RV Tire Safety: Importance of side-to-side motorhome weight balance

8

with RV tire expert Roger Marble

I received this question and thought that others may have a similar problem.

Hi. I have followed your postings on this forum and I own a 2017 Newmar Ventana 4002. I am trying to understand and resolve an issue with my coach where I have a 1000 lb. difference in weight on the front axle side to side. I have had the coach weighed on all 4 corners 3 times and get the same results. My understanding, and I think it may have been in one of your posts, is that the difference should never be more than 500 lbs. side to side.

I am having a conversation with Newmar about this and pushing them for answers why, as I am well under the GAVR and well under the GVWR. I have unloaded and moved the contents in the basement and inside the coach around hoping to make a difference and the reality is I don’t have much to move.

I am looking for any studies or evidence that I can show Newmar that this is not safe if indeed my information is correct that side to side should not be more than 500 lbs. I am hoping you might know of something I can get my hands on or someone I can talk to.

Thank you for taking the time to read this PM.

Sincerely,  Newmar owner

My reply:

You may have misunderstood the side-to-side weight comments.

It is suggested that people get “4 corner” weights rather than just axle weights, as it is known that some coaches are unbalanced side to side.

We do this because if you only get axle weights and simply divide by 2 and assume your side-to-side weights are even, you could end up with an overloaded or underinflated tire if the sides are not close to even.

Not sure where the 500# figure comes from other than looking at the load increments in the tables for each 5 psi. You will see that with some large tires the load capacity can increase by a few hundred pounds with an increase of 5 psi.

I do not remember ever seeing a “should” not be more than 500# difference statement.

You have confirmed that your coach is not balanced side to side and it appears you have made a good effort to get more balanced but have not been able to because of the design/layout of your coach.

With that in mind, and knowing the load on the “heavy end,” you need to consult the Load/Inflation tables and use the heavy-end weight to learn your minimum inflation for all of the tires on that axle. I still recommend you add 10% to the table inflation number as long as you do not exceed the max inflation rating for the wheels. This 10% helps avoid TPM (tire pressure monitor) low-pressure warnings due to an occasional drop in ambient air temperature.

I trust you have confirmed with your RV manufacturer that the wheels are capable of supporting the heavy-end load.

I hope this clarifies what you need to do and answers the question of “why” we suggest you get the weights on each end of each axle.

 

Read more from Roger Marble on his blog at RVtiresafety.net or on RVtravel.com.

 ##RVT942

 

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Fred
5 months ago

Roger, your answer seems to not answer his obvious concern. Will a 1,000lb difference side to side affect his steering, braking & tire wear? In other words, is that 1,000lb difference a safety issue? I can understand you not wanting to tangle with a manufacturer on their design specs, but a 1,000lb difference seems like asking for trouble with tire & brake wear. But then I’m not an expert, just an old fulltimer that’s trying to roll down the road as safely as possible, since my rig is my only home. I’ve experienced blowouts & they are heart stopping events.

Asher
5 months ago
Reply to  Fred

Exactly.

Roger Marble
5 months ago
Reply to  Fred

yes a significant unbalance could cause handling problems but the primary focus for me is to ensure you are using the correct tire inflation level. Since inflation minimums are based on the maximum expected load you can only discover a side to side unbalance by knowing the load on each corner of the motorhome ie. “4 corner weights.
Also for better handling and steering response, you should inflate all tires on an individual axle with the same inflation (unless you drive at Indy on in NASCAR)
This is why we say 1. learn your weights. 2. Try and bring your RV into closer balance side to side. 3. Use the heavy end weight to learn your minimum cold inflation. 4 Inflate all tires on that axle to the level needed for the heavy end. 5 I suggest you increase the inflation by 10% if possible to lower the need for messing with your inflation every day.

Phil Justis
5 months ago

One of the possible problems/reasons could be mechanical. Weak spring or mismounted sway bar(s), or bent frame. This could cause a cross weight situation even if weight is perfectly balanced in the Rv itself. Disconnecting the sway bar(s) and redoing the corner weights might change the results and give some clues as to the solution to the problems. This is very similar to setting up race car, moving ballast (movable Rv items), and setting spring loading to get the tire loading the way you want it or needs to be.

Carlos
5 months ago

Roger, I have a friend with a 50 ft farm scale. Could we weigh each set of tires ( right side vs left side) by driving on one side weigh and turn around and weigh the other side. Would this give an accurate form of side weight.

Roger Marble
5 months ago
Reply to  Carlos

Yes that might work as long as the ground off the scale is close to level with the scale.

Donald
5 months ago

I always thought the trailer/ motor home /camper etc. should be balanced from side to side and end to end.Too much weight in the front or rear causes bad driving control and bounce. Too much weight on either side will cause the unit to want to lean too far on corners and put extra stress and wear on the tires??

Roger Marble
5 months ago
Reply to  Donald

Motorhomes almost never have Front axle and rear axle supporting similar loads. Just work on the side to side loading. RV Trailers in theory should have an equal load split between front and rear axles. If there is a big difference you need to learn why (broken spring or shackle) Side to side would be important to know to learn if you have a reasonable (15%) Reserve load. I cover this iin my blog http://www.rvtiresafety.net