RV Manufacturer versus Tire Company air pressure settings

I want to again thank everyone who responded- the past weekend we had by far the most comfortable trip with the tires closer to Winnebago's recommended pressures- I'll now need to find a weigh station and dial it in further. All the advice was greatly appreciated!

Hikerdogs wrote:
............ It can also apply to the same brand, model and size made at a later date.

Remove "brand" from this statement and I will fully agree with you .
All tires of the same model,size and load rating will follow the same load/pressure tables regardless.

Jackie Treehorn wrote:
Winnebago suggests 70 psi for my front tires and 75 psi for the dual tires in the rear. The tire company has the fronts rated at 110 and the rears at 90. Which is the right way to air the rig up?

Go read your tire sidewall again.
It does NOT say "Inflate to 110psi"
What it does say is:
"Maximum load is xxxx# at a Maximum pressure of xxxpsi." (These are reduced for a dual configuration)
I suspect your Winnie is not loaded to the point where you are loading the tires to the maximum.
The numbers on the tire placard are what Winnebago considers appropriate for when your rig is loaded to its axle ratings.
Post 2001 or so I recall Winnie suggested increasing those by 5psi. That was CYA action followed by a LOT of Manufacturers after the Ford Explorer/Firestone debacle.
I suggest you use 75psi front and 80psi rear as a starting point. Those pressures are adequate for the loads you are running.
IF the rig feels a little squirmy, then by all means increase them a little until it feels better.
But running at 110psi and 90psi will probably result in a very harsh ride.

Jackie Treehorn wrote:
Winnebago suggests 70 psi for my front tires and 75 psi for the dual tires in the rear. The tire company has the fronts rated at 110 and the rears at 90. Which is the right way to air the rig up?

Neither in my opinion and since Winnebago didn't weigh your coach fully loaded with passengers and ready for the road. The tire manufacturer didn't do so either and are only stating max withstanding pressures without any consideration given to actual weight or the wheel's rating, so pumping up to 110psi on an older wheel that's only rated for 90psi, isn't a good idea either. I've never heard of a wheel exploding under pressure, whether old, damaged and rusty or not, but if it was to happen, then one should probably be cremated or have a closed casket for the services.
Anyway, weigh the coach axles individually and add a 10-15psi cushion over what's listed on the inflation chart for the many variables that one will encounter on any road trip.

I would once again have to agree with those that say the tire pressure placard on the motorhome applies to the tires originally installed on the chassis. It can also apply to the same brand, model and size made at a later date. However sometimes the tire manufacturer changes the construction of a particular model and updates the inflation tables.

Case and point are the Goodyear G670 RV tires. A specific example is the G670 size 245/70R19.5. Those manufactured prior to 6/28/2006 (I was in error in an earlier post when I stated the change was in 2002) have a minimum recommended pressure of 70 psi.

The same size and model tires built after 6/28/2006 have a minimum recommended pressure of 80 psi. Here's a link to an older Goodyear load and inflation table with this information.

http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

In the case that the owner selects a different brand of tires the original tire pressure placard also may not apply. Michelin model XRV size 245/70R19.5 load range F require 95 psi to support a load of 4080 lbs. as singles. The Goodyear G670's of the same size and load range require only 85 psi to carry the same load.

https://www.michelinb2b.com/wps/b2bcontent/PDF/RV_Tires_Brochure.pdf

As for who sets the tire pressures, I'm not sure. I do know that when the recommended tire pressure and lug nut torque changed on our 2001 Winnebago Adventurer the letter with the information and the updated placards came from Ford.

I just want to point out that the tire load tables are MINIMUMS! (or maximums, if you looked at it the other way). They are NOT recommendations.

I think it is advisable to inflate tires so that the max load is less than 85% of the rated load at that pressure.

And, NO! 85% will not result in center wear. Tires are not that sensitive to changes in inflation pressure, There are other things that have a much greater effect - the steer vs drive affects for one! (Steers wear the shoulders, drives wear the centers.)

Also, there is a rule of thumb that tires should not experience a pressure buildup more than 10% of the cold pressure. If you experience more than 10%, you need to do something - more inflation pressure, larger tire, reduced speed, etc.

If you experience more than a 15% pressure build up - STOP. You must do something immediately.

This is an easy test to do and one you can do continuously.

kaydeejay wrote:

More To See wrote:
Those plaques the RV manufactures put on vehicles spelling out tire pressures are absolutely dangerous. But I think they are required by the feds.

