Tire pressure ???

[AustinBoston]

No, but my trailer, just like my car, categorically:
a) Carries MASS, designed to do so at an optimum setting.  PERIOD.

No, my trailer does not steer or drive, but nor do most cars' rear axle (all front-wheel-drive).  Sorry, dumb argument.

Only a dumb argument if cars don't have front axles.

Please look up the benefits of a pneumatic tire, and how they are superior to a solid tire (which is what an over-inflated tire approaches to acting like).

Nobody is talking about over-inflated tires but you.  A trailer tire at 100% of it's rated presure is not over-inflated.

Not me.  At rallies, I've carried my digital pressure gauge around and checked friends' tires to compare them to the labels (and found that about 80% have under-inflated tires).  The labels on trailers, just like cars are designed by the manufacturers to support a correct weight.

And have you compared the trailer label to the tire label?  I think you'll find it's always, always, always at 100% of the max pressure, just like yours is, even though the tire rating is 30-35% more than the axle rating, a comment I noticed you snipped out of your reply.

True, what I left out was that the tire manufacturer has no idea of the trailer it is installed on.  Given that, their only leeway is to use the tire label - because if the trailer says 80 PSI, but you put a 60 PSI tire on it, and inflate to 80, you may have a very bad situation.  Thus, all tire manufacturers say to inflate to their tire labels, because that is the only way THEY can protect them self.  I included that link in the wrong section (meant to bolster the argument where of course Discount Tire will say to use the tire labels).

No, that is not the only thing they can do.  They can easily say "for X pounds, inflate to Y, for Z pounds, inflate to W."  They can do this very easily, but they don't.  Because the tire is designed to always be at max pressure.  Always.

Tires "absorb" shocks by instead of transferring all those pounds-of-force IMMEDIATELY to the vehicle's shock absorbers, they instead bounce the force around inside the wheel and this enables the force to be spread out over time.  Not a time delay - huge difference.  (Illustrative example, not accurate--) Instead of 1000 instant pounds of force on the frame in 10 milliseconds, it does 100 pounds of force spread over 100 milliseconds.

Sounds like a delay to me.

This means that a shock absorber that can withstand 300 lbs of force can easily withstand the shock with a suitably "bouncy" tire.

Not many pop-ups with shock absorbers.

If you have a "solid" tire (one that is at max PSI without much load), in physics, it acts as a SOLID tire.

Wrong.  It acts like an over-inflated tire.  It just bounces a more.  A solid dire does not bounce at all.  In order for a tire to bounce, it must compress.

True; the over-inflated tire destroys shocks & bends frames.  They act as if you have a solid piece of cement you are "rolling" on.  You left out quoting my "they break a spring".

That "break a spring" part was wrong too.  Now are you happy?

Not true at all.  The rating of the axle is designed such that the tire absorbs a specific amount of the jolt of the gross mass of the trailer and spreads it out over time such that the axle can handle it.

This still happens with "over-inflated" tires.  But of course we are talking properly inflated; only you are talking over-inflated.

If the tires were solid blocks, the first pothole would smash the axle or springs.  This is high-school physics (force over time).

Again, I would agree, if we were talking over-inflated.  But a 90 PSI max tire with 90 psi in it is not over-inflated, and does not act like a solid tire

I am, however, a mechanical engineer.

...

Sorry, but the manufacturer must create a vehicle that can support its entire weight.  Period.  If you are going uphill, and your TV hits a bump, the entire weight (and more, some of your TV, hence the 20% leeway) can, and does get transferred to the trailer.

You know, every so often, I see things that just amaze me.  

If you are a mechanical engineer, then it's time to change careers.

There is absolutely no way for even one ounce of the weight from my tow vehicle to end up on my trailer's axle.  It can't even start to do so; before even one ounce could get on the trailer's axle, the tongue would be on the ground.

What does happen is that the dynamic load on the axle can be several times the actual weight of the trailer.  There may be a negligible amount of tow vehicle weight involved where there is more than one axle on the trailer, but it is negligible.

Additionally, just because you are supposed to have 10-15% on the tongue, does not mean that everyone does.  Thus, the manufacturer must factor in the chance that 100% of the trailer weight will be carried by the wheels.

If you really are a mechanical engineer, you'd have a better explanation than that.

That is why the axle must also be rated to carry the GVWR.

