tireman9

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.

I strongly support having a TPM system on all RVs including towed vehicles. If you get a puncture in your daily driver (car), there is a good chance you will feel it before it completely lets go but not in a big RV and especially not on a towed trailer of towed vehicle. I, however am not sure of the benefits of having a hose connect both tires of a dual pair. If you use a good hand gauge the 1 psi difference is not meaningful and there is a possibility of a leak in one tire causing the 2nd tire to also loose air.

When you say the alignment if "OK" do you have a full printout of all the numbers? Did you confirm the center of the rears point to the center of the front axle? I believe it is called "Thrust Angle" and it should be zero otherwise the rear of the coach "dog tracks" and one side sticks out relative to the front tires. Roger Marble (On vacation at Nurburgring race track in Germany)

J49 1. Load Range is a letter code D, E F, G etc with higher letters meaning a higher inflation stated for the max for that given tire. It really replaced "Ply Rating" as the actual number of plies on modern Truck Bus Radials,(TBR) as uses on Class-A RVs is 1 body ply of steel plus 3 or 4 plies of steel in the tread. So saying I have a 12 ply rating (1 actual ply) or a 14 ply rating (1 actual ply) was determined to be misleading. You can read the actual material in your tires if you simply read the sidewall. You will see something like this except it will probably be Steel not Polyester, + Nylon OK tire date. All tires have a DOT serial code. Most have a partial code on one side and the full code on the other side. It starts with DOT then letters and numbers like this. The last 4 digits will be numbers. In this example the tire was made the 51st week of 2007. If you want a 2012 tire then you want to see something like 4212 which would be the 42nd week of 2012 or 0313 3rd week of 2013. Read more about tire serial date and age HERE. I don't think that because your pick-up tires ride nice you can always assume your 22.5" TBR tires will be the same. This would be like assuming that because a Chevy Corvette is great handling then a Chevy Vega would also be great handling. Be sure your new tires have a Load Range equal or greater than the load range shown on your RV Placard or Certification label. Get your RV weighed when fully loaded (food, fuel water, bowling ball collection, co driver's shoes etc). Confirm you are not overloading your tires. using a good gauge I would run + 5 to +10 psi over the minimum needed for the actual load. Inflate all tires on an axle with the same inflation. Set the inflation for the load on the heaviest tire. Get and pay attention to a TPMS and have a safe Summer.

General comment on extensions. When I was racing I towed with 1-Ton dually and had steel braided extensions. Ran about 78,000 miles with no problems. When I got my Class-C my first add-on was TPMS followed by steel braided extensions. With only 16,000 miles no problems. Now there are TWO main things that I would consider a MUST. First you need bolt in metal valves. Second you need a hard attaching point on the outer end of the hose to prevent movement of the hoses. The hoses come in different lengths so you should run the shortest hoses that allow you to easily bolt the end down and you need to support the end of the hose when pushing on it with your tire gauge or air chuck. I can only guess as to why a metal valve would fatigue as without significant movement of the hose there should not be enough to stress the valve stem. Metal valve stems should be replaced or at least have all the rubber O-rings and gaskets replaced whenever you change a tire. The rubber parts age just as the rubber on your tire ages. Replacing when you replace tires eliminates the need of keeping track of the age of the O-rings and seals. There is a rubber interior to the hose and this will also age so when I replace my tires I will get new hose extenders along with new valve rubber parts. I have seen spring clips that are supposed to retain the steel braided hose but they don't look too solid to me. I have not looked at the rubber "grommet" that fits the hand holes but have to wonder if they hold the braided steel line solidly. Clearly they do not support the hose end so there will definitely be some movement. You can see in my set-up that I have the hose firmly attached to my hub cap. I do hold the extender hose when ever using a gauge or air chuck.

You might watch this Video

Not sure what your tire dealer is talking about. Almost all large shop air compressors top out at 150 to 175psi. Anything higher would be considered "Industrial". Here are a couple of links to companies that supply air compressors to body shops and garages. If you look at the specs you will see 175 psi is the max with many at 150 or lower. TIP Northern. Now back to your question. I think the reality is that you occasionally find that you need to top off your tires with just a few psi to reach your goal cold inflation. If you have a TPMS and a little experience you will know when you need to add 5 psi or so. You should be able to get air at high enough pressure at truck fuel stop if you have a Class A needing 95 to 120 psi cold. Here is a post from my blog on how to get your tires topped off for free.

I do not see a 295/75R22.5 size listed on the Michelin Load/Inflation chart. So along with size, are you considering changing brands? Nothing wrong with mixing brands or size on a motorhome but as Brett pointed out you will not be able to rotate tires in the future. You should always run the same tires on each axle. Also you did not mention if your 295's were LR-H or LR-J. This information would help those offering assistance to provide a more meaningful response. What ever you do, be sure your new tires can carry the actual load of your RV. Be sure you are looking at the correct LR when making your comparison. You can learn more about LR by reading this post "Load Range" .

While most CAT scales do not provide the side clearance to help ypu calculate individual tire loads you can check out their locations HERE. Penske has a scale locator site. BigRigs also has a Here you can get more info on the importance of weight and a worksheet to help you calculate individual tire loads. Once you know the actual individual loads you set the minimum inflation for all tires on each axle based on the heaviest loaded tire on that axle. Most suggest you add 5 to 10 psi safety cushion. You can contact me directly if you need help with the calculations. .

werni8 Can't speak for mechanic but if it were me I would say it depends. If you are temporarily replacing a front I see no serious problem with the size mis-match. However you should never mix size or brand or type in dual application. There are special matching dimensions to consider. Also you should never consider limping home on a failed dual. You can temporarily take both fronts and move to one side in the rear. Then use the good tire that was a dual and place it and your spare on the front. Now I am assuming you are making the change because you got a nail or such in one of the duals and you stopped because your TPMS warned you when you lost 20% or so of the minimum air needed based on the load. If you had an actual failure with serious loss of air on one dual you may have damaged its mate even with only a mile or so of travel and that tire should be considered as possibly damaged and not driven on until thoroughly inspected and pronounced OK by a rep from the manufacturing company.

KYOLDGUY If you aren't sure how to read the tire age thing HERE is a post with pictures. The posts above on replacing at 5-7 or 8-10 are correct with 10 being the absolute max for motorhome application. Don't be mislead by simply looking at the tread as it is the internal structure you need to concerned with and none of us have X-Ray vision. RE "Best Tire" Ask 5 people and you will probably get 5 different answers. I do offer some advice on how you can evaluate a variety of brands and how to find the one that best fits your needs. Sorry I can't give you a specific name as I don't know all your requirements. Hope this helps

Anyone reading my Blog knows I like data and prefer it over a simple opinion. The topic of tire covers has come up here and on a couple other forums. I did a simple temperature test and posted the results using the white covers I have. Some others think that black might be a better choice as they believe the carbon black in black vinyl gives better UV protection. I also have seen some covers that appear to be more of a screen material. Looks good at matching the color scheme of the RV but I'm not sure how well those covers are protecting the tires. I have decided to "up the ante" on this question and collect more hard data. Just received a UV meter and am designing a fixture to hold special UVC light bulb so I have a good light source of the most damaging type of UV light. Next I need a variety of materials used for tire covers. I don't have any sponsorship for this effort so can't go out and buy a few sets of tire covers. The UV meter and special light will run me $50 to $75. If anyone has an old or damaged cover and want to help the effort I could use a 6" square of the material to use in the test fixture. Send me a message so I can provide my mailing address if you want to support this study.