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Old 10-08-2013, 02:50 PM   #15
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Had the coach weight today. From the Michelin web site, I can have 70lbs front and 75 rear. Set the tires to those numbers and it feels a bit better. Next trip will tell. Thanks All.......
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Old 11-12-2013, 01:55 PM   #16
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So many theories on tire pressure. I had front and rear of '05 Sun Voyager 30' Gulf Stream, Ford Chassis Class A weighed and within limits. My new Goodyear 19.5 tires show 110 PSI max, motorhome manufacturer wall decal shows 80 PSI is correct. The Goodyear dealer says ride with 105PSI. Yesterday a tech online at Ford Motorhome sections says they recommend 85-90PSI.
Now I understand... will go with 90PSI while on next trip looking for teeth from last month's drive Texas to Yosemite.
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Old 11-12-2013, 02:01 PM   #17
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Check online goodyear inflation table and sdjust according to coach weight. I'm at 75 psi front now. No bubble and no excess heat after long drive. Much better ride and handles just fine.
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Old 11-12-2013, 03:11 PM   #18
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Originally Posted by dennis45 View Post
I agree, as long as they are carrying the same weight. Is this not the reason for weighing each corner?
IMHO, If the tire is carrying a higher weight it requires a higher operating pressure to prevent the side wall from over flexing. As per the Mfg Tire Chart.
friction caused by sidewall flexing, results in heat. Measure the temperature and you can tell if the side wall is doing its job that it is rated for.

Dennis, that is not information as I understand it. The manufacturer's say to weigh each corner and whatever corner is the heaviest that is the weight to use across the axle. If you have 105 on one side you should have 105 on the other side.

Here is a link that all RV owners should read:

RV Tire Safety with Roger Marble. Roger is known on this web site as Tireman9.

Edited:
From the Michelin RV Tire Guide.

"Let's consider an RV running on 275/80R22.5 XZA LRG tires, with actual corner weights of 5,400 lbs. on the left front tire, 5,175 lbs on the right front tire, 8,500 lbs. on the left rear duals and 9,200 lbs. on the right rear duals. For control of your RV, it is critical that the tire pressures be the same across an axle. Therefore we must "overinflate" the right front tire and the left rear duals......"

The bold in the above quote is mine to indicate their recommendation. They go on to use the charts to determine correct pressures for the maximum load based on the heaviest corner weight.

Double Edit:
Fond the link: MichelyinRV Load Inflations
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Old 11-12-2013, 03:56 PM   #19
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I just re-read this string again from the beginning. Great stuff everyone! So this is what I get..... inflate tires same pressure side to side on each axle. Done. Weigh each corner of coach. Can't so did each end. I looked on Michelin inflation chart and inflated 10lbs higher than the weight chart showed for the weight of coach. Results are 75 front and 80 rear duals. The coach handles great and much improved ride. MPG seems the same. Much less rattles!
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Old 11-12-2013, 04:04 PM   #20
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I just re-read this string again from the beginning. Great stuff everyone! So this is what I get..... inflate tires same pressure side to side on each axle. Done. Weigh each corner of coach. Can't so did each end. I looked on Michelin inflation chart and inflated 10lbs higher than the weight chart showed for the weight of coach. Results are 75 front and 80 rear duals. The coach handles great and much improved ride. MPG seems the same. Much less rattles!
You've done you homework & learned well. Just be sure to watch the age & decide in advance, what your replacement age is going to be.
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Old 11-12-2013, 04:05 PM   #21
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One more tidbit for everyone. I added air suspension to aft end of front leaf springs and simple airbags to rear suspension. Huge improvement in every aspect of steering, drifting and blowing around from other trucks passing and side winds.
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Old 11-20-2013, 10:25 PM   #22
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To be honest, I would not inflate my tires just enough to cover the weight I'm carrying just to do away with ride harshness. Having been a truck driver for 40 yrs now, I don't ever recall a trucker adjusting tire pressure for a particular load. On my coach, I run my 22.5 tires at 105psi cold. The pressure will go up to about 115-120 when they are hot. Works for me. Also, when you run more pressure, you may have a harsher ride, but you should have less rolling resistance, better mpg.

As for weighing each corner, well I've never seen that either in trucking. What if you are a little over on, say the right rear. What are you going to do, buy a higher load range tire for that wheel? That would seem kinda silly. If you're right at the load limit of your tires or axels, you probably ought to get rid of some weight or buy a bigger rig.
Exactly!

Talking about "weighing each corner," etc. doesn't the coach manufacturer 'weigh' before they install tires.

Read what the tire manufacturer says on the tire.

Automobile tire 'manufacturer' will say 44# max. right on the side of the tire. The Mexican manufacturer of the vehicle (GM), says on the driver's door placard that 35# is the max, on the very same tire! Who you gonna believe?

Split the difference and don't try an over analyze. The voice of experience like the man quoted is who I listen to.
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Old 11-21-2013, 10:00 AM   #23
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As a "former" tire man turned A.S.E. Certified technician working on RV chassis steering and suspension, I will have to say "NO" the coach manufacturer doesn't weigh each one before recommending tire pressure.There have been several "recalls" where the coach manufacturer has had to upgrade front tires due to overloaded conditions.Also they don't know how much your belongings add to the weight.We use the tire manufacturerers charts and go up from the minimum recommended pressure on an as-needed basis.Chassis manufacturers have "guidelines" that coach builders don't always follow.Just my two cents worth
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Old 11-21-2013, 10:05 AM   #24
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Exactly!

