Poor Quality Trailer Tires

[plocklin]

Originally Posted by DaveSchwartz

Its not underinflation when the inflation is proper for the tire loading. Most passenger tires have a max pressure around 45psi yet auto manufacturers, who stand to get their butts sued off if they get it wrong, put inflation labels on their vehicles that state somewhere around 30psi. Is that deliberate underinflation? No - because their engineers, working with the tire engineers have done the proper tire selection and analysis to determine the proper inflation pressure for the load their vehicle will put on the tire. You may choose to inflate your car tires to 45psi but it will ride like a buckboard and handling, traction and wear will all suffer.

Now why do trailer manufacturers always recommend the same inflation pressure as the max pressure for the load range they select? Because they almost always design the GVWR of the trailers to be close to (95%+) the load-carrying capacity of the tires. The cargo capacity of the trailer in the brochure is usually set to the difference between the sum of the tire load capacity minus the dry weight of the unoptioned trailer plus the hitch weight. Then when you get your trailer, you'll find your cargo capacity has been derated by all the options you added.

If you put G114's inflated to 115psi on a trailer that came with LRD tires those rubber rocks are going to eventually shake your trailer apart. An appropriately engineered amount of sidewall flex is supposed to be there to absorb some of the road roughness so that the axle and suspension doesn't have to do it all.

I agree with you DaveSchwartz. The maximum rating of a tire is the maximum weight a tire is designed to carry “at the maximum air pressure of the tire”. If you put less pressure in the tire the load capacity decreases.

If your Trailer weighs 95% of the maximum load capacity of your tires you are force to put the maximum pressure in the tire. If the tire is rated higher than your load you can put less air in the tire and it is not under-inflating.

I don’t like running tires at maximum pressure because I believe they are more susceptible to being punctured from road hazards (flats and blowouts) at maximum pressure. On the other hand tire pressure that is too low can cause excessive wear, heat build up and internal damage.


When I asked "do you under inflate" I was referring to "the maximum tire rating" and the "recommendation of the TT manufacturer." I asked the question with the understanding that people have different opinions on what exactly that is.

[plocklin]

Originally Posted by Jmkjr72

Remember it isn't just the tire pressure rating you have to worry about. Some rims are only rated to 65 psi not 80

Great point Jmkjr72!
If I go from 15" to 16" rims I can increase my capacity around 1000lbs per tire (depending on the rim). Of course this is the capacity of the wheels and not the trailer.

[emm-dee]

My E-load Maxxis have a combined capacity of 11,320. Axles have a combined load of 10,400. Cat scale shows combined axle weight of 7300 pounds. Final answer...tires are running at about 65% of capacity and axles are holding 70% of capacity. I like those numbers.

Oh, the axles are within 100 pounds of each other, both fore and aft and wise to side.

[jrk341]

Goodyear just came out with a new st tire made in the USA.https://redirect.viglink.com/?format...-selector.aspx

[Tireman9]

Originally Posted by plocklin

I agree with you DaveSchwartz. The maximum rating of a tire is the maximum weight a tire is designed to carry “at the maximum air pressure of the tire”. If you put less pressure in the tire the load capacity decreases.

If your Trailer weighs 95% of the maximum load capacity of your tires you are force to put the maximum pressure in the tire. If the tire is rated higher than your load you can put less air in the tire and it is not under-inflating.

I don’t like running tires at maximum pressure because I believe they are more susceptible to being punctured from road hazards (flats and blowouts) at maximum pressure. On the other hand tire pressure that is too low can cause excessive wear, heat build up and internal damage.


When I asked "do you under inflate" I was referring to "the maximum tire rating" and the "recommendation of the TT manufacturer." I asked the question with the understanding that people have different opinions on what exactly that is.

