Tire Pressure Questions

[TheArthurs]

Our winnebago sticker says cold pressure should be 95 PSI
Our actual tires say cold pressure should be 110 PSI

Which should we be going with?
Also, looking at the tire picture, what does the 138/135L mean?

We have 2005 Itasca Meridian P39k

Thanks
Raymond and Geni

[be happy]

There are tire pressure pros here who know a lot more than I. However I go by the sticker that Winnebago has on the side of your unit, or as close to it. My 07 Meridian a past owner has put tire pressure monitors on the rear that is set for 100psi so I leave that alone. As for the front I have what the sticker says. Can not help on the other question.

[creativepart]

Those are Semi-Truck tires, not RV tires. 135 is the Load Index and L is the Speed Rating.

The MAX tire pressure on the tire is not the same as the placard inside the RV. Plus, the placard is referring to RV tires not commercial truck tires.

I don’t know enough about Commercial Truck tires to comment. There are threads on this subject at iRV2 Forums. What I’ve heard people say is they are rougher riding tires and that Folks buy them because they cost less than RV tires.

[TheArthurs]

Originally Posted by creativepart

Those are Semi-Truck tires, not RV tires. 135 is the Load Index and L is the Speed Rating.

The MAX tire pressure on the tire is not the same as the placard inside the RV. Plus, the placard is referring to RV tires not commercial truck tires.

I don’t know enough about Commercial Truck tires to comment. There are threads on this subject at iRV2 Forums. What I’ve heard people say is they are rougher riding tires and that Folks buy them because they cost less than RV tires.

Thanks for the link creativepart! I found my answer. I will keep my pressures with the recommended placard psi as this is the safest per Winnebago

[creativepart]

Actually, you'll get a better ride and better handling if you get your FULLY loaded RV weighed and then use your exact tire's load rating chart to set the PSI based on your actual RV weight. The placard on the RV is generally too high by 10 psi or so.

My chart says 95 front and 100 rear but after careful weighing we are using 85 front and 93 rear. It made a huge difference in ride.

By FULLY loaded it means a worst case scenario - full water tank, full fuel tanks, all your stuff, loaded to go on a trip. Then you head to a CAT Scale and get each axle weighed. Then consult your tire charts and add about 5 psi to the number shown for your weight there.

[Gary the Wombat]

The pressure shown on the tire is the maximum pressure for that tire. But the tire manufacturer of course has no idea what vehicle you are using it on. The Winnie sticker is what they recommend based on the size of your vehicle and approximate weight.

Of course, the right way to figure it out is to have your vehicle weighed at each corner with all the stuff you normally carry, and then refer to the tire manufacturers charts if available.

[drurytr]

We have a Itasca Ellipse and the winnebago sticker told us 120psi all around. we had coach weighed at Freightliner and then told 120psi in steer and 90 psi in rears. the change made a huge difference in smother ride. Its the weight of your rig that determines tire pressure

[bamaboy473]

So long as you use your TPMS and all tires' pressure/temps stay in the same range, then the comfort of your ride is probably the deciding factor. Weight on front and rear axles gives you the best starting point, as previously stated.

I'm a bit of a renegade about pressures because I want the smoothest ride possible for my bride's comfort (even with air bags). My suggested pressure is 120psi, and I set fronts at 115 and rears at 112. While driving the pressures all go over 120, and there is a difference in smooth riding.

I use TPMS religiously, and temps are always within 5-10 degrees of ambient air temp. Low tire pressure makes temps go UP, so staying within that normal range suggests to me that all is fine.

[GTobey]

Originally Posted by drurytr

We have a Itasca Ellipse and the winnebago sticker told us 120psi all around. we had coach weighed at Freightliner and then told 120psi in steer and 90 psi in rears. the change made a huge difference in smother ride. Its the weight of your rig that determines tire pressure

The factory service at Freightliner in Gaffney, SC is one of the absolute best places to determine your actual proper tire pressure, by doing exactly this, weighing on all 4 corners. You do that by weighing a coach that is "fully loaded" with what you would fill it with, if you were leaving on a long trip, loaded to the max. It is the best way to get side to side weights, and front to rear weights, and to be sure you do not exceed the axle weight limits. Obviously you do not want it heavy on one side, and not heavily loaded in the rear. It can make the coach hard to handle, sometimes dangerously, in addition to riding roughly. There can and will be some variation in side to side, but the closer to balanced it is, the better it handles in curves.

Fully loaded, they determined that my coach's cold tire pressures(before the sun hits them and before we drive on them regardless of the temperature outside*) should be 108psi rears, and 100psi front. These load range G Michelin tires are rated to hold 110psi max cold. Michelin makes a chart available on line that shows the cold tire pressure for the weight that tire is carrying. You set all tires on an axle to the pressure recommended for the heaviest side. Do not set one side higher or lower than the other.

We have gone 30k miles keeping pressures where they recommended, and going over CAT scales occasionally to verify my weights, and tires are doing well. Performed flawlessly from VA all through Canada, Alaska, and back.

*According to Mike @ Freightliner, check and set your pressures before you drive on them. Doesn't matter if the temperature drops during the day while driving, just remember to check them again the next morning before leaving, and adjust as necessary. He advised us that tire pressures can vary 12% or more from cold to operating temperature. But we don't set our pressures at operating temperature, only when cold.

I wish you safe travels and enjoyable times!

