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Old 02-26-2014, 03:51 PM   #1
ocho
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What I learned, and now, know about tires!

After shredding two tires recently, the latest causing some minor damage, I've spent the last three weeks doing some in depth tire research. Here's what I came up with. Its all about load, load rating, pressure and temperature. I know sounds easy, and it should be, but I've read numerous post from several RV boards and was surprised how many threads there were on this topic. Tires are without a doubt the most overlooked yet the hardest working member on your team. They require the upmost of attention and any neglect will land ya on the side of the road.

There was also a lot of talk about the type of tire. LT vs. ST. I was surprised to see how many RV owners chose LT (light truck) instead of the ST (special trailer) tires that came on most if not all camping trailers. Fact is that while either of the two tires can be used on a trailer, they are completely different tires. ST tires are specifically designed for use on Travel trailers and 5th wheels. They typically will have a tougher sidewall and rubber compounds that resist heat. However, it usually comes down to the load rating on the tire.

I had load range E tires on my 300 mp when they blew. A couple of weeks ago I had a talk with Keystone to get some answers. I knew my exact weights of the trailer, the load in the garage, etc. They kinda beat around the bush and give canned answers to the questions I asked and could not get specific. Basically, they read from a sheet that the engineers give them. So I asked to speak with an engineer, the agent laughed, then caught herself. "Customers cant speak to Engineers" I asked why and was told, "well they just don't" Youd think I was asking to speak to God himself. Anyway, I eventually got enough information to make an intelligent decision.

Of the many things we talked about is how 14,000 lb axles could legally and safely carry my 300MP at a MGVWR of approx. 16,500 lbs. I don't recall the exact number but that is close. She had mentioned the percentage of the tongue weight that is reduced from the trailer weight, that's how they do it. So I say "The E rated tires you put on the trailer are certified to carry, on average, 3400lbs each". That's 13,600 lbs folks. Nearly 3000lbs less that the what the trailer is certified to carry. That's pretty scary. So I ask " then why cant the same tongue weight percentage be used to allow the tires to carry more than their certified to carry. Dead silence!! Hello? "Yes Sir, im here. I understand your question but I cant answer it". Uh huh, there's the answer. By loading my golf cart and Harley in the back with no water, no fuel for the Gen, and the usual things needed for a weekend camping trip im WAY over the weight limits for the tires. So just one thing wrong with any tire, like under pressure, over heated or as we see now, over weight and you run a high risk of blowing a tire.

It appears to me that the tires that come from the RV factories handle the shipping weight of the trailer just fine. Just don't load too much into it and you'll be fine. But, that doesn't work so well for a toy hauler. That's we buy them right? Answer? Put F or G rated tires on the damn things from the factory. Then your limitation becomes the axles. But, we've already seen that when you figure the tongue weight percentage that all changes.

Where am I going with all this? My fingers are sore, so here what I did. I looked further into tire manufacturers. I knew that I didn't want Chinese tires and LT tires weren't an option either. So my next call was to Carlisle Tire where I was quickly transferred to an actual Engineer!! My interest was the new Radial Trail RH. Size was the original ST235/85/16, but "F" load range. Now with each tire carrying 3950lbs each at 95 PSI I have 15,800 lbs I can carry with just the tires!!!! No longer will the tire be my limiting factor. "G" rated tires are available, but then your limitation becomes your aluminum factory rims. "G" rated tire run at 110 psi, but carry lots of weight.

Other issues have been brought up regarding the ST tires and why some choose LT tires is the speed limits. ST tire should be limited to 65 mph, but no longer. After speaking to the ENGINEER at Carlisle, he informed me that Carlisle will be lifting that limitation within the next couple months.

Now, after loading my trailer for that weekend camping trip as described earlier, im nowhere near my limitations, where as before I was at them. I just installed these new tires so I have yet to get them on the road, but ill let yall know. Im not affiliated with Carlisle tires nor am I an Engineer. Just a guy wanting to get from there to here with my toys safely as possible. This post is written because there is a lot of misinformation out there and folks that just may not know. I don't profess to be an expert and this is just my opinion.

I welcome yalls feedback!! Thanks, Ocho
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Old 02-26-2014, 04:35 PM   #2
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Good post, we all know the tires are junk and mostly underrated for what they are carrying.

