tireman9

Your LT225/75R16 LR-E tires probably show 2,680# @ 80 psi single and 2,470# @ 80 dual which would give you 5,360# capacity if you had perfect 50/50 side to side load balance on the front and 9,880@ for the rear axle. Once you know your real corner laods you need to be sure to select the inflation that would carry the heavier side as your MINIMUM cold inflation, but I would suggest at least +5 to +10 over that as long as you do not exceed 80. Again knowing the actual tire loads will help us give you the answers you are looking for. Before you buy new tires get your actual tire loads.

I think this post will answer your questions on "Ply Rating" vs "Load Range". Read the information on the sidewall of your tires. You should see the words "Load Range" followed by a "D" or "E" most likely. The "2 polyester, 2 steel, and 2 nylon" are just telling you the materials in the tire not the strength of each material. Load Range is what you are looking for. The Mfg sticker or "Tire Placard" is based on an estimate of what your actual load will be on the tires. It would help if you at least got the individual axle loads. Even better learn the individual tire loads. This post covers why individual weights are important. There is a worksheet with instructions you can download here.

I think running an RV without a TPMS would be like running without an oil pressure gauge or without engine temp gauge or without voltmeter.

I believe in this case Goodyear is talking about Ozone & UV damage. Don't know how they would add chemicals to a tire sidewall that would "protect" it from heat damage. Remember that UV and Ozone can attack the surface of a tire, but heat can attack the internal structure of your tires.

Something to consider if you have a hard to find size. You might consider keeping an old worn tire, unmounted, in a storage bay if you have one large enough. You can still pack a lot of "stuff" inside the tire and if you ever have a tire failure this spare would give you something that would at least get you off the road while you wait for a new tire. Here is my video on the topic.

If you bought a Road Hazard warranty should be no problem. Otherwise I have to wonder why Michelin should be responsible for a tire that suffered an air loss due to puncture, cut or valve leak? Simply Google Radial tire zipper failure and you will find numerous examples

Don't forget to have the valves, or at least the rubber grommets and O-rings replaced whenever you have a new tire installed. Rubber parts of valves age just like tires do. A good tire dealer that services trucks all the time should do the job properly and ensure the valve is installed with the correct torque.

For those that may not know what a "zipper" failure is, here is an example. This is what happens with a steel body tire, while Nylon or Polyester body ply melts, steel fatigues. Think of what happens when you bend a steel paperclip back and forth.

If you have the air pressure monitors in all your tires I think you have done a reasonable job. If you already have the "crossfire system" I guess this would mean you could save some $ and just get a 4 sensor TPMS. I do understand the concerns some have on hoses. This is my set-up Note how I have the ends of the hose BOLTED firmly down. I think that it is possible that many of the hose failures are due to inadiquate mounting of the hose so it can move which could fail the hose and/or valve.

I have two YouTube videos just on spare tires Should you carry a spare http://youtu.be/mRy9BYZL5RQ What you probably don't know about your spare http://youtu.be/WMxBIKl_wn8

Danshan432 I understand how easy it is to get confused about Nitrogen. One one hand you have the proponents using some of the data to support their position that N2 is just short of magic. I and some others will agree that there are some theoretical and even some real advantages. The question is: Do the advantages justify the cost? and If the advantages are real, what is the real cost of trying to maintain 95% N2 rather than 79% N2 in your tires? RE not using N2 in old tires. I would really like to see that original message. As a tire engineer, I can not think of any reason for this to be a concern. Also have to wonder what is meant by "old". Do they mean tires that are 7 to 10 years old? or are they talking about tires you might see in an auto museum that are 30 to 70 years old? You are correct about most "shop air" not being dry. We are talking about how wet or how dry. I doubt that even the dryers used in auto paint shops is as dry as what comes out of 2,000 psi tank. Back in June 2012 I provided a link on how to make your own air dryer that I believe will provide almost all the benefits you are looking for when it comes to moisture at a fraction of the cost of N2. RE tie problems. First there is no reason for the inflation gas to affect the rate of punctures so that is a red herring. I notice you didn't mention the number of punctures out of the 35. My biggest concern with these kinds of "studies" is that they probably did not have a tire forensic engineer examine all the failed tires to learn the real reason for the "problem". One possible explanation is that when they switched to N2 they also changed their tire inspection and maintenance program. RE wheels. Thermal expansion of steel or aluminum will not be affected by the gas used to inflate the tires period. Hope this helps. If you still have questions please go back and read my other posts in this thread and then follow the links in my posts. Roger

