wheel balancing machines...all the same?

[CapriRacer]

Originally Posted By: AstroTurf
CapriRacer,

Have a look at the John Bean BFH 1000.

I would be interested in your opinion.

Thanks, Jim


It uses run out, and in my opinion is not as good as Hunter's load wheel on the GSP9700.

Way back when, I asked one of our plants for a whole load of data correlating various properties to force variation - which as a tire guy, I know is THE most accurate way to determine the potential for tire vibration.

Run out only had a 60% correlation to force variation. That was many years ago, sand I am sure it is worse now. If you don't have anything else to use, ruout would be the way to match mount, but there are better ways.

 

[CapriRacer]

Originally Posted By: Strakes
Thank you for clearing that up. As stated before, my gut was telling me that they weren't doing a good job. The point I was trying to make is that time is usually sacrificed in the interest of production. If it means anything to you, the road force was 25 and 22 lbs on 2 wheels prior to dismounting and rotating the tire on the rim a few degrees. Also, they removed all the original weights... 225/45R17 tire size. After all was done, one tire was at 7 pounds and the other was at 9 pounds road force. A reduction in road force was also noted on the invoice for the other 2 wheels that the tech said probably weren't the cause of the felt vibration.


I realize it is a diffciult concept to understand, but force variation - the amount of variation in the deflection of a tire as it rotates - is a major player in ride vibrations.

It's difficult to understand because many folks think of it as balance and it isn't. It's a closest to "Out of Round", but that doesn't quite cover it either.

As a result, many tire busters aren't convinced it has value - hence the reason that particular tech bypassed the step. This guy truly missed the boat!

 

[Strakes]

This makes me wonder how many tires are sent back to the manufacturer because of the stubborn attitudes of these shops regarding tire installation. I felt that this shop's inability to balance was going to lead me to get sold a "better" (more expensive) tire from the same shop.

 

[FADEC]

Astroturf....I'm interested in your experiences with the Dyna Beads. I checked out their web site and they sound interesting with alot of positive accolades. Do they work as advertised?? Tom

 

[AstroTurf]

Tom,
I am currently on the third set of tires with the same beads.
The first belonged to an 01 Toyota 4Runner, Stock size Michelin LTX MS. I ran aprox 5 Oz of beads per tire. Vehicle was sold before the tires wore out. Beads removed, Vehicle sold.
The second set of tires were a stock size 215/70 16 of Nokian WR G2 SUV. I ran a five tire rotation to 64,500 miles. Beads weight per tire was aprox 8 Oz.
The third and current tire is a stock size 215/70 16 Michelin LTX MS. Also using a 5 tire rotation, each tire has 6 1/2 Oz per.

Would I recommend them? Yes.
Would I run more than is recommended? Yes.
I would say that if you want to give them a try, then do so.
But, you must be prepared to increase the volume of beads over the recommended weight or break down the tire to remove them.
Slow measurable increases of bead volume will net the best results.

Call them, they are very helpful.

Good Luck, Jim

PS If you have any further questions, just shoot me a PM.

 

[Rand]

I tried the dyna beads.. they worked best in LARGE tires at highway speeds..(where you need the balance really)

they were kinda wierd until I got used to them. Nothing bad really.

I'm not convinced they are the way to go for anything except 30" tires and bigger. Esp mudder type tyres or other very heavy tires that dont balance well. ie ground hawgs

But they definitely arent a joke.

 

[Ken2]

Road Force is like a stiffness measure of the sidewall. No tire is completely symmetrical...heavy & light spots, as we know, high & low spots (eccentric or out of round), and stiff & soft parts on the sidewall. Too many drivers think that any vibration is balance, and often it isn't--it can by out or round or road force variation, or a bent rim, or the wheel incorrectly mounted on the balancing machine.

The shops I've been to with a Hunter GSP9700 only use it when a customer brings back a problem tire. It takes the one or two tire busters trained in using the machine, and it takes more time to operate (and maybe that is just a function of training).

As said above, the person using the machine is usually more important than the brand of the machine, and also the calibration of the machine matters.

Balancing beads work pretty well for tall tires, 75 aspect ratio or taller. They do not do dynamic (side to side) balancing. They can be added to wide tires (less than 75 aspect ratio) for a possible fine-tuning of the balance, although I'm not sure that actually works. They can also work as a bandaid for a bent wheel or an out of round tire when you don't want to buy the new wheel or get a different tire.

 

[Grebbler]

Just wrapping my brain around this.

okay, 360 degrees of tire sidewall. Say the machine feels more road force (sidewall stiffness?) at 22 and 65 degrees. Does the machine instruct the operator to add some weight in those areas to counter the stiffness?

I assume that there would be a 'sweet spot' the machine is calibrated for since the sidewall stiffness would be constant at any speed while a rotating weight would increase the downward force as the rotation speed increased.

Please correct my misconceptions.

