Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: "Irish" on March 20, 2019, 11:40:03 am
Title: Tire pressure question - without scales
Post by: "Irish" on March 20, 2019, 11:40:03 am
Looks like we may be the new owners of a 99 U270, its 36' without a slide so I would assume the left right balance must be pretty even. If the deal goes ahead we will not be able to weigh the unit before driving 1200 miles home. THE QUESTION IS: what is the rule of thumb for this coach when inflating the tires, the LBS for the front and the rear. I have been all over the forum looking for a simple answer.
Title: Re: Tire pressure question - without scales
Post by: wolfe10 on March 20, 2019, 11:42:35 am
David,
The simple and safe answer before weighing (axle weights can be done at many truck stops) is to go by the GVWR plaque outboard of the driver's seat.
It gives proper PSI if each axle is loaded to its GAWR (Gross Axle Weight Rating).
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 20, 2019, 11:46:49 am
Looks like we may be the new owners of a 99 U270, its 36' without a slide so I would assume the left right balance must be pretty even. If the deal goes ahead we will not be able to weigh the unit before driving 1200 miles home. THE QUESTION IS: what is the rule of thumb for this coach when inflating the tires, the LBS for the front and the rear. I have been all over the forum looking for a simple answer.
There isn't a single simple answer. If you can weigh each axle then using the load/inllflation table for the exact tires you have set the cold inflation pressure to the minimum for your measured load plus 5 PSI as a safety margin.
One conservative approach would be to set the cold tire pressure to the minimum pressure for the maximum load, which is the pressure shown on the sidewall. This will result in minimum sidewall flex, but will also probably result in a harsher ride than is needed.
Title: Re: Tire pressure question - without scales
Post by: jor on March 20, 2019, 11:47:05 am
This is great news! Also, you will find that the coach is pretty well balanced so you don't really need to worry much about how you load it before you get actual weights. Need to see some photos of that baby when you get goin'. jor
Title: Re: Tire pressure question - without scales
Post by: Pierce & Gaylie Stewart on March 20, 2019, 11:50:40 am
Looks like we may be the new owners of a 99 U270, its 36' without a slide so I would assume the left right balance must be pretty even. If the deal goes ahead we will not be able to weigh the unit before driving 1200 miles home. THE QUESTION IS: what is the rule of thumb for this coach when inflating the tires, the LBS for the front and the rear. I have been all over the forum looking for a simple answer.
If your generator is on the driver's side, the propane and diesel fuel tanks are on the passenger's side and don't go all the way across the vehicle. So, as you use fuel and propane, the left and right weights change. Multiply 150 gallons of diesel by a rounded figure of 7 lbs per gallon and you can see that there is quite a bit off difference possible on not only the front tires but also a smaller difference in the back.
So, what difference does this make in tire pressures? None to me.
Pierce
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 20, 2019, 11:56:39 am
The simple and safe answer before weighing (axle weights can be done at many truck stops) is to go by the GVWR plaque outboard of the driver's seat.
It gives proper PSI if each axle is loaded to its GAWR (Gross Axle Weight Rating).
This answer is accurate if the coach still has the same brand, size and load-rating tires as it came with originally. If not, then it might not be accurate.
Title: Re: Tire pressure question - without scales
Post by: Mike Leary (RIP) on March 20, 2019, 11:58:33 am
Brett's answer is right......to a point. The GAWR is just that, a rating. Who knows how much 'stuff' is on board? Who knows if things have been changed in the coach? (battery type and placement comes to mind, as well as different tires)). It's worth the money to weigh all four corners, individually. Then you can either talk with the tire guy or go on-line to find the load rating and PSI for the particular tire. Case in point; when we bought this coach, she rode real hard, had it weighed, checked with Michelin and found the tires were overinflated by 20 psi! Went to 85 front, 80 stern and got my smooth ride back! b^.^d
Title: Re: Tire pressure question - without scales
Post by: Tim Fiedler on March 20, 2019, 12:20:08 pm
I would use Brett's answer 9as usual) until you can get a four corner weight.