So can I ask how much your new tires cost?
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Old 02-26-2014, 05:01 PM   #3
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Here's one site that has them for $130 per tire. That should be somewhere in the ballpark for cost...

http://www.treaddepot.com/tire/5151441.html
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Old 02-26-2014, 05:12 PM   #4
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Originally Posted by JRTJH View Post
Here's one site that has them for $130 per tire. That should be somewhere in the ballpark for cost...

http://www.treaddepot.com/tire/5151441.html
I got mine from Discount tire, but they matched the online price mentioned plus shipping. Thought that was fair. While most "Chinese" tires are junk, these I hold high hopes. If you decide on them make sure you get the "F" load rating, but only after its determined that your wheels can handle 95PSI.
Hope this helps.
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Old 02-26-2014, 09:42 PM   #5
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Just a brief technical note on pin weight that many owners overlook or are not otherwise aware of.

RV trailer manufacturers MUST comply with the minimum safety requirements provided to them via numerous DOT regulations.

Here is an excerpt from FMCSA 571.120. It is paragraph S10.2 and here is what it says:

“On RV trailers, the sum of the GAWRs of all axles on the vehicle plus the vehicle manufacturer's recommended tongue weight must not be less than the GVWR. If tongue weight is specified as a range, the minimum value must be used.”

That is the end of the trailer builders responsibility for tongue weight. Once you own it you’re responsible for the weight you put on your tow vehicle. So, my recommendation is to drop by some certified scales every now and then to verify your current weight conditions.

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Old 02-27-2014, 08:29 AM   #6
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...my recommendation is to drop by some certified scales every now and then to verify your current weight conditions.

CW
That is definitely sound advice. It seems as the camping season progresses, the front storage area and the stuff in the truck bed tends to grow in weight. What starts out as a 1200 lb pin weight can easily turn into 1800 lbs by mid September. Weighing once in a while is the best way to know where you "really stand" on TV/trailer GVW vs loading status.
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Old 02-27-2014, 06:43 PM   #7
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When my OE ST Chinese made "Duro's" cracked to pieces after 18 months I did some reading and have not had a tire problem since. OP is right, you really have to educate yourself on this issue if you want to avoid problems.
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Old 02-27-2014, 07:37 PM   #8
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I recently bought the new Carlisle Radial Trail RH from Discount Tire, also. I went in with the intent of buying another brand but the salesman insisted these were the best thing out there. Knowing about the reputation of Carlisle I was hesitant but the salesman won be over. Time will tell!
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Old 03-01-2014, 05:53 PM   #9
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Glad to see you upgraded the load range. Trailers should come with better tires. I do have disagree a little about st vs lt tires. Have you compared them side by side? Lt tires I have seen have much stiffer sidewalls and I think all the manufacturers for st tires put that out there as marketing hype. Oh and the special uv compounds in st tires...they make it sound like lt tires can't be used in the sun. I call bs. And now I've read st tires should be replaced after 3 years. Lts can easily go 5 years minimum. So in the long run st tires could cost more. Last year I replaced my tires but went for lts for these reasons and the stricter testing for lt tires, higher speed rating (reserve capacity), etc.
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Old 03-02-2014, 12:31 AM   #10
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I don’t think you can provide a reference where a manufacturer of ST tires advertises stronger sidewalls than LT tires. All the references I’ve found refer to ST tires having stiffer sidewalls than passenger tires.

Carlisle says they build their ST tires with designed flex areas in the lower sidewall area to help counter sway.

When conducting eyeball examinations of the differences between the ST & LT tires it would be best to insure you’re comparing like sized tires such as ST235/85R16E vs LT235/85R16E. Most LT tires will have an extra ˝” of tread depth. The tread material will consist of more dense compounding materials for mileage and retreadable tires. Commercial LT tires will have extra materials built into the sidewalls to prevent curb scrubbing damage to the tire’s carcass.

Just like LT tires, ST tires rely on proper servicing and load capacities. Improperly serviced or overloaded tires are most often destroyed internally before showing any external symptoms.

Because of the materials used in the construction of the ST tire they are capable of supporting much higher load capacities. The LT tire above has a load capacity of 3042# at 80 psi. The ST tire can support 3640# at 80 psi.

Testing comparisons are not a reliable argument when compared to other designs. LT tires are designed by their manufacturers to support the rigorous demands for use on light trucks, commercial vans and multi passenger vehicles and are tested accordingly. ST tires are a much simpler designed tire for a single use, trailer axles.

