A theory: improper wheel balancing due to temporary flat spotting

Vtx531

Vtx531

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My theory is that you are unlikely to get a proper balance at a typical tire store for in-service tires because the tires temporarily flat spot while the vehicle is parked waiting for service.


Tell me if this sound familiar:

You go offroad, maybe air down, and end up with tire vibrations on the way home (probably due to tire slippage on the rim).

Go to Discount Tire, they rebalance. Later you discover it still vibrates at high speeds (not as bad though but just annoying). So go back to Discount Tire, they rebalance and find it was off a little bit. Repeat, repeat.

Maybe you get some new tires. Wow, rides smooth as glass now. Must have needed new tires - amazing.
 
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Here is my data. Not a Jeep but my daily driver. 225-50-17 General Altimax RT43 Tire aired up to maximum pressure (44psi)

I measured unloaded radial runout using a dial indicator and charted the data points. The plot that shows maximum .059" runout was after the car was sitting for about 20 minutes. The plot that shows maximum .028" runout was after driving one loop around the block at 20mph (not far). It was enough to get rid of the flat spot though (mostly).

The way I realized this was because the first tire I measured (after driving 8 miles) was pretty uniform under .030". Ten minutes later, I measured the next tire and it showed what looked to be a flat spot and increased total runout. After another 10 minutes of sitting is when I measured the third tire and noticed the OBVIOUS flat spot shown below.

I drove around the block, jacked up the tire as soon as I parked,and measured again. I was amazed to see the plot was almost identical to the previous one but without the flat spot (mostly).

So how can you properly balance a tire with a flat spot? I thought it would take longer than 10-20 minutes for this to happen.

C63E7277-64C2-4602-B9D2-355611323AA6.jpeg
 
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My guess (and it's just that - a guess) is that the runout you are measuring (assuming 0.28" in your post was a typo and it should have been 0.028") is fairly insignificant and doesn't noticeably affect balance. I say this because I've been in a tire plant, and laying up rubber and steel into a mold is not an exact science. I don't think the numbers you're measuring are outside of normal production tolerances.

If you're going to conclude that this runout is causing balance issues, you need to show a balance issue that changes with the runout.
 
Don't go to Discount Tire. My local tire shop balances my 35" tires perfectly and they haven't been rebalanced in 2 years of DD. They also know if it isn't perfect, I'll come back 10 minutes later to make them do it right.
 
sab said:
My guess (and it's just that - a guess) is that the runout you are measuring (assuming 0.28" in your post was a typo and it should have been 0.028") is fairly insignificant and doesn't noticeably affect balance. I say this because I've been in a tire plant, and laying up rubber and steel into a mold is not an exact science. I don't think the numbers you're measuring are outside of normal production tolerances.

If you're going to conclude that this runout is causing balance issues, you need to show a balance issue that changes with the runout.
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.028. edited thanks.

I only have a bubble balancer myself so not really accurate enough to test the hypothesis.

I would be really interested in testing this with a spin balancer after letting a tire sit for various lengths of time so see if there is a significant difference.
 
Have you measured the flat spotting present after a longer period like 12-24 hours? A week? I'm curious how much runout it takes to be perceptible by the driver. If the runout isn't perceptible then I'd be surprised if the imbalance resulting from balancing with that runout would be.
 
Jerry Bransford said:
Not always and not necessarily. I stopped paying extra for Road Force balancing as it was not producing better results for me after several uses of it.
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I used to alway do road force balancing on my jeep. The problem is you can recheck them 6k miles down the road and they will be out again. Doing it properly is exhausting. Constantly breaking the tire/wheel down, doing a match, measuring runout. It gets old.
Now I just spin them and +/- weight accordingly.

I know it's not Jeep, but GM has a long lengthy procedure when you replace tires under warranty for road force concerns.
It involved pico reading, road force readings, mounting new tires, marking the valve/tire. letting it sit for 1 hour,so the tire lube dries, then driving the vehicle for 26 miles to ensure the beads are seated and there are no flat spots. Then balancing the tires.
If the readings are out, you get to start all over again,
 
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Jerry Bransford said:
Not always and not necessarily. I stopped paying extra for Road Force balancing as it was not producing better results for me after several uses of it.
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I wonder if it could be the difference in the tire store or employee? I use a tire store that mainly sells big truck tires and road force balance 22.5 and 24.5 steer tires. They have always had my tires spot on.
 