[SaltLife]

Originally Posted by TheArthurs

Thanks for the link creativepart! I found my answer. I will keep my pressures with the recommended placard psi as this is the safest per Winnebago

Perfect....

[rk911]

Originally Posted by creativepart

Actually, you'll get a better ride and better handling if you get your FULLY loaded RV weighed and then use your exact tire's load rating chart to set the PSI based on your actual RV weight. The placard on the RV is generally too high by 10 psi or so.

My chart says 95 front and 100 rear but after careful weighing we are using 85 front and 93 rear. It made a huge difference in ride.

By FULLY loaded it means a worst case scenario - full water tank, full fuel tanks, all your stuff, loaded to go on a trip. Then you head to a CAT Scale and get each axle weighed. Then consult your tire charts and add about 5 psi to the number shown for your weight there.

100% correct.

[BobC]

Tireman9, a Winnieoners member and retired tire engineer recommends adding 10% to the weight table PSIs as a safety margin.

[SaltLife]

Just like a car or truck, use the recommendation on the door, or placard in this case. The pressure has nothing to do with ride, but everything to do with tire wear and safety. A better ride just happens to be the result of the pressure being lower than the max rating on the tire..

[rk911]

Originally Posted by SaltLife

Just like a car or truck, use the recommendation on the door, or placard in this case. The pressure has nothing to do with ride, but everything to do with tire wear and safety. A better ride just happens to be the result of the pressure being lower than the max rating on the tire..

the problem with that is you don't know what the placard recommendation is based on....GVWR, weight of the empty coach as it rolled off the line, etc. the proper way is to inflate for the actual load being carried.

fully load your coach, get individual axle weights (at a minimum. 4-corner weights are best) and then consult the tire mfg's inflation chart. add a bit to that if it makes you feel better...5psi, 10psi, X%...whatever.

plan b, which some advocate, is simply using the max psi on the tire itself. that keeps things simple but you'll get a hard ride and possibly some handling issues.

[SaltLife]

Originally Posted by rk911

plan b, which some advocate, is simply using the max psi on the tire itself. that keeps things simple but you'll get a hard ride and possibly some handling issues.

That would be a bad idea. Terrible tire wear, center of the tire would wear out way before the edges. Less tire footprint on the road, less traction... That's why the best default is the placard...imo

[rk911]

Originally Posted by SaltLife

That would be a bad idea. Terrible tire wear, center of the tire would wear out way before the edges. Less tire footprint on the road, less traction... That's why the best default is the placard...imo

totally agree with regards to 'plan b'...max pressure. but totally disagree with regards to the placard. load the coach...fully.., weight it as i wrote and inflate for the load as per the inflation table. know. don't guess or assume.

[BobC]

If your tires are not stock for your rig, you can't count on the placard, but will have to locate the applicable weight/psi chart for your tires.

[Wyatt]

So, according to this tab on my coach, if I’m maxed out on weight at 16,000 lbs, I should be using 82 psi on all tires? The Goodyear table says lower... thoughts?

[Jim_HiTek]

Wow, so much info.

Here's the deal. That placard was put there when the RV was manufactured and left the plant with a certain brand and type of tire and with certain loading that they mysteriously determined.

Once they've been changed for a different brand, type, or even if a few years have past for that same tire type, that placard is worthless. Ignore it and get a weight for your axles, than use the tire manufacturers charts to set tire pressures based on that weight. If you get a four corner weight, recommended, then the highest weight on that axle determines the pressure in ALL the tires on that axle.

Keep in mind that RV manufacturers are trying to give the softest most cushy ride...without care for tire life. Whereas an RV owner might be more interested in tire life than cushioning. So even in a brand new RV, might check the weight you're running at, vs the tire manufacturers pressure charts, and again, set it at that, not what the placard says.

[NeilV]

Originally Posted by TheArthurs

Our winnebago sticker says cold pressure should be 95 PSI
Our actual tires say cold pressure should be 110 PSI

Which should we be going with?
Also, looking at the tire picture, what does the 138/135L mean?

We have 2005 Itasca Meridian P39k

Thanks
Raymond and Geni

You go by neither. The pressure on the placard is an approximate while whats stamped on the tires the maximum safe inflation at the highest load the tire is capable of handling. For best ride and tire life you need to get the coach weighed when loaded exactly as it will be when you travel with it and then inflate the tires according to the tire manufacturers inflation table for that size and type of tire.

You may need to redistribute your stuff too if the load is not balanced well front to back or side to side taking care to not go over the front or rear axles load rating or the tires. After the load is balanced and the tires are inflated to match the load then its time to take the coach as loaded the way you will be traveling with it to have it aligned.


Those other numbers are the speed and load rating of the Toyo M154 tires.

"The M154 is a deep all-position tire designed for regional and urban service in the highest-scrub environments, where tread wear is the primary reason for tire removal. Users can typically expect a return on their investment in less than a year with this SmartWay-verified tire. Excellent, even wear in miles per 32nd and a deep tread up to 22/32" deliver maximum removal mileage, even in the drive position. Excellent fuel efficiency and high mileage make the M154 the leading value alternative tire for regional to urban high-scrub applications."

Speed Rating is L so 75 MPH max and load rating is stated for single and dual use so 138 = 5205 lbs each in single application and 135 = 4805 lbs each in dual applications.

See: https://www.toyotires.com/commercial...-position-tire