RV Tech Q&A: October 2020

low tire pressure warning sign

Tire Pressure Monitors

Red letter QYour June and July issues both have very nice articles on tire-pressure monitoring systems (TPMS). When I looked at Amazon to consider purchasing I found many brands other than those highlighted in the articles. Many of them appear, on the surface, much less expensive. Do you have any opinion concerning “B-Qtech” or “Elikliv Solar” TPMS products? While they seem to provide the same information, they seem to be much less expensive. What are the differences between these lower-cost products and those highlighted in the articles? What are the hidden pitfalls?
James Siddle | via email

Green letter AWe aren’t all that familiar with those brands, James, and this situation is common but easily addressed. If you look at buying something that’s considerably cheaper — and that doesn’t just mean less expensive — than a known good-quality brand, the “pitfall” is you’re taking your chances. Lower quality, possible erratic performance, reduced durability and possible questionable warranty service are among the things you encounter if you’re buying a product based on cost alone.

A tire-pressure monitoring system is too important to take chances with by cutting corners. When it’s a safety- related product you should never go cheap. Peruse our recent buyers’ guides on the subject and you should be able to find a system that works well for you.

Stabilizers When Stored

Red letter QShould I use the trailer’s stabilizers when storing the RV in the backyard? We had high winds here in Pennsylvania in March, and my trailer blew off the A-frame-jack block and stabilizer blocks up front. The trailer was shifted 2 feet. I had to cut the sod, jack up the tongue and replace the two front stabilizers. I’ve heard that the trailer should be parked with only the tongue jack down. What method is correct?
Steven Fosbenner | Coopersburg, Pennsylvania

Green letter A A wind event that pushes a parked RV around that much is unusual, Steven, and although it’s not unheard of, we rarely receive any mail about it from readers except when it involves significant storms, hurricanes or the like.

But, yes, we’d recommend keeping the stabilizers down in storage. Those extra pads on the ground, even though they aren’t locked down to the ground with some kind of in-ground anchor, will help stabilize and support the trailer as it’s being pushed, and they may be just enough extra bracing to keep the RV in place. It’s a shame you had to go through the work and expense with your repairs after the fact, but we’d still keep the stabilizers down if it was our trailer.Reader Letter

Second AGM Battery

Red letter QI’m adding a second battery to my travel trailer so I can have more boondocking time. I have an Airstream Sport 22 with a single AGM battery. I’d like to put both batteries inside, but my understanding is that venting to the outside of the trailer should be added, and I don’t want to make a large hole through the side of my trailer. Reviewing the online forums, it seems that people do it all the time without adding venting. Is it too risky to add the batteries inside without adding venting?
Mark Landman | Sharon, Massachusetts

Green letter A Even though it’s a sealed battery that is quite different from a conventional flooded lead-acid battery, an AGM battery still needs to be vented, per code requirements. If you find a suitable location inside that’s on the floor, you can add the vent through the wood floor but you’ll still need to provide a vent opening on the top and bottom. Be sure the battery compartment is well sealed so any venting gasses are routed outside instead of inside to your living space, and you’ll need cross-flow ventilation with air entering from the bottom and exiting from the top, so two separate openings will be needed. To avoid any venting at all, you’ll need to choose a lithium battery system.

Cracked Rims Solution

also had problems with cracked rims as mentioned in the July issue by Debbi McCoy of Circleville, Ohio. I have a 2007 Montana 3485SA fifth-wheel that I special-ordered new. The rims were cracked in the spokes, so I contacted Keystone and was told the rims came from Tredit Tire and Wheel. I was advised to contact them, which I did. 

