Why tires fail

[rv4007]

Please understand, that none of this is a personal attack on anyone posting an opinion on this matter, only a desire to make sure that others have the opportunity to consider the facts or science surrounding dynamic balancing products. I am a degreed engineer who has researched this area, and I also have several years of balancing experience in automotive, aviation, and industrial settings.

"First, when a tire is not rolling, it is not generating any centrifugal force, so there is no balancing going on."

Answer: This is OK, no balancing is needed when the wheel assembly is not rotating.


"At what speed does the centrifugal force become enough to overcome the force of gravity to cause the balancing effect to dominate? I don't know, but it seems to me that since gravity never stops working, it is always a factor of some sort."

Answer: Gravity is a factor, however it is insignificant relative to the centrifugal force of the rolling wheel assembly. I am sure that you have twirled something weighted on the end of a string before. Gravity is at play, but the centrifugal force is much greater and allows the object you are twirling to move in any axis.


"Second, any separate piece that you mount on the wheel hub isn't doing any dynamic balancing. It's only doing static balancing in the plane it is operating."

Answer: This statement is incorrect. Any of the methods mentioned, Centramatics, balancing beads, balancing powders, are the very essence of dynamic balancing. They work just like the harmonic balancer on the crankshaft of your car. They automatically redistribute as a reaction to the tire moving in the opposite direction due to imbalance. Possibly the confusion is due to what some incorrectly call "Dynamic Balancing" where they take readings on a rotating assembly while it is rotating and then place weights on the assembly at locations determined by the balance machine. This is how we balance turbine engine rotating assemblies, helicopter rotors, and wheels and tires at the local shop. It is not truly dynamic balancing is more correctly called dynamic assessment of balance as it is only accurate for one single condition(rpm, condition of the assembly, etc) as soon as anything changes such as the tire wearing, or having a rock lodged in the tread, the balance is no longer accurate. Centramatics, bead, powders, do "dynamically" re-adjust to the changing conditions.


"And while "balance beads" are not constrained to operate in a single plane, I still have concerns about what they do to the insides of tires."

Answer: I respect the caution. I agree I have heard and read of many things that I would not do, and I would not just throw something inside of my tires without a lot of research. If you read the internet, some will suggest that golfballs, Airsoft Pellets, small pebbles, BB's will all do the same job. They will in fact balance the tires, but they will also possibly damage the insides of your tires. Dynabeads and Equal Powder are manufactured specifically for this purpose. They have been tested, and are widely accepted in the trucking industry with millions of miles to their credit. I have personally used them and have nothing but good things to report. And no, I don't have any financial interest in any of the products mentioned."


"And as a last thought: If these things were so good, wouldn't vehicle manufacturers install them in their factories? Think of all the warranty money to be saved - and all the dissatisfied customers they wouldn't have - if these things worked as advertised."

Answer: Follow the money.... who loses out if tires last longer....who loses out if they don't have to be rebalanced...... and last but not least, public skepticism. We don't often accept things we don't understand. It is hard to grasp that throwing some beads or powder inside the tire will "magically" balance the tire. Skepticism aside, it really does work. Here is a video that shows the principle

DynaBeads demo video - YouTube

The only negative I have personally witnessed, is when you hit a really large pothole or anything that disturbs very significantly the dynamic balance will attempt to fix the problem, and then as things return to normal, you might feel a very slight imbalance for about a second as the dynamic system readjusts. I consider this to be minor compared to the almost continuos imbalance that occurs in normal static balancing.

Dennis

[GCinSC2]

Dennis,

Thanks for the balancing info and you're explanations.

To all:
The original title and intent of this thread is Why Tires Fail.

I think that is the topic to be discussed, balancing would be better served as its own discussion and I think one exists currently.

[switz]

The Centramatics sure work well on my Honda GoldWing and we never even balance the tires with weights any more. By the time the bike is moving enough to stay upright, the wheels are balanced.

The up front $199 expense could be far less than the cost of repairs due to a vibration generated in the suspension system. Installing the best possible tires after being properly balanced means the Centramatics can compensate for the brake drum's out of balance state. If a wheel weight comes off due to a bump in the road or poor installation, the Centramatics can he keep the assembly balanced until the tire can be properly re-balanced.

YMMV

[CapriRacer]

First, I think the issue of balancing is a good one for debate. I also hope people won't get all caught up in defending their position that they lose civility. We can discuss these things without the need to get snotty or personal.

I also recognize that this thread is about tire failure - but since the subject has been brought up.......

