new vehicle - how much vibration is acceptable?

[BrianE22]

I noticed on my new SUV that there is a bit of vibration between 55 and 60 mph. I feel it both in the steering wheel and the seat. Is there a maximum vibration level that the manufacturers deem to be allowable at wheel hop frequency? I'm tempted to mount an accelerometer to the steering wheel just for fun.

 

[GregLocock]

Not really. . I don't know how other manufacturers currently set targets, 20 years ago it would have been a case of somebody like me (NVH engineer) or a manager saying that's no good, fix it, whether on a prototype or a production car.

Most likely is one of your wheelweights has fallen off



Cheers

Greg Locock


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[BrianE22]

Thanks Greg - kind of nice know there's still subjective feel that's being used. A bit surprising though. I'd of thought that these days dealers would be required to road test each vehicle to some objective standard before letting the vehicle out the door.

 

[GregLocock]

Dealers take the polythene wrap off, clean the windows and set the tire pressures.

Cheers

Greg Locock


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[FeX32]

If you can feel it in the steering wheel, it is not acceptable of a new vehicle.

 

[GregLocock]

Nonsense

People's sensitivity varies by about 5 dB, the goal of the manufacturer is to satisfy some percentage of the buyers, not all of them.

Cheers

Greg Locock


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[BrianE22]

It is an SUV and the tires are low profile so I don't expect it to ride as smooth as a car. I haven't brought it back to the dealer yet. I suspect their mechanic will say the vibration level is "normal". I'd love to go in with accelerometer data and tell them it's above the "limit". That's why I was hoping there was some sort of quantifiable vibration limit.

My fault though. When I test rode the vehicle I mentioned the vibration to the salesman sitting in the passenger seat. He said "...we just had a memo on that. For these vehicles, the sitting around not being driven for awhile is causing flat spots on the tires. They'll go away...".

 

[GregLocock]

Flat spotting certainly is an issue, try taking them up to 45 psi and see if it goes away. It is the dealers job to fix this.

Cheers

Greg Locock


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[FeX32]

Was just expressing my own expectations

 

[Tmoose]

Can you double integrate and throw the signal thru a frequency seive?

Maybe something along the line of curve b in Fig 2 here?

http://www.indofork.com/environment.htm

Probably have to measure pith accel point tangent to the wheel rim, vertical and ???.

 

[CWAnthony]

Greg,

In response to your comment, "People's sensitivity varies by about 5 dB, the goal of the manufacturer is to satisfy some percentage of the buyers, not all of them.". I would like to ask:

In your experience, would you say people's sensitivities can change over time, depending on what they are exposed to? For example, someone who has driven premium cars all his life will be more likely to notice the OP's noise issue than someone who has only ever driven beetles. Or is this variance bio-mechanical, depending on the different states of the ears of the people driving?

 

[GregLocock]

Both. People's innate sensitivity varies, just as hearing acuity varies, and then there is a learned response, and then there are expectations. It's a complex field, papers by MJ Griffin are a good place to start.

Cheers

Greg Locock


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[Brian1949]

Rotate the tires front to rear and see if you still get the same vibration. If not, then one (or both) of the front wheel/tires is out of balance and/or out of round.

 

[BrianE22]

I finally brought the vehicle in. I figured I'd wait for the first recall and get everything fixed. The mechanic said both the right side tires were out of balance. The ride is much better now.

The alarming thing for me was that the mechanic said it's not unusual for the new cars to need to have the tires/wheels balanced. Yikes, that might be it for me buying American made SUVs.

 

[BUGGAR]

Dealer service is paid for by the dealer's markup. Less service = more profit.

 

[IRstuff]

We had a CRV in storage for almost a year, and it was bumpy for a LONG time; I think we actually wound up getting all new tires to get rid of the bumpiness.

TTFN
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[GregLocock]

That's flatspotting. If you need to lay a car up again either chock it off the ground or put 50 psi in the tires.

Cheers

Greg Locock


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