Tire balancing no longer needed per tire rep

[threeputtpar]

Originally Posted By: CapriRacer
Originally Posted By: user52165
......Do the math. A car/small truck tire vs a big rig. It's tire rpm per mile that counts. There are calculators available. Size - in this case circumference - matters.


But over the road truck tires and over the road truck wheels are harder to manufacture and are worse for balance and uniformity than passenger car tires and wheels. So those properties may offset the gain for the change in Revs Per Mile.

Besides, I really really think this has more to do with the characteristics of the suspension, specifically the resonant frequency. Passenger cars don't really vibrate until you get to that frequency (or at least wheel end vibrations don't cause issues until you get to that frequency).

Pu another way, If cars never exceeded 45 mph, you wouldn't need to balance either.


When you link the resonant frequency to any wheel or tire vibrations, are you also saying that a car's frequency is dependant on spring rates? If so, can a car with well balanced tire/wheel combonations still show vibration issues if say the front end springs are getting weak? Would that lower the speed threshold of vibrations occuring or just increase the likelyhood of vibrations? Assume that all of the suspension components up front are new and good. Thanks.

 

[SwampSurvivor]

Well both.

A 42'' truck tire going 55MPH is going will have about 60% of the RPMs as a 24'' car tire going 55MPH.

The car's light duty suspension attached directly to the unibody will transmit any wobble, shimmy or shake through the cabin pretty easily.

A truck tire, going at a slower RPM needs to "wobble" a big beam axle in the front or rear axle with differential, then "wobble" leaf springs. On top of that, 18 wheelers have air ride cabs - so even if the slow turning truck tire manages to make the frame shimmy, the cabin is sill isolated from most of it.

 

[CapriRacer]

I see I have stirred up some interest.

Some more thoughts:

Yes, spring rates affect the resonant frequency (and you guys made me look this up), but the critical factor is the square root of the spring rate. In other words, you have to change the spring rates a HUGE amount to change the resonant frequency. Needless to say the difference in spring rates between cars and trucks IS huge.

Now there will be those who will point to heavy duty pickup trucks - and they are a pretty good example. Some things to consider is that even the heaviest duty pickup weighs 12K (or so) and over the road trucks are on the order to 80K (albeit with more tires, but do the math) There's quite a bit of difference.

And if you take a look at the suspension travel on those 12K pickups, you'll notice they have a bunch - ergo, the spring rates are relatively low for a softer ride.

Ans as was pointed out, over the road trucks have air suspension seats.

OK, onto a different aspect of things:

The resonant frequency of a vehicle's suspension vs the resonant frequency of the vehicles chassis (or body). You want these 2 things FAR apart - and that has been a problem.

Stiffening up a chassis does all kinds of wonderful things for handling and stability. Stiff vehicles just feel more precise and predictable. Unfortunately when you stiffen up the chassis, you bring the resonant frequency closer to the suspension's resonant frequency - and if you get too close, even small amounts of vibration will set the chassis off.

- AND -

What usually comes along with this stiffening is weight reduction, which further aggravates the situation.

- PLUS -

Any given component in the chassis has its own resonant frequency. The floor pan, the roof, the hood, etc. All have to be designed with resonant frequencies away from the suspension's resonant frequency. Occasionally, this won't be done correctly and you'll get a vehicle sensitive to wheel end vibrations.

Over the road trucks have a lot of mass and that helps damp out a lot of vibration. Plus, the level where vibration becomes a problem in a truck is much higher. (expectation)

So overall, there are a number of things that are different between cars and trucks and they are all playing a role.

 

[eljefino]

^ They say Miatas are real touchy about tire balance. The earliest ones rode on tiny 14" wheels. And they have all the other positive (negative?) attributes you list.

I personally can't stand steering wheel vibrations from dynamic imbalance. Floorpan/ seat vibes don't bug me so much. I assume the taller profiles of truck tires lessens this specific objection.

 

[Ken2]

Quote:
a rep come in for Michelin tires and Michelin swears that heavy truck tires no longer need to be balanced and they will wear fine.....