Hub and rotors? If you'll look, you will find some that have grind marks or weights added. This is obviously there because they not only measure it for balance, but corrected the imbalance.

Here's an illustration:

http://www.barrystiretech.com/rotorbalancemark1.jpg

Look at the first entry on the right hand side.

And cost for a vehicle manufacturer? With the normal balancing methods, car manufacturers have to have balance machines, buy weights, and install them. This costs money, so it isn't as though it's free. - and while Centramatics are fairly expensive, balancing beads aren't. Don't they work on the same principle? So why do 100% of the car manufacturers chose to use weights?


But in all fairness, I think it has been demonstrated that Centramatics work to some extent. The video does show that the balance is better:

Centramatic Automatic Wheel Balancers Demonstration - YouTube

- but the video unintentionally shows they don't work as well as a balanced assembly. Note the bit of vibration of the little red tab below the tire.

[CapriRacer]

I am going to truncate the post because I only want to address certain statements.

Originally Posted by rv4007

Please understand, that none of this is a personal attack on anyone posting an opinion on this matter........

Answer: Gravity is a factor, however it is insignificant relative to the centrifugal force of the rolling wheel assembly. I am sure that you have twirled something weighted on the end of a string before. Gravity is at play, but the centrifugal force is much greater and allows the object you are twirling to move in any axis......

And whenever I do twirl an object on a string, I do indeed feel the tug of the weight as it rotates - BUT - are my hands sensitive enough to note the effect gravity has? I don't think so.

Originally Posted by rv4007

......Answer: This statement is incorrect. Any of the methods mentioned, Centramatics, balancing beads, balancing powders, are the very essence of dynamic balancing........

I think we have a difference in definition of the term "dynamic balancing". In some respects it would be more properly termed "2 plane balancing". This is not to be confused with "changing over time".

Originally Posted by rv4007

......They work just like the harmonic balancer on the crankshaft of your car............

Ah ..... not exactly. Harmonic balancers aren't really balancers. They are dampers - of rotational speed variation and non-rotational movement. They dampen out the flexing caused by the firing of the cylinders and the pulses generated by the explosion.

Please note that internal combustion engines have balance weights on the crankshaft. Doesn't this say that this is the preferred method of balancing?

[QUOTE=rv4007;1348948]......This is how we balance turbine engine rotating assemblies, helicopter rotors, and wheels and tires at the local shop......[/QUOTE}

I note with great interest that in every case you cited, everyone is balancing with weights.

Originally Posted by rv4007

......It is not truly dynamic balancing is more correctly called dynamic assessment of balance as it is only accurate for one single condition (rpm, condition of the assembly, etc)......

Ah .... not exactly.

First, you are right about the use of the term "dynamic" - as I explained above.

But the beauty of balancing using fixed weights is that it balances independent of rpm, and condition of the assembly. In other words, it takes what is there and deals with it and the balancing doesn't change regardless of the speed.

Now the need to balance an assembly to tighter tolerances is a function of speed, but we are talking the amount of allowable tolerance, not the principle itself.

Originally Posted by rv4007

......Dynabeads and Equal Powder are manufactured specifically for this purpose. They have been tested, and are widely accepted in the trucking industry with millions of miles to their credit. I have personally used them and have nothing but good things to report. And no, I don't have any financial interest in any of the products mentioned." .....

And here is where our experiences differ.

Have I seen damage to the inside of tires due to a balancing compound? Yes!

Why? I suspect it is because there are so many tire manufacturers and each one has its own formula for the innerliner (the air retaining rubber on the inside of the tire). I just can not image that any of these balancing compound manufacturers have tested them all. The thing I can image is that there may be reports sent back to the balancing compound manufacturers - who may or may not make changes.

Originally Posted by rv4007

......Answer: Follow the money.... who loses out if tires last longer....who loses out if they don't have to be rebalanced......

I don't think this argument holds up as car manufacturers have to pay car dealers every time a new car has to be rebalanced. This is a cost to them, not a revenue stream.

Originally Posted by rv4007

......Dennis

Nevertheless, thanks, Dennis, for the discussion points.

[switz]

The owner of the trailer can do much to reduce early tire failure if they so choose.

