT's and MH's to clear up some of the misconceptions people have."

Here is my answer to the broad question

Yes, the proper inflation for MH and "tow-able" RV are different. There is actually strong science behind why there is a difference. THIS blog post is a short explanation. You can read the technical info HERE.

The other issue is that some folks just do not want to hassle with vehicle maintenance required with RV ownership. They are used to cars that have thousands of man-hours of engineering design, testing and development to make those vehicles extremely reliable.

Some of us are old enough to remember that when we learned to drive we were taught how to change a tire, as 10,000 miles was good tire life. Many probably learned how to change oil or adjust a carb. Some even knew how to set the engine timing and change a set of spark plugs. Nowadays it's hard to even see the plugs but with their life now at 50,000+ and the ignition computer controlled and many tires good for 40 to 60k miles who needs to know how to maintain a car?

RVs have a number of systems that do need maintenance. The tires on RVs are an outlier. While top tier tire companies use essentially the same rubber compounds and tire building equipment. This blog post explains the concept of "Tiers" in the tire industry. If you have a MH you will probably recognize the brands and names of the tires on your RV. 

However if you have a "towable" and by this, I mean both 5th wheel and more basic "Travel Trailers" many of you probably have tire brands that don't even fall into the 5th tier level. Some of these off-brand tires may not have a lot of up to date engineering built into them but IMO the main problem is the selection of tire size and load/speed capacity made by the RV company.

Again IMO many RVs are sold based on low cost and the unit has lots of "bling". I don't think I have ever heard of a salesman touting the benefits of the tires that come on an RV. I doubt that many even know the size or maybe even the brand provided on the various units they sell.

So the bottom line is that tires on RVs need more maintenance than the tires that came on their cars. Partially because of their usage but also because there is such a small margin of extra capacity provided based on the tires being undersized to keep costs down. Maybe if RV companies spent more, or even some time evaluating better options, i.e. had better quality for the tire sizes and type they offered, the incidences of tire failure on RVs would be less frequent just as they are less frequent on today's cars.