Towmax by Power King – Facts

[tireman9]

I think that is a great question by Grumpy, and a total lack of an answer to it. While I agree that the wheel diameter has nothing to do with it, the tire diameter would make a big difference. A taller tire is turning fewer rpm's than a shorter tire, while traveling at the same speed. Typically, the larger the wheel, the taller the tire is that is mounted on it. So a shorter tire mounted on a, lets say 14" wheel, is turning far more rpm's than taller tire mounted on a larger wheel, while both traveling at 65 mph. This whole 65 mph rating has to be directly related to how fast a tire is spinning, does it not? It would then seem that the shorter the tire, the lower the max mph should be. Anyone else confused about this? No way that one size fits all in this application of the 65 mph max speed ratings for ST tires. I'm not one to drive fast, but I sure would like to hear an explanation on this.

Hope my other post clears the air but to your specific question tires are tested to a MPH spec not an RPM spec. Yes a smaller tire has to turn more RPM to go the same MPH but again the performance spec is stated as MPH so the engineers have to compensate with various design changes to meet the performance spec.

 

[tireman9]

Re: Towmax by Power King – Facts

Bob,

Let say you switched from the Towmax 235/80R16 to the 235/85R16, which would change the outer diameter of the tire from 30.8 to 31.7". That's about a 3% change. But I noticed that the larger tire carries a slightly higher load rating - close to a 3% increase - so perhaps the increased tolerance to heat buildup was assigned to the load spec rather than to the speed rating.

We design engineers don't get a simple choice of which feature or dimension is used to compensate for dimension changes. The tire is a complete package that has to carry the specified load at the specified inflation at a specific speed. The 3% change you note is just chance as other sizes may be identical OD but be different section width (more air volume). Since it essentially is the volume of air (at a given pressure) that carries the load you can't simply look at tire OD. Here are two posts that may help clear this up.
http://www.rvtiresafety.net/2011/03/tire-loads-inflations-heavy-topic-part.html
pay attention to the contact pressure diagram that shows the forces from the pressure.
http://www.rvtiresafety.net/2011/03/tire-loads-inflations-heavy-topic-part.html

While heat buildup is a major controlling factor there is no formula that will accurately predict the tire temperature based just on OD and MPH.

 

[danemayer]

Re: Towmax by Power King – Facts

We design engineers don't get a simple choice of which feature or dimension is used to compensate for dimension changes. The tire is a complete package that has to carry the specified load at the specified inflation at a specific speed. The 3% change you note is just chance as other sizes may be identical OD but be different section width (more air volume). Since it essentially is the volume of air (at a given pressure) that carries the load you can't simply look at tire OD. Here are two posts that may help clear this up.
http://www.rvtiresafety.net/2011/03/tire-loads-inflations-heavy-topic-part.html
pay attention to the contact pressure diagram that shows the forces from the pressure.
http://www.rvtiresafety.net/2011/03/tire-loads-inflations-heavy-topic-part.html

While heat buildup is a major controlling factor there is no formula that will accurately predict the tire temperature based just on OD and MPH.

Ok, I get that there are other factors than OD and speed. But that leaves the question unanswered. Are all ST tires rated at the same max speed of 65 mph because it's convenient in the absence of a formula?

 

[caissiel]

To be right the axle goes at 65 mph and the tire is at 0 miles per hour.
That was the invention of the wheel that allowed zero wear in ancient times.


Sent from my LG-LS720 using Tapatalk

 

[BobX2]

Hope my other post clears the air but to your specific question tires are tested to a MPH spec not an RPM spec. Yes a smaller tire has to turn more RPM to go the same MPH but again the performance spec is stated as MPH so the engineers have to compensate with various design changes to meet the performance spec.