1. Cover tires with a light colored cover when the unit is stationary.
2. Check and keep tire pressure at correct psi.
3. Have new tires spin balanced before installation.
4. Rotate and balance the tires perhaps every 5,000 miles.
5. Use an infrared temperature reading device at every stop and check both wheel bearing covers and tire sidewalls on both TV and TT. Check more carefully any tire or bearing with a major temperature deviation.
6. Inspect tread for any inbedded glass, rocks or metal before any trip and when at destination.
7. Raise side of trailer and place a stone, brick, or board near tire tread and slowly rotate tire to see if it is out of round.
8. Check both side walls of tire for any damage or unusual sidewall deformation.
9. If funds allow, install a tire TPMS system for early warning of an impending tire issue.
10. Consider installing a device like the Centramatics or balancing beads to help balance the entire tire,wheel and hub (or rotor if disk brakes) assembly.
11. By judicious use of the scales, ensure that no one tire is overloaded on any one axle even though the total of the two tires seems correct when weighed together.
12. Respect the concept of a three (or four year max) year service life despite the mileage.

I am sure more suggestions could be added to the list, but an ounce of prevention is worth a pound of cure (especially in the UK).

[Inland RV Center, In]

Originally Posted by CapriRacer

First, I think the issue of balancing is a good one for debate. I also hope people won't get all caught up in defending their position that they lose civility. We can discuss these things without the need to get snotty or personal.

I also recognize that this thread is about tire failure - but since the subject has been brought up.......

But in all fairness, I think it has been demonstrated that Centramatics work to some extent. The video does show that the balance is better:

- but the video unintentionally shows they don't work as well as a balanced assembly. Note the bit of vibration of the little red tab below the tire.

Yes indeed, the model shows a little vibration.

Please note, that the tire size is only about 8 inches.

The operators hand is about half the size of the tire.

There are many causes of tire failures.

Lack of proper balancing, is just one of them.

Andy

[rv4007]

Switz did a great job of summarizing the various issues. One caution, most manufacturers of beads or powder recommend removing the lead weights before installation of the beads or powder.

I owned two businesses that between the two of them had 50-60 tires on the ground at all times (heavy trucks, trailers, heavy equipment). Our failures were almost exclusively on the trailers and were almost exclusively due to under-inflation compounded by heat buildup due to road surface temperature and speed. The typical scenario was to puncture a tire in a landfill or in the woods and develop a slow leak which was not noticed during pre-trip inspection. If the trailer were heavily loaded, then a blowout was common. Drivers who commonly drove below 55mph on country roads had fewer blow-outs than drivers who were on the interstate at 65-70mph. We had more blowouts in summer than in winter. Heat damage to a tire is cumulative, so even if the blowout did not occur on that trip, that particular tire would likely fail at a later date.

Many Airstreams are running at or near the rated tire loading, so their are similarities to my experiences above. The primary difference was that the blowouts did not damage my equipment trailers the way they typically damage travel trailers.

I have never had a tire failure that could be attributed to imbalance. I have replaced tires before their normal life expectancy due to tread damage caused by imbalance, but no failures.

If one is primarily concerned with tire failure I would focus on inflation and loading. Since we don't normally notice under-inflation until it is too late, I think a TPMS is a wise investment.

Dennis

[DryFly]

I just ordered Dynabeads for my tires. S/B here in a few days, then I'm off for a couple of trips. I'll let you all know what I think.

This is a great thread on a very important subject. I think Switz posting #26 is dead on.

[Andrew T]

I just thought I would point out that Airstream is the only trailer producer that I know of that ballances tires. All other trailers run alfresco. I am not saying it is a good idea just thought I would mention it.

We have our own mounting and balancing equipment and regualrly check tires. Most ST tires after a couple of years of use are substantially out of balance. LT and passenger tires we use on trailers almost never are even after 5 years.

Andrew T

[Tireman9]

Originally Posted by Andrew T

I just thought I would point out that Airstream is the only trailer producer that I know of that ballances tires. All other trailers run alfresco. I am not saying it is a good idea just thought I would mention it.

We have our own mounting and balancing equipment and regualrly check tires. Most ST tires after a couple of years of use are substantially out of balance. LT and passenger tires we use on trailers almost never are even after 5 years.

Andrew T

Interesting statement about ST tires going "out of balance". I wonder if the tires are slipping or rotating around the wheels or if the tires have developed "flat spot" from brake lock-up. Having actual data would allow corrective action. I know when tires are evaluated we marked the location of the valve stem on the side of the tire so we know if the tire slips on the rim. Sometimes this slip can be solved with the use of correct tire mount lube rather than dish soap that some use.

[BlackAces]

Originally Posted by Inland RV Center, In

Who, offers a warranty on lead weight balancing?