Charles, You said left side - front axle 4160, rear axle 7420 right side - front axle 3620, rear axle 6620 I know you said you were going to move stuff around but working with the original weights lets see what the next step would be. I want to provide this detail to help any readers that are not 100% clear on the process. Lets use the tires that Alan & Sandy mentioned XRV tires in size 235/80R22.5 When selecting MINIMUM inflation pressure we use the heavier end of an axle so that means 4160 for the Front and 7420 for the rear Looking at the Michelin Load & Inflation tables for RV application we find that 95 psi is needed to meet the requirement for the front tires and 90psi for the rear tires. I also reccoment adding 5 psi to this number so you aren't chasing your tail with adding a psi or 2 every couple of days as ambient temperature changes. So this is how Andy & Sandy arrived at their numbers. NOTE If you change the loading on the tires or the tire size is not as we have shown, then you need to make appropriate changes and recalculate. Also if you run a brand other than Michelin you should use that companies Load & Inflation tables as sometimes Michelin is different by 5 psi or so. While Charles was able to get the individual corner loads not everyone can find a scale to provide that information. There are a number of worksheets out there. The math is the same so any worksheet will do. You can check pg 5 or 6 of the worksheet available for download HERE THIS web site is focused on 5th wheel RVs but has good info and links to weighing RVs and how to find a scale. THIS post on my blog explaines why it is important to know the actual individual corner loads for your personal RV. Remember that just because your buddy has the same make, model and year RV you do doesn't means the tire loads are identical. Afterall you and he probably don't carry your bowling ball collections in the same place in your RVs.

Michelin is voluntarily recalling certain sizes of its MICHELIN® LTX® M/S 2, MICHELIN® X® Radial LT2 and MICHELIN® Latitude® Tour tires. These tires are typically found on light trucks and SUVs You can read the details HERE.

No it's not completely useless. The point I wanted to make is that the use of a hand held IR gun is are not sufficiently accurate as far as measuring the hot spot to use it as a substitute for tire pressure and knowing your actual loads. If I saw a reading like 180F or higher I would take that as a warning that something is seriously wrong and you need to learn why the tire is so hot before moving the RV another foot. You might even want to step away from the tire till it cools down some if you saw an external sidewall temperature approaching 200F as that could be an indication that serious damage has already been done to the tire and there is a posibility of a rupture. After the tire has cooled down (min 30 minutes) you could check the air pressure. If you saw those temps I bet you would find that you were more than 20% low which according to tire companies means you have been driving on a "flat" tire. The tire should be replaced and not driven on ANY distance if you discover you have driven on it "flat" as a sudden air loss could occur any time. RE the question Brett correctly answered. Here is my post on that topic with a few more details and even a formula for those with a calculator. Bottom Lime Tire Pressure Monitor Systems are jsut that. They monitor pressure. Temperature is just icing on the cake. I have done some preliminary tests on internal (air chamber) vs external (end of valve stem) TPMS but need more data before I publish the results.

<p>On this and other RV forums, I see mention of tire temperature and the use of IR "guns" to keep track of tire temperature.</p> <p> </p> <p>Using hand held "guns" on conductive metal objects such as wheels, hubs, brakes and engine components is OK but using them to learn what the critical temperature is, on tires, just a waste of time. The main reason this is not a good idea is that rubber is really a good insulator so the hot zone of tires which is buried internal to the structure as the heat is generated internal to cords and at the high strain (movement) locations between the steel at the belt edges. IR guns can only measure the surface temperature of the tire so you are not getting accurate reading of the critical location.</p> <p> </p> <p>The other problem with using the guns is repeatability. Locating the precise point of measurement if you are going to do a comparison of the same tire at two different times is critical. Even the angle you hold the gun can affect the reading.</p> <p> </p> <p>There is also the problem of why heat is bad for tires. A tire does not fail because of the average temperature of the tire but because of the hottest temperature at a specific location internal to the tire structure.</p> <p> </p> <p>Here is a sample graphic from Finite Element computer model showing the hottest area in red and coolest in blue.</p> <p> </p> <p><img alt="o5rr6t.jpg" src="http://i42.tinypic.com/o5rr6t.jpg" /></p> <p> </p> <p>If you look near the shoulder (just to the left of the red zone) you see very high changes in temperature with minor changes in location of temperature measurement. Since this is a computer simulation it is basic in that it does not introduce the variations in rubber thickness ( insulation) due to sidewall decoration or tread pattern. These variations simply add to the difficulty in getting accurate measurement in real tires.</p> <p> </p> <p>When I used laboratory quality IR thermograph equipment costing tens of thousands I was able to measure significant temperature differences over distances as small as 0.10" this is smaller than to normal target area offered by the Harbor Freight IR gun. This means that unless you measure at the identical location on a tire at +/- 0.05" location you will not get repeatable temperatures.</p> <p> </p> <p>The other variable is time and distance traveled since you were driving at your controlled speed. Based on my real life experience I would suggest that you need to drop from your constant highway speed of 60mph to 0 within 20 seconds and then take the tire temperature at the same time from stop (say 20 seconds +/- 5) or the temperature reading would not be providing you the information you would need to make a valid A-B comparison for load or inflation adjustment.</p> <p>When I was working Indy Car tire tests we would shoot for collecting the 12 tread temperatures using a needle probe always in the same sequence at 3 to 5 second intervals (less than 60 seconds total with 45 seconds the goal for all 12 measurements starting from the second the car stopped moving.)</p> <p> </p> <p>You might as well just use your hand to judge if the tire is hot or really hot.</p> <p> </p> <p>I have two posts on my blog on the topic of IR guns</p> <p><a href="http://www.rvtiresafety.com/2012/05/what-do-you-think-about-temperature.html">This one</a> has additional temperature pictures.</p> <p> </p> <p><a href="http://www.rvtiresafety.com/2012/05/what-do-you-think-of-ir-guns-part-2.html">This post</a> has data showing a direct comparison between internal TPMS, IR gun and a professional racing pyrometer as used by a major tire company race tire engineer.</p> <p> </p> <p><a href="http://www.rvtiresafety.com/2011/05/tire-temperature-pressure-hot-topic.html">This post </a>covers "Gas Law" and the mathimatical relationship between temperature and pressure and has a picture of my race car.</p> <p> </p> <p> </p> <p><strong>Bottom Line</strong></p> <p>Does this mean you can't use your HF $29 IR gun? Not at all. Just keep in mind that we are talking about trying to improve the safety of your travels. I am not sure if it a good practice to use a "toy" when making safety related decisions.</p> <p> </p> <p> </p>