On the way home, you can spend a few bucks at a truckstop with a "CAT" brand scale and get a total weight and a per axle weight if you want something that is more accurate.
Coaches are usually weighed as follows:
Fuel - Fuel Propane - Full Fresh Water - Full Black Tank - Empty Grey Tank - Empty
Normal occupants on board.
Have a great time - where are you taking delivery?
Title: Re: Tire pressure question - without scales
Post by: Travelin' Man (RIP) on March 20, 2019, 12:22:36 pm
we will not be able to weigh the unit before driving 1200 miles home.
You should be able to weigh it enroute. Most truckstops have scales, or a weigh station that's closed may leave the scale on. Run the maximum amount of air according to the sidewall info until you get to a scale, assuming that the tires are the correct ones for your rig and not outdated.
Title: Re: Tire pressure question - without scales
Post by: Mike Leary (RIP) on March 20, 2019, 12:38:09 pm
What Tim said, X-2. Except I added this to ours (as per Brett): 1/2 tank of grey water & half of black. It all counts.
Title: Re: Tire pressure question - without scales
Post by: Mike Leary (RIP) on March 20, 2019, 02:25:52 pm
You should be able to weigh it enroute. Most truckstops have scales, or a weigh station that's closed may leave the scale on. Run the maximum amount of air according to the sidewall info until you get to a scale, assuming that the tires are the correct ones for your rig and not outdated.
I know, in Washington & Oregon, they leave the scales on. By turning the coach around, it can be weighed on each of all fours. ^.^d
Title: Re: Tire pressure question - without scales
Post by: Dub on March 20, 2019, 03:30:10 pm
Glad you found one David.
Title: Re: Tire pressure question - without scales
Post by: jor on March 20, 2019, 03:38:54 pm
I imagine the 99 weight is very similar to my 97. If so, you will be pleased by the cargo carrying capacity. This 97 weighs 26.5K fully loaded as Tim indicated above. The GVWR is 30K, leaving an extra 3,500 pounds capacity. I never have understood how they arrive at these capacities. For example, our 95 300 (bigger engine & trans) had the same GVWR of 30K but when fully loaded we only had about 1K capacity remaining. Our 320 had a GVWR of 34,880#. It gets really interesting when you figure horsepower to weight ratios and different gearing. I asked Triana about it one time but he said he didn't know how it's figured. Glad you got your motorhome! jor
Title: Re: Tire pressure question - without scales
Post by: Keith and Joyce on March 20, 2019, 04:20:40 pm
As it's your delivery trip just inflate to the recommended pressures as Brett says. Better to be over than under inflated as that's what causes tire to overheat and fail. Have the coach weighed then you can decide on proper pressures as per the manufacture pressure chart. Make sure that the tire sizes are the same as on the plate by the drivers seat.
Keith
Title: Re: Tire pressure question - without scales
Post by: Old phart phred on March 20, 2019, 04:44:29 pm
GVRW is the sum of the axle ratings I believe My coach has a 9k front axle and a 17.5k rear so GVRW is 26.5k. coach weighed about 22k with pots, pans, basic tools and other stuff when I drove it home.
Title: Re: Tire pressure question - without scales
Post by: ohsonew on March 20, 2019, 05:11:29 pm
Congratulations on the new coach. Enjoy and yeah what they all said :))
Larry
Title: Re: Tire pressure question - without scales
Post by: Tom Lang on March 20, 2019, 05:28:11 pm
The sidewall pressures will be way too much air. Just go with what is on the plaque on the wall next to the driver seat. After having mine weighed on four corners, it ended up needing just that pressure, plus 5 psi for safety. And you can get it weighed per axle just about anywhere.
By the way, mine is just about dead even side to side.
