RV Construction Methods – Tires and Wheels

Who would have thought researching tires and wheels for a fifth wheel RV would be an involved task. I sure didn’t.

(Update 1/17/16) Most say go with the Goodyear G114 which is a 17.5″ H rated tire. In the 16″ G rated tire they are recommending Michelin XPS Ribs. Sailun is another brand worth considering.

I learned it is common that some RV tires are only rated for 65 miles per hour. Wish I had known that before we left on the trip in a rented RV!  No worries, we found it more enjoyable to drive five miles under the speed limit. Other drivers would just go around us while we enjoyed the scenery.

This will be the summary of what I learned. Additional details can be found on the Tires, Wheels and Brakes page.  I’ll publish the research on brakes in a future blog posting.

I found this great article written in Trailerlife.com. It worth reading for a quick reference.

A quick note for our family members reading this blog. Karen and I decided we wanted to stay home for at least one of the holidays each year. You are in our thoughts.  Happy Thanksgiving to all.

At the risk of looking like an idiot – here goes!

Before I get to deep into this I want to admit I’m no expert on this or any other RV construction methods. I’ve tried to do my best not to put out any bad information and always appreciate readers correcting any errors I do make.

Here is a quick list of valuable internet links I found on the topic:

• TiresandWheel site when shopping for prices.
• Mark Bruss blog goes into depth.
• RV Dreams always does a good job of explaining upgrades they make to their trailer.
• RV Tire Safety is a good resource. Roger is active on the IRV2 forum as a tire engineer.
• Huge forum post on the subject of tires.
• RV Weigh.com explains maintenance items, tire loading and other important details
• RV Tire Safety recommends the Accutire MS-4021B digital tire pressure gauge.  I ordered one! #1 best seller on Amazon.

Here is a picture of what our dog Huck would look like if I was to tell him about all the very important tire research.  As if he was saying – please stop!

There is much to cover in this topic and a lot of opinions out there. I discovered tires and wheels are part of the overall suspension system and included giving a little thought to axles, maintenance issues and more. Reading through the forums you will quickly discover others don’t trust the RV manufacturers to always put the best tires on rigs. Some went so far as to say the factory installs tires rated for only the trailer weight and not the contents. I found this a little hard to believe as one can check a plate on the rig where the minimum tire specs are posted to find if there is a discrepancy. For sure, if the wrong tires are not on the rig necessary to support the load or you want to upgrade later it will cost anywhere from $1,430 to $2,000 for tires and another $480 for wheels on a heavier class of fifth wheel. Right now we are looking at rigs in the range of 16,000 and up in weight. Therefore the research is geared to those size rigs.

Perhaps the best way to summarize is by answering a few of the question I found myself asking.

What kinds of tires are common and what do experienced owners prefer?

ST (special trailer) and LT (light truck/trailer) are the most common. ST tires generally have higher load ratings but are not engineered as well as LT tires that are designed to carry vehicle occupants. Many upgrade to LTs and most wrote in forums they would never own another ST tire because of blowouts. Most STs, but not all, are rated for only 65 miles per hour.  LTs hold up better to higher tire pressure.

I talked to the owner of the shop where I have my car worked on. He hauls cars all over the country with a large goose neck trailer. He has not had good luck with ST tires. He only had a blowout with an LT tire only once, after he loaned the trailer to a friend who damaged the sidewall.

An informal survey of the fifth wheels I’m researching revealed radial tires are what they come with. In the 16,000 pound and above rig class 16″ and 17.5″ tire size was the most common.

I’m leaning towards having LT tires.

What does tire pressure have to do with it?

The air carries the weight. The most common reason for tire failure and wear is under inflation. The most common tire pressures are 80 and 110 pounds. The higher tire pressure ratings allow for heavier weight loads.

What is the difference between an aluminum or steel wheel?

None of the trailers I’ve been looking at use anything but aluminum. Some wheels are rated for higher air pressure than others. So if you were to upgrade tires for a higher air pressure (or heavier load) than what the trailer shipped with then you will also have to upgrade the wheels. Some of the highest ratings were found in the commercial truck rated steel wheels. Aluminum are common for 80 and 110 pound air pressures.

Here is a quick example where I looked at the same tire (load rating E) with different wheels and lug bolts.

