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Mark, My Words: Q & A with Mark Nemeth – August 2013

August 15, 2013 by · Leave a Comment 


Hi, Folks. This month, we’ll be talking about RV tires and weights, with some maintenance and upkeep questions thrown in. I hope your summer RVing is going well, and please keep those questions coming!



The tires on my 5th wheel are a year old, the same as the RV, and are wearing differently from each other.  I’m told that alignment on a trailer is never required like it is on the truck.  Should the tires be rotated? Thanks, John.

Hi, John,

Trailer tires do sometimes show uneven wear patterns, and it can be caused by misalignment of the axles. It is possible to hit an obstacle or road hazard and bend the trailer axle. This can lead to uneven tire wear. Wear and tear on the bearings and springs can show up on the tires as well. A good trailer service place can check for such misalignments and often correct them, so there really is “alignment” on trailers. You can rotate the tires to help compensate for uneven wear, but if it becomes a long-term problem, it would be best to have the trailer axles and suspension checked for damage or excessive wear.


Hi Mark

We tow a year 2000 5th wheel Alumascape by Holiday Rambler. It is a heavy trailer and is equipped with 225R75-15 tires. These tires are operating near the top end of their load range but are the heaviest tires available in a 15″ size. I would like to be able to go to 16″ rims but there isn’t enough clearance in the wheel wells to accommodate the larger diameter tires. Since the axles are already under-slung, the options for lifting the trailer to provide the necessary clearance seem to be:

(a) Remove the existing spring brackets and install longer ones.

(b) Insert  1 1/2″ spacers between the spring pads and the springs.

The second option is the most attractive to me since it doesn’t run the risk of misalignment by accidentally changing the location of the spring brackets and it doesn’t involve cutting and welding.

I have three questions:

1. What are your thoughts about option (b) above for increasing the tire clearance?

2. Would such a modification have any effect on the behavior of the trailer on the road?

3. Are there any other aspects of such a change from 15″ wheels to 16″

wheels that I haven’t thought of.

Thanks, Doug

Hi, Doug,

Right away, I have some concerns with your trailer and your intentions to go up a size on tires. First, most RV trailers have the axle mounted above the springs. That is the normal configuration. You indicate that yours are slung under the springs. That is unusual, and may indicate that someone, possibly a previous owner, has already had the springs remounted to increase ride height on the trailer, or some kind of unusual repair has been done. With older RVs, we sometimes don’t know all of the history of the unit. I would be against adding spacers or doing suspension mods to increase your wheel well clearance. There are times when the ride height has to be raised to accommodate a taller tow vehicle, but in your case, raising the ride height may create hitch alignment issues, and also will make the trailer taller and raise the center of gravity a bit. None of that is necessarily a good thing, and could affect the road handling and stability. You indicated that you are “near the top” of your tire load range. I would suggest that you have the RV weighed (if you haven’t done so already) by a qualified RV weighing operation that uses individual wheel scales, so that you can get the actual weights that each wheel is carrying. Once you know the actual weights, you will be able to tell if you really do have a tire load rating issue. Most RVs come from the manufacturer with tires that are adequate for the axle weight ratings, so if you are pushing the tires, you are likely to be pushing the axle ratings and the GVWR (gross vehicle weight rating) on the trailer as well.



I have a 2000 34′ fifth wheel that weighs 14,000 pounds and recently purchased a new F350 crew cab truck with long bed and 4 wheel drive. When attached to the truck, the trailer rides at a slight angle. When I measured the distance from the ground in the front of the trailer and the distance from the ground in the back of the trailer it came out as 5 inches higher in the front. The person who installed the hitch and does all my RV work said he did not think the trailer needed to be raised. What is the rule of thumb, if there is one, on the difference allowed before having too much weight on the rear axle versus the front axle? Thank you, Jerry

Hi, Jerry,

The trailer really does need to be as close to level as possible and 5 inches is a lot. Just a few inches high at the front will shift quite a bit of weight to the rear axle and could cause an overload condition if you are already heavy. The only really accurate way to set up the hitch height on a tandem axle trailer is with scales, so you can see the weight difference between the 2 axles and raise/lower the hitch height until they are close to equal. The other alternative is to get on a large level surface and get the trailer level visually by adjusting the hitch height. Won’t be spot-on, but it should get you into the ball park. If you have to lower the front, make sure you have at least 6” of clearance from the top of the truck bed side to the underside of the trailer where it hangs over the truck. Any less and you run the risk of dinging the truck bed on driveways and uneven roads. If you can’t get the trailer low enough in the front and still maintain enough bed clearance, the only option is to raise the ride height of the trailer with suspension modifications, like longer shackles or an “axle flip”. My big concern is that you don’t operate with the rear axle over its rating, or exceed tire load ratings. If you do, bad things will happen!


Hi Mark:

We have a 1995 Coachmen “Santara” Motor Home, which we are in the process of doing some outside painting. We have taken off all the old decals and are preparing to sand paper off all the old clearcoat, to repaint the complete Motor Home. What paint can you recommend for the fiberglass, before a final coat of clearcoat is applied? Are there any web sites you can recommend to assist us with this job? Any assistance will be greatly appreciated. Thank You. Gordon

Hi, Gordon,

Wow! That is a very ambitious project! I am not an expert in painting RVs, but I have restored and painted a number of smaller vehicles, and I can tell you that surface prep is 90 percent of the work in any paint job. It is also absolutely critical that it be done correctly, or that beautiful new paint job will not hold up to the road. I would suggest that you consult with an RV paint facility, a boat painter (gelcoated fiberglass is common in boats) or a manufacturer that has experience in repainting fiberglass before you do anything to sand or remove the existing clearcoat (or gelcoat, if that is what you have). If it is in good physical condition (well attached, and fairly smooth) you may be better off leaving it in place and just correcting any surface irregularities with the appropriate surfacer or primer, and sanding. You will need to apply a primer that is compatible to the surface you are priming and correct for the paint type you are applying. A professional automotive paint store will have a wide range of cleaners, primers, and paints available, and would be your best source for the products you will need. It requires professional spray equipment, and the knowledge to operate it safely, to produce a good finished project, and many of the chemicals you will be working with are very dangerous if mishandled, so be sure you are well prepared for the job. I’m not saying it can’t be done, but it is not the kind of project that most do-it-yourselfers would take on.


Hi there,

Is there a good book on working on electrical wiring in a RV?  I have an old Executive that seems to be losing the 12 Volt electrics one circuit at a time.  I’ve tried to find the cause, shorts or loose wires, but it’s impossible to follow the wires. Any suggestions? Larry.

Hi, Larry,

I’m not aware of any books that address RV 12V wiring as their primary topic. For general RV repairs, the RV Repair and Maintenance Manual, written by Bob Livingston, and published by Trailer Life books, is one of the better overall RV maintenance manuals out there. You can find it on and at many RV parts stores. You might also look online for a forum for Executive owners, or search for manuals for your year and model coach. Sometimes it is possible to turn up service manuals for older RVs that way. Finally, you can peruse some of the other RV forums (,,, etc.) if you have general questions on 12V wiring.

mark mugshot 2013

Mark Nemeth has been involved with all things RV for more than 15 years, including almost five years on the road as a full-timer. He is the RV education director for Escapees RV Club and oversees the highly acclaimed RVers’ Boot Camp and SmartWeigh programs. Do you have a question for Mark? Please submit your question via email to

Please remember, material will be edited. Because of the large volume of material and correspondence submitted, individual replies will be limited to questions that are chosen for publication.

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