Vibrations in the steering wheel: VD RF85

[frederic944]

I have some pretty heavy vibrations in the steering wheel of my VD RF85, I balanced the front wheels, check if there's any play in the front bearing , it's pretty tight and I still have these vibrations.

Where should I look now or should replace?


Thanks


Frederic

[rmccown]

Alignment? Rack tightness?

[john f]

Check the rear wheels.

john f

[Brian]

Check the wheels for true and out of round.

Brian

[Clyde]

Vibrations in the front can be caused by too much or too little castor, about 4 degrees is a good starting place. Also, if you cannot drive through the vibration, it probably is NOT balance, as most of the time you can drive past the vibrations, wheel balance vibrations are around 50 to 60 MPH after that they seem to go away. BUT I always use a Snap-on balancer, not a bubble balancer or a spin type. The Snap-on uses twice as much weight but un-like the others it does away with the "Football" type of weights. The play at the end of the steering rack was also a good suggestion. If there is too much play in the steering rack the alignment will change when the rack goes up or down as the rack should ONLY go in and out.

[Dick R.]

I have some pretty heavy vibrations in the steering wheel of my VD RF85, I balanced the front wheels, check if there's any play in the front bearing , it's pretty tight and I still have these vibrations.

Where should I look now or should replace?


Thanks


Frederic

I "assume" you can see the wheels "hop" or vibrate and the tires don't have flat spots.

Straight line or corners or both?

Wheel/tire "roundness", rod ends, rocker pivot bearings, shocks, shock mounting?

Dick
RF-85 - autocross duty so no direct experience with track type issues.

[starkejt]

How's the runout @ each corner? Not just the wheel but the hub itself.

[kea]

Does your brake pedal pulsate when it is applied? Could be something in the brake/rotor area.

[ChrisW]

You may also want to check the bumpsteer.

[Frank C]

As I recall, I had instability that one might interpret as vibration after banging wheels with a FV (don't do it - they are way too sturdy!). The wheel-banging left me with a sustantial toe-out on one rear wheel.
- Frank C

[frederic944]

Thanks guys for the quick and numerous feedback, will go through all your suggestions...

[Keith Carter]

We had a bubble balancer that was bent after being dropped in the trailer. The bubble would show the wheel being balanced and the car would shake depending on how off it really was. Try having them balanced on different equipment and see if it fixes it. Is it set after set of tires, or is it just the current set? It could be a manufacturing defect in the tire.

[Hawke]

I had an issue like this. Seemed to be solved with some extra toe out.

After I fitted new bushes to the rack ends, the problem solved.

I surmised that with a little toe out, at speed, the front wheels shook backwards and forwards due to the slack at the rack ends. With a bit more toe out, the wheels and rack were forced to one side of the worn bush.

[Will Velkoff]

How old are the tires?

[t walgamuth]

Vibrations in the front can be caused by too much or too little castor, about 4 degrees is a good starting place. Also, if you cannot drive through the vibration, it probably is NOT balance, as most of the time you can drive past the vibrations, wheel balance vibrations are around 50 to 60 MPH after that they seem to go away. BUT I always use a Snap-on balancer, not a bubble balancer or a spin type. The Snap-on uses twice as much weight but un-like the others it does away with the "Football" type of weights. The play at the end of the steering rack was also a good suggestion. If there is too much play in the steering rack the alignment will change when the rack goes up or down as the rack should ONLY go in and out.

I don't have any experience with an out of balance wheel that vibrates less at a hundred mph than it does at sixty. I would like to hear a scientific explanation of how this might occur.

In my experience out of balance situation just gets worse the faster you go.

[DaveW]

I don't have any experience with an out of balance wheel that vibrates less at a hundred mph than it does at sixty. I would like to hear a scientific explanation of how this might occur.

In my experience out of balance situation just gets worse the faster you go.

An out-of-balance will almost always vibrate more as the speeds increase, because the forces increase as the square of the speed.

However, if the wheel/tire is out of round, it is common for that vibration to max out at the "natural frequency" of the tire/wheel/suspension mass (unsprung mass) which usually occurs at much lower speeds than the maximum attained.

This happens because you are inputting a displacement which is (mostly) not speed-related, and the speed at which the mass reaches its max displacement amplitude is dependent on the vibration characteristics of the unsprung mass, not the input force level.