Tow Vehicle tire inflation

[hilltool]

WEll- I googled this and found endless "discussions" on the Web. I'm running Goodyear Wrangler ATS on my 97 150 4x4. max sidewall rating on those tires is 44PSI. The "door" pressures, however, say 29 front and 32 rear-of course, the Goodyears are not what the F150 came with.

Some say run door pressure regardless- others say they run maximum sidewall pressure when towing. Right now I'm splitting it a bit---

What does everybody here say?

Rick

 

[PaulS-HILO]

if able try to go and have it checked out at a tire store or a similair place for there determination, when it comes to tires, a easy blow out can occur from improperly or over inflating, and towing a unit with a heavy hitch is not safe.

 

[JackandJanet]

Rick, Goodyear should publish the max load rating of those tires when inflated to a particular pressure. I know they are considered "safe" if inflated to the max cold pressure of 44 psi, but they could wear more in the center of the tread.

I suspect the rated load for those tires is at 40 psi cold. If this is the case, that pressure is what I would put in them.

My tires are Goodyear Wrangler Silent Armor, 44 psi max pressure. They are the same size and very similar to the OEM tires that were on the truck which had a recommended pressure of 40 psi. I keep them there.

- Jack

 

[jcurtis95]

Rick, I have a 2000 F250 4x4 7.3L and a heavy duty camper shell on the extended cab. Based on this, I generally run 65 PSI due to the heavy weight of the Ford Truck. When towing the Hi Lo, I will add about 5 pounds to that. Door Pressure states 70 PSI on my truck.

I don't know if this is the place to put the following information but I thought it would be good for Hi Lo owners to be aware. It deals with tire pressure on our Hi Lo's and what I have found through research:

Tire Pressure on Hi Lo:

I used this method to determine the weight and tire pressure ratio for a new set of 8-ply tires I had mounted this month. I researched before having the tires mounted. I tried to find the URL link information from an ‘expert’ tire professional but could not find it. I will condense the main points since I did copy and print it out at the time:

“When you get new tires mounted and they don’t ask you how much air for your tire, they will arbitrarily put the recommended maximum pressure allowed in the new tire. This causes over inflation that you may not require for the actual load. If you run the maximum pressure, it will cause unnecessary tread wear in the center area of the tire. From a safety standpoint, since you do not have a good ‘foot print” and the tread is not making even contact with the road, you have reduced its braking ability and that causes instability”.

He goes on to say; “let’s say you have a trailer weight of 4,000 pounds on a two axle trailer; that means the 4 wheels will be bearing 1000 pounds of distributed weight each. If you look at the chart [for a 205 75R 15], a tire pressure of 25 to 30 pounds will easily handle that weight and give you a good ‘foot print’ and soft ride”.

Armed with this information, when I took my trailer down to get it inspected and have the new tires installed, I provided this information to the manager of the tire shop and he agreed, that is what generally takes place. He also agreed that since I put 8-ply tires on, the maximum pressure of 65 pounds was completely unnecessary for the weight of the Hi Lo. Based on this, we agreed the ideal pressure, plus a little extra since I did not know what the exact payload would be, should be right at 40 PSI which he placed on the work order. Sure enough, when they finished mounting the tires, I asked one of the guys to check the tire pressure. Yep, they had placed 65 PSI in each tire. I watched as they reduced each tire’s pressure down to 40 PSI.

I don’t know if the forum has ever addressed this before but I would be willing to bet that a great majority of all Hi Lo RV owners are running around with over inflated tires.

The maximum load rating per tire for the Hi Lo trailer with two axles [4 tires] ST205-75R-15 for:
Load Range C 6-Ply = 1820 lbs. with maximum 50 PSI Maximum speed rating 65mph
Load Range D 8-Ply = 2150 lbs. with maximum 65 PSI Maximum speed rating 65mph

My 2406 Towlite weighs 4525 with an expected gross loading weight of around 1400 pounds; Total weight 5925 Average Loaded Vehicle Weight per axle = 1481 lbs. Since I am running 8-ply tires, my ideal pressure with the load I carry would be somewhere between 35 to 40 pounds.

Don’t ask me why I’m running 8-Ply [Load Range D] when I will never exceed the load recommended for 6-Ply, load range “C”, but I suppose it is knowing I have an extra 2 ply’s and on the occasions I do exceed 65mph, they will handle the speed and heat load better. Also, the manager made me a real good deal on a set of [4].

Maxxis has a graduated chart with different sizes shown here:

http://www.maxxis.com/Repository/Files/m8008load.pdf

Jerry Curtis
2406 T

 

[hilltool]

Thanks for posting that, Jerry. I ran a search but didn't find much in the forum on tow vehicle inflation- though I know there have been discussions on the trailer tires. Actually- I get confused by a lot of this...but your post and jack's helped.

