marc abrams

What type balancing do you prefer? Static to hide the wheel weights or dynamic for the best balance? Every alloy wheel I've seen on new cars seems to be statically balanced. I know I'm being a PITA lately, but I'm on the home stretch with my wheels and tires. Thanks

MAGK944

Do shops still do dynamic balancing? All I've seen in the last few years is road force machines.

Static is way out of date, maybe still used for large truck tires though. For any modern lower profile tire road force is the way to go.

marc abrams

Any of the tire balancing machines​ that spins (road force) the wheel do both Static (or mag wheel setting) where the weight is placed out of sight or dynamic where the weights are placed both on the inside and outside edge of the wheel and the weight is visible.
Wheels can be balanced statically with a bubble balancer or on the car where a motor spins the wheel and brake rotor together. A ring fits into the wheel to determine the weight size and placement.
What gets me is every car sold today with alloy wheels and wide tires are statically balanced. I'm guessing that alloy wheels are machine and don't have the run out that steel wheels have and therefore can get away with a static balance? I have little experience with passenger car tires as you have guessed but when I was working as a truck mechanic we did have a passenger car wheel balancer that spun the wheels. It could do both static and dynamic balancing. I chose dynamic balance when I replaced the the tires 4 years ago. But now I have new wheels and those weights are ugly and now I have to pay to get them balance. BTW I've never seen a class 8 truck that had is wheels balanced.

thomasmryan

The tire shop that I used to frequent in the 80s, had a motor on a cart that was pushed up against the suspended chalked wheel to spin it. The machine had a sensor that attached to the lower control arm that triggered at the heaviest point down, so you added a small weight to see which direction the imbalanced went on the rim.

This was for big rigs and probably got up to 100mph on the tiny car tires.

Voith

Dynamic because even the best is not good enough.

drive135mph

To be honest I would say in practical use there is no difference. I've done both methods for both street and track cars, even for very picky owners and have never had a complaint either way. Especially if it's a road car I would tend to hide the weights simply because if feel it looks a bit more professional. I think the bigger variable is the tire guy taking the time to confirm that each corner is perfectly right on before letting them go

Smike

Remember - you are balancing an assembly (tire and wheel).

"RoadForce" is a Hunter Engineering term. It is a calculated measurement of the assembly (wheel/tire AND any machine tooling error (how its attached to balance machine) radial first harmonic. RF1 is not a physical weight imbalance. It is also highly subjective to the vehicles sensitivity to harmonic inputs. The type of shake is a narrow speed window (e.g. 70-72 mph) then goes away if you go faster.

Dynamic imbalance is couple and static imbalance combined. 3 targets with 2 weight applications to correct. Couple is a low speed wobble defined as equal weight imbalanced on opposite flanges through the axis of rotation (picture an X and imbalances at top left and lower right). For pure couple to cause a shake it would have to be large magnitude (5+ ounces per side). And the shake would be a low speed (35-45mph) wobble. Car feels like its shimmying side to side. Goes away at highway speeds. Very rare condition.

Static imbalance is a single imbalance that is once per rotation. Can be addressed with one weight at one location. As this weight is "thrown" faster it generates more force. So this shake increases/worsens as you go faster. E.g. start feeling a shake at 70 and the shake gets worse and does not go away as you go faster.

OE wheel/tire assembly plants will preference towards correcting static imbalance. If the residual couple is under a preset amount, they will not bother with it.

For racing (and generally all of my other vehicles) we use static imbalance. Again pure couple shake is very rare. And I want to take care of any shake as I go faster or highway.

So long short - static is better if doing anything. Dynamic is OK but 3 targets and 2 weight to address. Harmonic forces are not weight imbalances.

Cheers

marc abrams

I aways assume all they do is a static balance. I was in a friend's Explorer a few weekends ago (he's got the twin turbo one with the fat tires). We were going down the NJ turnpike at over 100. Perfectly smooth and it looked to be only staticly balance. Damn, those Explorer are pretty fast.

Smike

They have some other trick machinery as well that match mounts the tire to the wheel for radial first harmonic. Ever notice those colored dots on a new tire and sometimes a sticker on the wheel when looking at new cars? That is for the optical camera on the automated tire machine to match mount the two together.

Some OE wheel suppliers also mark the inside (under tire side) of the wheel for radial run-out with a spray paint dot, symbol/mark, etc. You can use that with many tire manufactures tire markings (colored dots) to create R1H matched assemblies as well.

marc abrams

Interesting. Clears up a lot of the mystery.