• Modular aluminum with 6 lugs had a 3242 pound rating per tire.
• Modular aluminum with 8 lugs had a 3520 pound rating.
• Spoke aluminum with 6 or 8 lugs had a 3520 pound rating.

What about the number of lug bolts?

A year ago while walking through an RV show I would have thought the better constructed fifth wheels were the ones that had four steps leading to the door. The cheaper ones only used three steps. Selection of a well built rig of course is not based on how many steps lead to the door.

I’m trying to avoid the temptation to evaluate the better tire/wheel combination is as easy to judge as saying the ones with eight lugs are better.

Here is an example of the load ratings I could come up with for aluminum wheels based on my research:

• For 16″ wheels
  • 6 lug wheel: 3,580 pounds, max air pressure was 80 pounds.
  • 8 lug wheel: 3,960 pounds, max air pressure was 110 pounds.
• For 17.5″ wheels
  • 8 lug wheel: 4,850 pounds, max air pressure was 110 pounds.

And lug nut torque is something to watch for as a maintenance item. Wonder if I should put a torque wrench on the must have tool list?

What about the lettering system used for tire load ratings?

(Update 1/17/16) Experienced person told me to upgrade from an E rated tire (which eventually will blow out) you have to change the hubs. That must be why some new rigs don’t come with an option to upgrade.

Tire load ratings use a lettering system such as E, G and H.  The E rated carry a lower load weight rating with H being the higher rating. If I wanted a quick reference when choosing an upgraded tire I would go from a G to an H for example. The higher air pressures require a higher rated tire. There – I’ve done it – I’ve over simplified the entire topic!

Beware the actual weight sitting on a tire in any position of the trailer is not equal.  Weight balancing of all our stuff inside the trailer is important. For example a larger slide with a refrigerator could put more weight on the tires for that side of the trailer.  This is where having the rig weighed at each tire position is important. You might be fine with an E rated tire in three positions. But what about the load on the fourth tire which might weigh more and require a G rated tire.

What about using nitrogen in tires for air?

Most forum posts I read say nitrogen is a sales gimmick. I don’t want to carry a spare tank of nitrogen around. I looked at the stated benefits (less chance of air pressure changes and no moisture) and think I’ll pass on it.

What are the most preferred brands of tires for larger fifth wheel?

Michelin, Goodyear, Saliun and Hankook are the ones I read about. I assume just because its a Goodyear does not make it good. Lots of people were bad mouthing the Goodyear Marathon tire for example. The more dependable tires I read about in recent forum posts were the Michelin XPS Ribs for 16,000 pound trailers and the Goodyear G114 for the heavier H rated tires.

What are the least preferred brands?

You may have already heard or read about this one. Some say simply the the ones made in China suck. Actually even the preferred brands have tires that are not as good as others within the same company.  My goal in all of this research on RV construction methods is to be able to walk around a fifth wheel and understand what I’m looking at. We all know there are compromises to consider and we want to make informed decisions.  Or then again maybe it’s just easier to buy a Keystone Montana or DRV Mobile Suites and trust they are built to hold up to fulltime use. More on that later in this article.

What are the more standard tire sizes used with the trailers I’m considering?

Again, another informal survey of the fulltime trailer brands I’ve been researching revealed there is a difference by gross weight ratings of trailers. Seems there is a mix based on if you have 7,000 or 8,000 pound axles. For example, 8,000 pound axles on heavier rigs generally go with an H rated tire, aluminum wheels and 17.5 inch tires. For 7,000 pound axles they generally, but not always, go with E or G rated 16″ tires. I’ve done it again – over simplified the topic. This has value for more than provoking blog comments.

How much safety margin should the tires have?

I read 15-20% more than load capacity. In my humble opinion, great tires are not necessarily an alternative to a matching axle, suspension system, bearings, brakes, frame and the rest of the foundation.  I’d like to settle on a tire that is a little higher rated than the trailer manufacture suggests. If for no other reason then if I should happen to overload a single point above one of the four tires.

Will we feel comfortable with the tires the trailer comes with?  If not, how much should we budget to replace them while staying within the manufacturers tire size limits? Does this become part of the negotiation price when we buy our home?

What about valve stems? Do you have to change to steel valve stems for the higher tire pressures?

I wanted to include this topic because I knew everyone would be asking the same question.

