Max tire pressure or trailer recommended pressure?

[iamrwnut]

Sorry for another tire pressure question. Searched for 1/2 hour and did not come across an answer that I am sure is somewhere in the 12000 posts on tires.

My tires have a pressure rating of 80 psi cold. My trailer shows 65 psi cold.
Which one should I use? I have been setting them at 65 psi.

[SAD]

Originally Posted by iamrwnut

Sorry for another tire pressure question. Searched for 1/2 hour and did not come across an answer that I am sure is somewhere in the 12000 posts on tires.

My tires have a pressure rating of 80 psi cold. My trailer shows 65 psi cold.
Which one should I use? I have been setting them at 65 psi.

The 65 psi recommendation ~may~ be imposed by a limitation of your wheels mounted on the trailer.

Try and determine the rating for the wheels....

If you find that the wheels are rated for up to 80 psi as well, the recommendation may be simply the result of the fact of the load that is imposed upon the tires - i.e. your RV is not heavy enough to warrant an 80 psi recommendation.

All tire manufacturers have a "recommended pressure" based upon the specific weight they carry - not just the maximum rated weight.

Simply because a tire is rated for up to 80 psi, does not mean that it is "under inflated" at 65 psi.

[SAD]

Here's a load inflation chart for the Maxxis trailer tire....

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

See that the LR E tire is rated for 3420 lbs at 80 psi...

But also:

2870 @ 60 psi
3130 @ 70 psi
(ratings are inclusive across lower load ranges)

[iamrwnut]

Looks like I am going to have to hit the scales to find out my true weights, then adjust my tire pressure accordingly.

[hankpage]

Rob, According to Keystones webpage, your trailer came from the factory with 15 in. load rated D tires. (65psi max.) When the tires were upgraded to E rating (80psi) the rims should have been upgraded also. Before you increase tire pressure above 65psi be sure to check the rating of your rims. Have they been changed to 16in ??????

[Bugle Boy]

Originally Posted by iamrwnut

Looks like I am going to have to hit the scales to find out my true weights, then adjust my tire pressure accordingly.

A safe RV trip depends on knowing the weight and weight rating of your trailer, tongue weight, weight on the tires, weight ratings of your TV, weight rating of your tires, weight rating of your hitch etc.

Without knowing the true weights and these weight ratings you have no idea if anything is overloaded.

I think it very important to get hitched up, loaded for a typical trip, and head straight to a set of scales. We will do that Tuesday right after we pick up our new Cougar.

I don't mean to sound preachy here, but having spent 50 some years in the nuclear industry I have been conditioned to "what if" to a fault sometimes. "Questioning attitude" and fault/event review are burned into my old brain.

[gepaine]

My Keystone Cougar came with 15" tires rated at LRD. I was able to upgrade to 15" LRE's on the original rims because the rims were rated at 2830 pounds which was the max load of the new LRE's. (The LRE's have a max psi of 80.) However, I will inflate them based upon my actual load plus a 10-15 psi safety margin. That will be about 65 psi which happens to be the recommendation on the trailer label.

I'm just mentioning this so people won't assume they have to upgrade their rims if they upgrade their tires. It all depends on the actual ratings of their equipment.

[iamrwnut]

My tires are Carlisle ST 225/75R15s. The rims show 2600 lb limit.

[SAD]

Originally Posted by iamrwnut

My tires are Carlisle ST 225/75R15s. The rims show 2600 lb limit.

Hence the 65 psi recommendation.

[diugo]

So now we have two posters in this thread who have to run an LRE at 65psi instead of 80---instead of an LRD at the 65psi full sidewall pressure.

Am I the only one here who thinks this is bad?

[SAD]

It is not bad as long as the pressure chosen is appropriate for the weight placed upon the tire.

[Festus2]

Originally Posted by diugo

So now we have two posters in this thread who have to run an LRE at 65psi instead of 80---instead of an LRD at the 65psi full sidewall pressure.