I appreciate you trying to explain this, and I'm thinking it would be too difficult for tire manufacturing to speed rate each tire size, and that is the reason for one blanket speed rating. However, I believe that tire RPM has to be the key to the speed ratings. The weight of the load doesn't change because of your speed changing, but mph are the only thing we can monitor while driving, so that is what they use. I guess that all I'm saying is that if two tires with equal section width, one tire being 29" tall and the other 31" tall, the 31" tall tire can travel at a higher mph than the 29" tire without exceeding the parameters set for the tires safety. I would find it hard to believe that they build each tire size differently, in terms of the physical properties of each size. Or do they? That would be the only way that a 13" tire and a 16" tire could both be rated for the same speed.

I don't know, maybe I'm totally out in left field about this subject and I'm about to get an education here.

 

[SeattleLion]

I may have this all wrong, but in terms of high speed tires for sports cars as well as luxury cars, as the sidewall height is reduced (low profile), the sidewall stiffness is increased. This reduces flex and heating, but has the penalty of a harsher ride. If the same rules apply to ST tires, if the profile is higher, the sidewalls can be built with less stiffness. If the standard for ST is 65mph, then I assume the design engineers work on belts, sidewalls, etc. to allow the tire to travel at that speed for the profile and diameter.

In other words, the way the specific size ST tire is built varies based on diameter, tread width and profile (80 vs 85, etc). Is that correct?

 

[tireman9]

Re: Towmax by Power King – Facts

Ok, I get that there are other factors than OD and speed. But that leaves the question unanswered. Are all ST tires rated at the same max speed of 65 mph because it's convenient in the absence of a formula?

All tires are designed to meet the various performance targets established for that tire. There is no "formula" like you may find for a cake mix.

Some targets are from Sales & Marketing i.e. estimated wear life or snow traction level as measured on test XYZ. Some targets are specified by the car companies i.e. Rolling Resistance (fuel economy), Steering forces, noise. Some Targets MUST be met as they are set by Law. These are the ability to pass certain speed, strength and durability tests that used the published Load & Inflation tables.
Tire design is a combination of Art & Science and it takes years of experience and lots of testing to arrive at the specification for each tire a company makes. Sometimes identical size tires with similar tread patterns have different performance requirements depending if the tire is sold to Ford or GM and sometimes even different model cars for a car company can have different specifications.

Now the RV market to my knowledge does not buy tires based on performance goals. I know of no RV company that has tire evaluation engineers on staff. RV companies seem to select the lowest cost tire that is of a size required to meet the GAWR and where sufficient volume can be delivered per schedule. Now some RV companies that build Class-A or C motorhomes don't specify the tires as the chassis company (GM, Ford, Freightliner etc) has already selected a tire for their other applications that use the same chassis as is used in the RV market. I don't think any towables do this though.

 

[tireman9]

I appreciate you trying to explain this, and I'm thinking it would be too difficult for tire manufacturing to speed rate each tire size, and that is the reason for one blanket speed rating. However, I believe that tire RPM has to be the key to the speed ratings. The weight of the load doesn't change because of your speed changing, but mph are the only thing we can monitor while driving, so that is what they use. I guess that all I'm saying is that if two tires with equal section width, one tire being 29" tall and the other 31" tall, the 31" tall tire can travel at a higher mph than the 29" tire without exceeding the parameters set for the tires safety. I would find it hard to believe that they build each tire size differently, in terms of the physical properties of each size. Or do they? That would be the only way that a 13" tire and a 16" tire could both be rated for the same speed.

I don't know, maybe I'm totally out in left field about this subject and I'm about to get an education here.

Every tire made has a unique specification of 15 to 20+ different materials, at different thicknesses, widths and shapes and is cured in a mold for that size & tread pattern at a time (to the second) and temperature (to 10F increments). All are developed for the end product to meet a specific set of performance requirements. One of the set of requirements are the speed, strength and durability tests. We also have to address the variation is a hand made product to ensure that ALL tires would pass every regulatory test. The requirement is not for the average speed or strength or durability to exceed target X but each and every tire is supposed to be able to meet the regulations.
DOT will select tires at random and conduct teats and every tire tested MUST pass every test 100% of the time. If they don't that's when there are Recalls which are really expensive and to be avoided at all costs if at all possible.