You know I wanted to leave the last comment untouched just to get a reaction out of the reader.  I never would have thought about valve stems had I not looked into tires.

Steel/metal seem to be always used with 110 psi rates. Most say never mind the pressure, get metal. You need them to support the weight of a tire monitoring system and are more durable if you bang the tire up against something.

What about wheel alignment?

There appears to be more to it than just aligning tires. The axle has to be in alignment as well. Seems reasonable to watch for uneven wear on tires and then decide what the problem could be. A good time to do this is when you have the brakes/bearings or whatever checked.

There are alternatives out there. For example, Lippert builds the Correct Track system which they say is used to “correct a misaligned trailer suspension system. Misaligned axles and suspension are caused by lateral, unbalanced weight. When the RV foundation is assembled, the bulk of the weight of the coach has not yet been placed on the axles and chassis. Slide-out rooms, appliances and cargo added by the consumer can cause  unbalance within the coach.

I plan to cover this topic later while researching suspension systems.

• (Update) According to a trusted source “The only real axle system normally available for  RV’s that allows true wheel alignment, like a car, is the MOR/ryde IS axle system.  Comes in various sized 7-8-9K, etc.  Most rigs have two 8 K’s or three 7Ks “depending.”

What about other maintenance issues?

Get new stuff when the old stuff breaks if you are still alive after the crash.

Like everyone else to some extent I’ll be learning as I go. Here is a general list for a few items coming from the research:

• Tire balance: I read about “bead balancing of tires” where a bag of beads is placed in the tire before mounting. There were concerns they may or may not invalidate a warranty. Personally, I’ve never been able to convince any garage my tires should be replaced under a warranty. This is a good time to mention what I’m sure you all have read about. RV tires need to be replacing in 5 to 6 years because of weathering rather than loosing the tread. Figure I’ll make sure they are balanced with the old fashioned lead weights when new and balance them again if they show uneven wear. I’ll  know to check the DOT code for the date the tire was manufactured to make sure I’m not stuck with two year old – “new tires.”
• For this research topic I’m not including what tire monitoring system to use – only that I’ll have one.
• Goodyear tire maintenance chart.
• Good article on weight distribution.
• Regarding rotation and balancing of a trailer tire. I read some owners rotate once a year, many don’t at all because fifth wheel tires are not used for steering. Some say no need to unless you see uneven wear. Some say they only rotate at the time they would balance tires. Some say weathering will cause you to replace the tire long before the tread is gone. In terms of balance, same answers. Some only balance when they are new. Some say no need to balance a trailer tire. Several said the factory does not balance them so get it done when you buy the trailer. Everyone agrees under-inflation is the big hazard and what kills a tire.
• Don’t forget about the effects of UV rays and other elements on tires. Then again I read this is not a concern. I’ll have tire covers when we are parked for a long periods of time even if the tires have built-in chemicals to protect against weathering. Here is what Goodyear says about one of their tires: “The Goodyear Unisteel® G670 RV® has technology that helps guard against the effects of ozone and UV rays. Anti-oxidant and anti-ozonant compounds throughout the tire help protect against weather cracking.”

Thank you for making it this far into the article.  If I have obviously misrepresented a detail please let me know.

Earlier I wrote why not just forget about RV construction methods and buy a brand of RV you maybe, hopefully, should be able to trust for the price  – such as a Keystone Montana or DRV Mobile Suites? Suppose you could do that.

While reading through other blogs I found a lot of detail about available upgrades to a trailer. Got me to thinking about just buying a trailer that comes with all the high end construction methods to start with. Unfortunately there are budget concerns.  And maybe I don’t want to start off with a six year old high end trailer that fits my budget.  Karen and I want to buy our third trailer first. Others might not. By that we mean we don’t want to trade out our trailer two times before we find the one we want. I’m of the opinion planning and research will minimize the chance we would have to trade out early and take a hit on depreciation.  Finally, for me, this is where compromise comes in. If I’m fine spending $70,000 on a trailer then I don’t see spending another $20,000 to upgrade my then existing $70,000 trailer for an amount which was not within my budget in the first place.  To once again over simplify the research; the trailer selection could come down to do we buy a home with standard 7,000 or 8,000 pound axles and what comes with it in terms of construction quality.