Go Back   Keystone RV Forums > Keystone Tech Forums > Tires, Tires, Tires!
Click Here to Login

Reply
 
Thread Tools Display Modes
 
Old 04-15-2018, 02:39 PM   #71
notanlines
Senior Member
 
notanlines's Avatar
 
Join Date: Oct 2014
Location: Memphis, TN
Posts: 2,527
Quote:
Originally Posted by Eastham View Post
What ever happened to just throwing some stuff in the camper and taking off and enjoying yourself.if you have to pack that much crap to go camping that you are over loading the truck and the trailer and the tires .it's to much work stay home or load less and enjoy your self. Life is to short to sweat all this small crap .Good night and lighting up.
I gave serious thought to picking up the stick and poking it through the fence, but I didn't think the dog would be sharp enough to even get upset.....
__________________

__________________
Jim in Memphis
Wife of 46 years is Brenda
2014 F-350 6.7 Powerstroke
2017 Mobile Suites
20K Reese slider
2001 Road king w/matching Harley sidecar
notanlines is online now   Reply With Quote
Old 04-24-2018, 10:02 PM   #72
CWtheMan
Senior Member
 
CWtheMan's Avatar
 
Join Date: Feb 2010
Location: Taylors, SC
Posts: 1,149
Tire load/Inflation Charts

Tire load and inflation standards are developed by three different organizations. North American, European, and Japanese.

Here I’m just going to be mentioning those from the North American Tire & Rim Association (TRA).

The charts are standardized. All tires of the same size and construction can use a chart from any manufacturer of that tire. For this discussion I’m just mentioning Special Trailer (ST) tires, Light Truck (LT) tires and Passenger (P) tires. All of those are highway tires and approved by the governing body (NHTSA) for trailer axle service, when approved for that fitment by the vehicle manufacturer. An approved tire size is like this; ST225/75R15 or LT235/85R16 or P175/50R15. A load range, load index, or speed letter in a tires suffix are not part of the basic size.

For our vehicles built under the guidance of the Federal Motor Vehicle Safety Standards (FMVSS), the need to use any of the charts is minimal. The FMVSS instructs the vehicle manufacturers to set an appropriate recommended cold inflation pressure for all vehicles they build and certify. Those recommendations are the minimum standard and none in the tire industry will recommend using less than what the vehicle manufacturer has set and certified on the individual vehicle’s placards for the Original Equipment (OE) tires.

Tires on our motorized vehicles provide a percentage of load capacity reserves and their recommended cold inflation pressures are almost always less than what is required for the tires maximum load. In those conditions the difference in recommended inflation pressure and tire maximum load pressure is an optional area. Some vehicles, such as pick-up trucks may even have vehicle manufacturer recommendations for the use of higher inflation pressures when the vehicle is being used for towing another vehicle.

We often see forum posters recommending tire inflation for the load being carried. The major fault with that is two fold. It’s a no-no to use less inflation pressure than what has been recommended by the vehicle manufacturer. And, inflation to the load carried may need to be adjusted every time you use the vehicle. One PSI inflation pressure below the load carried is a loss of about 1.6% of its load capacity. Heat generation for being under inflated comes to mind.

In these forums, everyone posting about replacement tires seems to have a different idea of how it’s supposed to be done. The tire industry wide rule is to always use replacement tires that are the same size as the tires that came on the vehicle. It’s a very complex explanation as to why it’s a misapplication to use tires that do not match the design of the Original Equipment tires and I’m not going to try and explain it here. This is about tire inflation charts.

Plus sizing is a very popular option many seek when replacing their RV trailer tires. It’s where the tire inflation charts are most needed and part of their basic design is to assist the installer of plus sized tires. Here again, is another tire industry standard that applies to plus sizing your tires. They MUST provide a load capacity equal to the load capacity provided by the OE tires at the vehicle manufacturer’s recommended cold inflation pressure. What that means, when looking at your tire placard you will find the OE tires size and their recommended cold inflation pressure. Now it’s time to find a tire inflation chart for that particular tire. From the chart you can find the load capacity the tire is providing at the trailer manufacturer’s recommended PSI. Let’s say the tire size is ST205/75R14 and had a load range letter of D with a recommended 65 PSI. So, from the chart we find that it’s providing 2040# of load capacity. There is not a LRE in that tire size so you’ll have to ask the vehicle manufacturer about a larger tire for replacement. We all know their answer. If the larger tire was never offered as an option for that trailer they are going to tell you to use another tire just like the ones that came on the trailer. They fitted the OE tires and said they were an appropriate fitment for that trailer and are going to stand with that original decision. To do otherwise would put them in a situation of decision reversal, they’re not going to do that.

