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Old 04-16-2012, 06:34 PM   #15
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Our 34' weighed 9720 lbs in the front and 16520 lbs in the rear, loaded how we travel.....but some years ago. I have GY670s and based on the tire load/inflation table from the GY site, I run 95 front and 90 rear. That equates to 12,570 lbs capacity in the front and 21,340 lbs capacity in the rear. I have a little over 40,000 miles on the rear (2006 tires) and they wore equally across the tread, which tells me tire pressure was pretty good. The fronts have worn a bit on the outsides and I did a rotation to the rear a couple of years ago. The rears are at 8/32, which is half worn. I decided for our trip to Alaska I would put two new tires on the front and the fronts to the rear. The best rear (one that was originally on the front) I am carrying in a compartment unmounted; that way I have a known good spare, should I need to use it. I had no cracking or anything suspicious on the tires. My alignment had changed a bit from the alignment done a couple of years ago.

By the way, tire prices are absolutely nuts and going up frequently. I was quoted $698 per tire and thirty something for excise tax. In two weeks the price went up to $721 and over forty in excise tax. Remember that excise tax is a "luxury" tax and is based on weight.
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Old 04-16-2012, 07:13 PM   #16
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Quote:
Originally Posted by Algoma View Post
I don't know why people who do not have an Alpine Coach feel they have to put their spoke in. The answer is that the manufacturer's recommended pressures for a fully loaded coach are listed on the VIN plate located on the forward face of the bulkhead. When your coach is configured how you normally use it you should get it weighed and then you can reduce the pressure if your axle weights are below the maximum ratings. The Bridgestone website has a tire loading chart that you can use to determine the correct pressure. The H or G rating does not affect the tire pressure only the maximum load that the tire can handle.
FYI. The plate on my coach says 95psi front and 95psi rear. I run 95 front and 85 rear.
Didnt know you had to be an Alpine owner to know how to put air in a tire..

Quote:
Originally Posted by tiredvet View Post
Thanks for all the advice every one. I am going to go with 100 lbs front and 90 lbs in the rear. I will get more specific with the air pressure after I get back and load some items. Then I will get the coach weighed and adjust the tire pressure.Thanks for the offer Old Forester but I have down loaded the load data from Bridgestone already. If my coach was any bigger or it had any extra load I would run 105/95. Thanks again everyone, after We get back this Saturday I'll post a photo and add our coach to the Alpine Registry. Jim & Elissa Edmonds (not the ball player,I had the name first).
Sounds like a plan! Another reason to put a little more air in than your might need now is that you have no idea how long those tires have sat, or if they were inflated properly while doing so. By overfilling a bit, you take some of the flex out of the sidewalls and 'exercise' the tire more gently..
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Old 04-16-2012, 07:20 PM   #17
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Quote:
Originally Posted by Old Scout View Post
You cant exceed 110 PSI with your particular tires, but you can under-inflate them and under-inflation can definitely harm/ruin a tire.
I don't know about Bridgestones but on Michelin and GoodYear tires the pressure on the side of the tire (and in the charts) is the MINIMUM to support the maximum weight stated. You can exceed that if you want and lots of people do just to have a reserve for slow leaks.
Over pressure is not good, but still far better than under.
The pressures given on the weight sticker are for the rig with the tires as equipped at the factory at it's full rated weight. That weighted weight could be determined by the max weight the axles will take or the max weight the tires will take.
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Old 04-16-2012, 09:56 PM   #18
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Quote:
Originally Posted by Rich and Cork

By the way, tire prices are absolutely nuts and going up frequently. I was quoted $698 per tire and thirty something for excise tax. In two weeks the price went up to $721 and over forty in excise tax. Remember that excise tax is a "luxury" tax and is based on weight.
Rich, FET is based on the load capacity of the tire. It has been the same for 7 years. Calculated as follows:

As of January 1, 2005, the new method for calculating FET bases the amount of tax on the load capacity of the tire.

The new formula is:

For most radial truck tires:
FET = ((Max. single load capacity
in pounds - 3,500)ų10)x$0.0945

Much simpler, right?

But you said this is true only for "most" radial tires.

Yes we did. As it turns out, calculating FET for bias-ply tires is different. And, interestingly, it's also different for calculating FET for wide base radials. Here's the formula for those:

For bias and wide-base radials:
FET = ((Max. single load capacity
in pounds - 3,500)ų10)x$0.04725

That doesn't look simpler.

We didn't think so either, but that's the law Congress passed, effective January 1 of this year.

How do these new rules affect what we pay?

In virtually every case, FET has changed. Here are a few examples:

FET (before 1-1-05):
[Assumes all tires 295/75R22.5]
R287: $20.50
M726 EL: $31.10
R195F: $16.60

FET (after 1-1-05):
[Assumes all tires 295/75R22.5]
R287: $25.28, increase of $4.78
M726 EL: $25.28, decrease of $5.82
R195F: $25.28, increase of $8.68

Difference for 2 steer,
8 drive and 8 trailer tires:
$32.44 increase

That's an increase of almost $2.00 per tire.