This is rediculous.  I can't believe I am reading this.  Many pop-ups are at the rated weight for the axle, after you subtract the tongue weight.  They MUST be rated to hold the GVWR?  Then why are so many pop-ups NOT rated to hold the GVWR?

It would be incredibly foolish and fatal not to assume that all the mass may be on the wheels/axles.

How many trailers out there have under-recommended tongue-weights?  I'm sure many do, since people may have a load of firewood in the back of the trailer, things on the back bumper, full black & grey tanks with empty fresh, etc (or vice-versa, whichever puts the most load on the back).

Ever had a trailer sway?  If you don't have that 10%, you will sway.  Manufacturers don't need to worry about this; the laws of physics correct the problem for them.

Last, simply one thing to consider about trailers...  There are 3 weights for a trailer:
1) Trailer Mass (weight)
2) Axle weight
3) GROSS vehicle weight

Very coincidentally, the GVWR for most campers may well be the tire's max PSI, because that is the LEGAL MAXIMUM you can carry!  If the tires are rated for 2880 lbs (2 tires at 1440), then the GVWR cannot exceed that, and the manufacturer puts that on the label.  On most campers, the frame and axles can support more, but the tires are the limiting factor.  Usually, however, the tires are closely matched to the axle, making BOTH the limiting factor.  Replace both of those, and then you branch into how much can the frame support.

However, if the tires are beefier than other parts (NOTE: SEE ROCKWOOD HYBRIDS FROM 2+ MORE YEARS AGO), then the limiting factor is not the tire, so is not labeled to be at the max PSI.  No, in some cases, the max rating is the AXLE capacity.

And the trailer manufacturer will still recommend max pressure.

If you put tires on your trailer that are different from the trailer manufacturer's rating, then simply contact the tire manufacturer and ask for the correct PSI to support the trailer's GVWR.  Thus, you ensure you have the correct "bounce" (shock absorption) in the trailer tire for your camper.

I'm going to try that.  I bet I get max pressure every time.

Austin

[mike4947]

Austin, I hate to say it but there are people who are instant experts and know more than the company engineers that have over 100 years of experience to rely on when giving recommendations for inflation and usage of the proper grade/type of tire.
You are argueing with one, and no amount of facts will convince them they are wrong and the rest of the world is right...LOL
It don't "fool" them that every tire company that manufactures ST ( special trailer) tires recommends that they only be used at maximum inflation pressure listed on the sidewalls. They know better.
 
They "know" that "tires are tires" and P, St, LT, commercial don't have a thing to do with anything and most likely also perpetuate myths such as:
you have to leave tires a few pounds low when inflating them because they build up pressure and don't care that tire engineers have realized that for at least the last 80-90 years and have set their maximum pressure ratings to account for the increase.
 
As for me I just keep an eye out for them along side of the road with the blown out tire (and maybe body damage) so I can honk and smile and be glad they "knew" what they were doing...LOL

[brainpause]

[Moderator ON]
Let cooler heads prevail here, please. I'd hate to lock a thread about tires. Yes, it is animated, and there potentially is a safety issue here.

[Moderator OFF]

I pulled our PU on hot summer roads nearly 10000 miles over the past 5 years. Maxed out the pressure every time. No problems at all. And trailer was likely underloaded (below the tires max weight).

This thread has made me concerned that my ATV's tires are aired up too much....at 4 psi. They are supposed to be at 3 psi. That is a 33% increase!!!  :yikes:  

Larry

[AustinBoston]

Austin, I hate to say it but there are people who are instant experts and know more than the company engineers that have over 100 years of experience to rely on when giving recommendations for inflation and usage of the proper grade/type of tire.

I know how that works, and it's one thing I will cut some slack on.  The reason is I've been caught doing things like that myself.   :yikes:

Austin

[austinado16]

...I pulled our PU on hot summer roads nearly 10000 miles over the past 5 years. Maxed out the pressure every time. No problems at all. And trailer was likely underloaded (below the tires max weight).Larry

This is exactly my point:  You can armchair jockey this kind of stuff all day long and play engineer-of-the-day quoating theory/specs/websites/etc.  Or you can get out there in real world conditions and experience real world results.

I've never owned or towed a PUP before so had no experience with the little 5.30x12's on my Starcraft Nova.  On the day I picked it up, the tires looked like eggs and maybe had 20psi in them.  I drove around the corner to an auto repair shop and put them at the 80psi it says they should be.  Why? Because I had this sneaking suspicion that they needed to be super hard, not only to hold the weight, but to reduce rolling friction and thereby reduce the heat build up in the tire. I've been around cars and tires long enough to know lower air pressure creates a big contact patch on the road, forcing the tire to really flex alot as the tread strikes the road, and this creates friction and heat in the belts and causes tire failure big time.