Title: Re: Tire pressure question - without scales
Post by: Barry & Cindy on March 20, 2019, 10:22:59 pm
We try to keep about 100 psi in each of our Michelin xza-3 load-range-H tires. All deduced from 9 weigh points done a several closed truck weigh stations and at feed stores.
Here is our Excel spreadsheet that puts our nine points of measurements together to make information out of data. . .
Title: Re: Tire pressure question - without scales
Post by: TulsaTrent on March 20, 2019, 11:49:59 pm
We had our coach weighed at Escapees in Livingston, TX. Using the weights and the Michelin charts AND after adding 5 extra pounds, our pressures are:
Front: 105 psi,
Rear: 85 psi.
The balance from the side-to-side weights seemed to impress the technician.
Trent
Title: Re: Tire pressure question - without scales
Post by: Tim on March 22, 2019, 06:09:10 am
I do not weigh my U270, and SIMPLY use 105 PSI cold in ALL tires because pressure varies with temperature due to:
- Asymmetrical sunshine - Daily temperature variation - Driving
There were no issues in last 12,000 miles. My tires are rated at 120PSI cold maximum, and I don't succumb to "Pressure Shaming". ;)
I HIGHLY recommend a TPMS.
Title: Re: Tire pressure question - without scales
Post by: turbojack on March 22, 2019, 09:05:39 am
I was looking at Barry's spreadsheet and seeing the rear axle being overloaded. I have never weighed our and wondering if mine is overloaded also
Title: Re: Tire pressure question - without scales
Post by: Chuck & Jeannie on March 22, 2019, 10:02:41 am
We got our coach 4-corner weighed at Escapees in Livingston, TX. Found out we are slightly overweight on our front axel, and 900 pounds over the total GVWR. We weighed with full water and fuel tanks, and 1/2 tank of propane. The tech suggested we could travel with less fresh water on board to reduce overall weight. We have since adopted that procedure. We also upgraded from the old G rated tires we had, to new H rated tires. This gave us some additional safety factor in the tire load department. I figure (hope) the axle ratings are probably pretty conservative, and our placarded GVWR looks suspiciously low to me...especially when compared to the same model year U300:
Regardless of what method a driver uses to set tire pressures, getting 4-corner weighed is a interesting exercise. Like most other reports, our side-to-side balance was fairly close. I guess Foretravel got that part of the engineering right!
Hanging At Camp FOT (http://www.foreforums.com/index.php?topic=33952.msg310838#msg310838)
Title: Re: Tire pressure question - without scales
Post by: Mike Leary (RIP) on March 22, 2019, 10:31:36 am
Whenever I hear those stories about coaches being overweight, I think of that scene in 'The Long Long Trailer' where Desi discovers Lucy's rock collection! ;)
Title: Re: Tire pressure question - without scales
Post by: Gary and Kathy on March 22, 2019, 02:50:55 pm
If you don't know! Go with Max pressure on side wall of tire. Example g rated 110psi
Title: Re: Tire pressure question - without scales
Post by: Tom Lang on March 22, 2019, 03:23:53 pm
When I didn't know, I went tire FT placard pressures plus five psi. Still under sidewall Max.
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 22, 2019, 07:50:34 pm
If you don't know! Go with Max pressure on side wall of tire. Example g rated 110psi
Just remember that for truck tires (the ones on our motorhomes) the sidewall pressure is the MINIMUM pressure for the maximum load. The maximum pressure for the tire is higher than the sidewall pressure.
Title: Re: Tire pressure question - without scales
Post by: Mike Leary (RIP) on March 22, 2019, 08:02:03 pm
Easy to download specs these days. Here's our Michelins:
Title: Re: Tire pressure question - without scales
Post by: ltg on March 23, 2019, 02:11:32 am
Just remember that for truck tires (the ones on our motorhomes) the sidewall pressure is the MINIMUM pressure for the maximum load. The maximum pressure for the tire is higher than the sidewall pressure.