 

[tireman9]

I may have this all wrong, but in terms of high speed tires for sports cars as well as luxury cars, as the sidewall height is reduced (low profile), the sidewall stiffness is increased. This reduces flex and heating, but has the penalty of a harsher ride. If the same rules apply to ST tires, if the profile is higher, the sidewalls can be built with less stiffness. If the standard for ST is 65mph, then I assume the design engineers work on belts, sidewalls, etc. to allow the tire to travel at that speed for the profile and diameter.

In other words, the way the specific size ST tire is built varies based on diameter, tread width and profile (80 vs 85, etc). Is that correct?

Short answer is yes.

 

[tireman9]

Watch this video on tire manufacturing. It may help you understand.

or this one

or this one just on tire assembly

or Here

Now you have a better understanding......I hope

 

[JohnDar]

Thanks! Very interesting stuff. A lot of the production depends on the skill and experience of the operators in the process.

 

[Rddocatt]

I agree with him and the others. Goodyear G14's

 

[Miltp920]

Tireman, just installed my TireTraker on my Towmax tires until I figure out which way to go onnreplacement. IF you were asked your opinion on your top three replacements foe OEM, you would say?

I appreciate your feedback. I have learned ALOT about tires and NOT taking anything for granted on this website, and owners forum. THANKS to all those who help keep us informed. Can you recommend an add on tire pressure monitoring system. I do not recall even seeing this as an option when I ordered the 3100 Cyclone, 2axle. I just saw the add for the TPMS. On your blog. Looks like a good insurance policy. THANKS AGAIN TIREMAN. Does anyone recommend putting TPMS on both tow vehicle and 5th wheel? OR typically just put on 5th wheel?

 

[tireman9]

Tireman, just installed my TireTraker on my Towmax tires until I figure out which way to go onnreplacement. IF you were asked your opinion on your top three replacements foe OEM, you would say?

Did a post on "Best Tire". Sorry there is not enough data to provide a more focused answer.

I would point everyone back to the first post with the NHTSA data. As you can see the numbers of RV owners that make the minimal effort to file a complaint sends the message to NHTSA that there are no significant problems with RV tires. I also know from looking at some of the complaints the quality of th information is spotty even if a complaint was filed. Examples include wrong size, wrong tire brand, missing or incomplete DOT serial. Expecting information on actual load, speed etc is unrealistic and expecting an accurate description of the real failure is just a dream.

Engineers react to and work with facts. I have been trying to educate a few folks on another forum that melted body ply cord is physical evidence of a tire having been run under-inflated at highway speed. The discussion ended with one poster accusing me of hiding the facts and lying to keep my job. Of course he had no idea why the body cord melted but was certain I didn't know either. That ended my participation on that thread.

I know of no data to indicate that anyone is intentionally making "bad" tires. I do know of data that confirms the majority of RVs have tires in overload and that a significant % of tires on the highway are under-inflated. I also have personal observation that a good number of trailers are exceeding the speed limit of their tires. Multi-axle trailers place unique and high side loading on tires. This cause internal forces that contribute to the short life for tires in this application. This is a fact based on engineering and all tires are subjected to this structural overload.

All I can suggest is you read my post on "Best tire", inflate your tires to the sidewall inflation 100% of the time, at least once confirm your side to side and axle to axle unbalance is not giving you an overloaded tire, use TPMS w/metal valve stems and do a free spin inspection at least once a year and cover your tires with WHITE cover whenever parked in the sun for more than a day.
You will probably still only get 4-5 years out of your tires because of the internal stress load but hopefully they will be 5 years with no problems.

 

[DW_Gray]

I also have personal observation that a good number of trailers are exceeding the speed limit of their tires.

I second that.