When we headed to the Grand Canyon I kept them at 80psi cold and headed off.  The only thing I monitored during the 5 day 1,200mi trip was tire tread tempurature, and I only checked that when we stopped for fuel or to use a restroom.  As I mentioned, I wasn't towing easy,70mph, and it was hotter out in the Mojave, Barstow, Needles, etc. then I think I've ever personally experienced (which was 114 in Tuscon, AZ)

It ain't rocket science, and we're not flying them to the moon.

[brainpause]

I drove around the corner to an auto repair shop and put them at the 80psi it says they should be.  Why? Because I had this sneaking suspicion that they needed to be super hard, not only to hold the weight, but to reduce rolling friction and thereby reduce the heat build up in the tire. I've been around cars and tires long enough to know lower air pressure creates a big contact patch on the road, forcing the tire to really flex alot as the tread strikes the road, and this creates friction and heat in the belts and causes tire failure big time.

This is why I keep them at their max pressure.

Larry

[waygard33]

First of all...I would like to say Thanks to this thread and it's participants. As a trailer 'Beginner', I have learned a lot from both sides of the argument, if in no other regard than it makes me think.

As a totally objective observer (I know very little about the subject and I don't know the participants) I thoroughly enjoy the banter, the links to websites where facts or other information and opinions reside, and the detailed 'picking apart' of eachothers arguments. This is as good as a thread gets in my opinion.

However, the problem is that the participants have to ride a fine edge of continuing the argument without getting personal. We're on that edge now and it makes it all the more enjoyable. I for one hope AB and Zamboni can agree to disagree and keep the banter going. I see merit on both sides and would like to continue my education. I think that we can all agree that you can put a stack of facts in front of a group of people and come away with many interpretations.

Thanks again and when you hear the BELL, come on out for round 2...or 3...or whatever round we're at now.

'DING'

[flyfisherman]

First of all...I would like to say Thanks to this thread and it's participants. As a trailer 'Beginner', I have learned a lot from both sides of the argument, if in no other regard than it makes me think.

As a totally objective observer (I know very little about the subject and I don't know the participants) I thoroughly enjoy the banter, the links to websites where facts or other information and opinions reside, and the detailed 'picking apart' of eachothers arguments. This is as good as a thread gets in my opinion.

For sure, a lot of good and useful information has been posted on this board over the years.  But as a relatively newcomer you need to know that all that is posted is not necessarily correct. Sometimes it can be just a matter of opinions. Indeed, sometimes there will be some real superfluous B.S. (and I don't mean Brown Sugar!), and that will be sorted out most directly.



Fly

[wavery]

:book: Darn :swear: .....I was gone for the Holiday and missed all the fun.

Zamboni.....calm down....it'll be OK

I posted some stuff on here that was wrong when I first started out and got my butt kicked for it.........That's how we all learn.

However, I would just caution anyone about making definitive statements like, "The pressure you should use is NOT NOT NOT what is printed on the tire". It may be wiser to state, "In my opinion........." because that is exactly what it is, your opinion. Anyone can have respect for another person's opinion, even if it may be contrary to his own. However, when you make definitive statements like that, it suddenly puts people that really know the facts on the defensive and they feel like they need to correct that mis-information in a clear and meaningful manner to avoid any problems for the OP.

Had the original poster acted on your advise and that resulted in an accident and/or injury, I don't think you would feel very good about it. Even if you felt that your potentially flawed laws of physics were correct.

[M Baxter]

Well we made it!!!! The pop up pulled GREAT with the MAX pressure. Thanks to all involved I learned something and wont be afraid to ask if I run into somethin else. Any tips on getting the campfire smell out of the PU. Thanks again MB.

[austinado16]

Glad you had a good pull home.

We pop ours open when we get home and leave it sit unzipped, door open for a day or so to air it out.  That also gives us a chance to clean it out, clean it up, and have it ready for next time.

[M Baxter]

Thats what we usually do and did this time. The first night the smoke was going the other way. Second night it came right in. It usually isnt that strong of a smell. This time it was though. We sprayed her down with Fabreeze when we cleaned up tonight. It should be OK. MB