TowMax STR II Tire Pressure above maximum sidewall

[NMWildcat]

So... How about those Cowboys?

[itat]

Someone earlier in this thread said that Maxxis’ ST tires are only rated to 65 mph. That’s no longer true. Here is a statement from Maxxis Canada in a recent email they sent me:

“Regarding to the speed rate, the ST225/75R15 Load Range E (10 Ply) tire is 160 km/h or 99 mph.”

This is for their M8008 tire.

[Airdale]

Originally Posted by itat

Someone earlier in this thread said that Maxxis’ ST tires are only rated to 65 mph. That’s no longer true. Here is a statement from Maxxis Canada in a recent email they sent me:

“Regarding to the speed rate, the ST225/75R15 Load Range E (10 Ply) tire is 160 km/h or 99 mph.”

This is for their M8008 tire.

Is it written on the tire?

TRA says if it's not written on the tire it's a 65 MPH tire.

[Airdale]

Originally Posted by DieselDrax

That guide is for passenger and “light truck” tires, not trailer tires or commercial truck tires. As I have said at least twice before in this thread, the standards are different. P-metric tires list both max load and max pressure. Trailer and truck tires only list max load at the rated pressure, which is not the max pressure.

I’m not going to keep repeating this info which is available from multiple sources (the last image I included was from Michelin, BTW). As long as people keep assuming P-metric tires and trailer or commercial tires have the same standards and keep applying the wrong standards to these tires or reading words that aren’t there then there will continue to be confusion and misinformation.

Take it or leave it, but at least look at applicable documents and standards. Have a good night! Not interested in talking in circles anymore.

Obviously you failed to research the reference provided. Chapter #4 - where the orange quote came from - is all about tires used on RVs, all RVs.

https://www.bing.com/images/search?v...vt=0&eim=1,2,6

[DieselDrax]

Originally Posted by Airdale

Obviously you failed to research the reference provided. Chapter #4 - where the orange quote came from - is all about tires used on RVs, all RVs.

https://www.bing.com/images/search?v...vt=0&eim=1,2,6

Sigh, I'm not sure where the difficulty in reading is coming from but the doc you are referencing is for passenger and light truck tires, not RV tires. Not commercial tires. Not trailer tires.


This thread is discussing trailer tires. Trailer tires are not passenger car or light truck tires. They do NOT comply with the same standards as passenger car tires.


Please stop referencing passenger car and light truck tire standards when talking about trailer tire standards and nomenclature. They are not the same.


RV Tires 101 | Trailer Life also echoes what others have been saying.

Another important distinction between LT and ST tires is their speed ratings — something a lot of RVers tend to overlook. Goodyear, maker of Marathon trailer tires, states in its bulletin PSB 2011-13: “Industry standards dictate that tires with the ST designation are speed rated at 65 mph under normal inflation and load conditions. Based on these industry standards, if tires with the ST designation are used at speeds between 66 and 75 mph, it is necessary to increase the cold-inflation pressure by 10 psi above the recommended pressure for the rated maximum load. Increasing the inflation pressure by 10 psi does not provide any additional load-carrying capacity.

/thread

[BriaBeck]

Originally Posted by trailerlife.com/tech/diy/rv-tires-101

Goodyear, maker of Marathon trailer tires, states in its bulletin PSB 2011-13: “Industry standards dictate that tires with the ST designation are speed rated at 65 mph under normal inflation and load conditions. Based on these industry standards, if tires with the ST designation are used at speeds between 66 and 75 mph, it is necessary to increase the cold-inflation pressure by 10 psi above the recommended pressure for the rated maximum load. Increasing the inflation pressure by 10 psi does not provide any additional load-carrying capacity.

“Do not exceed the maximum pressure for the wheel. If the maximum pressure for the wheel prohibits the increase of air pressure, then the max*i*mum speed must be restricted to 65 mph. The cold-inflation pressure must not exceed 10 psi beyond the inflation specified for the maximum load of the tire.”

Thanks DieselDrax! That is the answer to my question in post #1 and post #21 of this thread. It looks pretty cut and dried, black and white, to me.


I wonder if the "ChinaBomb" syndrome might be, at least in part, the result of all the misunderstanding and subsequent misinformation flowing across all these forums being put into practice?

My TowMax STR II's are going to run at 75psi from now on. Not because I want to run at elevated speeds, but because these tires have a track record of being a bit weak. If they are OK to run at 75psi, it should hopefully help their longevity at any speed below their 75mph "L" speed rating.

[NMWildcat]

Read this from the Towmax website for another interpretation of proper inflation and the 10lb over idea. http://www.towmaxtires.com/tires/Lan...on=maintenance

[BriaBeck]

I'm not putting a lot of weight on what the TowMax website says...


It is just site set up by TBC brands, which is a marketing firm that markets and sells various tire brands such as TowMax, Sailun, Sumitomo, etc (you can look on the website).



TBC Brands


The tires are marketed as "L" speed range (75mph), and there is NO maximum pressure listed on the tire... only Maximum Load @ minimum Pressure.


