Tire pressure

kraftengr · 04-03-2015, 08:14 PM

I just picked up my new (actually used a little) pop up camper. I've skimmed thru the pack of manuals that came with the unit and can't find a word about tire pressure. Any suggestions-guidance?

OldCoot · 04-03-2015, 08:20 PM

Quote:

Originally Posted by kraftengr

I just picked up my new (actually used a little) pop up camper. I've skimmed thru the pack of manuals that came with the unit and can't find a word about tire pressure. Any suggestions-guidance?

Look on the side of the tire, it should have max pressure. Inflate to that pressure when cold (in morning). Never deflate during the day. Just check every morning and inflate accordingly.

kraftengr · 04-03-2015, 08:21 PM

Thanks

GreenImp · 04-03-2015, 08:29 PM

Quote:

Originally Posted by OldCoot

Look on the side of the tire, it should have max pressure. Inflate to that pressure when cold (in morning). Never deflate during the day. Just check every morning and inflate accordingly.

This is the easiest and most common answer, but not necessarily the best. All major tire manufacturers have "load inflation tables" that will tell you the correct pressure for any given load the tire will see. You would have to find out what the load on your tires is to determine the best PSI for you (which may very well be the same as the tires "Max PSI"...especially with the tires the factories install as they usually just squeak by load rating wise).

P.S. There may be a white/yellow sticker on your trailer giving factory recommended tire PSI...often at the front driver side.

OldCoot · 04-03-2015, 08:40 PM

Quote:

Originally Posted by GreenImp

This is the easiest and most common answer, but not necessarily the best. All major tire manufacturers have "load inflation tables" that will tell you the correct pressure for any given load the tire will see. You would have to find out what the load on your tires is to determine the best PSI for you (which may very well be the same as the tires "Max PSI"...especially with the tires the factories install as they usually just squeak by load rating wise).

P.S. There may be a white/yellow sticker on your trailer giving factory recommended tire PSI...often at the front driver side.

I maintain the tire mfgrs are better judges of their products than FR. As you say, with the tires being borderline on load, why take a chance by not going with the max pressure recommended by the tire mfgr?

f5moab · 04-04-2015, 09:29 AM

I'll agree with OC but primarily due to the fact, most will not weigh their trailers; especially popups so the max air pressure should keep you safer in the long run. Also, not sure about those load inflation pressure charts. I wrote a manufacture once and the reply back was basically, "WHAT."

But I will also add that a purchase of a tire pressure monitoring system can help put a person's mind at ease while towing. Many on the market, but I recommend TST.

grumpyer · 04-04-2015, 09:53 AM

Quote:

Originally Posted by OldCoot

I maintain the tire mfgrs are better judges of their products than FR. As you say, with the tires being borderline on load, why take a chance by not going with the max pressure recommended by the tire mfgr?

I agree, go by what is on tire & use max. psi.
Can't go by sticker on trailer because maybe tires were changed out, upgraded.

Zolin · 04-04-2015, 10:23 AM

I agree with the above posts. On many smaller trailers people will actually install passenger car trailers. That's why it's always best to go by what the manufacturer of the tire suggests. Max inflation will help keep your tire temperatures lower. The number one cause of tire failure is under inflated tires or insufficient tire capacity for the load being carried. Good idea to load your camper and find a scale to see how much is on your axle. Divide that by 2 and you should know what your tires are carrying. Check the load capacity of the tire by looking at the sidewall and compare this. Lastly, your axle weight should never be exceeded even if the installed tires can handle a higher capacity. Refer to the placards on your camper for the GAWR figure. This is your gross axle maximum. A lot of info, but hopefully some important things to consider in keeping your family safe and Off the side of the highway.

DaveSchwartz · 04-04-2015, 10:56 AM

I agree you won't (generally) go wrong inflating to the max cold pressure. The vast majority of failures are due to tire heating because of the excessive flexing of an underinflated tire. Once the carcass exceeds a certain temperature, its only a matter of time. However, you won't get the full life of the tire that way.

A tire is molded with a flat face (in cross section) where the tread is. With no pressure, everybody's seen that the center of the tread collapses inward. As pressure is added, the center will rise until it is starting to arch outward. Now when you put the tire on the vehicle on the road, the weight on the tire will flatten that arch out.

Too much pressure for the load and the 'contact patch' will not flatten out enough, there will be too much load on the center and too little on the shoulders and the result will be too much center wear and reduced life.

Conversely, too little pressure will mean that the center isn't being pushed down enough to flatten out the contact patch, the shoulders will bear more weight relative to the center and you will get premature edge wear (and there will be too much flex and the self-heating of the compound due to that may cause a failure).

At the right pressure for the load (what those inflation charts tell you - Goodyear's is here) the contact patch flattens optimally.

So its a Goldilocks thing but it requires you know the load (weight), the section numbers of your tire and have an inflation chart.

Personally, I don't always know my weight (can also change quite a bit depending on whether I'm alone or not, carrying water or not) so I inflate for (max GVWR - pin weight at max gvwr) / 4. This is especially important for folks like myself who went up a load range in the same size. If you went up a load range and inflate to max for that range, the tires will be like rocks and your camper will not be having a good ride.

