Roadforce Numbers OK But Possible Bad Lateral Runout?

[Jlaa]

I wonder if its possible to have bent wheels that a roadforce machine does not detect through the roadforce readings.
I have a car where the roadforce numbers are pretty good:

LF 14 lbs RF 15 lbs
LR 10 lbs RR 10 lbs

The tires are new Pirellis and I actually RMA-ed one tire back to the TireRack because that tire wouldn't roadforce below 33 lbs.

Anyways --- I wonder if its possible that the roadforce numbers do not detect LATERAL runout. I suspect that the roadforce machine can only detect vibrations that occur RADIALLY (up/down). This is because of the way the machine operates - the heavy roller presses against the the tire while it is spinning and measures up/down force, expressed in pounds.


What the roadforce machine DOES NOT do is measure LATERAL (side to side) inconsistency while spinning the wheel / tire assembly with the roller pressing against the tire. Now, the roadforce machine does have these little arms that the operator can press against the wheel rim flange to slowly measure the lateral runout of the wheel, but in practice, roadforce machine operators never use this feature.

So I suspect that it is possible to have vibration inducing lateral runout while having acceptable radial runout of the wheel / tire assembly such that the roadforce readings are fine. I would love to have more experienced folks prove me right / wrong.

Note --- in my own car --- I feel vibrations in the steering wheel at 70mph+ (not visually detectectable but I can feel them in the steering wheel). When I do some all-out data logging and put vibration sensors / accelerometers on the four corners of the dashboard / rear deck, I cannot find anything untowards -- meaning --- all four corners of the car measure the same amplitude of T1 (first order tire related vibration - 1 shake per rotation of the wheel or about 15 Hz at 70mph) . No one corner measures more strongly than the other.

But ... I can feel something through the steering wheel. And so --- I wonder if my wheels have some lateral runout that the roadforce roller is not detecting.

So for anyone that has deeper knowledge on how the roadforce machine works and what the numbers can tell you and what the numbers cannot tell you - Thanks for reading.

 

[Hall]

Move the tires from front to rear. Check your brake rotors. Are the wheels properly installed and torqued down ? I know these seem like basic things, but it could be something very simple.

 

[Jlaa]

Move the tires from front to rear. Check your brake rotors. Are the wheels properly installed and torqued down ? I know these seem like basic things, but it could be something very simple.

Thanks. I put the spare on each corner one by one -- checked brake rotors, measured runout of the rotor friction area, runout of the rotor hat, runout of the hubs, etc etc. Appreciate your thoughts.

I'm hoping this thread is discussion about the Hunter Roadforce tool specifically --- and whether it is possible that the Roadforce readings do not reflect lateral runout issues......Thanks!

 

[loneryder]

I have a similar problem with my new Pirellis. Vibration in the seat and floor. Will RF balancing help with that?

 

[charbaby]

After having my Pirelli tires RFB’d, one thing that I have noticed with every Pirelli tire(I’ve had at least 5 sets) is that they all flat spot even when sitting over night. However it goes away in a timely fashion(within a mile) and may take a bit longer if the tires sit for days but it’s never severe. Pirelli is still my favorite higher end brand.

 

[Jlaa]

Thanks @CharBaby and @loneryder! Appreciate your thoughts. I'm hoping that this discussion focuses on the roadforce machine and specifically about what the roadforce numbers can tell you and what they cannot!

I don't have any direct knowledge on how the machine is designed, but it seems to me that applying a heavy roller on a spinning wheel/tire combo can only measure RADIAL variations in force. There's no way for that heavy roller mechanism to detect LATERAL movement in the entire tire/wheel assembly ... .right?

 

[shortyb]

Roadforce balancing will have a difficult time detecting ABSOLUTE lateral runout, meaning that the deviation has zero to little radial runout. This is a very uncommon occurrence as to have lateral deviation, theoretically, there will some radial runout due to how a wheel is constructed.

A much more sophisticated balancer will detect the absolute lateral runout and show the weight and location needed.

 

[Jlaa]

Roadforce balancing will have a difficult time detecting ABSOLUTE lateral runout, meaning that the deviation has zero to little radial runout. This is a very uncommon occurrence as to have lateral deviation, theoretically, there will some radial runout due to how a wheel is constructed.

A much more sophisticated balancer will detect the absolute lateral runout and show the weight and location needed.

Thank you! Yes I can appreciate how if a wheel is bent then there is probably both lateral and radial runout ..... I get your qualifier! Super appreciate your thoughts that roadforce "balancing" (in quotes because roadforce refers to eccentricity and doesn't really balance) has a tough time measuring ABSOLUTE lateral runout.