So, now you’re going to have to do some decision making. Normally a smallish tire dimensional size change can work on RV trailer axles. Even those closely spaced. A 10% increase in tire load capacity is a ballpark figure to look for. The ST215/75R14 is the best fit. It will fit the OE wheels. It’s just .6” taller & .5” wider. The owner would have to make sure there is sufficient wheel well clearances. At 65 PSI the 215 will provide 2200# of load capacity. Looking at the tire inflation chart for the 215 tire shows a load capacity of 2120# @ 60 PSI.

A normal step for the installer to perform, is to identify the different sized replacement tire. For that purpose, NHTSA approves the use of an auxiliary tire placard. On it, the installer can put the new tire size and from a tire inflation chart for that tire size, a recommended cold inflation pressure that insures the tire will provide as much load capacity as the OE tire did at the vehicle manufacturer’s recommendation. The AUX placard can then be placed adjacent to the original tire placard. Then a notation should be made in the vehicle owner’s manual.

There really is no need to fool around with RV trailer tire inflation pressures. Only a very few owners travel enough to ever see their trailer tires wear out. They are age-out tires.

Our RV trailers have a very different center of gravity than our motorized vehicles. Trailers tend to fish-tail, bob and weave and travel in an unbalance condition most of the time. All tires are designed to safely operate at their maximum load capacity.

What many trailer owners do not consider is the load on their tires. (Probably the most damaging thing a new trailer owner does to their tires is over load them. Fill-up the water tank, get all the stuff in the basement and other storage areas and hit the road. POP - BANG). Trailers are built to minimum standards for their maximum allowed loads. The tires are not required to have any load capacity reserves. Even when you load your automotive vehicle to it’s limit it still has tire load capacity reserves. It’s part of the fitment differences between automotive and trailer tires.

You want full life expectancy from your trailer tires? Give them 10% - 15% in load capacity reserves.
__________________

__________________
An Old Navy Aircraft Mechanic that writes about tires.
The Black one is mine: http://www.irv2.com/photopost/showfull.php?photo=20678
CWtheMan is offline   Reply With Quote
Old 05-16-2018, 06:42 PM   #73
CWtheMan
Senior Member
 
CWtheMan's Avatar
 
Join Date: Feb 2010
Location: Taylors, SC
Posts: 1,149
ST Tire Inflation

What seems like a long time ago, Probably about 15 years, I started researching ST tires. At that time there were very few tire manufacturers building the ST tires. The largest and most well known was Carlisle. They saturated the industry with information about their ST tires and were probably the most prolific OEM provider for at least 5 years. (There was also a new and upcoming ST tire builder, Goodyear. They, for a time, overtook Carlisle as leading OEM provider. Then, there was/is CHINA).

When large tire retailing chain stores started stocking Carlisle ST tires, Carlisle provided them with oodles of information about their tires and how they differed from other highway tires.

Carlisle said ST tires could degrade by as much as 10% a year. They had and still have one of the shortest warranty periods of all ST tires. Carlisle recommended their tires be used at 60 MPH or less (TRA sets unmarked ST tires at 65 MPH). Carlisle recommended their tires to be operated at the inflation pressure molded into the tire’s sidewall (that’s for MAX load capacity). Carlisle was very stern about their ST tires life expectance saying 3-5 years was the maximum regardless of mileage.

In interviews with information outlets line Modern Tire Dealer, Carlisle spokespersons would spout out their recommendations and ST sellers/users took notes. Almost everything you read about ST tires in Discount Tire’s on-line publications are excerpts from Carlisle PDFs. So, their recommendations became the norm.

