Tire psi

[macnut]

My good years say the tire pressure on the sidewall IS the max pressure for the tire, and the pressure on the sticker inside the coach is the minimum for the maximum weight. Sounds like it is very important to get this right...

[macnut]

X2 on Tireman9's web site....great resource.

Al

[cbeierl]

Originally Posted by Teamdjcc

So just to confirm, until I can weigh my MH. I should fill the tires up to what the placard says affixed to driver side, not what is on the side of the tires correct? Tire sidewalls say max 110 psi, however placard inside says 70 front, 75 rear. Thanks is for the help

And it's a 1996 winnebago adventurer 32. Has new tires from the previous owner. Can't wait to get out and use it.

If the current tires are the same as the original equipment ones (should be on the driver side placard) you should be able to use the pressures from that placard. Those pressures should correspond to those required to support the front and rear GAWR (Gross Axle Weight Rating) of your coach.

If the current tires are different from OEM then you should consult the tire manufacturers pressure tables for the pressure required to support the front and rear GAWR of your coach.

Once you can get axle (or ideally individual wheel) weights you may be able to reduce your pressure based on the tire manufacturer's tables if you are under your front and/or rear GAWR.

Finally many folks (myself included) will add 5lbs or so to the indicated pressures to allow a bit more margin for changing vehicle weights, etc. without having to be worried about being underinflated.

[Steve Ownby]

Originally Posted by macnut

My good years say the tire pressure on the sidewall IS the max pressure for the tire, and the pressure on the sticker inside the coach is the minimum for the maximum weight. Sounds like it is very important to get this right...

Here is a "cut & paste" from the Michelin RV Tires brochure:

PRESSURE REQUIREMENT The amount of pressure required in each tire depends on the weight of the fully loaded vehicle. So the RV owners cannot determine the tire’s correct pressure unless they know their vehicle’s actual weights. The maximum load capacity allowed for the size tire and load rating and the minimum cold inflation pressure needed to carry that maximum load are located on the tire’s sidewall. The lower the pressure, the lower the load that the tire can carry. A complete load and inflation table is available at www.michelinrvtires.com; MICHELIN®RV Tires: Guide For Proper Use and Maintenance and RV Tire Information –MWL43146; and the MICHELIN®Truck Tire Data Book –MWL40731.

So the pressure/weight molded into the sidewall on a Michelin tire is the minimum psi required to support the maximum weight.

[macnut]

Here is a cut and paste from theFord F53 manual....

"Always inflate your tires to the Ford recommended inflation pressure even if it is less than the maximum inflation pressure information found on the tire. The Ford recommended tire inflation pressure is found on the Safety Compliance Certification Label ."

Maybe someone out there can explain why there is a difference between Ford and Michelin statements....I have Goodyears on the Ford F53 chassis...could that be the reason?

Al

[jadatis]

Originally Posted by macnut

Here is a cut and paste from theFord F53 manual....

"Always inflate your tires to the Ford recommended inflation pressure even if it is less than the maximum inflation pressure information found on the tire. The Ford recommended tire inflation pressure is found on the Safety Compliance Certification Label ."

Maybe someone out there can explain why there is a difference between Ford and Michelin statements....I have Goodyears on the Ford F53 chassis...could that be the reason?

Al

There is a lot wrong in tire-pressure calculation , especially in America, I found out. Also the maximum load of some kind of tires are calculated to high in their maximum load by the tire-makers. I suspect the Firestone tires on the Ford Explorer to be one of them. A offroad looking tire with profile-blocks wich cover a large part of the sidewal. The tire-makers know this, but dont want us custumers to know it.
That is the reason , why Michelin and Ford give contradictionary information ( forgive missspelling, I am Dutch) .

About the pressure stated like this "maximum load xxx lbs AT yyy PSI( cold)".
This yyy is called the reference-pressure ( further Pr) and is lower then the maximum pressure of a tire. Concluded the maximum 1,4 times the referencepressure, by lists in wich 2 times the maximum load may be carried standing still, at 1,4 times the Pr. Normal car tires ( P-tires) and XL/reinforced/Extraload( different names for the same kind of tire) only give the maximum pressure on the sidewall , Pr is 35psi and 41psi for american tires. Extra is used for higher speed ,camber angle( alignment) and more load then printed maximum for lower speeds.
Even the TRA supports higer pressure then Pr for sertain conditions, of 10 psi for LT tires and even 20 psi for truck tires.
Read the next pdf from goodyear begin bottom of page 1 Inflation limitations.
http://www.goodyear.com/truck/pdf/edb_loads.pdf

[Steve Ownby]

Originally Posted by macnut

Here is a cut and paste from theFord F53 manual....

"Always inflate your tires to the Ford recommended inflation pressure even if it is less than the maximum inflation pressure information found on the tire. The Ford recommended tire inflation pressure is found on the Safety Compliance Certification Label ."

