Dynamic vs Static Balance

[CharBaby]

It's all spin balancing to me!
I ask because IDK the difference between the two terms for balancing tires. Or the difference between, what most tire shop are doing. Most tell me that they "static balance".

What are the differneces and how so?

 

[eagle23]

Most tire shops dynamic balance, or what I have always called dynamic balance, i.e., they mount the tire/wheel vertically to the balancer and spin it to x-mph, whatever the machine does. It then tells them where the weight is needed and how much.

This can also be done on the car though I haven't seen it in years. Part of the plus was that it added the hub/brakes to the balance consideration, or alleged to. I'm not sure if that was really true or not. Part of negative was it was possible that rotating the tires to a different position (front, rear, other side) could mean the tires weren't as smoothly balanced since they are on a different hub.

Static balance I always knew as "bubble" balance, where the wheel tire was mounted horizontally to a gimbal-type device. The heavy "side" would show up as the bubble would move off center. You could then take 4 equal weights and start offsetting the imbalance using a kind of "V" configuration until things were back on center. Two weights went on the outside of the wheel at those points, and two on the inside.

It wasn't as precise as spin balancing, but it worked pretty well in that it distributed the needed weights in an opposite zone to offset the original imbalance. For decades it was all that was around. I heard NASCAR used this approach (true? no?) until spin balancers came into their own.

Others may have different interpretations.

 

[rcefstsfecr]

Dynamic balancing is where two weights are added to each wheel.... one on each side (in and out) of the wheel. This can be a sticky or stick on weight or hammer on weights.

Static balancing is where only one weight is used on the wheel.

I've always known that Static balancing isn't as precise as dynamic balancing.

 

[Cardenio327]

^^eagle23 nailed it dead on^^

My Dad has a factory repair manual for 1970 Ford Trucks that explains it best. There are two type of tire imbalance; tramp and wobble. Tramp is the action of a tire hopping up and down like a basketball. Wobble is obviously movement side to side.

Static balancing gets rid of tramp, but doesn't get rid of wobble. Static balancing is done with a bubble level stand or by deprogramming a computerized spin balancer so that it does a simpler job.

Dynamic balancing gets rid of both tramp and wobble, and must be done by a computerized balancer. The first dynamic balancing machine was invented shortly after WWII.

If a tire isn't too far out of balance, static imbalance can usually be felt under 50 mph, but dynamic imbalance isn't felt until over 50 mph.

The next step is road force balancing, which takes into account the variations in flexibility found throughout the sidewalls of a tire.

Around here, we are the only tire & alignment shop that regularly dynamic balances. Most other shops have more expensive balancers, but just do a static balance out of laziness. I believe a huge tire shop that was built in our town with ex-hacienda money had a Hunter 9700 road force machine before they went out of business, but if they did I am certain none of their employees had a clue how to use it.

In conclusion, you want the best, most precise balance possible, a good balance equals less money spent on ball joints, tie rods, bushings, &c. Road force if possible, dynamic if not. The only time a static balance is viable is if your tires are uneven (mud or Chinese tires) or if you have Chinese rims, or deep offset rims that don't have lips for clip-ons and have the spokes set too far inwards to effectively use adhesive counterweights.

 

[eljefino]

A dynamically balanced tire will also show zeroes for static, however the opposite is not necessarily true.

 

[stephen9666]

Originally Posted By: Char Baby
Most tell me that they "static balance".


Most any shop with modern equipment will be able to do a dynamic balance, and probably does a dynamic balance on most vehicles. I don't know what shops you're going to where they either have old balancers that can't do a dynamic balance or they don't know what they're talking about.

When I worked in a tire shop about 8 years ago all we had were dynamic balancers. Of course, there were situations where you would set it to static balance mode, but that's uncommon.

http://www.vibratesoftware.com/html_help/2011/Diagnosis/Tire/Hunter_Tire_Balance.htm

This Bridgestone article on truck tires also has more info:
http://www.bridgestonetrucktires.com/us_eng/real/magazines/97V2Issue1/7v2i1doctor.asp

A very watered down explanation is that a dynamic balance also balances out side-to-side imbalances in the tire/wheel assembly, not just the up-and-down imbalances created as a tire spins.

Again, that's a very crude, nontechnical way of explaining it. So everyone here, don't jump down my throat saying I'm not giving a good explanation that delves into axis and planes.

 

[CapriRacer]

http://www.barrystiretech.com/unifandbal.html

 

[CharBaby]

Originally Posted By: Char Baby

Most tell me that they "static balance".

Stephen9666:
Most any shop with modern equipment will be able to do a dynamic balance, and probably does a dynamic balance on most vehicles. I don't know what shops you're going to where they either have old balancers that can't do a dynamic balance or they don't know what they're talking about.

My fault, I had the terms in reverse!

It is "dynamic balance" that the shops are performing, not "static balancing"

Thank you all for your comments

CB

 

[Ken2]

I'll bet that most tire shop employees don't know that there are two kinds of balancing. They just put the tire on the machine, spin it, and hammer weights on where the machine says to do it.

I used a dynamic balancer when I was in high school in the early '60s. Nothing new there. The new machines are much simpler to operate and perhaps more accurate if correctly calibrated.

Runout (egg shaped tire, not truly round) and uniformity/road force are not balance. They'll make the wheel shake and people will say, "Those tires can't be balanced." Yes, they are balanced, but they shake because they're egg shaped or they have a stiff part and a soft part.

 

[stephen9666]

Originally Posted By: Ken2
I'll bet that most tire shop employees don't know that there are two kinds of balancing. They just put the tire on the machine, spin it, and hammer weights on where the machine says to do it.


Eh, I wouldn't be so sure about that.

In the shop I worked in during college we pretty much all knew about that difference.

Now, I obviously can't speak for every shop, but where I worked you would be wrong if you said "most tire shop employees don't know."