Talking about "weighing each corner," etc. doesn't the coach manufacturer 'weigh' before they install tires.

Read what the tire manufacturer says on the tire.

Automobile tire 'manufacturer' will say 44# max. right on the side of the tire. The Mexican manufacturer of the vehicle (GM), says on the driver's door placard that 35# is the max, on the very same tire! Who you gonna believe?

Split the difference and don't try an over analyze. The voice of experience like the man quoted is who I listen to.
Couple of problems with this ...

The coach manufacturer doesn't install the tire, the chassis manufacturer does, and that same chassis can be used by a number of coach builders for a number of different models and floor plans with different weights. The tire's maximum load capacity is only one factor limiting the coach weight for that wheel, and often not the critical one. If the GAWR for that axle or the GVWR for the entire coach effectively limits that wheel position to less than the tire's weight capacity, the tire will (or should) not be loaded near its max weight, and therefore doesn't need the pressure printed on the sidewall (which is the pressure required to carry the maximum load).

In the case of RV tires, yes, the tire manufacturer prints the pressure for max weight on the sidewall, but they also print the weight/pressure tables that show you how to determine the appropriate pressures for your particular coach, once you have it weighed. The coach manufacturer puts a tire pressure placard in your coach, but it is based on the maximum allowable loading, since the manufacturer doesn't know how heavily you will actually load your coach.

To sum up:
- the tire manufacturer gives you the pressure for the tire's max load capacity, but doesn't know what coach will be built on it
- the coach manufacturer gives you the pressure for the coach's max load capacity, but doesn't know what you will put in it
- the tire manufacturer gives you the info to calculate the correct pressures for your individual situation

Hey, if some folks don't want to go to that trouble, that's their prerogative. But I (and others) will use the tools made available to me BY THE TIRE MANUFACTURER to calculate the pressures needed for my coach, so I can have a safe and comfortable ride ... and then I'll add a 5-lb. or so fudge factor just for safety.
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Old 11-21-2013, 10:15 AM   #25
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Well put!. As I said earlier, I got front and back weights, adjusted the pressure accordingly (about 75lbs) and am happy with the improved ride and handling.
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Old 11-21-2013, 10:55 AM   #26
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I had my coach weighted at the FMCA Rally in Albany,Or (4 corner wt) and I'm over wt in the rear by 1150lbs and under in the front by 730lbs. In January I got a new set of Michelin 295/80R22.5 XZA2 with a max PSI of 120lbs. With a combined wt of 33,620lbs FR 6,405lbs-FL 6,065lbs RR 10,195lbs-LR 10,955lbs I have to run 105 PSI in the front and 100 PSI in the rear. This is the only way to get a true wt reading and now I know what PSI to run, money well spent. Must be the steel and brass radiator on the LR and not the way the wife packed the coach.
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Old 11-21-2013, 07:12 PM   #27
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I'll add some more fuel to this fire;

As for weighing each corner vs weighing each axle - without knowing your corner weights you can potentially be under your weight limit for an axle but still be overweight on a wheel. I'll use my own rig as an example. My corner weights are as follows:

right front = 3500 lbs
left front = 3240 lbs
right rear = 6280 lbs
left rear = 6870 lbs

Now, if I were to only weigh by each axle I would come up with:

front = 6740 lbs
rear = 13150 lbs

To use the load tables I would divide each axle weight in half to find out the individual weights - this gives me:

front axle would be 6740/2=3370 lbs
rear axle would be 13150/2=6575 lbs

Now if I use those weights to inflate each tire the right front tire would be underinflated by 130 lbs of weight. Admittedly that's not much, but it could mean the difference between safe and unsafe. The left rear, on the other hand, would be underinflated by 295 lbs weight - a more significant number.

So the solution is to know the weight of each corner, and use the higher weight on each axle as the weight when determining the inflation pressure. That way, no individual tire will be overloaded.

As for the numbers written on placards, sidewalls, etc. - the number on the sidewall is the maximum that a particular tire is designed for, and the number printed on the placard is based on the GAWR since the manufacturer has no way of knowing how you will load up your rig. They do, however, know how much weight each axle is designed to carry, so they use that number to assign a recommended pressure.

There is nothing wrong with using pressures based on actual weight, maximum weight ratings of the axles, or maximum design rating of the tire - all will result in a safe tire. But, you have to be careful: some manufacturers may spec their wheels based on the weight rating of the axle and not the tire. You could end up with a wheel rated for 100psi and a tire rated for 115 psi - if you inflate that tire to 115 psi it may compromise the wheel in a catastrophic way. This can also happen if you replace the original tires with a tire of a higer weight rating - you are likely to exceed the design specs of the wheels.
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Old 11-24-2013, 10:20 AM   #28
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Much Thanks, Wayne.

Here is a link that all RV owners should read:

RV Tire Safety with Roger Marble. Roger is known on this web site as Tireman9.

Double Edit:
Fond the link: MichelyinRV Load Inflations[/QUOTE]

Just read a few Roger Marble articles. Sometimes I'm amazed at how much I don't know.

If it wasn't 12 friggen degrees gusting to 25 knots, I'd go out and check my RV's tire pressures. Really appreciate the heads up sergeant and thank you for your service.

Key West NAS here we come.

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