Vibration / Shimmy at Cruising Speed

My Riviera's got around 64K on it. I just replaced the rear shocks and the front wheel bearings (which need to be replaced under warranty due to a defective ABS Sensor). Anyway, I notice a shake/shimmy that I can feel in the steering wheel and seat when driving around 60. I can also feel like a wobble if that makes sense around 30. This was happening before I replaced anything mentioned above, so that rules all that out. The struts in the front could use replacement. It's taking a long time when going over bumps to recover in the front. The vibration seems to vary depending on road conditions, throttle control, and if I'm turning. If I'm on the gas the vibration is not nearly as bad as when I'm just coasting. Also if I turn the wheel the vibration seems to change. Sometimes it'll be worse, sometimes it'll be better. It's not a constant vibration around 60. Sometimes it's there sometimes it's not. I thought it might be an engine or transmission issue, but even when putting it in neutral and going down the road when the vibration occurs it still vibrates. Also I've tried neutral while revving the engine just to see if that might have something to do with it, and I got the same results; the vibration was there still. I checked the engine mounts too, and all seem to be in good condition.

I guess my question is can bad struts cause this issue? Could just an out of balance wheel or a tire issue itself cause this? I would assume that if it was the balance or tire itself it would be a constant issue not one that varies. Anyway, any input is always greatly appreciated. Thanks, Kyle.

I've had the exact same problem with mine since I bought it almost 3 years ago. I haven't figured it out yet.
I have new struts and shocks. Didn't change the vibration issue after replacing them. Have checked all other front end components and hub runout along with rotor runout, all good.
I'm having my tires removed next week to check the rims for lateral and radial runout with dial indicators. If wheels are good I'm throwing away a set of Goodyear Eagle LS tires and trying something else.
I'm tired of the vibration at highway cruise speed and the low speed "wobble" just feels like a bent rim, but I don't know.

Rickw wrote:

I've had the exact same problem with mine since I bought it almost 3 years ago. I haven't figured it out yet.
I have new struts and shocks. Didn't change the vibration issue after replacing them. Have checked all other front end components and hub runout along with rotor runout, all good.
I'm having my tires removed next week to check the rims for lateral and radial runout with dial indicators. If wheels are good I'm throwing away a set of Goodyear Eagle LS tires and trying something else.
I'm tired of the vibration at highway cruise speed and the low speed "wobble" just feels like a bent rim, but I don't know.

You have Goodyear Eagle LS tires? I've actually got the same ones... You've got me wondering now...

Do they suck for traction on any surface too? I've got a little under half of the tread left and even on dry pavement the tires sometimes break loose unless I really ease onto the gas.

try rotating your tires and see if the shake moves to a new place.

deekster_caddy wrote:

try rotating your tires and see if the shake moves to a new place.

Yeah I gotta bring it in tomorrow for the wheel bearings to be changed. I'll have him rotate the tires too. I'm not sure how many miles are on the tires. I bought it with them on it. I can't imagine they could be too old considering it's only 64,000 miles old...

Sounds like worn tie rod ends to me. I replaced my originals at over 160k miles, but I think they needed done long before. Dramatically reduced the vibration during cruise in my case.

I have checked all front end components for even the slightest wear and found none.
Have had the balance checked twice on different machines since having these tires installed and have not needed rebalance. Have had the front end aligned twice, second time needed no adjustments.
Have rotated wheels and tires yet the vibration remains the same.
It is a chassis vibration and steering wheel vibrates at about 65 - 80 on smooth highway.
There is a TSB that has been published for many years regarding this problem and I followed the instructions and worksheet provided in the TSB up to the point of faxing the data to GM engineering. Which obviously we can not do.
I have a local shop that is going to let me bring my dial indicators and mounts to the shop. They are going to remove rubber from the wheels and let me do the run-out checks i want then remount the tires.
If the wheels check OK then I have to decide what I'm going to do after that. I want larger wheels and tires and if I can swing the money I might go that route or just put a reasonably good tire on these rims for the winter and do the larger wheels in the spring. I don't know yet.

Just some sort-of-random thoughts...

if I remember right the Riv's vibration sometimes has to do with a suspension harmonic. That is, if it's set up exactly as it left the factory then it'll roll smooth but there's a number of things that will let the suspension vibrate.

I have had such a vibration problem in the past. It is no fun. Took me a long time to get rid of it. Gabriel VST struts helped; when they wore out I replaced those with KYBs and it has not come back. In the interim I've only used high-line tires (Michelin, Uniroyal) and have been really persnickety about the brakes.

I *suspect* but am not sure that if you simply replaced the springs with new ones of OE spec that'd fix it. I considered that but did not end up doing that - although with 200+K on the car I'd think the springs would be "due."

There are a couple other things too.

One "trick" that works for me (I am not sure why) is to put the wheels on with the GM trademark upright and rest the weight of the car on the ground somewhat before completely tightening the lugnuts. I suspect this has little or nothing to do with "reality."

Another thing - do the GM TSB instructions have you checking the *hubs* for runout? You might need shims... I have not had to use shims, but I am replacing the hubs and suspect I might need them this time.

Just some thoughts.

Albertj

TSB # 00-03-10-007 latest Rev. Dec, 2000
Titled: Shake / Vibration in steering wheel, floor, seat at highway speeds on smooth roads.

TSB # 00-03-10-006 latest Rev. Nov, 2000
Titled: Tire Radial Force Variation

I believe both of these speak to the issue.

Does someone near you have a Hunter 9700?

Albertj

I found a local tire shop that does.

That's part of what it took for me to get rid of the vibrations at highway speed. THe blooming thing actually works, as long as the technician is kind of patient AND goes through the whole routine. Part of the routine is the balance. FOr a tech the 'pain' comes when you use the load wheel to check for radial force variation - the machine will tell you to demount/remount the tires.