There are trail americas on my trailer, now, and they show a max load rating per tire of 1350. I don't know what came with the trailer new, but these are on there now and they are 175/180 13. i don't know the load rating as I don't where on the tire it is listed. My eyes are bad enough now that I need a magnifying glass to read all that stuff anyway. But- max sidewall pressure is 50psi, cold. i assume that would be at 1350 lbs of payload per tire. Dual axle, four tires, and a GVWR of 4500lbs- which is a bit strange as the trailer sticker lists 2200 lbs per axles. I guess tw doesn't count? But- that would put the max per tire @ 1125 if loaded to max weight. Clearly, the 1350 gives me some safety room, I guess. The HI-Lo sticker says the tires should be at 35psi- and when I got it that is where they were at. All sort of posts on the web say run your trailer tires at the max, so last time out I put them at 50psi. Some how during the last moth of sitting I've lost 5lbs- so I am thinking of just running them, there, at 45. On the truck I kicked everything up to 38. The only logic, here, is that I'm splitting the difference of some of the suggestions I have gotten and it makes sense for me to increase inflation when I am increasing load---but, again, it is just something I have tended to do most my life and I really cannot say where I picked that idea up.

Anyway- the one annoying aspect of this Hi-Lo is the GVWR. Options installed include stableizer jacks, roof AC, Awning, electric ATWOOD front jack- and an extra battery. With both propane tanks filled and options it comes in right around 4000, which is why I have taken to loading food, chairs, clothing, and everything else in the truck when we go. 500lb of scrunch room doesn't leave me much---though, admittedly, 500 lbs of food and clothing should get us through most winters without re-supplying.

Your chart is helpful. It might be an interesting thread to post and keep going for awhile because opinions seem quite varied.

Thanks,

Rick

 

[raamw]

I posted a chart relavent to tire pressure and load dependent on tire size.
http://www.airforums.com/forums/attachment.php?attachmentid=16648
A properly inflated tire will have the most efficient tire foot print meaning the weight per square inch of rubber to pavement, either to much air or not enough will reduce this foot print, resulting in poor handling, traction and stopping and wear. To arbitrarily put a certain air pressure is a gamble.
I towed a 30 foot award 730 for quite a few years with a 1997 F150 supercab with a fiberglass case. If you look at the trailer sticker it states 5200 lbs, the truck weight was published at 3400 lbs and the cap was probably another 300 lbs so roughly 9000 lbs plus myself and wife and other stuff. My truck was list as a gross combined weight of 11, 000 lbs, so I felt I was within limits.
Entering Colorado I read the sign stating all vehicle trailer combination must get weighed so I pulled in amongst the semis. The operator of the weight station flagged me through but I requested to be scaled. To my surprise I weighed in at a gross of 10,800 lbs, 4800 on the trailer axle and 6000 on the truck. Now using that info it means 1500 lbs per truck tire and 1200 pounds per trailer tire.
You would use these weights plus a little fudge to figure what pressure would be recommended. I for years used the max 50 pounds in the marathon trailer tires I the dropped it down to 36 pounds allowing for an extra 1000 pounds in the trailer for the truck I kept the tires at 38 since max load at 2100 lbs was 44 psi
Evry tiremanufacture has this information

 

[hilltool]

Ok- so far, you have me convinced to dial the inflation the trailer back. obviously, I am not carrying more than about 1000 per tire on the trailer- so the 35 it came with seems about right and Hi-lo sticker does also. The guy who traded it in was the owner of a car dealership for many years---so maybe he knew a thing or two. Still- I can't find any links to the tire mfg on my trailer.

I'm off to chase down goodyear tire chart.

Thanks

rick

 

[raamw]

The federal gov't regulates the standard on tires so they meet minimum standard so a certain tire of certain dimension meets specific specs, the only good thing about known tire manufacturers is if they have been in business for a long time they are doing somethin right and should be there down the road to stand behind their products

 

[Atlee]

I always inflate my tires to 50psi. I do this for two reasons. I want to make sure I have enough reserve. The thing is this for me. I will not be visiting the CAT scales every time I load up and leave on a trip.

I have no way of knowing if the weight in my trailer is spread exactly even over the 4 tires.

Also, the sticker on the front left of my HiLo says 50psi.

 

[JackandJanet]

Ok- so far, you have me convinced to dial the inflation the trailer back. obviously, I am not carrying more than about 1000 per tire on the trailer- so the 35 it came with seems about right and Hi-lo sticker does also. The guy who traded it in was the owner of a car dealership for many years---so maybe he knew a thing or two. Still- I can't find any links to the tire mfg on my trailer.