After explaining to them what was happening, they sent me a new wheel like the one I had and was told the rims have a lifetime warranty. A couple years later the same thing happened to another wheel cracking in the spokes. Again I contacted Tredit and sent them pictures, and they sent me another rim. This past year the third one cracked, but this time they said because I have had so many problems with these rims and the ones I had were no longer available, they gave me a choice of four other rims. Tredit will always get my recommendation for wheels.
Carlton Nehring | Berlin, Wisconsin

More on Cracked Rims

Red letter QHere’s one to add to your not-too-frequently heard of files: I, too, have a cracked rim on an aluminum-alloy (110-PSI-rated) wheel on my 2013 Keystone Montana 3402RL. The crack is on the one single spoke. I have tried unsuccessfully to find and buy a replacement matching rim. This design apparently went by the wayside some time ago. As a temporary alternative, this rim and tire are committed to the spare rack, to be used only in the event of one of the grounded tires being punctured or otherwise not holding pressure. 

I do have a TST 507 TPMS on the rig that keeps tabs on the tires while traveling. I just wish I could locate a matching (without the crack!) rim for replacement. I thought about trying a brazing process from the back side of
the rim; the crack goes across and front to back through the spoke, using aluminum brazing rods, but that process may only weaken the whole rim due to the amount of heat needed to effectively accomplish the brazing process. Any input from any source to locate a replacement rim would sure be helpful.
Richard Blackwell | Indio, California

Green letter A Carlton, thanks very much for your report on working with Tredit Tire and Wheel. It’s a shame you’ve gone through this process with so many wheel failures but it’s terrific that Tredit took care of you with exemplary customer service. It would be a good idea to research the cause of the original failures, perhaps a run over a certified public scale to see where you stand on weights might be a good idea. Check the weight rating on the rims, usually stamped someplace on the back side, and you may discover you’ve been running on overloaded wheels.

Richard, for a trailer of that age, about the best you can do to find a replacement wheel is search online for used accessory sales and RV surplus websites and hope for the best. Popular wheel styles change and not all wheel manufacturers keep a stock of older styles on hand for a long period of time. As for the brazing type repair, that sort of job is best left to a professional. It may work, but unless you’re a professional welder or have extensive welding and brazing experience, it’s a high-load application you’re better off having a professional do.

Bouncing Fifth-Wheel

Red letter QToday was the first time I pulled my 34-foot Sierra fifth-wheel. I have a 2004 Ford F-350 four-door longbed Super Duty with a Power Stroke diesel. The bouncing of my truck and trailer was so bad that everything ended up on the floor inside the trailer, and the pedestal dining table broke. I don’t know if I should do something about the suspension on the RV or the suspension on the rear of my truck. Please help me figure this out.
Gene Foster | Thomasville, North Carolina

Green letter A There are any number of reasons a truck and trailer combination can bounce excessively, Gene, and you can check these items out to see which can help you. Part of it is road surface, and especially on certain types of older concrete highways with expansion joints, you can’t escape the bounce until you drive away from that area.

Your truck is old enough that the shock absorbers are probably worn out. Unless you’ve recently replaced them, consider the use of good-quality aftermarket shock absorbers such as a Bilstein or some other top-end product. It can help civilize your ride. You can also add shocks to your trailer using the new Roadmaster Comfort Ride hardware, a bolt-on kit that can likewise help tame some of your trailer’s rebound.

You may want to consider one of the cushioned shock-absorbing fifth-wheel hitches or trailer pin boxes on the market. There are many different styles available and they all work to help reduce the truck-to-trailer shock impacts from poor road conditions.

Finally, and most important, your truck and/or trailer tires may be overinflated and that can aggravate a rough ride because the tires aren’t soft enough to flex and help absorb road shock. Just because the tire sidewall may say something like “Maximum inflation pressure, 80 PSI,” it doesn’t mean you need to run that pressure, so you may be beating yourself up unnecessarily. Start by weighing your truck and trailer and noting the truck front axle, rear axle and trailer axle weights. Then calculate how much each tire is carrying: For example, 2,500 pounds front axle weight divided by two is 1,250 pounds per tire. Do this for each truck axle and the trailer axles. 