Ed

 

[CapriRacer]

Originally Posted By: Grebbler
Just wrapping my brain around this.

okay, 360 degrees of tire sidewall. Say the machine feels more road force (sidewall stiffness?) at 22 and 65 degrees. Does the machine instruct the operator to add some weight in those areas to counter the stiffness?

I assume that there would be a 'sweet spot' the machine is calibrated for since the sidewall stiffness would be constant at any speed while a rotating weight would increase the downward force as the rotation speed increased.

Please correct my misconceptions.

Ed


First, the Hunter GSP9700 - as do all uniformity machines - measures the difference in force variation (FV) around the tire. Force variation is a combination of sidewall stiffness variation and run out.

It takes a couple, 3 revolutions to get a good reading. Remember, on the Hunter GSP9700, the tire is mounted on a wheel - so the machine is measuring the variation of the assembly - the combination of the tire and wheel.

Tire manufacturers have production uniformity machines - high volume, feed by conveyors - and the important point - the rims are precision ground, split in the middle and part of the machine set up. It takes about 30 seconds to measure a tire on one of those machnines. BTW, the last time I checked - many years ago - they cost about $600K each. I'm sure they are bumping a million by now! One of our plants has about 30 of them - a serious investment! The Hunter GSP9700 is about $10K!

So keeping in mind that both machines get a FV curve, then they do a mathematical curve fit of a single sine wave to the data. This is called the 1st Harmonic. The high point of that sine wave can then be matched to the low point of the wheel runout to minimize the overall values for the assembly - which mean you need to know where the low point of the rim is.

In the case of the production machines, the size of the sine wave is compared to a specification. If the tire is below the spec, the tire MAY be marked for location (and sometimes value), then sent down the line.

A tire that does NOT meet specifcation is pushed onto a different conveyor. There are things that can be done to improve the uniformity value of a tire. The common method is called "Force Correction" - which is a fancy way of saying they grind off a few thousands of an inch of tread rubber at the high point, which lowers the overall variation. This is frequently done to OE tires to meet the OEM's specs, which are pretty tight.

The Hunter GSP9700 will tell you where the high point of the assembly is - and the machine has some built in tolerances that it compares against. The machine will alert the operator when that tolerance is exceeded. If that happens, the operator can take one of 2 steps.

1) The operator can dismount the tire and measure the bare wheel. This is the best way as this is measuring the surface that the tire sits on. However, it is labor intensive.

2) He can get an estimate of where the low point of the wheel is, by measuring the runout of some part of the wheel. This is always problematic as the tire is on the surface that needs to be measured. Any other location may not be a true picture of what is going on.

The Hunter GSP9700 takes the wheel runout data and subtracts it - point by point - from the assembly data, calculates the best fit 1st Harmonic to the both the rim and the tire, then tells the operator where the high point of the tire is and where the low point of th rim is. - which can then be matched up.

If the tire is not reoriented on the wheel, then the Hunter GSP9700 is no better than a normal balancer - except you know what the uniformity value is. Where the machines is valuable is that it can measure and minimize the run out.

OK, time for a lesson on the vehicle end of things:

Each vehicle has a certain sensitivity to wheel end vibrations. Some vehicles are very sensitive and some are very insensitive. You don't need to minimize EVERY tire and wheel assembly. You just have to avoid putting assemblies on that are above the sensitivity limt for that particular vehicle. If you know the vehicle's sensitivity, then using the Hunter GSP9700 can prevent a lot of vibration problems.

I know that was a little long, but I hope it was helpful.

I could go on about high speed vs low speed force variation - about putting weights on the rim to counteract the FV - but that is another long discussion!

 

[George Bynum]

Originally Posted By: CapriRacer
Each vehicle has a certain sensitivity to wheel end vibrations. Some vehicles are very sensitive and some are very insensitive.

Can you comment on the characteristics of a vehicle that makes it more or less sensitive to FV?

And, while I expect you can (and will) answer the above, I expect the response to this next question to be ... different.

Can you comment on (or furnish a link to) which vehicles are known to be "more" or "less" sensitive?

 

[CapriRacer]

Originally Posted By: George Bynum
Originally Posted By: CapriRacer
Each vehicle has a certain sensitivity to wheel end vibrations. Some vehicles are very sensitive and some are very insensitive.

Can you comment on the characteristics of a vehicle that makes it more or less sensitive to FV?....


I don't have a lot of experience in this area, but I remember someone telling me it had to do with the resonant frequency of the chassis.

Originally Posted By: George Bynum
......And, while I expect you can (and will) answer the above, I expect the response to this next question to be ... different.

Can you comment on (or furnish a link to) which vehicles are known to be "more" or "less" sensitive?


I only knew of a few - and the only one I can remember was a GM platform from the late 1990's / early 2000's on which Buicks and Caddy's were made. That one had aluminum lower control arms - and while that was cited as the problem, I think the real problem was the resonant frequency.