With all due respect, for Michelin tires, the sidewall pressure on the tire is the maximum pressure for the tire. I have no idea about other makes of tires. For Michelin tires, the max load for the tire and the maximum PSI are stamped on the tire. Michelin tire inflation charts also show the maximum load and inflation pressure for the tire.
Title: Re: Tire pressure question - without scales
Post by: wolfe10 on March 23, 2019, 08:59:26 am
Actually D.J. is correct, though we may be getting into a bit of semantics here.
The sidewall/inflation charts state MAX load and the PSI needed to carry that load.
If less than max load, it does not require that PSI.
But, adding air above that on the side wall will not increase carrying capacity.
And, all tire PSI's are for cold (before driving at current ambient temperatures).
Title: Re: Tire pressure question - without scales
Post by: Chuck & Jeannie on March 23, 2019, 09:57:43 am
The subject of tires and "optimum" (cold) inflation pressure always generates interesting discussions here. I haven't been around all that long, and I have witnessed a few. See first link below for one example. It seems to me that among our Forum members, there are two schools of thought.
One group thinks you should weigh your coach, as accurately as possible (4 corner?) and then set tire (cold) pressures according to load charts and recommendations published by the tire manufacturer. Following this method, if the weight of the coach changes dramatically, then the (cold) tire pressures might require adjustment to compensate.
The other group thinks you should just pick some "safe" (cold) tire pressure, up to and including the pressure embossed on the sidewall, and run that pressure all the time. "Safe" means a (cold) pressure that would always be at or above the pressure required to support the coach GVWR. This pressure (for OEM tires) is generally displayed on the placard affixed to the wall next to the driver seat.
Every coach owner needs to think about tire pressure. and decide for themselves which approach is best. The second link below is the opinions of some truck people who choose to take actual load weight into consideration when setting (cold) tire pressures. Take it for what it is worth.
One group thinks you should weigh your coach, as accurately as possible (4 corner?) and then set each individual tire (cold) pressure in according to load charts published by the tire manufacturer.
One correction-- all tires on an axle should be at the same PSI based on the heavier wheel position.
Said another way, even if left is 1000 pounds lighter than right, they both have the same PSI based on the heavier/right side. From: http://www.michelinb2b.com/wps/b2bcontent/PDF/RV_Tires_Brochure.pdf
MICHELIN® RV Tires HOW TO USE THE ACTUAL RV WEIGHT INFORMATION WITH THE TIRE DATA LOAD CHART
"Let's consider an RV running on 275/80R22.5 MICHELIN® X® LINE™ ENERGY Z 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. For control of the 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. Checking the load/inflation table below shows that a cold tire pressure of 95 psi will support 5,510 lbs. on a single front tire."
Title: Re: Tire pressure question - without scales
Post by: ltg on March 23, 2019, 11:03:16 am
Actually D.J. is correct, though we may be getting into a bit of semantics here.
The sidewall/inflation charts state MAX load and the PSI needed to carry that load.
If less than max load, it does not require that PSI.
But, adding air above that on the side wall will not increase carrying capacity.
And, all tire PSI's are for cold (before driving at current ambient temperatures).
I do not know how to post a link, so I am going to have to make a quote. At Michelinrvtires.com, Tires, Tires 101, how to read a sidewall, it states, "USA Regulation, Max. Load Per Tire, Single and Dual, Kg. and Lbs., Max pressure per tire, Single and Dual, Kpa. and PSI." Also, the Michelin Tire Inflation chart states, "Maximum Load and Pressure On Sidewall". In the English language the Maximum is an adjective and it applies to both the Load and Pressure. In other words, it reads Maximum Load and Maximum Pressure. I am reading all of this to say that the PSI stamped on the sidewall is the MINIMUM to support the load and the MAXIMUM pressure for the tire.
Title: Re: Tire pressure question - without scales
Post by: ltg on March 23, 2019, 11:44:02 am
I agree with Brett - the exact definition of the pressure on the tire sidewall is subject to semantic interpretation.