TT tires have more load than what is measured on a static scale. Side loading due to cornering and wind and road crown are obvious but a TT places up to 24% greater internal shear forces on the belts than if the same tire were on a motorhome with the same scale weight.
This shear is Interply Shear and is what contributes to the shorter life for TT tires vs Motorhome and truck applications.
Running at least 15% under the tire max rated load and running the tire inflation at the sidewall inflation can lower this shear.

[Tireman9]

Originally Posted by BandJCarm

They still make bias play tires? Why?

Because they are less expensive to make.

[Airdale]

JUST INFO:

I post this info over and over again with little agreement from the readers. If one is not willing to read and decipher the regulations the RV trailer manufacturer MUST follow when fitting tires and rims to RV trailers, how can they disagree with the following? There is but one authority for Original Equipment tire fitments, the vehicle manufacturer. True, tire manufacturer engineers and vehicle manufacturer engineers collaborate to insure safe and appropriate fitments, but, only the vehicle manufacturer can approve them for Original Equipment fitments.

The safety regulations written by NHTSA only require minimum standards. They are simple and direct. RV trailer tires (any design approved by the vehicle manufacturer) must provide a load capacity equal to the trailer’s GAWRs. The trailer manufacturer’s recommended tongue/hitch weight, when added to the total GAWRs must equal or exceed GVWR.

The regulations also require the trailer manufacturer to set recommended cold inflation pressures for all tire fitments, they must be appropriate for each fitment.

Tire fitments for cars, pick-up trucks, etc. cannot be compared to fitment of RV trailer tires. Automotive tires must have load capacity reserves provide by inflation pressures.

[Tireman9]

Originally Posted by JJaxon

This link doesn't work. Is there another path?

Sorry The forum is having some link problems. I suggest you just copy and paste
RV Tire Safety
into your browser.

[Tireman9]

Originally Posted by Iwannacamp

My minor experience with TPMS I set at 76 psi on the maiden voyage. The ambient was in the 70's and the alarm went off. D rated was set at 65 PSI

OK Are you sure you are running no more than 85% of the max load capability of your tires/ Did you exceed 65 mph?
I also suggest the high pressure warning be set to 125% of the CIP level or in your case at least 81.

You say your tires were set to 65 CIP. Was that using your hand gauge? What did the TPMS sensors think? I bet they were not all at exactly 65.

[Tireman9]

Originally Posted by plocklin

Thanks for the info. The shipping weight of the 306BHS is 7465LBS with a carrying capacity of 2070LBS. That puts me at close to 10000LBS loaded.
I will look for some better tires with a higher rating. I like the 3 tire rule in case a tire fails. I've heard if your tire capacity is near max in case of a blowout the tire left carrying the load can be internally damaged from the stress.

Never seen the "3 tire rule" but I am guessing it suggests it is OK to tow with only 3 tires. That might work if somehow you get the load always equally distributed between the 3 tires. Am wondering how you accomplish that.

[Tireman9]

Originally Posted by Trawlerphil

The ST tires have stronger sidewalls to take the torque of right angle turns, LT tires don't have the same strength. Remember, your truck takes a pin load worth of the GVW of the trailer so using the entire GVW isn't accurate when figuring out needed tire capacity. My Flagstaff Classic is around 9,000 lbs loaded and had load range "C" tires on it (2150 lbs). The GVW minus pin weight didn't have very much reserve in it so I replaced them with load range "E" (117L) tires (2833 lbs) and the "L" means good for 75MPH. Most ST tires are only good for 65 MPH so it makes sense to decipher the DOT codes. As for inflation, use the max PSI recommended, 80PSI for load range "E" tires.

Sorry but the stronger sidewall is an old wives tail. There is no test for sidewall strength that shows an ST is any stronger than an LT of the same size of Load Range.
ST are rated at a higher load capacity because the formula places a speed restriction of 65 mph.

[Tireman9]

Originally Posted by Airdale

JUST INFO:

I post this info over and over again with little agreement from the readers. If one is not willing to read and decipher the regulations the RV trailer manufacturer MUST follow when fitting tires and rims to RV trailers, how can they disagree with the following? There is but one authority for Original Equipment tire fitments, the vehicle manufacturer. True, tire manufacturer engineers and vehicle manufacturer engineers collaborate to insure safe and appropriate fitments, but, only the vehicle manufacturer can approve them for Original Equipment fitments.

