Do I need to balance my RV tires?

 I was recently asked about tire balancing.

Reasonable question but as always the answer starts off wit "It Depends"

Vibration can be because of a tire/wheel suspension component is out of balance. Vibration can also occur because the tire or tire and wheel assy is not "round". On a small (14' to 16") tire you can see and measure out of round when the tire & wheel are placed on a spin balancer.   I have shown that you can "balance" a square cement block

  so you need to be sure your tire & wheel assy is "round within at least 0.030"

The person asking the question, said that they had done some research and learned there were three methods. They wanted to understand the advantages of each and which they should use for their Class-A RV.

The basic method is static or "bubble balance". as seen in this  video   https://youtu.be/hp3ShyNzK84

The mounted tire is placed on a balance and the heavy spot is counter balanced with weights.

This static balancing is lower cost but does not provide the best balance. This method is not usually done any more by full service tire stores as it only affects the "static" imbalance and with today's light weight cars the driver is more likely to feel even a minor imbalance. I once had a car with one front tire 1/4 oz out of balance and on a very smooth portion of the interstate on my way home from work I would occasionally got steering wheel movement. A re-check at the store solved the problem. The car was a small light weight sports car and it just happened to be sensitive at that level. My one-ton dually pickup was not sensitive at the two ounce level on the rear axle.


The next best method would be with the mounted tire on a "spin balancer", This rotates the wheel and tire at speed and electronically calculates where to place the weights.
When you buy a new passenger or pick-up truck tire, this is the method they are normally talking about.

But truck/bus size tires can also be balanced using a heavy duty version of this type of machine.

Spin balancers measures the up-down imbalance and the side to side balance and tells the operator how much weight to place on both the inside and the outside of the wheel to counteract forces in both directions.

 Finally there would be "On-Vehicle" spin balance this would give the balance for the tire, wheel and the brake drum and hub of the vehicle so if the drum was slightly out of balance it would be included and weights would counter balance all the spinning components. If you get this type of balancing done it is important to mark the wheel position on the hub if you ever remove the wheel to check brakes and to re-mount the wheel in the exact same orientation. A downside to this method is that it can't be done to tires on drive axles.

Many drivers of Class-A do not balance their tires as they do not feel the imbalance. Some others always balance the fronts because the driver & co-pilot are sitting almost on top of the tires. On-vehicle spin would probably give the best results but this would be for the front only. Here is a video showing the process on a Corvette
 but RV tires would be the same process but with HD bigger equipment.

I see little reason to balance the rear duals on a Class-A as you will not feel the balance problem unless something was very out of balance.

Some additional info in another post.

https://www.rvtiresafety.net/2011/11/do-you-need-to-balance-your-motor-home.html

BOTTOM LINE
For Class-A I think you can just take the RV out for a quick test drive on a nice section of smooth Interstate. If you feel shaking either through the steering wheel or floorboards then you would go and have the front tires "on-vehicle spin balanced".

For Class-C and smaller vehicles using 16" diameter LT type tires I would spin balance all six assemblies.

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Tire "Flat Spotting" when parked

Another post from an RV forum
"I'm no tire engineer but I always thought of a "flat spot" as an area ground off from a long skid. The old bias ply tires of years ago would "deform" or become "out of round" (especially in cold weather) but a few miles of rotation would flex it back into shape. But that's all just semantics."

Well I am a Tire Engineer and the correct terms are "Flat Spot" for an out of round condition. and "Brake Flat Spot" for having an area of the tread worn off due to locking up the brakes so the tire is dragged along the road and does not rotate. When I was racing I would sometimes lock-up the brakes to avoid a spinning car. This would give a strong vibration and we would have to change the tire at the next pit stop.

You can develop "Flat Spot" from long term parking. The degree or level or amount of this type of flat spotting depends on time, temperature load, inflation pressure, rubber chemistry and tire construction.

You can decrease this flat spotting with:

Lower Load  or Higher inflation or not parking when the tire is still hot or keeping the tire out of direct sunlight

The owner has no control over the rubber chemistry or tire construction.

FYI In general tires with Nylon cap ply (seen in tires with higher speed rating) tend to develop and hold the flat spot longer, but I would not reject tire purchase because of the Nylon cap ply as that might give you more life of the tire.

You can see and probably measure the amount of flat spotting from either brake lock or long term parking if you check with a "Free Spin" inspection as seen in the video in THIS blog post. 

##RVT952

Truing tires. Is the tire properly mounted? Is the tire even to cause of vibration?

Had a question from "Fred" on "Truing Tires"
On a different subject, on the Escapee's forum, there was a conversation about tires, and someone mentioned truing new tires. IMO, truing of new tires today only covers up poor mounting procedure, vs 40-60 years ago when tire construction was not as advanced. What are your thoughts on this?

 First, let's be sure everyone knows what we are talking about.
The process of "Truing " a tire involves shaving part of the tread rubber off to make the mounted tire more round. HERE is a YouTube video showing the process.
I tend to agree with "Fred" that most out-of-round problems can be traced to a tire not being properly mounted and seated on the rim. It is also possible that the wheel itself may not have been properly mounted on the hub or it is even possible for the wheel itself to not be round.
 If you have a vibration problem you first need to ask "What has changed?" Did you just get new tires? Are the tires the same but the wheels were off the vehicle for something like a brake job? Have you been driving on especially rough roads with many large potholes? This is a "new to you" vehicle and you have no history with the tires and wheels on this vehicle. On some vehicles "Heat Set Flat-Spot" may be the cause. This happens when tires have been run, getting hot and you just stop and park the vehicle. Sometimes leaving the vehicle parked for weeks or months can also allow the tire to get a flat spot which could take a couple of hours running to work the flat spot out. High-Performance Passenger tires are more susceptible to this problem than large 22.5" size radials but even 22.5 tires can develop a flat spot.

The problem of vibration can usually be traced to either out of balance or the tire/wheel assembly being "Out-Of-round".
If you have vibration on a new tire, I would first confirm it was balanced. Next, I would measure the assembly on the vehicle and confirm it is in-tolerance. This usually means less than 0.030" radial runout goal with 0.125" the upper limit.
If you are exceeding the above, the next step would be to try and confirm which component is not "round". Ideally, you would confirm the wheel, with no tire mounted, was below the limit. If the wheel is "round" when measured on a mounting machine then we would need to confirm it is round when bolted to the hub. Some wheels are "Hub-Centric" and others are "Lug-Centric". Hub centric means the wheel centers on the ledge of the hub on the brake drum. Lug centric means it centers on the bolts holding the wheel to the hub. A lug-centric wheel can easily get "off-center" if one lug nut is fully tightened before the other lug nuts are snugged up. There are patterns for the sequence and steps of tightening lug nuts depending on the number of lug nuts. Here is the sequence as published by Chilton, a publisher of numerous automotive repair manuals.

 
 In addition to the above sequence, it is advisable to tighten the nuts in three steps of 1/3rd of the torque level. Example: if your torque spec was 90 Ft-Lbs you would first do all the nuts to 30 ft-lbs then again following the sequence tighten to 60 Ft-Lbs. The finally to the 90 Ft lb spec, again following the pattern
If the pattern and amount of torque are not followed it is easy to end up with a round tire & wheel assembly to be mounted off-center to the hub which results in an out of the round situation and unacceptable vibration.

Before I resorted to shaving a new tire I would measure the out of round. If you have confirmed all the above yet still have vibration on new tires, I would work with the tire dealer to confirm there is nothing in the individual tire that might contribute to some vibration by simply switching tires around or trying a different set of tires.
In all probability, by now you would have found and fixed the cause of the vibration.