Since the tires have to meet the ST specifications with DOT, and no maximum pressure is listed, only a maximum load at minimum pressure, I'm going to go with the industry standard.

[NMWildcat]

Can be said about info in any website.
Well, let us know how your experiment goes. Seems to me if 10lb over when cold, is going to be considerably more when the tire and outside temps are both hot. Should be interesting!

[BriaBeck]

Originally Posted by NMWildcat

Can be said about info in any website.
Well, let us know how your experiment goes. Seems to me if 10lb over when cold, is going to be considerably more when the tire and outside temps are both hot. Should be interesting!

Very True!!


Like you said, it's an experiment... but I think after reading all the information, I'm confident that I'm operating well within the ST limitations that the tires are DOT certified under. If I were to upgrade to a "better" tire, that is an experiment also... and that is what will happen if I have a problem.



In the end, we make our decision and hope for the best, no matter what brand is on the sidewall, or how much pressure is inside.


I had TowMax tires on my 12' dump trailer, and I got I think 6 years of "extreme duty" service out of them before they needed replacing last year because of cords breaking (HEAVY loads, you know, you ask the end loader operator at the quarry for 4 1/2 tons, and when you weigh out, he gave you about 5 1/4 tons... tight turning WITH the HEAVY loads)... These tires on the RV will see gentle usage comparatively. I'm going in with a good TowMax experience rather than bad... albeit different sizes and Load ratings, so we'll see. As we have seen, the "better" brands are not immune from blowouts either.

[MR.M]

Originally Posted by BriaBeck

I'm not putting a lot of weight on what the TowMax website says...


It is just site set up by TBC brands, which is a marketing firm that markets and sells various tire brands such as TowMax, Sailun, Sumitomo, etc (you can look on the website).



TBC Brands


The tires are marketed as "L" speed range (75mph), and there is NO maximum pressure listed on the tire... only Maximum Load @ minimum Pressure.


Since the tires have to meet the ST specifications with DOT, and no maximum pressure is listed, only a maximum load at minimum pressure, I'm going to go with the industry standard.

Can't say i never saw a tire with out a max psi stamped on it . my ST tires say 80psi max and a cold inflation of 80psi

but learn new things everyday and things are always not as the seem

[jadatis]

@ BriaBeck
Mind that if the tire is already damaged by only once using to low pressure for speed and weigt, that the 10psi extra will speed up the damage-buildup, and the when tire blows, the 10 psi extra is blamed, and "experiment " gives false outcome.

Only on a new tire , this experiment can be suxesfull.
If though the "old tire" lasts 6 years or more with no problems, the " experiment " is also succesfull.

[BriaBeck]

Originally Posted by MR.M

Can't say i never saw a tire with out a max psi stamped on it . my ST tires say 80psi max and a cold inflation of 80psi

but learn new things everyday and things are always not as the seem

As I have learned in this thread, some tires DO have a maximum pressure molded in the sidewall information. Some (most?) ST tires do not.


One thing I have learned in life so far in my 49 years, is to NEVER read more information into something than what is actually presented. So, with that said, "Maximum Load 2540lbs @ 65psi" DOES NOT mean the same thing as "Maximum Load 2540lbs @ 65psi MAXIMUM". Make sure you are NOT adding a "Maximum" where there is none!!



If you have an ST Tire that lists a maximum load at a minimum pressure (as most ST tires do it seems), then you should operate in reference to the ST industry standard and inflate to 75 psi if you are going to be operating above 65mph.



If you have an ST tire with 65psi MAXIMUM molded into the tire, then I would definitely agree that 65psi is truly the maximum allowable pressure for that tire.


You make your decision, and take your chances, no matter what.

[frank4711]

OK my head hurts a little, just read all of this. So my E rated Castle Rocks should be cold inflated to 80 lbs and I can drive at 65mph?? This has been almost as good as a Max Tow thread for a 1500 ....

[Airdale]

Originally Posted by BriaBeck

One thing I have learned in life so far in my 49 years, is to NEVER read more information into something than what is actually presented. So, with that said, "Maximum Load 2540lbs @ 65psi" DOES NOT mean the same thing as "Maximum Load 2540lbs @ 65psi MAXIMUM". Make sure you are NOT adding a "Maximum" where there is none!!

A tire with a maximum load of 2540# on it's sidewall will have a PSI value to obtain that load capacity. In the case above it's 65 PSI. That 65 PSI may be displayed any way that particular tire manufacturer wants to display it as long as it's on the tire sidewall. No matter how they do it it's the amount of inflation pressure necessary for that tire to provide it's maximum load capacity.

Here is an example of a ST tire size with its manufacturer's way of saying it.

IMG_4262 - iRV2.com RV Photo Gallery

The FMVSS provides all instructions for the vehicle manufacturer to abide to meet the minimum standards for all RV trailer OE fitments. The only dissimilar distinction for individual tire designs is for the Passenger (P) tire to be derated by about 10% for use on RV trailers or pick-up trucks/SUVs. Chapter #4 in the USTMA publication previously discussed is all about the use of any of the DOT certified highway tires chosen by the trailer manufacturer for fitments to their trailers.