So if your FET went up, the capacity of the tire went up ( G to H) or the dealer made a mistake. :-)
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Old 04-16-2012, 09:56 PM   #19
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Quote:
Originally Posted by Mr_D View Post
I don't know about Bridgestones but on Michelin and GoodYear tires the pressure on the side of the tire (and in the charts) is the MINIMUM to support the maximum weight stated. You can exceed that if you want and lots of people do just to have a reserve for slow leaks.
Over pressure is not good, but still far better than under.
This is absolutely wrong for Toyos, according to the Toyo load tables, which state (in red):

NEVER exceed the sidewall markings for the maximum loads and inflation pressures.


Furthermore, everyone here is talking about axle weights, but you need to be aware of the corner weights. Our passenger side rear is a couple of hundred pounds heavier than the driver's side, so those tires need a higher pressure. And since tires on both ends of an axle must be at the same pressure, all four tires in the rear must be inflated at a higher pressure than would be the case of simply weighing the axle and dividing by four.
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Old 04-16-2012, 10:33 PM   #20
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Originally Posted by JohnLori View Post
This is absolutely wrong according to the Toyo load tables, which state (in red):

NEVER exceed the sidewall markings for the maximum loads and inflation pressures.


Furthermore, everyone here is talking about axle weights, but you need to be aware of the corner weights. Our passenger side rear is a couple of hundred pounds heavier than the driver's side, so those tires need a higher pressure. And since tires on both ends of an axle must be at the same pressure, all four tires in the rear must be inflated at a higher pressure than would be the case of simply weighing the axle and dividing by four.
Please reread what I posted. No where in my post did I mention Toyo tires. In fact I SPECIFICALLY said it applied to Michelin and GoodYear (now I see it also applies to Firestone/Bridgestone as well). And yes, TOYO does follow different rules on their tires after all the problems they had on Country Coach MH's

Here's what Michelin, Firestone/Bridgestone and GoodYear say:
Quote:
From page 2 of the 04/09 Michelin RV Tire Guide: "If you look at the tire's sidewall, you'll see the maximum load capacity allowed for the size tire and load rating, and the minimum cold air inflation needed to carry the maximum load."

From the Firestone/Bridgestone RV tire guide:
Bear in mind that these are maximum ratings. The sidewall of the tire shows maximum load and minimum inflation pressure for that load

From page 6 of the GoodYear RV Tire and Care Guide
"How much air is enough?
The proper air inflation for your tires depends on how much your fully loaded RV or trailer weighs. Look at the sidewall of your RV tire and you’ll see the maximum load capacity for the tire size and load rating, as well as the minimum cold air inflation, needed to carry that maximum load."
Quote:
From TOYO
Q: What are the consequences of inflating the tires to accommodate the actual loads?
A: If the inflation pressure corresponds to the actual tire load according to the tire
manufacturer’s load and pressure table, the tire will be running at 100% of its rated load at that pressure. This practice may not provide sufficient safety margin. Any air pressure loss below the minimum required to carry the load can result in eventual tire failure.
But then they go ahead and publish a weight/pressure chart allowing lower pressure for RV's!! Go figure, they say one thing then recommend something different!

Also, you should ALWAYS use the heaviest "end" of an axle to determine the pressure across all tires on an axle.
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Old 04-16-2012, 10:56 PM   #21
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Relax. I was not accusing you of being incorrect--I simply felt that owners of Toyos should be made aware that the recommendations were different for Toyos. Thanks for expounding on the GY and Michelin recommendations.
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Old 04-16-2012, 11:18 PM   #22
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Originally Posted by JohnLori View Post
...


Furthermore, everyone here is talking about axle weights, but you need to be aware of the corner weights. Our passenger side rear is a couple of hundred pounds heavier than the driver's side, so those tires need a higher pressure. And since tires on both ends of an axle must be at the same pressure, all four tires in the rear must be inflated at a higher pressure than would be the case of simply weighing the axle and dividing by four.
Absolutely.. BUT If you do not know those corner weights, or even the actual axle weight, using the data plates weights, dividing by four, and adding in 10psi or so should suffice well enough to get home. He can weigh and do the exact calculations at a later date and when he's loaded for travel.
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Old 04-16-2012, 11:22 PM   #23
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The weight that a tire can support goes up as the air pressure in the tire increases. The limit that a tire can carry is based on the maximum weight it can carry at its MAXIMUM rated pressure. The max weight rating on the side of a Michelin tire is that maximum amount of weight the tire can support at the maximum air pressure the tire is designed to withstand. Which is the max inflation rate also printed on the tire.