But if you have the same load range as originally supplied (on the tire placard) you will be safer at max cold pressure than by getting it wrong on the low side.

OldCoot · 04-04-2015, 11:05 AM

Quote:

Originally Posted by DaveSchwartz

...Too much pressure for the load and the 'contact patch' will not flatten out enough, there will be too much load on the center and too little on the shoulders and the result will be too much center wear and reduced life...

ST trailer tires very rarely, if ever, wear out in the center (disregarding axle alignment/bend axle/bent spindle/loose brg), they age out due to weather cracking, etc. I personally would never inflate to less than max cold temperature.

GreenImp · 04-04-2015, 11:47 AM

Quote:

Originally Posted by OldCoot

I personally would never inflate to less than max cold temperature.

Yes, and you also felt the need to add shocks to a trailer that didn't come with any....just sayin'.

GreenImp · 04-04-2015, 12:10 PM

Well, I am obviously fighting a losing battle, but here goes...

Here is what Goodyear has to say about it... (hint...it isn't "inflate to max and call it good")

The Inflation Loading - Goodyear RV

Here is what Michelin has to say about it...(hint...it isn't "inflate to max and call it good")

Tire Inflation Basics | Michelin RV Tires

Here is what Maxxis has to say about it...(hint...it isn't "inflate to max and call it good")

Trailer Tire Care and FAQ | Maxxis USA

And to admit that not everybody agrees...here is what Carlisle has to say about it... (hint...it IS to inflate to max and call it good)

The Carlstar Group

Oakman · 04-04-2015, 12:24 PM

For trailer tires, I’m in the camp with the “inflate to the max” folks. I’ve never had any issues with the ST tires that were on the fifth wheels I’ve owned. I’m on my third fifth wheel and I’ve been RVing since 2003.

OldCoot · 04-04-2015, 12:40 PM

Quote:

Originally Posted by GreenImp

Yes, and you also felt the need to add shocks to a trailer that didn't come with any....just sayin'.

You bet and it sure beats any other way of improving truck/trailer ride that I've seen. Don't know of any vehicle suspension without shocks except rv trailers.

OldCoot · 04-04-2015, 12:48 PM

Quote:

Originally Posted by GreenImp

Well, I am obviously fighting a losing battle, but here goes...

No battle here, I just stated what I do and prefer. Naturally, you are free to do whatever you so desire.

grumpyer · 04-04-2015, 12:54 PM

Quote:

Originally Posted by GreenImp

Well, I am obviously fighting a losing battle, but here goes...

Here is what Goodyear has to say about it... (hint...it isn't "inflate to max and call it good")

The Inflation Loading - Goodyear RV

Here is what Michelin has to say about it...(hint...it isn't "inflate to max and call it good")

Tire Inflation Basics | Michelin RV Tires

Here is what Maxxis has to say about it...(hint...it isn't "inflate to max and call it good")

Trailer Tire Care and FAQ | Maxxis USA

And to admit that not everybody agrees...here is what Carlisle has to say about it... (hint...it IS to inflate to max and call it good)

The Carlstar Group

Nowhere from above did I see anything about not inflating to max!

kraftengr · 04-04-2015, 12:55 PM

Well thank you thank you for all of the feedback! Awesome!

Here's where I think I'm going with this. Following some of the suggestions, I've done some research. My tires are rated at 1,520# at 80 psi. That translates to 19 sq. inches in contact with the road at full load.

Based upon the pop up axle weight plus cargo capacity, the tire rated capacity is approximately 150% of the max unit weight; so to approximately maintain the designed contact area for the tire/ full load combination, I should inflate my tires to 55 psi.

But...recognizing that the "full inflation" point of view also has merit, I intend to maintain pressures in the 60 to 65 psi range. Thanks again-what a great resource you all are!!

grumpyer · 04-04-2015, 12:58 PM

Quote:

Originally Posted by GreenImp

Yes, and you also felt the need to add shocks to a trailer that didn't come with any....just sayin'.

Don't know about anyone else..but my tt did not come from manufacturer with battery or propane tanks! ......just sayin!

grumpyer · 04-04-2015, 01:47 PM

So now I have a question!
If sticker on TT states 50psi max. and Class c tires are being used they too are marked on sidewall at 50 psi
What happens when you upgrade to D range and 65 psi max?
.....same load on TT. Do you run at
50 psi or 65 psi. No I'm not trying to be a smart ass!

Witch Doctor · 04-04-2015, 01:59 PM

Quote:

Originally Posted by grumpyer

So now I have a question!
If sticker on TT states 50psi max. and Class c tires are being used they too are marked on sidewall at 50 psi
What happens when you upgrade to D range and 65 psi max?
.....same load on TT. Do you run at
50 psi or 65 psi. No I'm not trying to be a smart ass!

I have changed just as you said and I run them at 65 PSI sidewall CP. By GY chart I can run them at 50 PSI for the load, but I would rather run them at the CP 65 lbs. That is also the max my series 6 rims says I can inflate to. I have no problem with bounce or anything. Tires look like new after 2 years and thousands of miles on them. I buy them so I figure it's my choice. Also it gives me a good cushion for the weight per tire/wheel. Some folks may disagree but they aren't paying for them either. Just my choice.....

PS: good question

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