Or for that matter, issues a written warrant that the wieghts "WILL NOT" fall off and the balancing, without exception, lasts X miles.

Many theory's about many things, in their days, were great, including tire balancing.

By today's advancement in Physics and simple running gear balancing, the old methods are outdated, and totally useless for the long term.

Any balancer that out lasts the tires life, is not even in the same class as lead weight balancing, especially when it comes to RV's.

But, as always the decision rests with the owners.

Centramatic owners have never, ever, stated any complaints, but most of them, have complained about the lead weight issues, from many stand points.

Progress is extremely important to most Airstream owners, at least based on my 47 plus years of working with them and finding many ways for them to better enjoy AIRSTREAMING!

Andy

All sorts of tire balancing techniques are being developed. Take a look at this one.

http://www.bridgestonetrucktires.com...0ask%20doc.pdf

[Tireman9]

Thanks for providing the document BlackAces.
Biggest issue is that I would be surprised if any ST type tire or possibly even any 3rd party importer markes their tires for dynamic balance.
If someone knows which tire companies do then I am sure we would all like to know.

I do note that this system has been in use for many years in the OE car tire market. I also note the closing paragraph that still talks about balancing assemblies even with tire high point mark.

As I said a spin balance on the vehicle will include the tire, wheel, hub & brake drum which would be better than just balancing the tire & wheel assy alone.

[Inland RV Center, In]

Originally Posted by Tireman9

Thanks for providing the document BlackAces.
Biggest issue is that I would be surprised if any ST type tire or possibly even any 3rd party importer markes their tires for dynamic balance.
If someone knows which tire companies do then I am sure we would all like to know.

I do note that this system has been in use for many years in the OE car tire market. I also note the closing paragraph that still talks about balancing assemblies even with tire high point mark.

As I said a spin balance on the vehicle will include the tire, wheel, hub & brake drum which would be better than just balancing the tire & wheel assy alone.

Then the question becomes which is better, installing a lead weight 180 degrees opposite the heavy spot, or install 2 weights, 120 degees away from the heavy spot, as Snap-on recommends.

Obviously, the 2 weight system balancing, in normal service, will last about 10,000 miles. Not so for the single counter balance.

Andy

[Tireman9]

Originally Posted by Inland RV Center, In

Then the question becomes which is better, installing a lead weight 180 degrees opposite the heavy spot, or install 2 weights, 120 degees away from the heavy spot, as Snap-on recommends.

Obviously, the 2 weight system balancing, in normal service, will last about 10,000 miles. Not so for the single counter balance.

Andy

Yes split weights are usually better just as on vehicle spin is better than wheel& tire only spin which is better than static.

[switz]

So, if one gives up on the drum brakes and switches to disk brakes, the assembly balance issue gets resolved?

One would still need to spin balance the tires, but the rotor would be balanced and the Centramatics would fine tune the balance and compensate for the tire wear or garbage that gets stuck in the treads.

[ROBERTSUNRUS]

Originally Posted by CapriRacer

I am not a fan of anything except traditional balancing methods.

Hi, I wasn't either until I bought a trailer and noticed that trailer brake drums are not balanced. Centramatics make up for the drum and then some. I still have my tires/wheels machine balanced. Spin balancing on the vehicle is something that was more common about 40 years ago and virtually unheard of today.

[ROBERTSUNRUS]

[QUOTE=CapriRacer;1349238]
Hub and rotors? If you'll look, you will find some that have grind marks or weights added. This is obviously there because they not only measure it for balance, but corrected the imbalance.

QUOTE]

Hi, Yes you will find grind marks, drill marks, and added weights on motor vehicle drums; You will also find similar things done to motor vehicle rotors, but you won't find any of these on trailer drums.

[ROBERTSUNRUS]

Originally Posted by rv4007

"At what speed does the centrifugal force become enough to overcome the force of gravity to cause the balancing effect to dominate? I don't know, but it seems to me that since gravity never stops working, it is always a factor of some sort."


Dennis

Hi, working at new car dealers since 1968, I can tell you that most out of balance wheels can be felt at freeway speeds, mostly between 60 and 65 MPH. I have seen cars on the freeway with wheels so out of balance that you can see the wheel actually bounce off of the ground. The out of balance seems to come and go as speed increases, but at about 65 MPH it feels the worse.

[r carl]

Hi, Yes you will find grind marks, drill marks, and added weights on motor vehicle drums; You will also find similar things done to motor vehicle rotors, but you won't find any of these on trailer drums.[/QUOTE]

I did.