Also I am curious - what such "much more sophisticated" balancer exists that is able to detect absolute lateral and radial runout of the entire tire/wheel assembly?

 

[CapriRacer]

First, road force is a version of tire uniformity. Uniformity comes in 3 directions: Radial, Lateral, and Tangential. The Hunter machines give you Radial 1st Harmonic, but if you dig a bit you can find the 2nd Radial Harmonic. I do not think the Hunter machines measure lateral Harmonics, and definitely not Tangential. However, it's possible to measure each of those through the road wheel if you have the right sensors, which I don't think Hunter has on their machines. In other words, the fact that the road wheel applies a force to the assembly doesn't mean you can't measure the other forces. In fact, TUG Machines (Tire Uniformity Graders) that tire manufacturers use do the same thing, but with much more sophistication.

That answers the basic questions you are asking. But let's see if we can figure out how to fix your vibration issues.

15# is a little high, but if you've measured each corner and the vibration is the same on each corner, then it's not likely the tire/wheel assemblies. That 10# tire/wheel should be very different than the 15# assembly.

What is possible is that each assembly is mounted off center - and about the same amount, and so much so that the difference between 10# and 15# is undetectable. So are these aftermarket wheels - which sometimes aren't center piloted?

You could just have a sensitive vehicle. Year, make and model, please!

Yes, it is possible to have excessive lateral forces that aren't accompanied by high radial forces - BUT - that is very unlikely.

Personally, I suspect there is something else going on. Do you have another set of wheels that you can use to help diagnose this?

Also, swap the fronts with the rears. Those larger forces currently on the front should feel different when put on the rear. If they don't that points to something in the vehicle.

BTW, if the vibration is coming from the front, you should feel it in the steering wheel, and if the vibration is coming from the rear, you should feel it in your seat. Swapping tires around should change things.

And here's my webpage on Vibration, balance and uniformity: Barry's Tire Tech: Vibration: Balance, Runout, and Uniformity

 

[Jlaa]

First, road force is a version of tire uniformity. Uniformity comes in 3 directions: Radial, Lateral, and Tangential. The Hunter machines give you Radial 1st Harmonic, but if you dig a bit you can find the 2nd Radial Harmonic. I do not think the Hunter machines measure lateral Harmonics, and definitely not Tangential. However, it's possible to measure each of those through the road wheel if you have the right sensors, which I don't think Hunter has on their machines. In other words, the fact that the road wheel applies a force to the assembly doesn't mean you can't measure the other forces. In fact, TUG Machines (Tire Uniformity Graders) that tire manufacturers use do the same thing, but with much more sophistication.

That answers the basic questions you are asking. But let's see if we can figure out how to fix your vibration issues.

15# is a little high, but if you've measured each corner and the vibration is the same on each corner, then it's not likely the tire/wheel assemblies. That 10# tire/wheel should be very different than the 15# assembly.

What is possible is that each assembly is mounted off center - and about the same amount, and so much so that the difference between 10# and 15# is undetectable. So are these aftermarket wheels - which sometimes aren't center piloted?

You could just have a sensitive vehicle. Year, make and model, please!

Yes, it is possible to have excessive lateral forces that aren't accompanied by high radial forces - BUT - that is very unlikely.

Personally, I suspect there is something else going on. Do you have another set of wheels that you can use to help diagnose this?

Also, swap the fronts with the rears. Those larger forces currently on the front should feel different when put on the rear. If they don't that points to something in the vehicle.

BTW, if the vibration is coming from the front, you should feel it in the steering wheel, and if the vibration is coming from the rear, you should feel it in your seat. Swapping tires around should change things.

And here's my webpage on Vibration, balance and uniformity: Barry's Tire Tech: Vibration: Balance, Runout, and Uniformity

Thanks Barry!! Indeed I have consumed all of your "Barry's Tire Tech" blogs with GREAT interest before! I'm amazed that the legendary Barry of the "Barry's Tire Tech" blog has responded! I learned so much from your blogs before. SUPER APPRECIATE your comments on what the Hunter Roadforce machine can and cannot measure.

Appreciate your comments, @CapriRacer, on roadforce values. I have been using 15 lbs as my personal limit because that's what Tire Rack recommends for passenger car low profile tires (as opposed to the 26 lbs that Hunter used when they first released the GSP9700) but I digress --- it sounds like 10 lbs is a significantly better number than 15 lbs.

