Tire/Wheel to Hub Indexing?

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http://www.moderntiredealer.com/article/729143/the-present-and-future-of-mounting-and-balancing

Quote:
Augmenting off-car balancing with on-car correction will help eliminate NVH issues

Off-car wheel balancers do an excellent job of measuring dynamic unbalance — static and couple, says Dave Scribner, product development manager, CEMB USA/BL Systems Inc.

“Many also now measure tire/wheel assembly eccentricity, or what we will simply define as RFV (Radial Force Vectoring) to help eliminate vibration.

“We must ensure the tire and wheel assembly is balanced and round when rolling; and ultimately this is when it’s on the vehicle’s hub because this is where it rolls against the pavement.”

On-car balancing solves many issues that off-car balancing cannot address, he says. “Because of gravity, the assembly centerline changes from the balancer to the vehicle hub on virtually all wheels with hub bores and lug nuts and studs securing the wheel to the vehicle. “The small clearances can make a big difference in radial force variation ride quality.”

Scribner says use a wheel balancer that measures RFV if you want to solve vibration on sensitive vehicles. “Vehicle and tire manufacturers have known for decades that virtually every vehicle can benefit from using hub-bore indexing to assist in canceling the remaining eccentricity and/or static imbalance in the assembly during vehicle mounting.

“Index the high point of RFV at the balancer and place it on the vehicle at TDC (Top Dead Center) before torqueing the lug nuts. Do it on everything. It will save time, reduce the need to match mount and always provide better quality ride.”
 
Correct me if I am wrong but by balancing wheels/tires arent you removing the "high point"

I have heard of hub centric vs lug centric balancing though
 
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The article references some research that shows when installing the wheel & tire on the vehicle there is a couple thousandths of droop that happens. It can reduce the RFV a few pounds.

Balancing a tire does nothing to fix roundness...you can balance something out of round. Shops without a RoadForce balancer do it every day and face the comebacks.
 
Probably just OCD on my part but when I put the wheels back on my Mustang I mount the lug hole that aligns with the valve stem to the one stud on each corner with a paint marking. That stud also gets the wheel lock.
 
During balancing I have the tire marked for where the weights will be and then break the tire off the bead. I have them rotate the tire to align the lighter of the two weights to index with the tire air valve. We re-inflate, apply the weights and recheck the balance. Sometimes this requires 2 or 3 attempts to get it "dead on". This counter acts the Radial Vectoring Force by 1 magnitude. I use stock lug nuts but the whole group of 20 nuts have been weighed and those that deviate beyond 5% are culled and replaced with good replacements. High weight nuts can be machined down on the exterior ring face to lighten.
 
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Oh Boy! Lots to comment on:

The OP quoted an article about the future of balance machines and tire mounters. They interviewed 5 balance machine manufacturer's reps - and they all read like an ad for their current product. These were sales guys, not technical folks - and it showed. There were a number of errors and falsehoods. So let me start by filling in the blanks for those folks who are new to the subject.

There are 2 things that can cause a wheel end vibration: Balance and - oh, let's call it runout.

We are all familiar with static and dynamic balancing - but runout is a different kettle of fish and has to be treated separately.

No, runout is NOT affected by balancing a tire and wheel assembly. You can have a perfectly balanced assembly and still have a vibration caused by the runout. You can also have a perfectly round assembly that is out of balance. In fact, tire manufacturers measure it at low speeds - speeds where balancing isn't an issue.

Not only can the wheel be out of round, but the tire can be too - except with a tire there is the additional structural stiffness variation and when combined with runout, we call it Uniformity. We tire engineers use the term RFV (Radial Force Variation) as another way of expressing uniformity. Why the CEMB rep used the word "Vector" is a bit of a mystery.

Every vehicle has a certain sensitivity to out of balance and uniformity. Some are very sensitive, some very insensitive, most are in-between.

My experience says that vehicle sensitivity is pretty much always lower than the 1/4 oz. (5 gram) balance weight increment - meaning there is no need to balance an assembly more accurately than that. Add the fact the roads are affected by freezing and thawing and heave during the winter, makes the small amount of potential vibration improvement a moot point. It can't be felt because of all the road input.