It is the sole responsibility of the RV trailer manufacturer to select tires suitable for fitment onto the trailers they manufacture. Your owners manual is going to tell you to consult with the vehicle manufacturer about replacement tires. When you do you may feel you’re getting canned answers. Unless there are options for other sizes in your owner’s manual the canned answer is the only one that can be applied by the manufacturer. They built your trailer following all of the DOT guidelines for doing so. They cannot officially offer information differing from their certification of your trailer.

CW

p.s. When examining tires you can also compare some of the materials used in their construction by reading that information right off the individual tire’s sidewall information.
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Old 03-02-2014, 11:13 AM   #11
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Originally Posted by CWtheMan View Post
Because of the materials used in the construction of the ST tire they are capable of supporting much higher load capacities. The LT tire above has a load capacity of 3042# at 80 psi. The ST tire can support 3640# at 80 psi.

Testing comparisons are not a reliable argument when compared to other designs. LT tires are designed by their manufacturers to support the rigorous demands for use on light trucks, commercial vans and multi passenger vehicles and are tested accordingly. ST tires are a much simpler designed tire for a single use, trailer axles.

It is the sole responsibility of the RV trailer manufacturer to select tires suitable for fitment onto the trailers they manufacture. Your owners manual is going to tell you to consult with the vehicle manufacturer about replacement tires. When you do you may feel you’re getting canned answers. Unless there are options for other sizes in your owner’s manual the canned answer is the only one that can be applied by the manufacturer. They built your trailer following all of the DOT guidelines for doing so. They cannot officially offer information differing from their certification of your trailer.

CW

p.s. When examining tires you can also compare some of the materials used in their construction by reading that information right off the individual tire’s sidewall information.
I don't buy that st tires use superior materials and cost less? I have read post by tire engineers on other forums that the reason for the higher load rating is due to the fact that st tires are intended for occasional non passenger use. I don't want failures on my 5th wheel and try to use it more than occasionally.

For testing I guess we can disagree...I myself want a tire that is over rated for my speed and load.

So if a manufacturer calls for lt tires from the factory than are st trailer tires a misapplication to use on a trailer?

I wonder the tire failure rates on trailers with st and lt or p tires? It just seems like years ago before st tires came on the scene that there weren't as many failures....but now the trailer manufacturers are looking for us and as you state use st tires with superior materials, oh and they cost less. If st tires realy solved a problem wouldn't you charge more for them?
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Old 03-02-2014, 04:27 PM   #12
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Because of the materials used in the construction of the ST tire they are capable of supporting much higher load capacities.

Actually I did not say the materials were superior. Most often that type of information is not available to the public. What they do make public is the fact that the construction cording is larger thus providing increased load capacity abilities.

So if a manufacturer calls for LT tires from the factory than are ST trailer tires a misapplication to use on a trailer?

It would depend on the qualities of the LT tire. Goodyear presents their steel cased RST G614 tire as a trailer tire. Off shore manufacturers of like sized tires approve them for low platform trailer service. Therefore, ST tires of equal load capacity would not be a misapplication when used to replace those sort of LT tires. On the other hand, tires such as the LT235/85R16E commonly used a few years ago on many trailers with 6000# axles were the vehicle manufacturers choice. You would have to dig deep into the vehicle certification regulations for an answer. IMO it still rests in the hands of the vehicle manufacturer.

I have read posts by tire engineers on other forums that the reason for the higher load rating is due to the fact that ST tires are intended for occasional non passenger use.

Sometimes tire engineers are not well versed on the regulations vehicle manufacturers are required to follow. All DOT certified tires for highway service can legally carry passengers. It becomes a safety concern for many states and they are the ones that will or will not allow riders in RV trailers. On my last count I found 22 states that allow passengers to ride in RV trailers.

ST tire market values are mainly determined by their point of origin. Those - almost all - from offshore manufacturers cost less because their manual labor force is not being paid $25.00 an hour to build them. On the other hand, we have the G614 steel cased tire - built in the USA - and it’s right up there as the most expensive trailer tire.

CW
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Old 03-06-2014, 06:58 PM   #13
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Ocho, I see I'm not the only one who takes the time to research tires. I too checked out Carlisle a couple of years ago and I've been pleased with mine. You can find some tire load information here.
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Old 03-07-2014, 08:53 AM   #14
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Dave. Great post. You just said what i was going to in a follow up. ST tires are just that, Special Trailer tires and LT tires are just that as well Light Truck tires. Different engineering, different demands. Its funny how people get convinced that their way is better and wont back down. Us on the other hand feel its important enuf to do the research and make safe sound decisions based on our findings. Did anyone catch it when i said that Carlisle is lifting the speed limits on their ST tires?
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Old 03-07-2014, 09:46 AM   #15
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Quote:
Originally Posted by ocho View Post

ST tires are just that, Special Trailer tires and LT tires are just that as well Light Truck tires.
With the exception of the G614, can you provide a current reference where an LT tire manufacturer recommends it for trailer service?