Earlier this year, after spending a week with some good Heartlanders from Crossville, TN, Amy and I were heading south toward Florida. While driving my normal speed of 58 MPH, a truck towing a double axle 5th wheel flew by probably at the speed limit of 70 MPH. I commented to Amy, "If that guy keeps driving like that, he's going to start blowing tires." Well, guess what... About 10 miles down the road, the same rig was on the roadside in front of trailing tire pieces and there was significant damage to the RV.

Folks, if you have ST tires on your rig, don't tow over 60 MPH.

 

[JohnD]

I second that.

Earlier this year, after spending a week with some good Heartlanders from Crossville, TN, Amy and I were heading south toward Florida. While driving my normal speed of 58 MPH, a truck towing a double axle 5th wheel flew by probably at the speed limit of 70 MPH. I commented to Amy, "If that guy keeps driving like that, he's going to start blowing tires." Well, guess what... About 10 miles down the road, the same rig was on the roadside in front of trailing tire pieces and there was significant damage to the RV.

Folks, if you have ST tires on your rig, don't tow over 60 MPH.

Funny . . .

My old 1978 Coachman Cat 24-foot travel trailer with light truck tires on it, I'd go 75 mph with no problems or worries what-so-ever!

Owned that trailer for 12 years and never once worried about the trailer tires.

NOT ONCE. . . . EVER!

Those tires are still on that trailer with the new owner . . .

Now, with my 2013 Heartland Trail Runner with BlowMax ST trailer tires on it . . . I'm afraid to drive the darned thing around the block!

Last summer I drove the new Trailer Runner a couple of times at 75MPH . . . and it sways big time!

Now, after reading here I never go over 65MPH . . . and I don't have a sway issue.

I guess what I'm try to say is this . . .

With LT tires I never worried about tire issues . . . in 12 years of hauling that trailer!

With the ST tires that Heartland supplied with the trailer when brand new . . .

I'm almost afraid to pull the darned thing out of my driveway!

What does that say . . . ?

Heartland . . . are you listening????????????????????????????????????????????????????????????????????????????????????????

 

[Ric_Flair]

You're right to worry. My BlowMax shed it's tread 5 months from purchase. I was driving under 60, for the record. But I'm sure that it was something else I did, like believing the ST apologists that these tires are good enough. Shame on me. I wouldn't trust one to make a tire swing.

 

[wdk450]

I second that.

Earlier this year, after spending a week with some good Heartlanders from Crossville, TN, Amy and I were heading south toward Florida. While driving my normal speed of 58 MPH, a truck towing a double axle 5th wheel flew by probably at the speed limit of 70 MPH. I commented to Amy, "If that guy keeps driving like that, he's going to start blowing tires." Well, guess what... About 10 miles down the road, the same rig was on the roadside in front of trailing tire pieces and there was significant damage to the RV.

Folks, if you have ST tires on your rig, don't tow over 60 MPH.

Dave:
I saw the same thing happen in Wyoming on I-80 last summer on my way back to California after the Goshen rally.

 

[caissiel]

All I know is that the tires on our previous SOB trailer were trouble free for 7 years.
The tires on our BC are now 6 years old and trouble free.
Both units had or have LT tires and I have no concernes. Because they have enough rubber on the threads unlike STs.
It's also a first for me being told trailer tires are only good for 3 to 4 years.
What trailer owner ever changed tires after 4 Years.
In my area trailer tires lasts years. My neighbor has a 70's trailer with original bias ply tire.
He takes his unit on hunting trips every fall. The roads are 4x4 quality.
The saying use to be "use trailer tires because of the special rubber, reason for costing twice regular car tires".

Sent from my LG-LS720 using Tapatalk

 

[AAdams]

We had a 09 Landmark, I ordered it with GY GS 614 tires and never had a problem with them. When we ordered our new RW390 I ordered the same GY tires. In short I know any tire can blow, but if I avoid one blowout and the subsequent damage then the tire upgrade paid for itself.