Now look at the manufacturer’s load and inflation charts for your specific tire brand and size. For example purposes only, say the tire is an LT265/70R17. At 80 PSI it’s rated at 2,910 pounds capacity. At 70 PSI, it’s 2,735 pounds, at 60 PSI it’s 2,510 pounds, and at 50 PSI it’s 2,270 pounds. If you started at 80 PSI and the tires were only carrying 1,250 pounds each per the previous paragraph, you could drop the pressure to 50 PSI and still have more than 1,000 pounds of extra load capacity per tire. You can imagine the difference in ride quality you experience at 50 PSI instead of 80 PSI. Run the numbers on your towing setup and tires and you may be amazed at what a difference it makes in ride quality.

You can also refer to the data sticker on the driver’s side door jamb, and as long as the truck still has the same size and rating of tires as listed on the sticker, it also lists a recommended inflation pressure for the vehicle. That generally is for the solo vehicle and doesn’t take into account all the variable weights that the truck may be carrying, so with your weigh-scale figures in hand, including trailer weights, it’s best to use the already mentioned load and inflation charts for inflation accuracy.

As a side note, going with a more accurate inflation figure means the tire tread is contacting the road in a more effective way and that can help improve handling and stability while enhancing tread life. Keeping an eye on those pressures is a win all around.

Keystone Decals

Red letter Q To add comments regarding Keystone’s poor decal-life expectancy, as reported in the June issue, we have a 2014 Keystone Bullet that has had serious fading and chalking for the last several years. The front-end cap is in terrible condition. This “defect” is really bad, considering the great shape this trailer is in otherwise.

The company needs to find a better product to use as decals. I will never buy another Keystone based on this experience. The body should actually be painted rather than apply such poor decals. I realize that would be more expensive for them, but that would be better than degrading their reputation regarding producing a quality product.
Ernest DuVarney | Myrtle Beach, South Carolina

Green letter AAll RV decals will fade with age, Ernest, and given that your trailer is six years old, some fading is to be expected. To write off the rest of the trailer based on fading decals, “considering the great shape this trailer is in,” is a bit harsh. There are RVers who would love to have fading decals as their only significant trailer problem.

We’ve had a lot of reports of Keystone front fiberglass caps, especially the brown ones, fading, chalking and aging prematurely. Since your Bullet’s fiberglass is fading, as you indicated, you may want to consider having some body wrap décor added in place of the original decals. The body wrap, in addition to being visually attractive, can cover that aging front cap and maybe save you the cost of a repaint.

It’s a pretty slim chance that you could find any exact replacement decals. Vinyl body wraps are available in a virtually endless selection of colors and designs so you could choose something really cool to have applied to your trailer. Google something like “vinyl car body wrap” for example to locate a franchise dealer near you. Those vinyl graphics are said to have a realistic lifespan of around five years, and if the trailer is stored inside or otherwise protected from the sun, it could be more.

There are a lot of higher-quality, higher-price products that the average RV manufacturer could use that would bump up its product quality by a wide margin, but, unfortunately, that would add price to the RVs and keeping the cost down and profits up is a higher manufacturer priority.

Turn-Signal Markers

Red letter Q I have a 2017 34-foot Rockwood Windjammer. The side markers on our trailer are only on or off and we’d like to have them blink when changing lanes. It’s a safety thing. Because of the longer length, I want to let other drivers know my intention to change lanes. The RV repair shop seemed puzzled when I asked.
Gerald Odor | Yuba City, California

Green letter AMaking your side-marker light flash when you signal a turn would run afoul of DOT regulations, Gerald, since those side-marker lights, also called clearance lights, are supposed to be on when the headlights are on. You’d need to add new dual-filament bulbs like those used for taillights and turn-signal lamps so you could end up with the marker lights on all the time, plus the separate circuit for the turn signals. Then you’d need to wire the new turn-signal lamps to the left- and right-side bulb circuits. That would be a job but not impossible to do.

It might be easier to add a new set of fixtures, using LED bulbs to avoid overloading the turn-signal circuit, and wire them to their respective turn signals as above. That would provide a fully independent flasher circuit that didn’t interfere with the clearance lights. There are many thousands of trailers safely and happily on the road without these extra turn signals but adding them can’t hurt, other than the extra work or cost.

