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Old 06-17-2014, 03:08 AM   #15
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One sure has to wonder why all tire makers publish a load chart telling people the recommended pressures for a given load. Could it be that through research and testing they have determined what pressure will give the best tire life, ride and handling characteristics? That would also result in the safest pressure. I guess I will go with what the tire maker thinks is best.
I would assume they publish this cause so many believe less pressure equals a smoother ride ( I don't, but won't argue the fact ) and the tire will fail under a heavy load at that psi?

I'm not saying that running max pressure won't shorten tire life ( I've never experienced it, but maybe I'm lucky ) but I don't believe that's the reason they run the charts. I'm with the other post, lawyers and accountability now falls on the consumer since you know what they're rated for.
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Old 06-17-2014, 03:22 AM   #16
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so if the weight of your front left corner requires you to run at 60 pounds and the weight on the right front corner requires you to run 90 pounds, how do you think that rigs is going to steer ? Would you weight police out there do it ? Now I suppose the air pressure difference in the back tires wouldn't make as much difference as the front tires would in the steering input.
All tires on the same axle are inflated to the same psi. Use the numbers for the wheel position carrying the most weight + safety margin.
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Old 06-17-2014, 04:15 AM   #17
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All tires on the same axle are inflated to the same psi. Use the numbers for the wheel position carrying the most weight + safety margin.
Wouldn't this theoretically mean you're over inflating one tire which would lead to crowning tire wear and rougher ride, which is the reasoning for doing the four corner weigh to eliminate?
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Old 06-17-2014, 04:42 AM   #18
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FWIW, tire technology has changed over the years. My Dad relayed to me when he was a young 1000 miles on gravel road was all you could expect from a tire, today if I don't get 70k I feel like I'v chosen poorly. Goodyear Marathons, when I was running them, per factory guidance said to inflate them 10psi over the sidewall max for continuos speeds above 65mph.

I've found over the years that old trucker wisdom has value. Back in the day of gasoline truck engines the valves would float before the motor would be hurt, so to get max performance without the benefit of a tach, turn on the windshield wipers and shift when they stopped.

That all said, I use the tables to set tire pressure. My engineering background makes me a firm believer in the science. There are a few safety concerns with inflating to max sidewall pressure. My concern is where does the tire perform best? Max pressure may hydroplane sooner. Max pressure will have a smaller tire patch to brake and turn with. When not loaded to max weight. How much difference? Enough to make a difference? Maybe.
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Old 06-17-2014, 06:52 AM   #19
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I would assume they publish this cause so many believe less pressure equals a smoother ride ( I don't, but won't argue the fact ) and the tire will fail under a heavy load at that psi?
I can imagine that there are several factors at play so it may not work for everyone/every situation. However; my single experience is that it actually does make a difference in ride quality and handling. After weighing and confirming with the charts, I reduced pressure from 110 psi to 85 psi and am very happy. I am extra happy when I consider the amount of money I was considering dumping into my suspension and which is no longer necessary.
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Old 06-17-2014, 08:39 AM   #20
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This topic has been discussed ever since radial tires came onto the market. Fifty years ago, we just aired new tires up to 32 psi (an auto) and drove off. Sometimes 12,000 miles later, we replaced those worn out tires with another set for $100. When I bought my first Avalanche in 2002, I weighed it and set the pressures at 28 psi F&R as they were close to the same weight. When I pulled a trailer, I added air to the rear tires depending on the load. Yea, I know I was being anal, but the OEM tires wore evenly and at 85,000 miles the tread was still safe, but i replaced them for a long upcoming trip. I thought that was pretty good for a 6200# 4 wd truck. It made a believer out of me and have done that with all of the hundreds of trucks in our businesses over the years and our personal vehicles as well. Everyone has their reasons, so this is mine. To each his own.
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Old 06-17-2014, 08:53 AM   #21
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[QUOTE=oildriller83;2098480]I would assume they publish this cause so many believe less pressure equals a smoother ride ( I don't, but won't argue the fact ) and the tire will fail under a heavy load at that psi?

You are correct that any overloaded tire will fail in time. Once loaded, a motorhome's weight will not increase more than a couple hundred pounds distributed over six or eight tires, so if inflated correctly for it's load plus 5% for peace of mind, it will never be overloaded, so no failure due to underinflation. Truckers deal with a wide range of loaded weights and inflate for the heaviest load just as I do on my motorhome. A trucker is at his max load 80% or more of the time and a motorhome is close to the same weight 100% of the time.