ST tires on today’s market have come a long way from where they started. But, don’t get me wrong. I’m not against max pressure for ST tires. It’s almost always recommended by the vehicle manufacturer’s and when that’s the case the max is also the min. But, that’s not so for replacement tires with excess load capacity. The canned answer from the replacement tire rep will be to use what is recommended by the vehicle manufacturer. So use as much extra load capacity as you are comfortable with. Most of the time it’s not going to be the 110 PSI the tire needs for max load. 90 or 100 PSI may provide the extra load capacity you need for excess load protection and a better ride.

Just about every ST tire now purchased has a speed rating of 75 MPH or higher. Every MPH you travel under the tires speed rating provides a little more protection from overheating a tire when it’s close to its maximum load. Before the higher speed ratings all we had was 100% inflation protection at 65 MPH.

Back to the Carlisle thing. If you did not archive any of their old PDF forms you’re out of luck. Their new ST tires are up-to-date and in line with all other ST manufacturer’s and with speed letters in the 81 MPH range. At a recent BASS fishing show the only tires close to outnumbering the Carlisle’s were Passenger tires. A lot of the large dual axle rigs really liked the low profile passenger tires. (RV trailers and boat trailers are built to the same FMVSS standards, the vehicle manufacturer decides what fitment is appropriate).
__________________
An Old Navy Aircraft Mechanic that writes about tires.
The Black one is mine: http://www.irv2.com/photopost/showfull.php?photo=20678
CWtheMan is offline   Reply With Quote
Old 07-02-2018, 01:43 PM   #74
CWtheMan
Senior Member
 
CWtheMan's Avatar
 
Join Date: Feb 2010
Location: Taylors, SC
Posts: 1,149
RV trailer tire brand lovers

One thing the China tire manufacturers have shown us is their ability to rapidly enter new tire designs and sizes into the market places.

Here are the specs for the all steel Carlisle trailer tire.

ST235/85R16 Carlisle CSL 16 Radial Trailer Tire (14 Ply)
The CSL 16 from Carlisle is an all steel radial trailer tire. The CSL 16 was specially built with heavy duty carrying ability for large equipment and heavy loads. With a heavy duty all steel casing, the CSL 16 offers larger carrying capacity than you typical trailer tire. CSL 16 tires are designed to provide long service life and dependable performance.

Manufacturer: Carlisle Tire
Manufacturers Part Number: 6H08111
Load Range: G
Ply Rating: 14 Ply
Mounted Diameter: 31.7 inches
Mounted Width: 9.3 inches
Recommended Rim Width: 6.50 inches
Alternate Rim Width:
Max Load Capacity Single: 4400 lbs
Max Load Capacity Dual: 3850 lbs
Max Pressure: 110 psi
Tread Depth: 11.6 (32nds)
Speed Rating: M
Max Speed: 81 mph
Tire Weight: 50 lbs


I'll post more brands and sizes whenever I find they are available in the USA market places.

Because I post information like this does not mean I'm supporting brands. Other manufacturers are building these tires and have been for some time. There are also some 15" all steel tires being built with a LRF that have a 3195# load capacity @ 95 PSI. Greenball has them in their line-up in size ST225/75R15 and is touting them in their Towmaster brand.
__________________
An Old Navy Aircraft Mechanic that writes about tires.
The Black one is mine: http://www.irv2.com/photopost/showfull.php?photo=20678
CWtheMan is offline   Reply With Quote
Old 07-02-2018, 02:27 PM   #75
FlyingAroundRV
Senior Member
 
FlyingAroundRV's Avatar
 
Join Date: Oct 2017
Location: Brisbane Australia
Posts: 164
Quote CWtheman
"CSL 16 tires are designed to provide long service lifeand dependable performance. "
This appears to be an interesting concept in the realm of trailer tires. From all that I read, trailer tires perish before they wear out. So what is the definition of "long sevice life"? I don't know what the average yearly mileage a trailer tire would do, but it seems by all accounts that the rubber hardens, cracks and decays long before the tread is worn out, on most "average use" RVs.
Currently, my TT has the "China bombs" that came with it. I expect that next year, when I return to use the trailer after 9-odd months storage, I may have to put a new set of tires on the trailer. Even at $150/ tire, we're not talking a lot of money.
Are we over-thinking this?
FlyingAroundRV is offline   Reply With Quote
Old 07-02-2018, 03:19 PM   #76
sourdough
Senior Member
 