Also, you have to be careful to specify what type of tire in this discussion. Some tires are designed to be run at (cold) inflation pressures above the pressure embossed on the sidewall. Which can just add more confusion to the discussion. See 3rd paragraph in link below:
Please read paragraph four in that link. Where it talks about the tires maximum inflation pressure.
Yes, you are correct. I misread the 3rd paragraph. I got "sidewall max pressure" and "pressure required for maximum load" confused.
NEVER MIND!
(Went back and deleted my post - it was not beneficial to the discussion)
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 23, 2019, 01:32:52 pm
Everyone would do well to download and then completely readl Michelin's Truck Tire Service Manual and their Recreational Vehicle Tire Guide. They make it clear that truck tires are built to different requirements than are passenger tires. Truck tires are specifically built for heavy-duty service and (unlike passenger tires) the sidewal pressure is the MINIMUM pressure for the maximum load. Under certain conditions the pressure can--and should-- be set higher than the sidewall minimum for the maximum load. Our tires will serve us well if we fully understand them, but may disappoint us if we make incorrect assumptions.
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 23, 2019, 01:37:19 pm
Please read paragraph four in that link. Where it talks about the tires maximum inflation pressure.
Please understand the difference between passenger tires and truck tires and the fact that they are built to entirely different requirements. Understand that different rules apply to them. Go to Michelin's truck tire Website and download their truck tire service manual.
Title: Re: Tire pressure question - without scales
Post by: ltg on March 23, 2019, 01:42:12 pm
Everyone would do well to download and then completely readl Michelin's Truck Tire Service Manual and their Recreational Vehicle Tire Guide. They make it clear that truck tires are built to different requirements than are passenger tires. Truck tires are specifically built for heavy-duty service and (unlike passenger tires) the sidewal pressure is the MINIMUM pressure for the maximum load. Under certain conditions the pressure can--and should-- be set higher than the sidewall minimum for the maximum load. Our tires will serve us well if we fully understand them, but may disappoint us if we make incorrect assumptions.
Again, with all due respect, the sidewall pressure is the MINIMUM pressure for the maximum load and the MAXIMUM PRESSURE for the tire. There is an exception: if you are checking the tires when they are hot, you may add up to a certain amount to compensate when they are hot. Please read the following link. How to Read a Sidewall | Michelin Truck (https://www.michelintruck.com/tires-and-retreads/tires/tires-101/tire-basics/how-to-read-a-sidewall). Max Load, Max Pressure, Max speed.
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 23, 2019, 01:52:36 pm
Again, with all due respect, the sidewall pressure is the MINIMUM pressure for the maximum load and the MAXIMUM PRESSURE for the tire. There is an exception: if you are checking the tires when they are hot, you may add up to a certain amount to compensate when they are hot. Please read the following link. How to Read a Sidewall | Michelin Truck (https://www.michelintruck.com/tires-and-retreads/tires/tires-101/tire-basics/how-to-read-a-sidewall). Max Load, Max Pressure, Max speed.
Please take the time to read the entire Michelin Truck Tire Service Manual. After you do you will understand that for truck tires the sidewall pressure is the minimum pressure required for the maximum load. Online graphics are onteresting--bit don't necessarily accurately represent to information in pfficial documents.
Please take the time to read a passenger tire sidewall and compare it to a truck tire sidewall. The passenger tire will read "maximum load" and "maximum pressure" while the truck tire will read "maximum load xxxx lbs @ yyy psi cold." The truck tire sidewall does NOT" read "maximum pressure."