A good discussion, but you are probably not going to change your program for your reasons, and I won't either. Over the 7 to 10 year life span of a motorhome tire, maybe none of it matters.
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Old 06-17-2014, 05:32 PM   #22
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[QUOTE=Crasher;2098725]
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Originally Posted by oildriller83 View Post
I would assume they publish this cause so many believe less pressure equals a smoother ride ( I don't, but won't argue the fact ) and the tire will fail under a heavy load at that psi?

You are correct that any overloaded tire will fail in time. Once loaded, a motorhome's weight will not increase more than a couple hundred pounds distributed over six or eight tires, so if inflated correctly for it's load plus 5% for peace of mind, it will never be overloaded, so no failure due to underinflation. Truckers deal with a wide range of loaded weights and inflate for the heaviest load just as I do on my motorhome. A trucker is at his max load 80% or more of the time and a motorhome is close to the same weight 100% of the time.

A good discussion, but you are probably not going to change your program for your reasons, and I won't either. Over the 7 to 10 year life span of a motorhome tire, maybe none of it matters.
That was basically my point. If a person were to "wear" a set out, rather than "time" them out, I could see good reasoning to possibly spend the extra money and do the research to know what to run. To me, driving 7k miles a year, doesn't warrant the risk of maybe the math being off. I've personally (like I said before, not saying it doesn't happen and maybe I've been lucky, or my rough ride tolerance is higher) not had to change tires out do to abnormal wear, crown wear or noticed a difference of ride quality while running max pressure.

I definitely wasn't trying to say anyone was wrong in doing so, just was trying to see if there were any other benefits that I hadn't heard of yet that might out weigh the ease of just running max and always being safe haha.
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Old 06-17-2014, 07:32 PM   #23
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Here is what I do. After weighing on six individual scales, I went to the load chart and found the recommended pressure for that weight. The fronts called for 108 psi. I set it at 115 psi when the morning temp was 60*. Different pressures on the drive 90*, and tag 80* due to less weight per tire and added 10%. I check the TPMS each morning before driving and after several months and over 6000 miles have found that the morning tire pressures are always between the recommended pressure and the max pressure on the tire. That includes elevations from 1000' up to 11,600' and temps from 40* up to 85* I have not added or released any pressure in that time. So, once the pressures are set, I just monitor them in the morning and watch for any adverse change during the day. Works for me.
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Old 06-17-2014, 07:46 PM   #24
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The reasoning for doing the four corner weighing of your coach, is to make sure you're running enough psi in each tire for the weight on that corner, right?

If this is correct, why not fill your tires to maximum air pressure for maximum weight rating per tire manufacture specs? Wouldn't this eliminate the need for constant weighing, if you change your load? I don't for see running them this way to take away life, since motor home tires time out anyways?
You weigh the 4 corners of your coach to ensure your load is distributed properly over each axle and tire in accordance with your vehicles weight allowance. improper weight distribution affects the suspension, braking, steering and tire wear. If weight is distributed properly, tire pressure will be the same in the rear tires and the same in the front tires.
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Old 06-17-2014, 08:04 PM   #25
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You weigh the 4 corners of your coach to ensure your load is distributed properly over each axle and tire in accordance with your vehicles weight allowance. improper weight distribution affects the suspension, braking, steering and tire wear. If weight is distributed properly, tire pressure will be the same in the rear tires and the same in the front tires.
Sorry, but it doesn't work that way on a 40'+ diesel pusher.Because of the length, a disproportional amount of weight is carried on the steer axle. A common scenario is 15,000# on the steer, 19,000# on the drive and 5500# on the tag. That equates to 7500 on each front, 4750 on each drive, and 2750 on each tag. There is no way to get them equal, thus different pressures are necessary for the best ride, traction and control.
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Old 06-17-2014, 09:47 PM   #26
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I don't drive a truck, I drive a motorhome. My weight stays pretty much the same. My old bones don't need the harsh ride of max inflated tires when a lesser pressure will do the job according to the manufacturer of the tire. If someone else wants to run unnecessary max pressure, go ahead, it's their their comfort that is being sacrificed.
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Old 06-17-2014, 11:08 PM   #27
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Still a newbie when it comes to driving class a's. When we picked up the coach the tires were at 110#. Started reducing psi by 5# until I got to 85# which seems to produce the best ride and handling. 20k miles so far and the tires look great and I still have all my fillings.


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Old 06-18-2014, 12:19 AM   #28
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why weigh all 4 corners, if your only going to air up both front tires the same no mater if 1 side is heaver than the other in the front ?
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