Join Date: Feb 2014
Location: W. Texas
Posts: 5,274
Quote:
Originally Posted by FlyingAroundRV View Post
Quote CWtheman
"CSL 16 tires are designed to provide long service lifeand dependable performance. "
This appears to be an interesting concept in the realm of trailer tires. From all that I read, trailer tires perish before they wear out. So what is the definition of "long sevice life"? I don't know what the average yearly mileage a trailer tire would do, but it seems by all accounts that the rubber hardens, cracks and decays long before the tread is worn out, on most "average use" RVs.
Currently, my TT has the "China bombs" that came with it. I expect that next year, when I return to use the trailer after 9-odd months storage, I may have to put a new set of tires on the trailer. Even at $150/ tire, we're not talking a lot of money.
Are we over-thinking this?
I agree. I think the term "long service life" from the manufacturer is relative to their concept of trailer tires. "Long service life"? 3 years instead of 2 or ??? Trailer tires being what they are I don't think any ST tire manufacturer has put out a tire that shatters the norm for the type tires they are. Now, if we're talking about tires from Shandong province, yes, most anything can shatter their record (china bombs).
__________________
Danny & Susan wife of 50 years
2014 Ram 2500 6.4 4x4 CC
2014 Cougar High Country 319RLS
sourdough is offline   Reply With Quote
Old 07-25-2018, 05:53 AM   #77
CWtheMan
Senior Member
 
CWtheMan's Avatar
 
Join Date: Feb 2010
Location: Taylors, SC
Posts: 1,149
The Federal Vehicle Certification

To view the entire document you can put; 49 CFR Part 567, in your search engine.

I mention the vehicle certification label in many of my tire posts. Lot’s of owner’s view the label as just another meaningless bit of information and others never even take the time to find it’s location on their trailer.

When the trailer manufacturer completes the building process, the final step before shipment to an owner or dealer is to verify and certify that the vehicle meets ALL federal motor vehicle standards. That’s a bold statement and not only did they make it to you, the owner, they did likewise to the DOT.

Below I have used logic to form the opinion.

On the certification label your will find the tire size and recommended cold inflation pressures to assure those tires meet the requirements of the trailer’s GAWRs. Because FMVSS are written to insure minimum standards are met, those tires and inflation pressures are the minimum requirement for that trailer. To use anything less would be a safety violation. Now, I’m just a tire researcher, what do I know, right? Well If I can figure that out, how long do you think it would take an experienced litigator to do so?
__________________
An Old Navy Aircraft Mechanic that writes about tires.
The Black one is mine: http://www.irv2.com/photopost/showfull.php?photo=20678
CWtheMan is offline   Reply With Quote
Old 08-01-2018, 01:30 PM   #78
CWtheMan
Senior Member
 
CWtheMan's Avatar
 
Join Date: Feb 2010
Location: Taylors, SC
Posts: 1,149
RVIA Tire Standards, Condensed

“The RV Industry Association is the national trade association representing RV manufacturers and their component parts suppliers who together build more than 98 percent of all RVs produced in the U.S., and approximately 60 percent of RVs produced worldwide.”

RVIA has mandated changes in Original Equipment (OE) tire load capacity recommendations and design upgrades that are probably already showing-up on all new RV trailer models that display their RVIA membership placard.

IMO, any RV trailer manufacturer member that wants to remain a member is going to comply with RVIAs recommendations.

The basics are very simple. All RV trailer tires larger than 13” in OD must be radial designed tires.

RVIA recommends RV trailer manufacturer’s provide a 10% load capacity reserve, above the certified GAWRs for all OE tires. That means, a RV trailer with 3500# GAWR axles must have tires that that can provide 1925# of load capacity when inflated to the trailer manufacturer’s recommended cold inflation pressures found on the vehicle certification label.

I hope anyone that has a 2018 or later model RV trailer with a RVIA placard, will challenge the validity of their OE tires, if they do not meet the new RVIA standard.