Trailer-Axle Capacity

Red letter QMy wife and I are looking to purchase a fifth-wheel. I have towed travel trailers for several years and have had problems with axles in the past. My question is how can two 7,000-pound gross axle weight rating (GAWR) axles be sufficient to carry a fifth-wheel that has a gross vehicle weight rating (GVWR) of 15,000 to 16,800 pounds? I see those specifications listed all the time in the descriptions on the dealer websites. 

Is there a formula that subtracts all or a portion of the pin weight from the GVWR and that’s how you get the weight on the axles below the 14,000-pound GAWR the two 7,000-pound axles can carry? Can you help me understand this?
Doug Harris | Las Vegas, Nevada

Green letter A This question has both technical and rhetorical answers, Doug. Rhetorically, some RV manufacturers cut any expense corners they can, such as by using axles that are rated at just barely enough to carry the load and keep the vehicle technically DOT legal. The right thing to do is use axles that are rated to handle the full trailer GVWR, but as you’ve discovered, that doesn’t always happen in the real world.

Some manufacturers figure if the trailer weighs 12,000 pounds on the axles the axles can be rated at 7,000 pounds each or 14,000 pounds total capacity because that leaves 2,000 pounds of payload available on the axles. If the trailer chassis is rated at 16,000 pounds, that means at least 4,000 pounds needs to be carried on the hitch to maintain that 12,000-pound weight on the axles. 

We’ll use some examples to illustrate the process of making sense of these numbers. Start with the trailer’s GVWR, at 16,000 pounds. The manufacturer supplies a hitch weight figure, 3,000 pounds, and a trailer overall weight figure, 13,500 pounds. Deduct that hitch weight figure from the overall weight and you have 10,500 pounds of weight on the axles. If the trailer has those 7,000-pound GAWR axles or 14,000 pounds of axle capacity, you deduct the 10,500 pounds from the axle capacity and you arrive at 3,500 pounds of additional payload capacity on the axles. On paper, so far so good.

If you deduct the 13,500-pound trailer overall weight from its 16,000-pound GVWR, you have 2,500 pounds of payload capacity. Some of the trailer’s payload weight is carried on the hitch so as long as you don’t exceed the trailer’s GVWR of the axles, with 3,500 pounds of capacity, will be fine.

As a rule of thumb, fifth-wheels should have around 20 to 25 percent of the trailer weight on the pin, and travel trailers should have 10 to 15 percent on the hitch. Remember that those manufacturer weight figures usually don’t take into account the weight of water, LP-gas and, in many cases, some of the factory or dealer-installed options on the unit. You’d be surprised at how much those details add to a trailer’s weight. The only way you know for sure what it weighs is to take the trailer to a public scale and record some real-world figures, then you can add the weight of freshwater, at 8.33 pounds per gallon, and LP-gas, at 4.2 pounds per gallon, based on the trailer’s established fluid capacities. This will give you a good starting point on knowing your rig’s weights and how they affect its use

Replacement RV Roof

Red letter QI have a 2012 38-foot Keystone Copper Canyon and the roof is going bad. It is not currently leaking, but it is only a matter of time until it will be. I have cleaned it and treaded it twice a year, but the sun has taken its toll on it. I would like to get one of the spray-on bed-liner-type roofs put on. We live in Georgia and have read about companies that will come to you. Do you have a company you recommend to do this kind of work?
Anthony McGinnis | Georgia

Green letter A Doing a roof replacement before the roof has gone bad and started to leak is a good idea, Anthony. That saves you some potentially expensive repair work by the new roofing company.

There are several nationally distributed franchise operations that do that kind of RV roof treatment and some are offshoots of the companies that have been doing spray-in truck bedliners for many years. ArmorThane and Rhino Linings are two of the companies doing this kind of work. It’s a fairly expensive process but the end result, when appropriately applied, is a tough, durable roof for an RV that’s a great way to go for long-term durability. An internet search will show you dealers for this project in your general area. In addition, and well worth considering are the companies that chemically “build” a roof on your RV. RV Armor, FlexArmor and Crazy Seal are examples. We know RV Armor has a lifetime warranty that follows the VIN, and Crazy Seal has a 50-year product warranty. We have done installs and tests of these products, which you can find on our website. 

