Proper Tire Pressure...

[sloman2001]

I am changing all my tires on out 5ver from STs to LTs. I have looked for an answer to my question but to no avail, so I will try here, you have all been helpful in the past.

I'm going to put 80lb psi in the tire per the RV recommendation. The max tire pressure is also 80lbs. I'm putting on Michelin LT235/85R16 size tires. They are load range E tires (3042 lbs. at 80 psi), I have 5200 lb. axles.

While driving, this pressure will increase to various levels depending on the ambient temperature as well as speed (we drive 55 mph).

So 2 questions,
1) What is an acceptable level of psi above the 80lbs, and
2) If the pressure exceeds that, do I merely stop and remove some air?

I do not want another tire failure.

I have a TPMS in place so I can monitor the pressure real time.

Thanks in advance. I'm learning the hard way.

Tom

[jadatis]

Me Again wrote:
OP asked for an inflation table. Chris

www.goodyear.ca/truck/pdf/product_brochures/RV_Brochure_P.pdf

I see at the bottom of page 1 that its a brocure of may 2008.
There is a lot of old information still standing on the internet.

Calculated the sise 235/85R16 the pressure/loadcapacaty list back to what power is used and it apeared to be power 0.7 wich is still used in America for C-load/6PR and up but gives to much deflection in the lower pressures/loadcapacity-range.
Also the different loadkinds like D to G-load are placed in one list. wich is also wrong. In Europe for every Loadkind a seperate list is made. A stiffer tire ( higher loadkind)has lower loadcapacity for the same pressure. You can notice that by the steps around the fatt printed loads that are not in line whith the other steps.
Probably they calculated the whole list for for instance E load and placed the fatt printed maximum loads of the D,F,G in to that.

Made my own pressure/loadcapacity-lists and planted them in next map.
In time I can add other lists if what you need is not given.
So if its only for the needed pressure better use my lists.
They give lower so saver loadcapacity's for the pressure , mayby even somewhat pessimistic. Even lower then the European calculation to wich American TRA swiched over to for P-tires and XL for a reason as late as 2006.
I still not understand why they did not do it for C-load and up.

Open the PDF out of the USA map with lbs and psi given, that begins with the reference-pressure ( Pr)/pressure needed for the maximum load/maxloadpressure ( that 80 psi in TS tires).
it is grooped by given per tire( as is usual in America) and given per axle single and Dual ( as is done in Europe). so you dont have to do the division yourselfes ( deviding axleload by 2 or 4).
Then search on loadindex or LBS maximum load in the first colom and use the list behind it as you are used to of the other lists.
Leftclicking opens it in the browser, but rightclicking makes download to your computer possible.
Extra save Pressure/Loadcapacity-lists

[sloman2001]

Thanks, this is perfect!!!!

Tom

[Me_Again]

OP asked for an inflation table. Chris

www.goodyear.ca/truck/pdf/product_brochures/RV_Brochure_P.pdf

[jaycocamprs]

Me Again wrote:

Cummins12V98 wrote:

jaycocamprs wrote:
When we changed our Jayco 285RLS with 5200# axles over to a LT235/85R16 LRE BFG's. I found that 70psi was the max I could run and make tread contact all the way across. I started at 80psi and worked down 5psi at a time. We ran those tires 2 years on the Jayco before selling that trailer. Kept the tires and they have been under the Mountaineer now for 2 more years (@80psi).

Ding Ding we have a winner!

This person understands that you DONT HAVE TO run max psi.

I will drink a beer to that! Ho! We did that Sunday afternoon didn't we!

If one has around 10K on the axles like the OP and myself, and these tires are good for two fully load axle with 12K on them at 80 lbs inflation, why would you put 80 lbs in them with 10K on the axles.

I asked this question of Michelin CS several times and always got the same answer. Over inflation decreases the contact patch and braking, and increases the chance of impact damage! I run 71 lbs in the same tire that OP installed and trailer is similar in size and weight. Has been working great for many years.