Larry, Thanks for the additional info. While I don't think it is tire roll it is understeer that goes to oversteer (vehicle turnes more than you want) probably due to the toad pushing the rear of the RV to turn more after you are into the turn. The hint to this is the fact that is happend when going down hill when the toad may not be slowing down as fast as the coach. When I was racing I was pulling a 26' enclosed trailer with a Camaro and all our tools and support equipment. My tow vehicle was a 1-Ton dually w/slide in camper. I had electric brakes on the trailer with controller under the dash so I could gently apply the trailer brakes when there was a downhill sharp turn. This would immediately get things under control and the trailer was no longer pushing the truck. Now your toad is lighter than my trailer relative to the total loading but 5,200# is still going to push a little and when the coach in long and at an angle it is easier for a lighter load to generate a larger leverage force. Now how do we fix this? Your tire sidewalls at 100+psi are pretty stiff so I don't think changing tires is going to make much difference but increasing the coach tire pressure will decrease the tendency. I won't get all technical with cornering coefficients etc but increased coach tire pressure gives the coach tires more control in cornering. A lighter toad will generate less of this turning force in corners. If you can apply the toad brakes lightly but not the coach brakes (as I could with my set-up) that will also improve things. Also slowing down more before you enter the turn will decrease the rear swing out. I see you mention "70 degree day" but this does not apply to tire inflation and the load tables. Set your tires when they are not in the sun, are the same temperature as the surrounding air and haven't been driven on for at least two hours. "Evertread" seems to be a marketing item aimed at long thread life which for most RV owners is not an issue. RE Ride. I am not aware of anyone doing a controlled test to compare tire-A vs Tire-B. Also based on my experience in evaluating hundreds of passenger tires on many dozen different cars it is not unusual to find Tire -C on vehicle X is better than Tire-D but when we test the same tires on Vehicle Q many times Tire-D is better than Tire-C. Simply relying on what you felt with an old worn set vs a new set of tires is not a valid engineering comparison. In my opinion this is about as helpful as trying to compare your wife's chocolate cake vs your mothers or grandmothers.

Thanks Brett for the heads up. With 7 different forums on my list to monitor and two blogs to write I don't always catch every post that has a question. I do accept direct email ( tireman9 at gmail )and a notice that there is a post and you would like a comment would be no problem at all. By using the post to ask questions we can hopefully help others who have similar questions. Now to the question. I note that the understeer problem seem to occur in downhill travel. Do you notice any problems on uphill or flat road steady speed travel? I note mandalay40F has a Tahoe toad. Any idea on its total towed weight? **** & Lois do you have a toad? If so what is it? Weight? My response will be shaped by this information. RE inflation. Glad to hear you have had the coach weighed to learn the "minimum" cold inflation. However I see no problem with running plus 10% as long as you are not going above the tire max as molded on the sidewall. Will check back this weekend to see what info you can provide.

I wonder how many think about the fact that a tire running higher pressure can carry more load than one with lower pressure. If an inner dual runs hotter due to less cooling air it obviously can carry a bit more load. OD growth differences are essentially meaningless on steel body radials. Road crown is already managed with the Load tables that give lower load rating for tires in dual application. I would rather have TPMS that would warn me as soon as a tire started to loose a few psi rather than have one tire sacrifice part of its load capacity to try and keep its mate inflated when there is a slow leak due to a puncture or valve leak.