With not a clue in the world of what tires you are running on your rig how could they possibly be able to tell you what air pressures to run with.

How many rigs are out there right now running down the road with severely under inflated tires because somebody use those stupid plaque recommendations?

Perhaps a little work with a hammer and chisel might save some lives.

I call BS on these statements.

I suggest you retract them as what you are saying is incorrect, misleading and potentially dangerous!

The tire placard pressures stated by the Manufacturer are those required for the tires to run with axle loads at their maximum. Tires at the pressures on that placard are NOT "severely underinflated" unless the vehicle is also overloaded. You are right in that "they are required by the Feds". The Feds also require that the pressures are as I have stated.

Turning your statement around, the tire manufacturers have no idea what weight the tires will be carrying, so how can they know what pressure you should run?
(They provide load/inflation charts for that purpose. The numbers on the tire label will be very close to those chart numbers for the weight being carried)

(In the interests of full disclosure, those labels used to be part of my job at one of the "Big 3" so I do know what I am talking about!)

Keith,

I agree the placard is not under inflated, but I do not find it useful either. Placard says 120 psi just like max psi on the tires for all tires.

After weighing my MH I have 110 psi front 100 psi rear.

Placard pressure while safe is not a replacement for weighing my MH

Jackie Treehorn wrote:
Winnebago suggests 70 psi for my front tires and 75 psi for the dual tires in the rear. The tire company has the fronts rated at 110 and the rears at 90. Which is the right way to air the rig up?

Uusally Neither.. First you failed reading.. The tire does not say 100 PSI (or 90) it says

Maximum load of xxxxx pounds at maximum pressure of 110 (or 90) PSI

The key is in the part you failed to read, MAXIMUM LOAD and MAXIMUM pressure

The tire company has a chart or your tire

You park the tire on a scale (Instructions all over the forums for how to do this) find out the weight on the tire and inflate per chart.. NOTE; all 4 corners could end up diferent pressures.

The RB maker's pressure suggestions are or what they consider a typical loading of the RV.... And the odds of you being "Typical" approach zero,,, (That is not an insult, it is just a comment on whtat the manufacturer thinks is typical, Nobody loads the RV that way save the maker)

JohnnyT wrote:

wolfe10 wrote:


FACT: The GVWR sticker installed by the coach manufacturer is for the OE tires (yup, they DO know what they put on there) when loaded to GAWR.

Please provide facts that are contrary to this statement.

And, no, I would never suggest any method of accurate tire pressure determination without weighting each wheel position. Then, take the heavier wheel position on each axle to determine the correct minimum PSI for all tires on that axle from your tire manufacturers inflation table.

Unlike car tires, the correct PSI for the tires on our coach (per Michelin, not me) is 70 or 110 DEPENDING ON LOAD. That is a huge range and over or under inflating is quite likely if you don't know your actual weights.

Wolfe10 is on target with his post.. I would add in addition to weight the tire pressure is determined by make and tire model, tire size and whether single or dual position.


As was pointed out know your weights, and inflate according to tire manufacturer specification for model, tire size, and tire position

JohnnyT

Your both correct, but in the real world few people weigh their MH and even fewer get 4 corner weights. If you do not have a solution using axle weights your comments are next to worthless to the guy that has to go to truck scales to weigh their MH. Truck scales are available at 90% of the places I fuel my MH.

I bump my tire pressure on the tire pressure tables 5 psi. Perfect - NO But I am not significantly under inflated either.

The correct tire pressure is the pressure that gives you the best ride while going down the road. You will have to experiment with tire pressures (every time that you go out) to find what works best for you. I own a Winnebago and the manuals (Winnebago & Michelin) said 75 lbs. psi rear and 90 lbs. psi front. That didn't work for me it caused my coach to have tire squirm (wishy, washy, side to side feeling) I experimented with tire pressure and found 100 lbs. psi all around (all 6 tires) gave me the best ride! I got a good ride and my tires lasted 10 years at that tire pressure. Also be aware the lower the tire pressure (psi) that you run inside your tires the more heat builds up inside your tire! High heat is a enemy to tire wear and tire failure. Not trying to scare you just inform you to help you make a correct decision. I'm not a tire expert but I'm a retired over the road trucker 44-1/4 years driving and have owned a RV since 1976 so I know a little bit about tires, I've been around them most of my adult life. Great Question