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John Cooper said:
I wonder if it could be the difference in the tire store or employee? I use a tire store that mainly sells big truck tires and road force balance 22.5 and 24.5 steer tires. They have always had my tires spot on.
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I suspect either the employees were not adequately trained on it or, more likely, the store didn't give them enough time to to a good job. Insufficient time is my usual suspicion when they finally give it a good balance when they are allowed to spend more time on the job after I complain about a previous bad balance job.
 
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freedom_in_4low said:
Have you measured the flat spotting present after a longer period like 12-24 hours? A week? I'm curious how much runout it takes to be perceptible by the driver. If the runout isn't perceptible then I'd be surprised if the imbalance resulting from balancing with that runout would be.
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I havent measured after a longer period but I have seen literature online that Nissan says balancing needs to be done within 10 mins of driving and Hyundai says the car needs to be put on a lift immediately after driving. And by driving they mean 20-30 minutes at highway speed.
 
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Vtx531 said:
I havent measured after a longer period but I have seen literature online that Nissan says balancing needs to be done within 10 mins of driving and Hyundai says the car needs to be put on a lift immediately after driving. And by driving they mean 20-30 minutes at highway speed.
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if manufacturers say that then there's probably something to it.

For about 3 years I frequented two different discount tire locations. One near my work, where I would go during the week and just wait while they did it, and one closer to home that I would use on the weekends and just leave the vehicle for hours. The balance always came back better when I did it during the week, and I blamed the different locations. Maybe it was flat spotting from sitting there half a day before they touched it?
 
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It makes sense to balance tires when they're still warm from driving but wow I've just never seen a tire shop start on a balance job unless the vehicle has been sitting at least an hour or more. My last two jobs I had to drop it off the night before.
 
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Jerry Bransford said:
Not always and not necessarily. I stopped paying extra for Road Force balancing as it was not producing better results for me after several uses of it.
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I have had the same experience with road force balancing, the biggest difference was in the wallet.

My absolute best tire balancing experience was with my last set of 35” KM3’s. They were initially balanced great but after chunking from a Moab trip they started the typical slight shimmy at highway speeds. I left the original weights in place and added 2 oz’s of copper coated BB’s to each tire and they were still perfect when I sold the Jeep a year later.
 
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Vinman said:
I have had the same experience with road force balancing, the biggest difference was in the wallet.

My absolute best tire balancing experience was with my last set of 35” KM3’s. They were initially balanced great but after chunking from a Moab trip they started the typical slight shimmy at highway speeds. I left the original weights in place and added 2 oz’s of copper coated BB’s to each tire and they were still perfect when I sold the Jeep a year later.
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I've thought of doing that, how did you get them inside? Will they fit in through the valve stem? Do you notice the noise of them falling to the bottom of the tire when you slow down to stop? Actually now that I think about it I've gotten half deaf enough that I may not hear them no matter what. 🤣
 
There's no such thing as road force balancing. They are two separate processes.

Hunter refers to it as a "Road Force measurement".

The way I have seen Discount Tire do it, all they do is verify the Road Force measurement is within limits and send you on your way. They typically don't use the machine to its full ability to minimize the road force by matching the high spot of the tire to the low spot of the rim, which Hunter refers to as "Force Matching". So, unless there is a severe problem, most the time a so-called road force balance doesn't do anything different than a regular balance.
 
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Jerry Bransford said:
I've thought of doing that, how did you get them inside? Will they fit in through the valve stem? Do you notice the noise of them falling to the bottom of the tire when you slow down to stop? Actually now that I think about it I've gotten half deaf enough that I may not hear them no matter what. 🤣
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I broke the bead using a hi-lift and dropped them in. I never tried through the valve stem but doubt they will fit.
Honestly, never really noticed any noise from them other than when I was rolling them around during tire rotations.
 
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Jerry, you said you noticed no difference. No difference in that they were smooth either way or no difference in that there is slight vibration either way?
 
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