Vehicle suspensions are - in engineering terms - Spring/Mass/Damper systems (the damper being the shock absorber). SMD systems have a resonant frequency where the vibration isn't damped out effectively. For most vehicles this is in the 50 mph to 70 mph range. We also refer to this as the wheel hop frequency. Outside that speed range, the SMD system does what it is supposed to do - damp out the vibration.

In the old days, other rotating components such a brake rotors and wheel hubs were problematic - and an on-car balancers could correct some of that. Even during that time, on-car balancers were somewhat hard to find.

But nowadays the components are much better and the need for an on-car balancer is virtually nil.

- EXCEPT -

We are seeing brake rotors and the like coming from .... ah .... let's call them sources that new to the game and as yet aren't quite up to speed - and because they are inexpensive, many parts store carry them. Anything on a new car or from an OEM source will meet the OEM's quality level, but the aftermarket is a free-for-all!

OK, now to the questions:

Originally Posted By: thescreensavers
Correct me if I am wrong but by balancing wheels/tires arent you removing the "high point". .......


No. You are thinking about "heavy spot" Balancing does not affect runout. It has to be dealt with separately.

Originally Posted By: Piston_slap
During balancing I have the tire marked for where the weights will be and then break the tire off the bead. I have them rotate the tire to align the lighter of the two weights to index with the tire air valve. We re-inflate, apply the weights and recheck the balance. Sometimes this requires 2 or 3 attempts to get it "dead on". This counter acts the Radial Vectoring Force by 1 magnitude. ......


Ah ..... Mmmmm ..... Not exactly.

The RFV (Radial Force Variation) is unaffected by balance - and shifting the tire around relative to the wheel to reduce the amount of balance weights only reduces the amount of weight. It's largely a time wasting activity because once the weights are applied, the assembly is balanced and there is no residual force due to balance - EXCEPT that the wheel has some amount of runout and rotating the tire relative to the wheel does change the amount of RFV, but since the indexing process isn't trying to reduce that (it isn't even measuring that!), the result is a random RFV - it could be large, it could be small.

- BUT -

There is a company that makes a machine that measures a form of RFV: The Hunter RoadForce machines. They aren't prefect, but they are a significant help in trying to diagnose wheel end vibrations.
 
Wheels on a Volvo go back on in the same place, so simple to do, but I don't see any other cars that do it.
 
Originally Posted By: Silk
Wheels on a Volvo go back on in the same place, so simple to do, but I don't see any other cars that do it.


Are you saying there is something peculiar about Volvo's that the wheels fit on in only one orientation?
 
Yes, like on an early Fiat (or Lada) the bolt that holds the rotor on has a pin, there is only one location on the wheel that will accept the length of the pin. So the wheel goes on in the same location.
 
Originally Posted By: LotI
The article references some research that shows when installing the wheel & tire on the vehicle there is a couple thousandths of droop that happens. It can reduce the RFV a few pounds....


Wasn't the adoption of "hub centric" wheels by the automotive industry supposed to eliminate the off-centering influence of gravity when mounting the wheel onto the hub? Looks like the answer is "no". It probably helps reduce it, but does not totally reduce it to zero influence.
 
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Wheel to hub indexing can significantly reduce RFV , says the author of this article.


....two problematic assumptions are made with off-car balancers:

1. That the technician has centered the wheel on the balancer. If the wheel is not centered, all of the measurements and attempts to repair the unbalance are compromised.

2. That the measured centerline of the wheel remains unchanged from the balancer when it is placed on the vehicle hub.
The purpose of this article is to address assumption No. 2, which is often overlooked. The assembly centerline does not remain unchanged from the balancer to the vehicle hub on the majority of vehicles.