Title: Re: Tire pressure question - without scales
Post by: ltg on March 23, 2019, 05:05:49 pm
Please take the time to read the entire Michelin Truck Tire Service Manual. "
Ok, I read it. You are saying that because Michelin said that in the unusual situation when a trucker has a steer tire on an axel that has reached the maximum load for the tire, and is having unusual wear issues, the trucker can increase the pressure from 110 psi to 120 psi, that there is no maximum pressure for the tire. So, a forum member that has tires that have maxed out on the load, can add 5, 10, 15 psi as a safety factor. Like is sometimes recommended on the forum when the tires are not maxed out on load. And, when forum members have not yet weighed their coach, they can add 5 or 10 psi above what is on the placard just as another safety amount. Say the placard says 110 psi, they can put 120 psi and be OK.
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 23, 2019, 05:33:50 pm
Ok, I read it. You are saying that because Michelin said that in the unusual situation when a trucker has a steer tire on an axel that has reached the maximum load for the tire, and is having unusual wear issues, the trucker can increase the pressure from 110 psi to 120 psi, that there is no maximum pressure for the tire. So, a forum member that has tires that have maxed out on the load, can add 5, 10, 15 psi as a safety factor. Like is sometimes recommended on the forum when the tires are not maxed out on load. And, when forum members have not yet weighed their coach, they can add 5 or 10 psi above what is on the placard just as another safety amount. Say the placard says 110 psi, they can put 120 psi and be OK.
The short answer is that you finally have the right idea. However, for Michelin truck tires you would need to study their Truck Tire Safety Manual and the load/inflation table for the tire's specific size and load range to learn exactly how much additional pressure can and should be added under certain specific conditions. Most other truck tire manufacturers follow the Tire and Rim Association (TRA) guidelines and those are similar--but not identical--to Michelin's recommendations. Therefore, it's essential to get the detailed information for whatever tire you are running.
Title: Re: Tire pressure question - without scales
Post by: ltg on March 23, 2019, 06:29:17 pm
The short answer is that you finally have the right idea.
Yeah, I am kind of slow. Funny that in two MICHELIN RV publications they would say that the tire pressure on the tire sidewall is the MAXIMUM tire pressure, but in their TRUCK TIRE publication they would give contradictory information. Be advised that the 22.5 inch size tires for RVs are listed in their RV publications.
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 23, 2019, 06:40:33 pm
Funny that in two MICHELIN RV publications they would say that the tire pressure on the tire sidewall is the MAXIMUM tire pressure, but in their TRUCK TIRE publication they would give contradictory information. Be advised that the 22.5 inch size tires for RVs are listed in their RV publications.
The tires on our Foretravels are definitely truck tires and therefore conform to the Federal Motor Vehicle Safety Standard that controls truck tires. Thus, while any RV publication might have some useful information, the Michelin Truck Tire Safety Manual is the "bible" regarding our Foretravels' Michelin tires.
Title: Re: Tire pressure question - without scales
Post by: ltg on March 23, 2019, 06:54:03 pm
the Michelin Truck Tire Safety Manual is the "bible" regarding our Foretravels' Michelin tires.
Would you please provide a link to the "Michelin Truck Tire Safety Manual."
Title: Re: Tire pressure question - without scales
Post by: ltg on March 23, 2019, 07:22:45 pm
Another Michelin publication that shows maximum tire pressure on RV tires. Please see page 8. https://www.michelintruck.com/assets/pdf/Truck_Tire_Data_Book_Jan2007.pdf
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 23, 2019, 07:39:38 pm
It really doesn't matter whether a given culumn in a table in this document is correctly or incorrectly labeled. The important and accurate information is clearly stated in several places in the Michelin Truck Tire Safety Manual. In addition, look at your motorhome's tires' sidewalls and you will NOT see "maximum pressure" on the sidewall, while you WILL see "maximum load" there.
Title: Re: Tire pressure question - without scales
Post by: ltg on March 23, 2019, 07:56:23 pm
It really doesn't matter whether a given culumn in a table in this document is correctly or incorrectly labeled. The important and accurate information is clearly stated in several places in the Michelin Truck Tire Safety Manual. In addition, look at your motorhome's tires' sidewalls and you will NOT see "maximum pressure" on the sidewall, while you WILL see "maximum load" there.