F-350 Wheel and Tire Swap

Red letter Q We have a 2019 Ford F-350 diesel single-wheel-axle, four-door, 4×4 with 20-inch tires. We’d like to know what size slide-in truck camper we could get, and if we would need to change the tire size from 20 inches to 18 inches. Any help and suggestions you could offer would be appreciated.
Steve Kortum | Columbia Heights, Minnesota

Green letter A Steve, Ford makes it easy for you. The company’s trucks that are “certified” for truck-camper use have a consumer information sheet in the glove box with center of gravity information. Combine this with the information in the 2019 Ford RV and Trailer Towing Guide, and you’ll be all set. You can find it at: www.fleet.ford.com/content/dam/aem_fleet/en_us/fleet/towing-guides/2019_Ford_RVandTrailer TowingGuide.pdf

In Ford’s case, they tell you in the guide how much camper you can carry, and what options you need to do it. Even if your truck is not truck-camper “certified,” you can make it safe to use by adding aftermarket suspension accessories, like sway bars and load levelers. The rating is based on the wheelbase length and model. It appears that the models that have the 20-inch wheels are rated the same as the 18-inch. 

In a more general fashion, you start by noting your truck’s bed length, because campers are built based on shortbed or longbed, which, besides size, also affects center of gravity. Then you’ll need to determine the truck’s GVWR, which is on the data placard on the driver’s-side door jamb. You’ll also need to learn your truck’s GAWR for the front and rear axles, which is also on the door-jamb placard. Now take the truck to a public scale, preferably with whatever passenger and cargo load you’d normally have in the truck during an RV outing, and record its overall weight, front and rear axle weights.

Deduct your truck’s overall weight from its GVWR to determine its payload capacity. For example, 11,000 pounds GVWR minus 8,000 pounds curb weight leaves 3,000 pounds payload capacity. Now do the same math for the front and rear axles, deducting each axle’s weight from its GAWR to arrive at your payload capacity for each axle. That tells you how much camper weight your truck can handle, and when selecting a camper, be sure to accommodate for the weight of cargo, fluids, options and so forth in the camper.

If you’re buying a new or recently new camper there should be a label that lists the unit’s weight. That label will also include information about how many gallons of freshwater the camper can hold, at 8.33 pounds per gallon and propane at 4.2 pounds per gallon, so you can make an accurate estimate about the camper’s weight before you have a chance to buy it.

Don’t be surprised if the truck’s combined axle capacities equal more than the truck’s overall payload capacity. The manufacturer establishes GVWR as a result of many mechanical factors such as engine cooling, braking, steering hardware and so on, and axle capacity is just one of those variables. 

Tire capacity is one of those variables and as long as you haven’t replaced the truck’s tires with something with a lower payload capacity per tire, the tires on your truck should be adequate for the load, as long as you don’t overload the truck and exceed its GVWR or GAWR. The tire’s maximum load capacity is molded into the tire sidewall, so add those up for each axle and compare the figure to the axle’s payload capacity as determined above. You’ll probably find the replacement wheels and tires aren’t necessary. 


Man leaning over engine wearing blue shirtJeff Johnston served as technical director of Trailer Life for 20 years and has been an RV enthusiast, mechanic and writer since he could hold a wrench. In his monthly RV Clinic column, Jeff replies to Trailer Life readers’ technical questions about RVs and tow vehicles. He also serves as associate producer of Rollin’ On TV, a nationally syndicated television program for RV enthusiasts.

 

1 COMMENT

  1. We have a 2016 Jayco Northpoint 301RETS 5th wheel…we love it except since we purchased it new we had once while in warranty and once out of warranty the large slide out that carries the frig,cook range. and sofa go out .New motors have been installed. We do as the techs advise us to take the slide completely out. which we have always done. The slide is currently showing signs again of pulling more to one side and moving slower. Nothing appears to bein the way. We also have been told that these large type of slides are problematic. Having new slide motors installed and synced is costly{ over $1500 easily). Any suggestions would greatly help. Thank you

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