I obviously disagree with this as I have been mounting tires since High School.
What has your High School experience have to do with the newest truck tires?
Quote:
My old 40s and 50s pick ups with typically 6.50 16 tube type bias plies never shimmied from out of balance tires. Maybe it had something to do with the leaf spring suspensions.
Or, you didn't notice it. An out of balance old bias ply tire certainly could shake a steering wheel, unless everything was so worn that the shake was absorbed in the sloppy parts.
Quote:
A 42'' truck tire going 55MPH is going will have about 60% of the RPMs as a 24'' car tire going 55MPH.
But the tires' treads are going the same peripheral speed. And, the last time a saw a truck driving 55 was in moderately heavy traffic. 70 to 80 is more like it.


So far all the talk is about the vibration transferred to the chassis and the driver. What's happening in the tire, bearings, suspension with the vibration? Does the out-of-balance tire run warmer? Does it wear faster?

 

[Errtt]

So if tire balance is no longer needed, would they still check balance anyway? Who knows, the wheel itself could be out of balance.

So get a rep to get the word out to not balance tires, then some may be out of balance a little, little enough that even if noticeable, might be minor enough a percentage of those drivers wouldn't bother to do anything about it, might knock a few miles of tire life, sell more tires, get that going good then up the rotations, then eliminate rotations, sell more tires, - make more $$

 

[Black_Thunder]

I notice you guys are saying they are bigger and the RPM's are a lot lower at highway speeds.

yes I suppose that a big factor but these tires are also carrying a lot more weight then passenger tires.


Yes I see goofy wear on tires weekly, we call it river wear or diagonal wear and we have ******s in the office that scream alignment wear for any kind of tire wear because they can't see anything else from there office chairs.

Alot of guys swear that using centramatics double there tire life and I figure it must better then not balancing tires at all.


I just think its funny that they are now saying they don't need to be balanced but the truck manufacters are having the tires balanced when the truck is assembled.

 

[CapriRacer]

I spend some time on the RV.net forums and there is a lot of discussion about balance and the use of balancing devices (Centrmatics, Equal, etc.) I know some of that discussion is for travel trailers and smaller motorhomes, but the discussion still takes place for Bus sized RV's. So I think there is still a need out there.

 

[AboutTires]

Originally Posted By: CapriRacer
I see I have stirred up some interest.

Some more thoughts:

...


I worked with auto vibration and resonant freqs for 10 years and you still just took me to school. Effing brilliant, man.

 

[grampi]

Originally Posted By: rslifkin
Originally Posted By: JHZR2
Heavy truck does not equal passenger car. Can't say I've ever seen balancing weights on a heavy truck rim.

I thought they put some water or beads in there for a dynamic balance?


A lot of places do use dynamic balancing beads in the tires. However, it's entirely possible to actually balance the tires as well (dynamic balancing works fine for highway running, but not so well in stop and go situations as it takes a few seconds for the tire to come into balance after getting moving).


On the plus side, tires balanced using beads never require re-balancing...

 

[Traction]

Here is a video demo on balancing beads. I tried it with a 2 liter bottle with a valve stem in the cap, 1/4 oz. weight taped to the bottle, put in the beads, and spun with a drill. Smooths it right out. http://www.youtube.com/watch?v=eq263AYgyYg

 

[SubLGT]

Originally Posted By: CapriRacer
I see I have stirred up some interest.

Some more thoughts:

…………….Stiffening up a chassis does all kinds of wonderful things for handling and stability. Stiff vehicles just feel more precise and predictable. Unfortunately when you stiffen up the chassis, you bring the resonant frequency closer to the suspension's resonant frequency - and if you get too close, even small amounts of vibration will set the chassis off. ………….


From what I have read, stiffening of the chassis has also led to an increase of road noise in the passenger cabin.

 

[Lapham3]

I worked at a tire shop in the late 60's and back then we saw lots of 'out of round' tires. Our rule was no more than 0.030"-if more, we used a tire truing machine that shaved the high area. That is an area that has pretty much gone away today-most tire folks now have never heard of such. I horse around with older cars and it's often a problem with the wheels, too. Dan Mpls. Mn.