[jadatis]

The 10% reduction of maxload for " P-tires" for SUV or whatever is not done in Europe.
In my spreadsheets I add 10 % to given axleload and this has same effect.
For normal cars the advicepressure are given for GAWR's in earlyer days, and this was enaugh because normal use not fully loaded,wich gave the reserves.

[Airdale]

Originally Posted by jadatis

The 10% reduction of maxload for " P-tires" for SUV or whatever is not done in Europe.
In my spreadsheets I add 10 % to given axleload and this has same effect.
For normal cars the advicepressure are given for GAWR's in earlyer days, and this was enaugh because normal use not fully loaded,wich gave the reserves.

I know you may not be a study of the USA tire regulations. The following paragraphs are from the FMVSS (standards). The vehicle manufacturers MUST derate passenger tires when they have decided to use them on the vehicles described in these paragraphs from the FMVSS (standards).

S4.2.1.1 The vehicle maximum load on the tire shall not be greater than the applicable maximum load rating as marked on the sidewall of the tire.

S4.2.2.1 Except as provided in S4.2.2.2, the sum of the maximum load ratings of the tires fitted to an axle shall not be less than the GAWR of the axle system as specified on the vehicle's certification label.

S4.2.2.2 When passenger car tires are installed on an MPV, truck, bus, or trailer, each tire's load rating is reduced by dividing it by 1.10 before determining, under S4.2.2.1, the sum of the maximum load ratings of the tires fitted to an axle.

When reading various tire manufacturer data books, an explanation for such reductions is given. Explanations are also found in the USTMA publications.

For all readers: Those paragraphs are from FMVSS and are only applied by vehicle manufacturers. They are not applicable to consumers unless the consumer is using some sort of plus sized tire that must also comply with the standard.

[Everyday is Saturday]

Can someone clear this up for me? I have read that for RVs, the tire pressure is set separately for each tire because each tire is under a different load. On my fifth wheel with dual axels and 4 tires, I need to establish each wheels load. One way is to get to a scale and have the RV weighted for each wheel if possible at the maximum loading of the RV.
The other method I heard was to estimate the following.
20% of GVW is for the pin weight in the truck
80% of GVW is distributed over the 4 tires.
It is estimated that because of the no. of slides and location, the 80% GVW is split 55~57% to the heavy side and 45~43% to the lighter side.
Taking it one step forward the weight on each side is further split between the front tire and back tire. I have no % break down for this.
My question is can any one shed light on these assumptions of left to right and front to back on the tires?
My tires are ST 225/75R15, speed rating is “L”, 75mph max, load rating “E”, max load: 2830# at 80 psi CIP
Tks

[Airdale]

Originally Posted by Everyday is Saturday

Can someone clear this up for me? I have read that for RVs, the tire pressure is set separately for each tire because each tire is under a different load. On my fifth wheel with dual axels and 4 tires, I need to establish each wheels load. One way is to get to a scale and have the RV weighted for each wheel if possible at the maximum loading of the RV.
The other method I heard was to estimate the following.
20% of GVW is for the pin weight in the truck
80% of GVW is distributed over the 4 tires.
It is estimated that because of the no. of slides and location, the 80% GVW is split 55~57% to the heavy side and 45~43% to the lighter side.
Taking it one step forward the weight on each side is further split between the front tire and back tire. I have no % break down for this.
My question is can any one shed light on these assumptions of left to right and front to back on the tires?
My tires are ST 225/75R15, speed rating is “L”, 75mph max, load rating “E”, max load: 2830# at 80 psi CIP
Tks

Follow the directions on your trailer's certification label, tire placard and in the owner's manual and keep them inflated to 80 PSI.

Read chapter # 4 in the following reference. It will explain the importance of a balanced load and how to use commercial scales to achieve the best balance.

https://www.ustires.org/sites/defaul...TruckTires.pdf

[Herk7769]

Originally Posted by Everyday is Saturday

Can someone clear this up for me? I have read that for RVs, the tire pressure is set separately for each tire because each tire is under a different load. On my fifth wheel with dual axels and 4 tires, I need to establish each wheels load. One way is to get to a scale and have the RV weighted for each wheel if possible at the maximum loading of the RV.
Tks

According to the CAT scale folks and the attached Firestone "How to weigh and set tire pressures for your RV" you weigh each wheel and then set the pressure of the tires on each axle based on the highest loaded tire on each axle. Always balance the pressure of the tires on each axle equally.

For example on a 5th wheel, the deck (towing) angle can shift load from the front trailer axle to the rear in a nose high tow.

Never exceed the max rated weight of your axle or tires.

I see the CAT folks have amended the web site:
https://catscale.com/how-to-weigh/

They no longer offer individual wheel weights as a service. You will need to do total axle weights there or find someone with a wheel scale or buy the set.

https://www.amazon.com/ProForm-67650...gateway&sr=8-2