On-car balancing solves many issues that off-car balancing cannot address because the wheel assembly is not perfectly centered on the vehicle due to small clearances that can make a big difference in radial force ride quality. Nominal clearances between the wheel hub bore and the vehicle hub are often at least +0.1 mm (+0.005”) in order for the wheel to slide onto the vehicle hub. When the wheel is installed, gravity imperceptibly pulls it downward to induce a radial runout change of at least +0.010”. The wheel is now off-center enough to add or subtract from the runout of the assembly and the residual static unbalance in the wheel depending on the angle of the remaining radial force vector. This claim is backed by numerous NVH tire service engineers, and Ford and Jaguar have TSBs that address on-car corrections of residual tire/wheel RFV by taking advantage of the wheel hub-bore-to-vehicle-hub clearance.

Virtually every vehicle that is measured for eccentricity, road force or static unbalance can benefit from using a hub-bore-to-vehicle-hub clearance indexing to assist in canceling the remaining RFV or static force in the assembly during installation.

RFV wheel balancers should be used to index the wheel to the vehicle hub to greatly reduce on-car eccentricity and RFV. This will also, in most cases, save time by eliminating the time-consuming match mounting.

Simple Index Process:

1. With the wheel properly centered on the balancer, measure RFV and balance the tire assembly.
2. Before removing the assembly from the balancer, rotate the high point/stiff spot to 12 o’clock (TDC) using the prompts on the balancer screen.
3. With a tire crayon, mark the high point/stiff spot of the assembly on the inside rim edge and inner sidewall.
4. Place the assembly on the vehicle hub with the index mark at TDC.
5. Install and torque the lug nuts/lug bolts per factory specification.

Understanding that there is no longer a need (on a majority of vehicles) to match mount or add a third wheel weight will save you time. As an example, an assembly that measures 35 lbs. of road force (or ~0.30” R1H radial runout) when indexed at TDC will drop down, subtracting approximately +15 lbs of road force, and end up with approximately a 20 lb. assembly that is well within vehicle tolerances to ensure a smooth ride. Many hub bore clearances are higher than the nominal 0.1 mm (0.005”). If the assembly is not indexed and ends up at BDC, the clearances work against the technician when trying to repair the vibration and ensure the best ride quality.
 
Wheel to hub indexing can significantly reduce RFV , says the author of this article.
Ah ..... Mmmm ....... Not exactly.

Every vehicle manufacturer center pilots their wheels onto the hub. The only time this is a problem is when aftermarket wheels with a "universal" (Large!) hub hole are used and the wheel doesn't center on the hub. That's why many aftermarket wheel manufacturers use hub rings.

Further, vehicle manufacturers have determined it is better to use the hub to center the wheel rather than the lugs, because it is more difficult to not only center 4, 5, or 6 studs, but also make them perpendicular to the hub surface.

What the author is advocating is on-car balancing - a technique (and machine) that used to be used with sucess before the days of tire and wheel uniformity. Today, not a single vehicle manufacturer uses on-car balancing.

However, with low quality brake drums and rotors, balance may be a problem - and on-car balancing will correct that. But I think the real problem is the low quality, not the balancing technique.

Plus, there are vehicles that are super sensitive. I know that GM produced a lot of these - and, Yes!, on-car balancing will fix that. But ultimately these vehicles will be replaced by vehicles designed correctly in the firat place and fewer vehicles will have these kind of issues.

What this article's author is advocating is something that is doomed to become obsolete, just like it did before.
 
...What the author is advocating is on-car balancing - a technique (and machine) that used to be used with sucess before the days of tire and wheel uniformity. Today, not a single vehicle manufacturer uses on-car balancing.
I don't think the author is opposed to off car balancing.
Step 1 of his Simple Index Process is:

" With the wheel properly centered on the balancer, measure RFV and balance the tire assembly."
 
Tire equipment manufacturer CEMB sells a balancer that seems suited to shops where the employees don't want to take the time to match mount the tire on the wheel. CEMB calls this feature HubMatch.


The new CEMB HubMatch combines refined off-car balancing capabilities and features with a guided on-car eccentricity cancellation process. HubMatch guides the operator during the process, significantly reduces floor-floor cycle time and provides an improved ride quality.

In one single spin, HubMatch detects the unbalance as well as the highest point of the wheel (1st harmonics), and displays it on-screen to enable mounting of wheel on vehicle so that simply matching mechanical clearances when positioning the rim on the hub will eliminate the eccentricity.

 
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