 

[TheScaryOne]

We balance our truck tires if they come in to the shop. On road calls we don't bother. And we always balance RV tires. The machine even has a special more sensitive setting for RV's versus trucks. Heck, most of the commercial tire manufacturers have a special RV customer service line. And it's not because RV's are that special. PEBWAS. Problem exists between wheel and seat.

I mean, you can quote an OTR driver on a $1400 pair of super singles and they won't bat an eye. You quote an RV driver on 6 $200/each 19.5" tires and they lose their minds. What did you think you were buying for $200,000? Then again, BMW drivers have the same problem. $80,000 car, "What's the cheapest tires you have?" I mean, it's not like they're the only part of the car that touches the ground, or anything....

Originally Posted By: eljefino
^ They say Miatas are real touchy about tire balance.

You have no idea. When I balance the tires on mine I have to disable the rounding function built into the machine, and then I trim weights down to get exact balance as close to .00 as possible. I can notice a .25 oz imbalance. And when one of my coworkers stuck a 3 oz tape weight on my wheel I thought someone loosened my lugs. With the Miata the drivetrain is only bolted to the body by like 16 bolts in the front and rear subframe. It's pretty easy to get the whole assembly shaking. You can drop the entire drivetrain by removing the shock bolts and the subframe bolts and cutting any wires and lines that hang up.

Originally Posted By: Lapham3
... we used a tire truing machine that shaved the high area. That is an area that has pretty much gone away today-most tire folks now have never heard of such.

I wish someone other than Tire Rack still did it. I've had to order in tires from them for cheapskates who don't want to replace all four tires on their 4x4 or AWD vehicles. It's a shame to see a brand new tire at half original tread depth.

 

[Lapham3]

Some years ago I tried to find/buy an old tire truing machine as I'd used years ago and I couldn't find one in my area. Maybe time to look again-they should not have disappeared as my dial indicator tells me there is still a justification for them Dan Mpls. Mn.

 

[CapriRacer]

Originally Posted By: Traction
Here is a video demo on balancing beads. I tried it with a 2 liter bottle with a valve stem in the cap, 1/4 oz. weight taped to the bottle, put in the beads, and spun with a drill. Smooths it right out. http://www.youtube.com/watch?v=eq263AYgyYg


I am not a fan of any sort of balancing liquids, beads, or devices - so take what I am about to say with that in mind.

The question isn't if these things HELP. The question is whether they are BETTER than regular balancing. I think the video demonstrates that there are STILL vibrations - not to mention that we don't know what would happen if you did a conventional balance (if that is possible on a bottle)

 

[CapriRacer]

OK, tire shaving to improve vibration.

First the physics: Tire shaving (truing) is only slightly correlated to vehicle vibration (once you take the effect of balance away) - which is why the practice of truing new tires disappeared. Truing only takes care of the DIMENSIONAL variation of an UNLOADED tire - and that doesn't cover enough to be worth the trouble.

Second, there are still tire shavers available - used most for racing purposes.

And, yes, it might be possible to save some money by shaving tires, but I think the amount of business a shop would get as a result wouldn't justify the costs.

 

[CapriRacer]

Originally Posted By: SubLGT
From what I have read, stiffening of the chassis has also led to an increase of road noise in the passenger cabin.


Noise and vibrations are the same thing, just different frequencies.

 

[CurtisB]

The trucking company I currently drive for exclusively uses Michelin tires on our steers, and they are always balanced with weights. Drive wheels never get balanced here or at any other carrier I have ever driven for.

Steers normally get replaced here because of the inevitable river wear, and it is a problem not directly related to balance or alignment. River wear is greatly amplified at this carrier because we pull very long multi-trailer, A-train combinations on horribly rutted highways; all that extra trailer sway emanates into your steering and hence more river wear (huge problem on single/tandem axle trailers here too).

If Michelin truck tires are perfectly balanced from the factory than this carrier should have no need to balance them, this does not appear to be the case. As I mentioned previously, premature wear on steer tires is inevitable and there must be additional reasoning/need for balancing them in the first place.