Maybe someone out there can explain why there is a difference between Ford and Michelin statements....I have Goodyears on the Ford F53 chassis...could that be the reason?

Al

This is not necessarily a difference. Since this is coming from the chassis builder, they must base the inflation pressure on the GAWR of their axles. Unless you are overloading your coach, that approach will protect you from under inflating your tires. I have to imagine most owners never weigh their coach and so would have no other guidance. If you inflate to the psi on the sidewall then you could possibly be substantially over inflated and this could effect your tire wear and result in a harsher ride. The very best method is to weigh each wheel position when loaded as normal and base your inflation on those weights. Use the heaviest wheel position on each axle. The Goodyear G670 has a reputation for "river wear" on the steer axle so many people add 5-10 psi to the steer tires to stop that wear pattern.

[Wayne M]

I posted this earlier:

"For every degree of temperature increase change there is a 2% increase change in air pressure. For every 1000 feet of increase in altitude there is a 0.48 degree increase in pressure."

The paragraph should read:

For every 10 degrees of temperature increase change there is a 2% increase change in air pressure. For every 1000 feet of increase in altitude there is a 0.48 degree increase in pressure.

( The information is taken out of the Goodyear manual, and other scientific studies.)

the inverse is true. For every 10 degrees of temperature decrease there is a 2% decrease in air pressure.

[lshew]

I have followed this thread about tire pressure. It has been interesting to see all the info. One thing that has been left out of this discussion is the wheel often has a maximum pressure rating. Certainly my aluminum RV wheels are stamped with a maximum pressure. It is also the same as the pressure recommended by the manufacturer. The weight of each coach would be important and then use the tire manufacturer's recommendations up to the maximum of the wheel max pressure.

My 2 cents.

[Wayne M]

Ishew,
Back several years ago the Keystone Montana had a wheel pressure metal embossed stamp on the inside of the rim for 80 psi max at such and such load rating. Keystone wanted that increased so the manufacturer of the rims placed a paper stick on the inside stating good for 110 psi.

Go figure.

You are correct though and everyone should know what that pressure is for the wheel before increasing to a tire that holds more pressure than the wheel was designed for.

[palehorse89]

It is a good thing trucking company's don't mess around checking their tire pressures (at service time unless trouble appears) as we would never have goods in our stores where we shop! Atruck weighing in at 80,000# unloads 50,000# of goods now the truck and trailer is at 30,000# and down the road he goes....... No tire adjustment. Only at service time would I check the pressure in my semi tires but I check them several times a day when stopped with a tire bat and when hitting them the sound should be the same and if it wasn't I would check that tire to make sure there was not a pressure problem. I understand that RV'ers are trying to adjust for the best ride they can get. You had ought to feel the hit on a bump in a semi that is empty at max tire pressure compared to loaded , but it is what it is, no time to adjust pressure all the time.As stated your all tires have a max inflation pressure right on them and you can run that, If you want to seek a better ride, weigh it and adjust pressure, it does not have to be exact. As far as temperatures and elevation...... what do you think truckers do when going from Canada in the winter on a trip to Florida or out west over the rockies......... THEY ROLL ! EMPTY OR LOADED max tire pressure (on sidewall, usually 120 psi on all big truck tires) Temperature and elevation is all factored into the tires when made. My opinion here is this subject is thought into way to much, but as always, what ever works for ya.....

[stuhly]

X 2

[monkey]

I just contacted Cooper Tires for an inflation chart as I just couldn't find one anywhere... Hopefully they will get back to me... Anybody else out there have one for Coopers ?? (Discover HT LT215 85R 16) I didn't mean to hi jack this thread, but I have read through many others here and couldn't find it anywhere. I do have a current weight on the mh.. Thanks.
Monkey

[Coaster1]

Originally Posted by palehorse89

It is a good thing trucking company's don't mess around checking their tire pressures (at service time unless trouble appears) as we would never have goods in our stores where we shop! Atruck weighing in at 80,000# unloads 50,000# of goods now the truck and trailer is at 30,000# and down the road he goes....... No tire adjustment. Only at service time would I check the pressure in my semi tires but I check them several times a day when stopped with a tire bat and when hitting them the sound should be the same and if it wasn't I would check that tire to make sure there was not a pressure problem. I understand that RV'ers are trying to adjust for the best ride they can get. You had ought to feel the hit on a bump in a semi that is empty at max tire pressure compared to loaded , but it is what it is, no time to adjust pressure all the time.As stated your all tires have a max inflation pressure right on them and you can run that, If you want to seek a better ride, weigh it and adjust pressure, it does not have to be exact. As far as temperatures and elevation...... what do you think truckers do when going from Canada in the winter on a trip to Florida or out west over the rockies......... THEY ROLL ! EMPTY OR LOADED max tire pressure (on sidewall, usually 120 psi on all big truck tires) Temperature and elevation is all factored into the tires when made. My opinion here is this subject is thought into way to much, but as always, what ever works for ya.....

What he said.