vibration

[Bruce W.]

Hey Guys, I have a slight vibration between 30 an 40 miles per hour. Have new tires, bias ply also have been balanced. Anyone know where to start to find this Problem?
Bruce

[Larry M.]

Re: vibration

Bruce:

Some of the reproduction bias ply tires have a history of balance issues. Some things to consider:

1. Did the problem start with the new tires?

2. Do you have a nearby friend that could swap out tires with you for a test ride to see if that fixes the problem??

3. Mark the tires to identify each one and then switch them into a few dffrerent positions on the car to see if the affects the vibration.

4. Have a second shop rebalance them all using a modern, recognized spin balance machine.

5. Did you change anything with the driveshaft or u-joints?? Or front or rear suspension??

Larry

[Gary C.]

Re: vibration

Bruce,

Where's the vibration?
- steering wheel
- bottom of the seat

Gary
....

[Richard G.]

Re: vibration

Yes more information is needed. But their are some things you can do along with the above suggestions that may help identify the issue.

I typically start by jacking up the car and spinning each wheel by hand. Watch the perimeter, while its spinning, and look for out of round tires. A bent rim can be balanced but still have lots of run-out as can the tire. A tire shop can also do this if you can get them to take the time. If the brakes are not dragging check if the tire comes to rest in the same spot or reverses direction before it comes to a stops as a balance check. I used to like to watch the tires spin on the balancers and watch for defects. Now the balance data is acquired so quickly the tire barely has to spin up. And with the guards it is difficult to see anyway.

Have some one drive the car and you follow. Simple but sometimes it helps. I once followed a car down the freeway with one tire coming completely off the ground every revolution.. Driver was clueless this was happening!

Stand in the middle and have someone drive the car in a circle around you. A couple times in each direction while you observe the car.
Although it take specialize equipment to fix the issue(s) on can often identify the problem with good observation skills and a little time.

Let us know if any of this helps you identify the issue.
Rick

[Bruce W.]

Re: vibration

Gary, vibration is in the steering wheel
Bruce

[Gary C.]

Re: vibration

Bruce,

You've received lots of good recommendations.

Steering vibration = front suspension area
Seat vibration = driveline such as u-joint or something in the rear

Troubleshooting - if vibration wasn't there previously to making a change - test/investigate the change.

Start by: jack up each side individually and 1) as suggested check the tire rotation for out of round, etc., 2) check the wheel bearing play, by rocking the top and bottom of the tire back and forth.

Gary
....

[Dan P.]

Re: vibration

Jack the car up in the back and run it to see if it still vibrates.If it does not problem is in front . If it does take the rear wheels and tires off and put nuts one to hold the drums on . Run it if it still vibrates take the drums off . If it still vibrate look at the drive shaft.

[James O.]

Re: vibration

all of the above seem legitimate ways to troubleshoot. here is another. if you have no problem at 60+ mph and had them spun balanced, i have found that the current spin method sometimes misses the vibration at low speeds like 30-40 mph. i found that using an old micro bubble balancer on bias ply tires and following the instructions EXACTLY with the old-style clip-on weights corrected the problem. make sure that bubble is dead center before and after the balance. jim

[Bruce W.]

Re: vibration

Dan thanks a very good suggestion. BTW do you think it could be the front shocks. I already replaced the rear from you so I know those are good!!
Bruce

[Bruce W.]

Re: vibration

Gary thank you for the suggestions. I will implement your recommendations thanks
Bruce

[Richard G.]

Re: vibration

I haven't found it a good idea to run the rear wheels with the wheels hanging.
The high angles at the half-shaft U-Joints that are generated by letting the wheels hanging cause a lot of other vibration that might not be there if the car was on the road.
I would support each wheel at the outboard end.

[Timothy B.]

Re: vibration

How about a front wheel bearing. If you can turn the wheel left or right and the vibration stops for a split second look up front.

[Jim D.]

Re: vibration

BTW do you think it could be the front shocks.
Bruce

I doubt it, but there was a member on another forum that was justifying the low selling price of his C-1 because, in his words "the front end needed rebuilt". Turns out the new owner replaced the front shocks and now the car drives like new.

[Duke W.]

Re: vibration

Static unbalance or out-of-round will cause steering wheel "shake", but it's usually at about 60-65 MPH when wheel RPM corresponds to the natural frequency of the front suspension, which is about 12 Hz. Dynamic unbalance can cause the wheel to "wiggle" back and forth. The advice to check for out of round is good, but do it immediately after driving as tires can develop a slight flat spot from sitting a few hours that can give a false reading. You need to state how the wheels were balanced. Statically? Dynamically (weights on both sides)? What equipment - manufacturer and model? Also, what's the tire brand/model? Coker bias plies are notorious for out-of-round.

[David M.]

Re: vibration

Have the wheel balance tech leave the safety hood up on the balance machine while its spinning and look for tire hop and wobble. Could be a bad rim or a tire. Bad shocks can allow road imperfections to migrate through the chassis, where a good shock would absorb it. Inspect front wheel bearings and other front end components as mentioned. All bushings, bjs, tie rods etc...