CW
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Old 03-07-2014, 09:00 PM   #16
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With the exception of the G614, can you provide a current reference where an LT tire manufacturer recommends it for trailer service?

CW
No, for the simple reason that, while you can put any tire on your trailer you wish, to do so might not be prudent. Can you qoute where LT tire manufacturers specifically recommend running LT tires on a heavy trailer? If so, please, do tell. My guess would be no. To do so would expose them to a myriad of liability issues.
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Old 03-07-2014, 09:01 PM   #17
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Did you mean to say ST tire?
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Old 03-08-2014, 03:47 AM   #18
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Interesting information I found on tirerack.com.

http://www.tirerack.com/tires/tirete...jsp?techid=219

I really found the speed rating info interesting since I had never heard that before. I personally use ST tires on my RV, car trailer, and utility trailer and have been very happy with them. Have used multiple brands and put thousands of miles on them. I keep a constant eye on air pressures and temps, and never exceed the recommended speed limits. I get passed by other campers/trailers on a regular basis and can't tell you how many times I've later passed the same rig while they are changing their flat.

As for tire life, most trailer tires are recommended for replacement after 3 years, some say 3-5 years vs. 5 years for most LT tires. I don't have a problem with that. My trailer tires are holding up 3500 lbs each 24/7/365, and for the most part the stress is placed on one part of the tire for long periods of time since I don't give them an occasional spin. My truck tires support half that weight at 1750 each. The tires are stopped at a different point daily, distributing the load bearing pressure on a sidewall. They are also rotated and balanced regularly and have the benefit of a steering axle as well as a differential axle to help them around corners vs. the scrubbing that my trailer tires endure. Trailers tires go through a lot more abuse than many people give them credit for.
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Old 03-08-2014, 06:09 AM   #19
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Interesting information I found on tirerack.com.

http://www.tirerack.com/tires/tirete...jsp?techid=219

I really found the speed rating info interesting since I had never heard that before. I personally use ST tires on my RV, car trailer, and utility trailer and have been very happy with them. Have used multiple brands and put thousands of miles on them. I keep a constant eye on air pressures and temps, and never exceed the recommended speed limits. I get passed by other campers/trailers on a regular basis and can't tell you how many times I've later passed the same rig while they are changing their flat.

As for tire life, most trailer tires are recommended for replacement after 3 years, some say 3-5 years vs. 5 years for most LT tires. I don't have a problem with that. My trailer tires are holding up 3500 lbs each 24/7/365, and for the most part the stress is placed on one part of the tire for long periods of time since I don't give them an occasional spin. My truck tires support half that weight at 1750 each. The tires are stopped at a different point daily, distributing the load bearing pressure on a sidewall. They are also rotated and balanced regularly and have the benefit of a steering axle as well as a differential axle to help them around corners vs. the scrubbing that my trailer tires endure. Trailers tires go through a lot more abuse than many people give them credit for.
So true. They do take a beating. The engineer at Carlisle spoke specifically about the Radial Trail RH when he said they had enuf test to feel comfortable with lifting the speed limit. I didnt ask about their other ST tires or any other ST because i was interested in only that tire. I asked him if the RH stood for Radial and the H for the speed rating. He chuckled and said no. It wasnt that technical. He said it is the initials of the designer or that tird. Hows that for putting your name behind your product!
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Old 03-09-2014, 07:25 AM   #20
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Carlisle Tire Co. has more reference material posted on the WWW than any other ST tire manufacturer. They keep it up-to-date and explain all aspects of their trailer tires.

Here is a quote from one of their documents that is often overlooked. It explains why trailer tires being operated close to their maximum capacity fail early, sometimes very early.

“3 to 5 years is the average life expectancy of a trailer tire, regardless of mileage. It is estimated that in approximately three years, roughly one-third of a tire's strength is gone.”

Strength relates to load capacity. If your original equipment ST tires have 12-15% load capacity reserves above the trailers GAWR and you’re not overloading it, 3-5 years are good expectations. Lower reserve load capacity tires are going to need replacing much sooner than the 5 year mark.

CW


p.s. The life expectancy for LT and P tires are expectations based on their normal design function. They are out of their element once installed on RV trailer axles.
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