I'm off to chase down goodyear tire chart.

Thanks

rick

I thought we were talking about tow vehicle tires, not trailer tires.

I'd be hesitant to reduce the pressure on trailer tires much. With lower pressure, they flex more which causes heating. Heat destroys tires. You don't need to concern yourself too much with traction on trailer tires, except maybe for hydroplaning on wet roads. But to counter hydroplaning, you want to use the highest pressure possible.

- Jack

 

[hilltool]

@Jack

I started the thread on talking tow vehicles but it morphed into all tires a bit---jcurtis wrote:

"I don’t know if the forum has ever addressed this before but I would be willing to bet that a great majority of all Hi Lo RV owners are running around with over inflated tires.

The maximum load rating per tire for the Hi Lo trailer with two axles [4 tires] ST205-75R-15 for:
Load Range C 6-Ply = 1820 lbs. with maximum 50 PSI Maximum speed rating 65mph
Load Range D 8-Ply = 2150 lbs. with maximum 65 PSI Maximum speed rating 65mph

My 2406 Towlite weighs 4525 with an expected gross loading weight of around 1400 pounds; Total weight 5925 Average Loaded Vehicle Weight per axle = 1481 lbs. Since I am running 8-ply tires, my ideal pressure with the load I carry would be somewhere between 35 to 40 pounds. "

The post by jerry and by raamw included inflation charts- so maybe this is now a discussion on side wall markings vs charts vs general practice. That said- I found goodyear charts which covered their passenger tires and their trailer tires- so I'm wondering ,now, if your comment about not overinflating wouldn't also apply to trailer tires. AT this point- my hi-lo sticker on the 2001 says inflate to 35psi and so do the various charts. I'm still trying to interpret the good year charts for the ATS WRangler vs the door sticker on the 97' f150.

Rick

 

[raamw]

Tires are tires whether they are on a bike truck atv etc. The company that produced the vehicle know the weight of the vehiccle, they put the proper weight rating tire. For instance let say you have an F250 with an empty weight of of 4000 pounds and a Gross vehicle weight of 7000 lbs. Since the truck is rated to be a max of 7K the tires put on will be rated to carry a minimum of 7K or 1750 per tire. More than likely it will have a D rated tire with a max wight of 2150 each at some predetermined pressure. That doesn't mean you can haul 8600 lbs because was not set up to handle it (IE brakes cooling gearing ratio etc) If you check the tire charts you would look what pressure you should run to carry the load you have in this case 1800Lbs, it will be less than the max this way you get a proper foot print meaning stability, traction stopping and longevity.

At some point you must have seen pictures of tire wear for overinflated tires (worn out in the center with outside edges like new, the tire was only riding on the center until it wore down to engage the rest of the tire, loss of tire live Underinflated tire has the outside worn and the inside like new. It doesn't matter what the application is

The factory is required to list the pressure as it comes out of the factory since they are require by the fed to list the empty weight and max weight, if you add additional weight you may need to increase the pressure. How can this be done before loading weigh it, to run a couple pounds over the listed pressure is no big thing.

Once you get a general idea of what you carry will be your guide to proper tire pressure

Now if your trailer weighs 4500 empty, about 400 to 600 pounds of that weigh goes to the tow vehicle via the hitch meaning the axle weight of the trailer is now 3800 to 4100 pounds and the tow vehicle picked up this additional weight on the rear axle. If you use load bars the bars will take some of that 600 pounds and push it to the front tow vehicle tires (front end of TV goes down to maintain proper steering)and some back to the trailer. So this will change everything so keep that in mind.
What I do is at every stop I walk around and place my hands on all the tires to see if they are running hot which is an indicator of overweight, under inflation and either adjust to pressure to minimize side wall flexing or plain slow down to decrease heat build up. Heat is the leading cause of tire failure and premature tire wear.

 

[jcurtis95]

The post by jerry and by raamw included inflation charts- so maybe this is now a discussion on side wall markings vs charts vs general practice. That said- I found goodyear charts which covered their passenger tires and their trailer tires- so I'm wondering ,now, if your comment about not overinflating wouldn't also apply to trailer tires. AT this point- my hi-lo sticker on the 2001 says inflate to 35psi and so do the various charts. I'm still trying to interpret the good year charts for the ATS WRangler vs the door sticker on the 97' f150.

Rick[/QUOTE]

Rick,

The first paragraph of my post was in response to tire pressure on TV's which I answered. The greater part of my response was actually referring to my particular Hi Lo [2406 T] and what I had found out when I researched the new tires I was purchasing.