Yes, I measured, with the https://vibratesoftware.com/ accelerometer app, vibrations on the four corners of the car (dash and rear deck) --- same stretch of road, same time / ambient temperature --- and all four corners were pretty equal. That said, we're talking forces on the order of 0.03G (3/100 of gravitational force). The vibrations can be felt much more strongly in the steering wheel than on the four corners of the car, but still not visible to the naked eye..... and these forces are DEFINITELY first-order-tire-speed related harmonics.

I should mention I tried putting the spare tire on each corner of the car and running the car for 100 mies to see what difference there was - totally inconslusive results. That said, it is still possible my spare tire assembly is out of round, or perhaps I have runout issues with BOTH the front pair and the rear pair of wheels.

Anyways, I will do more on car research, including measuring stud circle runout (already verified hub runout and brake rotor hat runout (at 0.02mm - 0.04mm) [0.008" - 0.0016"] and swapping wheels/tires and dismounting all tires from the wheels and measuring lateral / radial runout manually with my dial indicator tool.

BTW it is a 2006 MB S350 with MB wheels -- so the wheels are hubcentric with no aftermarket adapter rings.

 

[Jlaa]

Here is the result of me using the NVH app / accelerometers on the four corners of the front dash / rear deck. The BIOTG website seems to reduce to resolution so please let me expound - Blue is speed and orange is elevation. What's really useful is grey and green. The grey and green lines (grey in the top 2, green in the bottom 6) are are first order Tire speed related vibrations measured in G.

 

[SC Maintenance]

Which hunter machine?

The new ones are supposed to have sensors for lateral run out as well. Whether there using it properly is another matter.

 

[TCL]

Try cleaning the wheel hub and rotor surfaces where they contact each other.
Make sure they are shiny metal and not black corrosion/dirt especially on the wheel itself.

 

[Jlaa]

Try cleaning the wheel hub and rotor surfaces where they contact each other.
Make sure they are shiny metal and not black corrosion/dirt especially on the wheel itself.

Yes, I did that! After cleaning the hub and backside of a rotor hat, I brought one rotor hat lateral runout down from 0.20mm (yikes!) to 0.04mm. Great thinking!

 

[Jlaa]

Which hunter machine?

The new ones are supposed to have sensors for lateral run out as well. Whether there using it properly is another matter.

The Hunter GSP9700 that the local shop was using was an older one - 12+ years old and definitely was not new and doesn't have any sensors for automatic lateral runout measurement. Note that these old roadforce machine GSP9700s (as opposed to new ones which aren't even called "GSP9700" any more) can do manual measurement of lateral runout with these arms like below .... but its not automatic and it doesn't show up in the roadforce numbers.

 

[JohnnyG]

First of all, those numbers for the front tires are NOT that great. Second, if you suspect a bent wheel, just get it checked, or check it using a dial indicator as above.
Those posted numbers are generally acceptable as "PASS" but not all cars can handle numbers above 10# road force.

 

[SC Maintenance]

The Hunter GSP9700 that the local shop was using was an older one - 12+ years old and definitely was not new and doesn't have any sensors for automatic lateral runout measurement. Note that these old roadforce machine GSP9700s (as opposed to new ones which aren't even called "GSP9700" any more) can do manual measurement of lateral runout with these arms like below .... but its not automatic and it doesn't show up in the roadforce numbers.

View attachment 315914

Well see if there is a shop around with the new ones. Discount Tire here has them.

 

[shortyb]

Check next post for edited content.

 

[shortyb]

View attachment 315917
First of all, those numbers for the front tires are NOT that great. Second, if you suspect a bent wheel, just get it checked, or check it using a dial indicator as above.
Those posted numbers are generally acceptable as "PASS" but not all cars can handle numbers above 10# road force.

This. I'm surprised that you didn't do this in the first place when you discovered the vibrations, especially with acceptable RF numbers. And having that kind of runout with the rotor/hub interface before cleaning it? Have you cleaned/measured the rest of them? Also, how old are your struts/dampers? These can easily set up a har

 

[Jlaa]

Yeah, checking wheel runout is kind of a PITA because one has to dismount the tires from the wheels. Taking the measurements (4 of them - inner barrel radial, inner barrel lateral, outer barrel radial, out barrel lateral) is not difficult .... but just need to go through the hassle (and cost) of dismounting tires from wheels. And of course I'm anal enough that I only trust my own runout reading, so that means putting the car on jack stands, taking all four wheels to get the tires dismounted, taking the wheels home, measuring, etc etc.

I've talked to enough Discount Tire (America's Tires here in the West) that I trust exactly ZERO of them for this kind of precise work.