The safety regulations written by NHTSA only require minimum standards. They are simple and direct. RV trailer tires (any design approved by the vehicle manufacturer) must provide a load capacity equal to the trailer’s GAWRs. The trailer manufacturer’s recommended tongue/hitch weight, when added to the total GAWRs must equal or exceed GVWR.

The regulations also require the trailer manufacturer to set recommended cold inflation pressures for all tire fitments, they must be appropriate for each fitment.

Tire fitments for cars, pick-up trucks, etc. cannot be compared to fitment of RV trailer tires. Automotive tires must have load capacity reserves provide by inflation pressures.

All true. BUT the load formulas for ST tires is based on decades old speed restriction of 65 mph MAX. The Service Factor for trailer application also was established when highway speeds were 55 mph.

The formula for the number of pounds a new tire can carry for a couple hours has not changed while usage 65 - 75 -80 mph sustained has changed.

Can anyone show me where the speed limit for ST type tires is clearly communicated to the RV owner?

Yes I know that as of late last year ST tires started to come out with "Service Description" showing Speed Symbol for faster than 65 (done to get around some import restrictions) but the Load & Inflation tables show the inflation must be increased by 10 psi for speeds above 65 ( similar to your reserve capacity). The TRA tables also say for speeds of 75 to 85 in addition to a + 10 psi the load capacity must be decreased by 10%.

But none of the above addresses the reality that it is the air that supports the load and there has been no change in the physics that can justify why placing ST on a tire sidewall somehow makes the air in that tire capable of supporting 18% more load.

[Iwannacamp]

Originally Posted by Tireman9

OK Are you sure you are running no more than 85% of the max load capability of your tires/ Did you exceed 65 mph?
I also suggest the high pressure warning be set to 125% of the CIP level or in your case at least 81.

You say your tires were set to 65 CIP. Was that using your hand gauge? What did the TPMS sensors think? I bet they were not all at exactly 65.

Hello Sir. Thank you for the response. New 5er(maiden voyage) and unsure of actual weight. Advertised gross weight of 9650 and unladen as 7660#, Castle Rock D-rated tires as 2540# ea @65 PSI. Trailer wasn't loaded heavy?? maybe 500# Might have gotten 67-70 MPH a few times(lots of hills) mostly 55-60(took scenic route mostly). I have reset(as per an e-mail from you. Thank you.) and PSI was prolly 63-66(as per TST507) cold. Did not recheck after TPMS install in campground.

Thanks for what you do

[Tireman9]

Originally Posted by Iwannacamp

Hello Sir. Thank you for the response. New 5er(maiden voyage) and unsure of actual weight. Advertised gross weight of 9650 and unladen as 7660#, Castle Rock D-rated tires as 2540# ea @65 PSI. Trailer wasn't loaded heavy?? maybe 500# Might have gotten 67-70 MPH a few times(lots of hills) mostly 55-60(took scenic route mostly). I have reset(as per an e-mail from you. Thank you.) and PSI was prolly 63-66(as per TST507) cold. Did not recheck after TPMS install in campground.

Thanks for what you do

Some TPMS use the initial pressure when installed as the intended CIP so it is important to be sure of the set-up settings. Also some allow you to adjust the High & Low warning pressures.

I suggest you review my blog post on TPMS settings.
and re-read the TPMS instructions for your personal brand system

[CaptnJohn]

Originally Posted by Tireman9

Yes I know that as of late last year ST tires started to come out with "Service Description" showing Speed Symbol for faster than 65 (done to get around some import restrictions) but the Load & Inflation tables show the inflation must be increased by 10 psi for speeds above 65 ( similar to your reserve capacity). The TRA tables also say for speeds of 75 to 85 in addition to a + 10 psi the load capacity must be decreased by 10%.