You didn't mention the age or condition of the tires currently on your coach. Putting two new on the front is a smart move. Have you had a dealer inspect the 6 tires you have and does he say, in writing, there are 4 that are good enough for 1 year service? Tires stored indoors for a number of years can have hidden issues as moisture has not been "driven" out of the tire so the steel could be corroded but not visible externally.

The term "drive" tires means different things to different people. It would help if you could provide actual tire design, tire size, Load Range and the actual load on each tire position of the new to you RV, so we could answer all your questions without having to make a lot of guesses. First "Drive" vs 'Steer" In general steer tires have continuous rib design like the XZE Real drive tires have a traction pattern more like the XDY Now I doubt that you have anything like the XDY on your fronts as this would give some vibration through the steering wheel. Another difference is that steer tires usually have shallower tread depth than drive patterns which means they deliver better fuel economy and since most RV applications "age out" before they wear out I would think fuel economy is more important than high tire mileage. Regarding the load. Both Drive & Steer tires of the same Load Range and size will be rated for the same load capacity when inflated to the same level so I am not sure what your comment means about 30,000 Lbs as I'm sure this is not the load on the front two tires. A quick review of the 22.5 rim sizes (I am guessing here at what you need) on the Michelin RV tire web page will show that all the "Class-A" tires are rib pattern and suitable for steer axle application. Please give us a little more information and please clarify your question so we can properly answer it.

Are you running so close to your Max tire loads that a loss of 5 psi moves you to overload? Are you sure your hand gauge is accurate to that level? If you use a +5psi or +10psi above the min you need for your ACTUAL tire load you should not see a need to add air in the morning and can probably wait till you get to a truck stop that has high pressure. How I would "Top Off" and add a few psi to a tire that is no more than 5 psi below minimum for the actual load. 1. Measure all your tires cold and writ down the actual cold infl 2. Calculate how much air, in psi, is needed to get to your goal. 3. If actually below min. Drive to nearest truck stop at 50 mph or less or If just below your goal of + 5 or 10 psi gust drive to your next fuel stop. 4. Measure your "hot pressure" 5. Add the number of psi calculated in #2 above plus 2psi to the hot reading and inflate your tires to that pressure while hot. 6. Next morning I think you will find you are +/- 1 psi of your goal. If you discover you are really low i.e. -10% or lower you need to find out why. You should NEVER drive on a tire that has lost 20% of its air at any speed as this is considered "flat" and you may do internal structural damage. A Servie call is called for. If you have been monitoring your TPMS you should only see minor variations of +/- 2 to 5 psi in cold due to Ambient temperature changes and 1 to 3 psi due to elevation. Hope this helps.

Based on some stated shipping weights I think you will find that a long metal valve weighs about 0.8 or 0.9 Oz more than long outer dual metal valve. Maybe if you have short metal valves then the difference might be 2.3 OZ. On rear duals you will probably not feel a 1 Oz out of balance and maybe not even a 2.3 out of balance but Bretts suggestion is reasonable if you want to worry about it.

Super single, which I believe is a trade name, is not a new technology asa I worked on similar tire designs in early 70's. The main issue is that the cost of replacing tires & wheels when used does not work out but if the vehicle manufacturer applies new the saving in fuel does pay for the added up front cost when you are looking at the life of a set of truck duals. I don't think we will see this option be of value till diesel get higher due to RV shorter life.

IMO running tires without TPMS would be like eliminating your engine temperature and oil pressure gauges. If you think running without a TPMS is OK, I would challenge you to give yourself this test. Get some tape or even a post-it and cover your water temp & oil pressure and Tach and any other gauge other than speedometer. Then set of you your days travels. If you take a rest stop just check to see if you are leaking any fluids by looking under the coach. NO PEAKING under the taped over gauges. See how long you are really willing to go without having this information available to you as the driver. If you peak even once then you are indicating you really know you need to know the operating pressure & temp of the engine, so what makes you think that checking the tires once in the AM and simply looking at your tires at each rest stop is good enough? Yes, TPM is relatively new technology while engine gauges have been around longer than most of us. but why not use the benefit of TPM. The data says on average the RV owner will have at least one tire failure per set of tires. The cost of a single tire failure is more than the cost of TPMS and some TPMS can be transferred to your new vehicle or just replace the batteries. I think they are a definite plus when it is time to sell your rig.

Before you add "sand" or anything else to your tires be sure: 1. You are not going to void your tire warranty 2. You get an appropriate filter to prevent particles of the balance material from plugging up your TPM sensor. They are not cheap to replace.