Periodic Suspension Vibration
Periodic Suspension Vibration
(OP)
Dear Experts,
Since I am no expert on vibrations, I was hoping that some-one could shed some light on the cause of vibrations in my car.
Unfortunately, I accidentally ran into a kerb with the 2 right side wheels (Low profile tyres). Ever since, the car has been vibrating in the following manner.
1) Accelerating / braking 20Km/hr above and below 100km/hr or constant velocity - The steering wheel shudders.
2) No acceleration or braking at this velocity - no vibrations.
Straight away, this tells me vibrations are a function of possibly damaged drive shafts or brake caliper?.....
3) Beyond 100km/hr, vibrations travel from the steering wheel to the driver seat and back seat.
4) The strange bit – mild periodic vibrations of the whole car approximately every 10 seconds along with normal vibrations when car is running at constant velocity above 100km/hr.
My understanding is that if the alloys are slightly damaged and are rotating constantly then vibrations should be constant, instead I get periodic vibrations. Why is this? What is causing this periodic vibration?
I assume that there is resonance happening somewhere with the suspension system and some other external frequency. Would damage engine mounts cause the frequency of engine to resonate with suspension system? Are there any remedies I can try to resolve this problem?
The 2 front tyres are balanced and to no avail. Would tracking / rotating the wheels have any effect?
One final question, if some component of the suspension system is permanently bent (impact with kerb), does this change the natural frequency of the system?
Sorry for the long winded thread. Any suggestions or comments will be greatly appreciated.
Kind Regards
Eddie
Design Engineer
Since I am no expert on vibrations, I was hoping that some-one could shed some light on the cause of vibrations in my car.
Unfortunately, I accidentally ran into a kerb with the 2 right side wheels (Low profile tyres). Ever since, the car has been vibrating in the following manner.
1) Accelerating / braking 20Km/hr above and below 100km/hr or constant velocity - The steering wheel shudders.
2) No acceleration or braking at this velocity - no vibrations.
Straight away, this tells me vibrations are a function of possibly damaged drive shafts or brake caliper?.....
3) Beyond 100km/hr, vibrations travel from the steering wheel to the driver seat and back seat.
4) The strange bit – mild periodic vibrations of the whole car approximately every 10 seconds along with normal vibrations when car is running at constant velocity above 100km/hr.
My understanding is that if the alloys are slightly damaged and are rotating constantly then vibrations should be constant, instead I get periodic vibrations. Why is this? What is causing this periodic vibration?
I assume that there is resonance happening somewhere with the suspension system and some other external frequency. Would damage engine mounts cause the frequency of engine to resonate with suspension system? Are there any remedies I can try to resolve this problem?
The 2 front tyres are balanced and to no avail. Would tracking / rotating the wheels have any effect?
One final question, if some component of the suspension system is permanently bent (impact with kerb), does this change the natural frequency of the system?
Sorry for the long winded thread. Any suggestions or comments will be greatly appreciated.
Kind Regards
Eddie
Design Engineer





RE: Periodic Suspension Vibration
Tobalcane
"If you avoid failure, you also avoid success."
RE: Periodic Suspension Vibration
RE: Periodic Suspension Vibration
The phasing is typically because the two wheels run at slightly different speeds. You are hearing them coming into sync and out again, like a WW2 bomber's engines.
You have probably bent the rims. If you persist in driving on them you will explode the shock absorbers.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Periodic Suspension Vibration
Really, how would the shocks explode? Maybe I should rotate the wheels so and see how that effects the periodic vibrations. Im not prepared to chenge my rims just yet
If i make any progress, I will update this thread.
Thanks again folks
Eddie
RE: Periodic Suspension Vibration
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Periodic Suspension Vibration