Chris

My above post is what I did when in the OP position. That little 9200# GVW Jayco only ran a little over 7K on the axles. I didn't need the LT235/85R16 LRE for load carrying, but wanted the tall tires to help level the trailer after buying the DRW truck. Michelins load charts say I could have run 40/45psi. But I just don't like running at the low end, I wanted all the reserve capacity I can get. I guess this is one of the questions that has a wide range of RIGHT answers, like gas or diesel!

[Me_Again]

rjsurfer wrote:


I have BFG 235/16's also on a small 26 foot 5th wheel and 70psi is about perfect for it.

I did an simple test my dad showed me, paint a white 2" stripe across the tread of your tires and run the car/trailer a few miles loaded. It's easy to see how the tread is wearing by taking a look at the wear of the stripe. This works for checking tire alignment as well. Tires have to be fairly new for this to work well.

Ron W.

People also use chalk on the tread and drive a short distance or drive over a piece of white paper.

In my case we started with 65 lbs with the XPS Ribs in Feb 2005. That is what the placard called for and matched the load table. After a couple years I measured a slight more wear on the outer edges and adjusted pressure to 71 pounds. Tires wore evenly after that.

One is hard pressed to wear out a RIB or R250 on a RV trailer. Just watch for cracking as they are getting older and enjoy them for 6-8 years. They both have low rolling resistance due to the steel ply carcass.

Chris

[JIMNLIN]

Yeah the LT is a very forgiving tire which is one reason we use them on trailers.
They can better with stand abuse such as using low pressures in a tire that spends much of its life sliding sideways around curves and corners which tries to tear the tire apart or bust the bead loose or constant load changes in strong side winds or from a tall heavy trailer with a high COG. Loads change constantly on a tall heavy boxy RV trailer unlike the tow vehicle.

A better choice for a small 26' trailer or 5200 lb axles is the LT225/75-16 E or a LT215/85-16 E both at 2680 lbs capacity. That way the tires can be pumped to the max for max performance and max reliability.

Now if the owner has over tired the trailer such as a LT G at 3750 lbs capacity on 6k axles or a E tire replacing a C tire then the tire may need to be derated to a lower pressure. IMO not the best idea.

Plus sizing tires on a trailer can have benefits but at some point there will be no benefit.

[rjsurfer]

Me Again wrote:

Cummins12V98 wrote:

jaycocamprs wrote:
When we changed our Jayco 285RLS with 5200# axles over to a LT235/85R16 LRE BFG's. I found that 70psi was the max I could run and make tread contact all the way across. I started at 80psi and worked down 5psi at a time. We ran those tires 2 years on the Jayco before selling that trailer. Kept the tires and they have been under the Mountaineer now for 2 more years (@80psi).

Ding Ding we have a winner!

This person understands that you DONT HAVE TO run max psi.

I will drink a beer to that! Ho! We did that Sunday afternoon didn't we!

If one has around 10K on the axles like the OP and myself, and these tires are good for two fully load axle with 12K on them at 80 lbs inflation, why would you put 80 lbs in them with 10K on the axles.

I asked this question of Michelin CS several times and always got the same answer. Over inflation decreases the contact patch and braking, and increases the chance of impact damage! I run 71 lbs in the same tire that OP installed and trailer is similar in size and weight. Has been working great for many years.

Chris

I have BFG 235/16's also on a small 26 foot 5th wheel and 70psi is about perfect for it.

I did an simple test my dad showed me, paint a white 2" stripe across the tread of your tires and run the car/trailer a few miles loaded. It's easy to see how the tread is wearing by taking a look at the wear of the stripe. This works for checking tire alignment as well. Tires have to be fairly new for this to work well.

Ron W.

[jadatis]

To my experiënce an LT tire ( Me living in Europe calling it C(omercial)-tyre) can have a livetime of 6 to 10 years.

Last year we hired a motorhome ( Hymer 3100kg/6800lbs gvwr) with A-brand tires and because it was the first time the people rented it
They asked that if something was missing or not ok us to let them know.

The tires I ofcource checked and only one had the DOT code with the production week and year on the outside , so asumed the others to be of same production date. Apeared to be 10 years old but enaug profile and I could see no cracks. In the time it was used ( build about 1998 so old) pressure advice on the papers was 4 bar all around ( 59psi).
I calculated with my spreadsheet for absolute savety going from the gawr's that 4,8bar/70psi rear and 4bar/59psi front.
The motorhome tires where at 3.5bar/51psi when I measured it at home so pumped them to a good 4 bar front and 4.5 bar behind ( with bicicle pump) and did about 3000 km/1300miles And made it to Pisa Italia Toscane and back with no tire problems.