Am I the only one here who thinks this is bad?

diugo -

I may be wrong here but in another and earlier thread you indicated that you were going to run your newly-acquired Maxxis D's at 55psi rather than the stated sidewall pressure of 65 psi - a reduction of 10 psi - based on the weight on the tires.

In this thread, someone will be running their E rated tires at 65 psi instead of 80 psi - a reduction of 15 psi.

Perhaps I am not following, but why do you think it is "bad" for this person to reduce the pressure but it is ok for you? I realize there is a slight difference of 5 psi but the end result is the same - a reduction in pressure other than what is stamped on the tire. Is it an issue of wheel/rim size?

Puzzled.

[diugo]

Festus2,

It's not a question of "just 5 psi", but of proper load range. In my case, 55psi is simply too high for LRC---yet 65psi results in "gross overinflation", according to RVSEF.

If my trailer were just a little lighter---such that 50psi was indicated---I would have seriously considered LRCs when I bought my Maxxis. Because I contend that an LRC at 50psi is superior to an LRD at 50psi. Simply put, the LRC is designed for 50psi. The LRD is not. It is underinflated at 50psi---it no longer has the rigidity necessary for trailer use, and the extra plies only make it less pliable and run hotter. If you don't believe me, Google is your friend.

[gepaine]

Diugo,

I can find nothing on RVSEF to support your position. (If support is there, please point it out to me.) If a Google search will return support for your position, why not save us the time and provide us with a URL?

Thanks,
Gene

[iamrwnut]

Just an FYI. I did not purchase the tires. They came on the "new to us" trailer when we purchased it last year. I had been following alot of the posts about tires and was still confused. The trailer was 5 years old when we purchased it. It is my un-educated guess that the original owner replaced the tires one or two years ago. I would like to neither over or under inflate my tires. Just looking to do "the right thing".

[iamrwnut]

Another FYI. We purchased from a dealer not a private owner so no way to know when they were replaced.

[diugo]

Gene, the RVSEF document citing my "gross overinflation" reference can be found at http://rvsafety.com/2011/09/tire-loa...lation-ratings . There you'll find their general recommendation that towable tires be inflated to the sidewall pressure. If you only inflate an LRE to 65psi, then you're not doing that. There are posts on numerous other forums debating the equivalence of LRD/E at 65psi, all easily googleable.

OP, I share your concern about doing the right thing. Many RVers---myself included---find ourselves in a similar dilemma: we all seem to be a load range too high with our tires, and there's just no good solution. My advice to every RVer casually considering a higher load range: look before you leap!

[gepaine]

Diugo,

Your RVSEF reference says:

"Note: Towable – Travel Trailer/ 5th Wheel owners Due to the severe use conditions experienced by tires when axles are very close together – tire industry experts recommend maximum (sidewall) inflation pressure for towable tires unless this causes a severe over-inflation situation (20psi+), often referred to as the ‘basketball effect’. If this is your situation allow a 10 – 15psi safety margin above the minimum required inflation pressure."

I am doing exactly what this paragraph says when I inflate my LRE's to 65 psi. That is, I am avoiding a severe over-inflation situation by allowing a 10 – 15psi safety margin above the minimum required inflation pressure.

[diugo]

Gene, yes, and I am doing the same thing with my Maxxis LRD's at 55psi. However, that doesn't make it right/ideal. Neither of us is running a trailer tire at the designed sidewall pressure---our load range is too high, and as a result, extra heat is being generated in our tires.

In your case, you could run LRDs and still have your 10-15psi margin, right? In my case, I would have to run an LRC at 5psi over the sidewall, which is something I will personally discuss with RVSEF when I get each wheel individually weighed, a month from now.

There's a good discussion here: http://forums.woodalls.com/index.cfm...print/true.cfm

[gepaine]

Diugo and all,

I read the discussion you pointed me to on Woodall's forum. Even though it was all opinion with no verifiable authority to support the opinions (as opposed to what we see on RVSEF), it has convinced me that I need to do more research. The good thing in my case is that my rims can handle 80 psi should I decide to go that way.

Thanks for your input. Good discussion.

Gene