Please read the text on the top of page 13. This is the page for RV tires that are on some Foretravels. It is not only whether a table is incorrectly labeled. This text clearly states maximum tire pressure.
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 23, 2019, 08:04:11 pm
Please read the text on the top of page 12. This is the page for RV tires that are on some Foretravels. It is not only whether a table is incorrectly labeled. This text clearly states maximum tire pressure.
Youu may choose whether or not to believe the Michelin Truck Tire Safety Manual. Our Motorhome tires are truck tires and must conform to the Federal Motor Vehicle Safety Standard that governs truck tires. I must ask you once again to read the sidewall of your motorhome time and look for the phrase "Maximum Pressure." You won't find it because the sidewal of our truck tires on our Foretravels does NOT show the tire's maximum pressure! It lists the minimum pressure for the maximum load.
Title: Re: Tire pressure question - without scales
Post by: ltg on March 23, 2019, 08:12:47 pm
Youu cmmay choose whether or not to believe the Michelin Truck Tire Safety Manual. Our Motorhome tires are truck tires and must conform to the Federal Motor Vehicle Safety Standard that governs truck tires. I must ask you once again to read the sidewall of your motorhome time and look for the phrase "Maximum Pressure." You won't find it because the sidewal of our truck tires on our Foretravels does NOT show the tire's maximum pressure! It lists the minimum pressure for the maximum load.
What you do not seem to understand is that when Michelin truck tires are put on a RV, they fall under Michelin RV tires rules. The top of the Michelin RV tire charts clearly State, "Michelin Inflation Charts For RV Use Only."
Title: Re: Tire pressure question - without scales
Post by: D.J. Osborn on March 23, 2019, 08:24:23 pm
What you do not seem to understand is that when Michelin truck tires are put on a RV, they fall under Michelin RV tires rules. The top of the Michelin RV tire charts clearly State, "Michelin Inflation Charts For RV Use Only."
Not true! You may choose to believe any falsehood you like--but that doesn't change the truth. Look at your tire's sidewall: Does the phrase "maximum pressure' suddenly appear because it knows it's on a motorhome? Nope! The tire is still built to the requirements of FMVSS 119 because it's a truck tire. It doesn't know whether it's on a truck, a motorcoach or a motorhome!
Title: Re: Tire pressure question - without scales
Post by: Caflashbob on March 23, 2019, 09:19:25 pm
"G" rated? 107 front .97 rear.
That's for my U320. You will be 5-8 pounds high for your actual weight but will ride and steer well.
Only for Michelin's. Probably good for others.
Subtract 10 pounds if "H " rated tires installed which would be weird
Title: Re: Tire pressure question - without scales
Post by: wolfe10 on March 23, 2019, 10:51:01 pm
OK, how about we stop quibbling about what boils down to semantics.
I think we can all agree on ways to determine the correct tire pressure for our coaches.
Thanks.
Title: Re: Tire pressure question - without scales
Post by: Realmccoy on March 23, 2019, 11:16:01 pm
Brett has good advice for trip home, but you also want to check if the tires on the coach are same weight rating and size as OEM. A lower range tire would need more air. Also check date of manufacturing. Old tires will blow. I made tires a part of my purchase, and made sure they were the same load rating as OEM. The tire dealership put 110 pounds in them and I pounded my way home over every pavement strip from Wichita to Dallas. I downloaded the Data sheets for the tires, ended up letting a lot of air out and the ride improved greatly. Also had a sleepless night when I highlighted the metric rating for the tires instead of the pounds rating. Big difference between kilograms and pounds, I thought my tires were way undersized. As others will recommend, try to drive home in the daylight because the headlights are terrible.
Title: Re: Tire pressure question - without scales
Post by: "Irish" on March 24, 2019, 08:12:33 am
That is really good advice, the tire rating as well as the pressure Thanks