There are a lot of bias ply tires still available from wholesalers. The RVIA bias ply tire recommendations do not include replacement tires. The recommendation is not legally binding in any way. Therefore, they can still be used as replacements for any tire fitments above 13” OD. They are much less expensive than radials. For those that only travel locally and only a couple times a year, they are the most economical solution.

Remember, RVIAs recommendations are in no way binding on the RV trailer industry. There is nothing to prevent the vehicle manufacturer from just leaving the RVIA seal of approval off the trailers they manufacturer. The vehicle manufacturer is still free to use the FMVSS without any government repercussions.
__________________
An Old Navy Aircraft Mechanic that writes about tires.
The Black one is mine: http://www.irv2.com/photopost/showfull.php?photo=20678
CWtheMan is offline   Reply With Quote
Old 08-01-2018, 02:00 PM   #79
sourdough
Senior Member
 
Join Date: Feb 2014
Location: W. Texas
Posts: 5,274
Quote:
Originally Posted by CWtheMan View Post
“The RV Industry Association is the national trade association representing RV manufacturers and their component parts suppliers who together build more than 98 percent of all RVs produced in the U.S., and approximately 60 percent of RVs produced worldwide.”

RVIA has mandated changes in Original Equipment (OE) tire load capacity recommendations and design upgrades that are probably already showing-up on all new RV trailer models that display their RVIA membership placard.

IMO, any RV trailer manufacturer member that wants to remain a member is going to comply with RVIAs recommendations.

The basics are very simple. All RV trailer tires larger than 13” in OD must be radial designed tires.

RVIA recommends RV trailer manufacturer’s provide a 10% load capacity reserve, above the certified GAWRs for all OE tires. That means, a RV trailer with 3500# GAWR axles must have tires that that can provide 1925# of load capacity when inflated to the trailer manufacturer’s recommended cold inflation pressures found on the vehicle certification label.

I hope anyone that has a 2018 or later model RV trailer with a RVIA placard, will challenge the validity of their OE tires, if they do not meet the new RVIA standard.

There are a lot of bias ply tires still available from wholesalers. The RVIA bias ply tire recommendations do not include replacement tires. The recommendation is not legally binding in any way. Therefore, they can still be used as replacements for any tire fitments above 13” OD. They are much less expensive than radials. For those that only travel locally and only a couple times a year, they are the most economical solution.

Remember, RVIAs recommendations are in no way binding on the RV trailer industry. There is nothing to prevent the vehicle manufacturer from just leaving the RVIA seal of approval off the trailers they manufacturer. The vehicle manufacturer is still free to use the FMVSS without any government repercussions.
Thanks CW!! Very useful information. I would encourage every prospective buyer/owner to read the information in red and double check that on any trailer you are thinking about buying. There seems to be a line at the upper end of travel trailers and the smaller/mid size 5vrs where tires are really skimped on. I don't recall seeing any trailer I've looked at that didn't have the RVIA sticker on it so chances are that whatever you are looking at (new) will have it. If so, the above would come into play and could certainly be useful.
__________________
Danny & Susan wife of 50 years
2014 Ram 2500 6.4 4x4 CC
2014 Cougar High Country 319RLS
sourdough is offline   Reply With Quote
Old 08-03-2018, 12:12 PM   #80
CWtheMan
Senior Member
 
CWtheMan's Avatar
 
Join Date: Feb 2010
Location: Taylors, SC
Posts: 1,149
Gawr

There seems to be a bit of misunderstanding here. The Federal Motor Vehicle Safety Standards (FMVSS) are a mandatory safety net, written by the National Highway Traffic Safety Administration (NHTSA) to insure all vehicles - including all RV trailers - are built in compliance with minimum safety standards.

The final step a RV trailer manufacturer must do before it leaves the factory is certify that all those standards have been met.

Minimums and maximums are confusing to many owners. Especially with tire fitments.

First I’m going to establish a couple of facts.