I'm running Carlisle 235/80/R16 LR E after selling OEM tires to my tire dealer. Cold pressure 80 PSI. They are speed rated at 75 MPH. During rare passing situations they have seen 70. Would be difficult to increase 10 PSI as the wheels are only rated to 80, stated by the manufacturer. If they were rated higher I would have gone to load range F at 95 PSI, only being cautious as I believe they would hold 95 plus the heat increase.

[Tireman9]

Originally Posted by CaptnJohn

I'm running Carlisle 235/80/R16 LR E after selling OEM tires to my tire dealer. Cold pressure 80 PSI. They are speed rated at 75 MPH. During rare passing situations they have seen 70. Would be difficult to increase 10 PSI as the wheels are only rated to 80, stated by the manufacturer. If they were rated higher I would have gone to load range F at 95 PSI, only being cautious as I believe they would hold 95 plus the heat increase.

80 for CIP is good in your situation.

[plocklin]

Originally Posted by Airdale

JUST INFO:

I post this info over and over again with little agreement from the readers. If one is not willing to read and decipher the regulations the RV trailer manufacturer MUST follow when fitting tires and rims to RV trailers, how can they disagree with the following? There is but one authority for Original Equipment tire fitments, the vehicle manufacturer. True, tire manufacturer engineers and vehicle manufacturer engineers collaborate to insure safe and appropriate fitments, but, only the vehicle manufacturer can approve them for Original Equipment fitments.

The safety regulations written by NHTSA only require minimum standards. They are simple and direct. RV trailer tires (any design approved by the vehicle manufacturer) must provide a load capacity equal to the trailer’s GAWRs. The trailer manufacturer’s recommended tongue/hitch weight, when added to the total GAWRs must equal or exceed GVWR.

The regulations also require the trailer manufacturer to set recommended cold inflation pressures for all tire fitments, they must be appropriate for each fitment.

Tire fitments for cars, pick-up trucks, etc. cannot be compared to fitment of RV trailer tires. Automotive tires must have load capacity reserves provide by inflation pressures.

Thanks for the information Airdale,

You do bring valid data to the discussion. However a key word phrase here is “minimum requirements”. As long as trailer manufacturers meet these minimum requirements they have done there job. They are also in the business of making money and if they can save a few hundred dollars by using tires and wheels that only “meet the minimum requirements” that is exactly what they will do.

Yes, it is fine and safe to use the wheels and tires your trailer came with. However there are some of us who plan to pull their travel trailer on a 1000-mile trip and don’t want to be rolling on a set of May-Pops. All I want is to reduce the chance that I will be changing flat tires and hopefully get a better ride on my road trip.

[ependydad]

Originally Posted by Tireman9

Yes I know that as of late last year ST tires started to come out with "Service Description" showing Speed Symbol for faster than 65 (done to get around some import restrictions) but the Load & Inflation tables show the inflation must be increased by 10 psi for speeds above 65 ( similar to your reserve capacity). The TRA tables also say for speeds of 75 to 85 in addition to a + 10 psi the load capacity must be decreased by 10%.

I recall reading something from Goodyear and Maxxis on this, but it was before the new speed symbols came into play.

Do you have a current link/table showing the increased pressure and decreased load capacity that you referenced?

[plocklin]

Originally Posted by Tireman9

Never seen the "3 tire rule" but I am guessing it suggests it is OK to tow with only 3 tires. That might work if somehow you get the load always equally distributed between the 3 tires. Am wondering how you accomplish that.

You would only do that if you didn’t have a spare!

Maybe you could start a forum on your website telling peopled how to load their TT for 3 tires.

[lbrjet]

You folks you need to be careful how you interpret this +10 psi to travel 10 mph faster verbiage. This does NOT mean putting 90 psi in an 80 psi tire. What it does mean is if you only need 70 psi according to loading/psi tables then putting in 80 IS +10 psi.