Vibration at 80 MPH to 90 MPH - Primary Amplitude 15HZ at 85 MPH

dsddcd · August 8, 2019

Well I have read quite a bit and there are no obvious answers and lots of guessing going on. So I pulled out my phone and took some simplistic vibration samples which indicate that my truck has a balance issue at roughly 15HZ.

Based running some quick maths I figure that this directly correlates to the wheel speed.

85 MPH @ 630 Revs/Mile

1.416 Mile/min

892 Revs/min

14.9 Revs/sec

Based on this I have ruled out the drive shaft and transmission to focus on the wheels and axles. This was a concern since I have load leveling bags on the truck but I am at factory ride height and have completed a Trim Height Relearn. I have changed and rotated the tires so I don't believe this is the issue. There is a small amount of rotor runout felt at highway speed under heavy braking which I believe to be coming from the rear. So the game plan was to change the rear rotors, clean the wheel flanges, strip the wheel weights and have the tires balanced again and potentially change the axles.

If I do the axles would you buy new OEM or look for an aftermarket source?

Any suggestions for a Heavy duty rear rotors?

Grumpy Bear · August 9, 2019

No takers? Could be axle run out. Flanges not concentric to the bearing journals.

Yukon. Summers Brothers. Currie Enterprises. Moser. Mark Williams. Strange Engineering.

Bash74 · August 9, 2019

Then just dont drive 85-90mph. I mean I only know one place in the entire country that has an 85 speed limit.

dsddcd · August 10, 2019

3 hours ago, Bash74 said:

Then just dont drive 85-90mph. I mean I only know one place in the entire country that has an 85 speed limit.

Much of the Midwest is 75mph and there are pockets of 80mph!

HeySkippyDog · August 10, 2019

I'm not entirely following how you came to the conclusion that it can't be the driveshaft or the axle.

Your phone accelerometer was feeling vibration from where exactly? The dash?

How do you know whatever surface/object you placed it on isn't resonant at that frequency and showing you that spike? It's just too far removed from any driveline component to conclusively say "it can't be the driveshaft".

I do vibration testing at work, and for resonance detection for a device, you need to be monitoring as close as you possibly can to the device you want to test. Anything else is going to be inaccurate.

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Bash74 · August 10, 2019

Much of the Midwest is 75mph and there are pockets of 80mph!

If you want to spend the time and money to replace something so you can go five miles an hour over the speed limit when you are in those areas, it is your money.

Racindave · August 11, 2019

Just keep it at 90 plus....

Tahoe02 · August 11, 2019

Have you done a road force balance. Cured my vibration.

PPK · August 11, 2019

This is an interesting app on your phone. What is it? thank you...

Grumpy Bear · August 11, 2019

On 8/9/2019 at 10:23 PM, HeySkippyDog said:

How do you know whatever surface/object you placed it on isn't resonant at that frequency and showing you that spike? "

Lets say it is. Something is resonant at X frequency. What would be the frequency of the excitation? I would expect a single strike exciter to have a diminishing amplitude, right? Like a tuning fork. So, to sustain a constant amplitude frequency would the exciter need to be a multiple of the resonant or the same frequency as the resonant?

HeySkippyDog · August 11, 2019

Lets say it is. Something is resonant at X frequency. What would be the frequency of the excitation? I would expect a single strike exciter to have a diminishing amplitude, right? Like a tuning fork. So, to sustain a constant amplitude frequency would the exciter need to be a multiple of the resonant or the same frequency as the resonant?

It isn't enough information to say it is or is not a specific part of the driveline. There's a spike, that is for sure. But what's causing that spike? The accelerometer is too far removed to start eliminating components.

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mmmikkke · August 11, 2019

There's no substitute for round tires. Ever time you buy a set of tires you gamble because the retail tire industry always blames 60-90 mph issues as balance issues, rust jacking issues, or "they all do that."

Tire manufacturing is like sausage making. Bad optics and questionable results.

The tread belt has to overlap itself somewhere. Better hope those new tires get their tread belts properly placed on the ol' tire production line.

Grumpy Bear · August 11, 2019

6 hours ago, HeySkippyDog said:

It isn't enough information to say it is or is not a specific part of the driveline. There's a spike, that is for sure. But what's causing that spike? The accelerometer is too far removed to start eliminating components.

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I was asking a question Skippy, not making a statement. Okay I see I framed three. Just the last one then.

KARNUT · August 11, 2019

I would put that to something to keep an eye on to see it moves or gets worse. It wouldn’t be a speed most people live at. I had a noisy vibration with the first two sets of tires on my wife’s car. The first set with 5K rotations came in at 20K miles. They were performance tires that were gone by 30K. The second we’re touring tires at 20K noisy vibration. Discount tire warranty them and put on a different set. Almost at wear bars at 100K miles no problems. Those problems were evident from 30-60 MPH.

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dsddcd · August 12, 2019

On 8/9/2019 at 10:23 PM, HeySkippyDog said:

I'm not entirely following how you came to the conclusion that it can't be the driveshaft or the axle.

Your phone accelerometer was feeling vibration from where exactly? The dash?

How do you know whatever surface/object you placed it on isn't resonant at that frequency and showing you that spike? It's just too far removed from any driveline component to conclusively say "it can't be the driveshaft".

I do vibration testing at work, and for resonance detection for a device, you need to be monitoring as close as you possibly can to the device you want to test. Anything else is going to be inaccurate.

Sent from my SAMSUNG-SM-J727A using Tapatalk

I took several measurements in with different orientations & locations at several different speeds from 70-90 mph and was only able to see 1x & 2x wheel speed. I am an ME and do quite a bit of Vibration Analysis on rotating equipment as well. As for the phone I agree that a $10K meter properly mounted would be much better but this method is better than what the dealer did/will do!