I apologize for confusing the trailer versus TV tires; I guess I should have started another thread, I did not intend to change the discussion topic but I felt it important for Hi Lo owners to consider what I had learned from tire experts about inflating tires on a trailer.

rammw's latest post clarify's the point I was trying to make and I feel the information would be applicable to either the RV or TV.

Jerry Curtis
2406 T

 

[raamw]

The sticker on the door is the weight of the truck with all factory accessories, It is the proper PSI for that app[application, If you add equipment to the truck then you may need to adjust the pressure to compensate.
The truck company supplies the initial correct info. The tire company has no idea what that particular tire will end up on so they will supply the variable chart. Use the door sticker for starters and correct as necessary. If you change tire size the sticker will no longer apply but you should have a good guess at the weight per axle

 

[hilltool]

A quick follow-up.

I was leaving on an extended couple of days trip when i started the last thread. I have not gotten back to my good year dealer,yet, as far as the truck tires go-but as far as the trailer tires were concerned---i called th dealer that sold and installed the hi-lo tires and he said inflate to maximum on those tires----that the hi-lo sticker was for origninal tires and the guy upgraded. I realize that goes against the tire charts----but the prevailing response I am finding on many forums and from others is to go with full sidewall inflationfor the trailer.

rick

 

[raamw]

Not to beat a dead horse but you are getting bad information, if what you where told is true than what is the purpose of the pressure charts.
Here is Goodyear RV tire information brochure, read it and you decide who is telling you the truth, tires are tires no matter who the manufacturer is if it is sold in this country theymust all meet the same standards as set by the DOT

http://www.goodyearrvtires.com/pdfs/tire-care-guide.pdf

 

[RichR]

It would be nice if the tire companies and the RV manufacturers got together and came up with a unified set of standards so the end users, us, would know what is right. I would say that Goodyear would know as well as anyone what is right for tires.

 

[raamw]

There is a unified standard, any company that produces a vehicle for on pavement water or air use must comply with the rules as published by the Department of Transportation. DOT regulated any and all vehicles and the manufacturers would not be allowed to sell a vehicle in this country if they did not meet these standards. There are a high number of vehicles that are produced world wide that can not be sold or licensed in this country because they don't comply with DOT standards. If you look at commercial vehicles, trucks trains planes boats etc they list the certification on their vehicles when one of them get involved in an accident the Highway/transportation safety administration conducts an investigation to determine the causes and if any rules need to be changed. Overweight trucks are generally easy to spot but trains and planes are not.
That is why the sticker lists the size tire, the max axle weight for each axle and the GVW and GVCW for vehicles that can tow.

 

[RichR]

It would be nice if the tire companies and the RV manufacturers got together and came up with a unified set of standards so the end users, us, would know what is right. I would say that Goodyear would know as well as anyone what is right for tires.

I'm sure the manufacturers follow the standards, both trailer and tire makers, or they would be spending lots of time a courtroom. What I was meaning was that when the trailer says 50 psi and then the tire co. says that the pressure can vary for the exact same tire. I guess that when the sticker says 50 psi and tire says 50 psi max I would do 50 psi. To put variable psi on the sticker would create confusion and lots of tire failures which in turn would be blamed on the tire co. So they have to dumb it down to prevent that from happening. I suppose they could send a table of tire pressures with the tires and then when you put air in the tires you will have to weigh the trailer to get it right. How many people would actually do that?

 

[raamw]

If your trailer sticker states 50PSI, then that would be the psi it needs to be at, that tells me your trailer axles are at max weight, if not you will only get less mileage since overinflated for the load causes the tires center to wear out, if this is the case then that is a dangerous situation since the foot print of the tire has less rubber to pavement contact resulting in poor braking, skid control wind deflection etc. I would get your rig weighed at one of the truck stops that have scales ot a state weight station if they allow. I plan on doing this with my new 2510 when I take it out this way their is no guess work at all. My2510 is listed at empty weight of around 4500 pounds and a gross of 7500 with 205 R15 marathons on which has a max of 1820 lbs@50PSI (7280lbs) at empty weight the proper PSI would be roughly 30 lbs, so for me the minimum pressure would be 30 and the max 50. It looks as if I am overloaded at max but when you hook up approx 500 pounds of those weighs goes to the Tow vehicle. Figuring 90 gallons capacity (700 lbs) and probably another 1000 pounds for all the stuff you cam stuff I would be max at 6400, probably 5800 (5400 0n the ) road since I always empty my tanks for the road, my psi should be around 36 pounds minimum I would hand check the tires on the road to determine any heat build up and adjust is so needed. Also visual profile of the tire, if it is bulging on the sidewalls you should bring the pressure up since the flexing of the sidewalls causes heat build up.