The axles on your trailer may have two GAWR values. The axle manufacturer builds and certifies their axles to a weight value. It is defined as its Gross Axle Weight Rating (GAWR). The axle manufacturer is required to display that weight rating on each individual axle and the do so with a tag attached to each axle. Here’s the catch. Vehicle manufacturers have the authority from NHTSA to set GAWR values below the axle manufacturer’s values. Therefore, the official GAWR values for any RV trailer can only be found on its federal certification label. A common setting found on many older Keystone RV trailers was for axles manufactured with a 5200# rating from their manufacturer to be de-rated by Keystone to 5080#. They did that so they could mount tires rated at 2540# on those axles. That’s just one example. Numerous 7000# axles were also de-rated to accommodate Marathon tires that were rated at 3420#. That’s just some of the minimums Keystone complied with.

The standard for determining a RV trailer’s GAWRs has always been determined by the maximum weight it has been designed to carry, as determined by the vehicle manufacturer, in accordance with minimum standards set by FMVSS. Remember, the build target is the GVWR. To establish a trailer’s GAWRs the vehicle manufacturer does this simple math, which is a mandatory step in vehicle certification. They must set a recommended tongue/hitch weight. When that hitch weight is added to the total vehicle certified GAWR values they must not be less than GVWR. It’s the only time that tongue weight will be used unless an owner can perform the magic needed to duplicate it with a balanced load in their trailer. The weight difference between GVW and GVWR is cargo. Again, you must remember, the trailer GVW is not sitting on the tires. A percentage is always setting on the tongue/hitch of the tow vehicle or its landing gear.

Original Equipment (OE) tire selection for your RV trailer is driven by FMVSS and is the sole responsibility of the vehicle manufacturer. First and foremost is the absolute minimum standard, to provide a load capacity that will support the maximum load capacity of the vehicle certified GAWR axles. The bottom line is a provision in the FMVSS that reads - in part like this; The size designation and the recommended cold inflation pressure for those tires such that the sum of the load ratings of the tires on each axle is appropriate. The word appropriate at the end of that statement establishes the fact that the OE tires are the minimum requirement for that fitment and all subsequent replacements must have a load capacity equal to that fitment.

Recently, The Recreational Vehicle Industry Association (RVIA) has made a recommendation for all RV trailer tires to have, at the least, a 10% load capacity reserve above the trailer’s GAWR. IMO most RV trailer manufacturer’s will do just that and add the increased cost to them to the consumers.

Something to consider when researching tire safety is your trailer’s owner manual. Everything about tire safety found in those manuals are there in accordance with NHTSA mandates.

When linking standards and regulations to form a conclusion, don’t forget to add CFR 49 part 567 (Certification) to your list of references.

Here is a sample of a research topic. They all say it a little differently but the bottom line is the same. It’s a tire industry standard driven by a FMVSS minimum standard.

Goodyear: Never fit tires to a vehicle that have less load carrying capacity than required by the Original Equipment Manufacturer.

Michelin: Never choose a tire that is smaller in size or has less load-carrying capacity than the tire that came with the vehicle.

Cooper: The new tires must have a load carrying capacity equal to or greater than the maximum load carrying capacity specified on the tire placard on the vehicle.

Toyo: Any replacement tire must be of a size and load range that will offer equal or higher load carrying capacity compared to the original equipment (OE) tire on the vehicle.

This is another reference from the USTMA that is useful when discussing tire inflation pressures.

“Inflation pressure recommendations may be determined
based on the tire manufacturer’s specifications, which define
the amount of inflation pressure necessary to carry a given
load. These inflation pressures may differ from those found
on the vehicle tire placard or certification label.”

“However, never use inflation pressure lower than specified by
the vehicle tire placard, certification label or owner’s manual.
Nor should inflation pressure exceed the maximum pressure
molded on the tire sidewall.”
__________________

__________________
An Old Navy Aircraft Mechanic that writes about tires.
The Black one is mine: http://www.irv2.com/photopost/showfull.php?photo=20678
CWtheMan is offline   Reply With Quote
Reply

Tags
tires

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Powered by vBadvanced CMPS v3.2.3
Disclaimer:

This website is not affiliated with or endorsed by the Keystone RV Company or any of its affiliates in any way. Keystone RV® is a registered trademark of the Keystone RV Company.


All times are GMT -8. The time now is 11:35 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2018, vBulletin Solutions, Inc.