So that minimum inflation pressure you reference to support the maximum weight is also happens to be the MAXIMUM pressure to which the tire can safely be inflated. NEVER EXCEED THAT MAX PRESSURE!!!! No matter what brand of tire. (Ask Tom in post #18 if you don't believe me. He knows his business.)
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Old 04-17-2012, 07:43 AM   #24
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Seems most opinions and some facts vary when it comes to tire pressure. The old-timers say that 100lbs front and back will get you home [talking fullsize 275/295[22.5] truck/Rv tires]. Seems most tires have a max inflation of either 110 or 120 [usually G rated vs H]. Example: havent verified it but suspect even 100lbs in a range H tire will cover most Alpine coaches [save for the overloaded 40ft fulltimer--"may God bless their hearts"]. Because of corner weight shifts, aggressive maneuvering, wind load, slow leaks, etc, the front axle is more critical. Generally, the rear "duals" have more flexibility. As long as you dont exceed max inflation of 110 or 120 PSI, you can decide for yourself the trade-offs between more comfort and a minimum margin of safety for/from under-inflation. Think we can all agree that under-inflation is the real enemy here. Safe travels......
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Old 04-17-2012, 12:56 PM   #25
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Think we can all agree that under-inflation is the real enemy here. Safe travels......
Yep!
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Old 04-20-2012, 10:46 PM   #26
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Just for fun! I didn't have time to write this, especially on an iPhone, it came from Bridgestone's "Real Questions-Real Answers". See "So why not just add more pressure" about 2/3's of the way down.

How does a tire full of air support all that load?
First of all, the tire doesn’t support the load. The pressurized air inside it does. The tire is just the container.* That might sound obvious, but it is critical to understand.
Why is that?
Because once you see that the tire is just the container, lots of other things become clear.

For example?
Try this experiment: Check the air pressure on a tire, then raise it with a jack until it no longer touches the ground. Check pressure again.
**** You’ll find that the pressure doesn’t change when you remove the load.* If you had 95 psi when it was on the ground, it will still have 95 psi when jacked up.



How can that be?
Because the tire is somewhat flexible, like a balloon.* When you press it against the ground, the flexibility of the tire keeps the air pressure constant. The shape
of the container changes, but not the pressure.

Then why do we have to increase pressure
when we increase load?
To control the amount of change in the shape of the tire. Imagine that you have two balloons * identical in size and shape * and you’ve inflated them to identical pressures.
**** Put them both on a glass-topped table. Place a book on top of one balloon, and two books on the other. If you crawl under the table and look up, you’ll see that the area of the balloons flattened against the glass is different.
**** It should come as no surprise that the balloon with two books has a bigger “footprint.”



How much bigger?
If you measure the flattened areas, you’ll find that the one supporting two books has about twice the footprint area of the one supporting one book.
**** The other big difference is that the balloon supporting two books is a lot more flattened. And that’s one of the reasons you have to increase tire pressure when you increase load.

To reduce the “squash”?
Absolutely. Remember, as a tire goes round and round, it is constantly cycling between the squashed, or “loaded” shape, and the un-squashed, or “unloaded” shape.
**** The bigger the difference between the loaded and unloaded shapes, the more flexing takes place, and the more heat is generated. And heat is one of the biggest enemies of tires. In fact, more tires probably are damaged by heat than by road hazards.

That’s one reason why a higher inflation pressure is needed for a higher load.* With a higher pressure, the tire flexes less, generating less damaging heat.
So why not just put more air in every tire?
For one thing, tires play a part in cushioning the load against road shocks.
**** Second, and even more important, the tire has to be built to take the increased pressure. Every tire has a maximum usable pressure * and a particular load it can handle at that pressure.*
**** If you need to increase load beyond that maximum, you must change to a tire suitable for the higher pressure.
**** Third, the amount of inflation in a tire also affects the footprint size and shape. And that is critical to traction and wear.

In what way?
Let’s go back to our balloons. This time, put one book on each balloon, but put half the pressure in one balloon.* We know from experience that the balloon with half the pressure will be more flattened, and the footprint will be a lot larger.

How much larger?
Just as when we used two books, the footprint will have about twice the area. We find there’s a relationship between the inflation pressure, load and footprint area.

What is the relationship?
As an approximation, the number of square inches of footprint area is about equal to what you get when you divide the load by the inflation pressure. (It’s not perfect, but it’s close enough for our purposes here.)



Wouldn’t you want a big footprint for traction?
Not necessarily. A spiked heel digs in a lot deeper than a tennis shoe * on a soft surface. That’s because the load is distributed over such a small area. But if you’re on a hard, smooth floor, you’re less likely to slip with a tennis shoe.
**** If there’s just a thin layer of wet or slick material, a higher inflation pressure and smaller footprint may help the tread bite through and grab a solid surface below.
**** On the other hand, on a thick, but soft surface, like deep mud, sand or mushy soil, a lower inflation pressure can distribute pressure over a larger area, so that the tire almost “floats” * like a snowshoe.
**** And if the surface is hard and dry, a low inflation pressure and large footprint produce lots of contact and traction, which is why Indy cars run on “slicks.”
**** Since inflation pressure controls the footprint size, we can see that the right pressure is not only important for controlling tire heat, but is vital for proper traction.

Somehow, it always comes back to inflation pressure, doesn’t it?
Absolutely. Many things affect traction, load capacity, tire wear and casing durability. And proper inflation pressure produces a tremendous benefit in all these areas * for just a very small investment in effort.
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Old 04-20-2012, 10:59 PM   #27
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Talking

Finally.......

Itís not 95 pounds, but 95 pounds per square inch of air pressure thatís doing the work.

Stepping off my box.
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Old 04-22-2012, 09:24 PM   #28
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