I adviced them to put new tires on for savety, and they where suprised by the age of them.

If ST tires they have more deflection when you calculate the needed pressure with the conventional or my formula so they last shorter then LT . I have read of 3 years adviced to chanche them.
To my opinion an ST is not a better tire for a trailer but a lower quality.

Its like a painters quality door we once had placed and thougt it was even a beter quality then a normal door, yust by the name of it. But you had to paint it to cover the bad spots so even was a lower quality door.

So my answer to 'Me Again 'about me thinking the LT here was only slightly better then ST is that thoug the given maximum load of the LT is lower then the given maximum load of the ST . it is still sertainly not a worse tire, wich you would expect if you only compare the maximum loads .
Mayby because ST tires dont have to last that long, they even put less stuff in it to make them last longer , and this makes the difference in savety and livetime even more.

[Me_Again]

Cummins12V98 wrote:

jaycocamprs wrote:
When we changed our Jayco 285RLS with 5200# axles over to a LT235/85R16 LRE BFG's. I found that 70psi was the max I could run and make tread contact all the way across. I started at 80psi and worked down 5psi at a time. We ran those tires 2 years on the Jayco before selling that trailer. Kept the tires and they have been under the Mountaineer now for 2 more years (@80psi).

Ding Ding we have a winner!

This person understands that you DONT HAVE TO run max psi.

I will drink a beer to that! Ho! We did that Sunday afternoon didn't we!

If one has around 10K on the axles like the OP and myself, and these tires are good for two fully load axle with 12K on them at 80 lbs inflation, why would you put 80 lbs in them with 10K on the axles.

I asked this question of Michelin CS several times and always got the same answer. Over inflation decreases the contact patch and braking, and increases the chance of impact damage! I run 71 lbs in the same tire that OP installed and trailer is similar in size and weight. Has been working great for many years.

Chris

[Cummins12V98]

jaycocamprs wrote:
When we changed our Jayco 285RLS with 5200# axles over to a LT235/85R16 LRE BFG's. I found that 70psi was the max I could run and make tread contact all the way across. I started at 80psi and worked down 5psi at a time. We ran those tires 2 years on the Jayco before selling that trailer. Kept the tires and they have been under the Mountaineer now for 2 more years (@80psi).

Ding Ding we have a winner!

This person understands that you DONT HAVE TO run max psi.

[jaycocamprs]

When we changed our Jayco 285RLS with 5200# axles over to a LT235/85R16 LRE BFG's. I found that 70psi was the max I could run and make tread contact all the way across. I started at 80psi and worked down 5psi at a time. We ran those tires 2 years on the Jayco before selling that trailer. Kept the tires and they have been under the Mountaineer now for 2 more years (@80psi).

[Allworth]

We are very happy with the Commercial TA replacements and we tow about 12,000 miles per year. By the way, the 245/75 is much easier to find than the 235/80 (or 85) and fits in the same space.

[Pipeman]

I run ribs on my 5er and they are at 80 psi. I had them on my TH when I had that. No problems at all. Don't worry about what the ambient temp is. The tires are made for that air expansion. I also run Michelin on my TV and they are at 80 psi when hauling the 5er. When not hauling they are at 50 psi. I have a 1 ton dually and the ride is more comfortable for us at that pressure.my personal 1ton trucks do not ride like caddys...my personal decision...

[Me_Again]

sloman2001 wrote:
Sorry about that, Chris was correct. I had ST on the brain. I was planning on putting on LT235/85R16 LRE tires tomorrow. I think I am going to call the guy and check out the R250 or RIB tires he is suggesting to see cost difference. I'll let you know.

Like I said, it is not to late to do it right! LTX M&S 2 is a good pickup tire, trailer not so good of a choice!

If you are going to stay with a poly carcass LT, then look at the Firestone Transforce HT or BFG Commercial TA for less money.

HT


TA


Chris