The Hunter will not tell you, however, if there is a problem with the part of the wheel that contacts the hub. A buildup of corrosion on that surface could give you a runout problem and the Hunter will never find it. I reckon you'd have found that by now if it was a problem.

For benefit of the others reading this - a layer of corrosion the thickness of a good trash bag on the hub face or on the inside suerface of the wheel that contacts the hub can give you measurable runout at the rim edge. I am not sure how big the runout has to be before you can feel it using your butt dyno, but on a smooth machine like the Riv can be, it is not much at all. Rick is a fine mechanic - all you have to do though is look at how-to videos on You Tube posted by so called mechanics and it should be no surprise to you that there is a lot of variation in quality of work they do.

Albertj

albertj wrote:

.I *suspect* but am not sure that if you simply replaced the springs with new ones of OE spec that'd fix it. I considered that but did not end up doing that - although with 200+K on the car I'd think the springs would be "due."

I replaced the springs with OEM new when I did the struts.

albertj wrote:

Another thing - do the GM TSB instructions have you checking the *hubs* for runout? You might need shims... I have not had to use shims, but I am replacing the hubs and suspect I might need them this time.

And yes there are shims available from Raybestos if you need them in various thickness's. They are available at Rock Auto and other Raybesto's suppliers.

Rickw wrote:

albertj wrote:

.I *suspect* but am not sure that if you simply replaced the springs with new ones of OE spec that'd fix it. I considered that but did not end up doing that - although with 200+K on the car I'd think the springs would be "due."

I replaced the springs with OEM new when I did the struts.

albertj wrote:

Another thing - do the GM TSB instructions have you checking the *hubs* for runout? You might need shims... I have not had to use shims, but I am replacing the hubs and suspect I might need them this time.

And yes there are shims available from Raybestos if you need them in various thickness's. They are available at Rock Auto ot other Raybesto's suppliers.

It'll be great to find out what's going on here.

For the time being my 'money' is on radial force variation.

The other thing is you say you replaced the springs. Don't know whose struts you used but both KYB and Gabriel say their struts are designed to compensate for spring wear. I wonder if it may be that the replacement struts you got are compensated for spring wear that is not there, changing the harmonic balance of the suspension system and leading to the oscillations you get at certain speeds?!?

Naaaaah.

I'm sure you'll find it; for now I am stumped.

Albertj


Albertj

albertj wrote:

Rickw wrote:

albertj wrote:

.I *suspect* but am not sure that if you simply replaced the springs with new ones of OE spec that'd fix it. I considered that but did not end up doing that - although with 200+K on the car I'd think the springs would be "due."

I replaced the springs with OEM new when I did the struts.

albertj wrote:

Another thing - do the GM TSB instructions have you checking the *hubs* for runout? You might need shims... I have not had to use shims, but I am replacing the hubs and suspect I might need them this time.

And yes there are shims available from Raybestos if you need them in various thickness's. They are available at Rock Auto and other Raybesto's suppliers.

It'll be great to find out what's going on here.

For the time being my 'money' is on radial force variation.

The other thing is you say you replaced the springs. Don't know whose struts you used but both KYB and Gabriel say their struts are designed to compensate for spring wear. I wonder if it may be that the replacement struts you got are compensated for spring wear that is not there, changing the harmonic balance of the suspension system and leading to the oscillations you get at certain speeds?!?

Naaaaah.

I'm sure you'll find it; for now I am stumped.

Albertj

I used Monroe Sensa-Tracks

A number of people really like Monroes. I sold my set to Randall (99Rivman) some time ago, I think he was putting them on a Silver Arrow he was refurbishing at the time. Monroes are fine shocks but did not damp enough for my kind of driving (good 2-lane blacktop secondary highways through rural areas). The problem might have been that they were still new and jiggly. Anyway, Gabriels and KYBs work better for me. Stiffer struts would change the harmonic frequency of the suspension somewhat, come to think of it.

Albertj

I found the Monroe Sensa-Tracs to be much firmer than OEM. I almost ditched them after installing because I though they were too harsh, but after a few months they softened up a little. Now I like them!

deekster_caddy wrote:

I found the Monroe Sensa-Tracs to be much firmer than OEM. I almost ditched them after installing because I though they were too harsh, but after a few months they softened up a little. Now I like them!

Yes, the Monroes are firmer than OEM. IF the car was new they'd designate them "FE2" on the build sheet, and the KYBs or Gabriels would be "FE3" - they are really pretty stiff. Make the car feel much smaller than the OE struts. But they (Gabriels or KYBs) are just the thing for driving twisty country roads without getting seasick.

Albertj

has anyone tried the sachs struts and shocks? i can get these at my local autozone but don't know anything about them. i want a firmer ride in my riv for a more performance car feel to it.

sachs?

apparently sachs makes alot of performances shocks and struts for the corvette, bmw, porche etc. they are a german company. until recently i never heard of them either.

Sachs/Boge. They are part of the ZF group if I am not mistaken. Been around a *long* time.

Albertj

Any update on the shimmy and vibration issue?

Not on my end.
I had scheduled it with a shop that has a Hunter Radial Force Balancer, that is supposed to determine if the wheels and or tires or both are out of round.
Then they can try and eliminate the problem by breaking the tire from the bead and indexing the tire to the wheel for the least amount of runout while under a load.
The machine applies, I believe 1500 lbs of, pressure to the wheel tire assembly while rotating it like a normal balancer would, then it will read out various amounts of runout, etc. The pressure mimics the weight of the car to some degree and provides a much more accurate picture of what's going on. This shop gets $25.00 per tire. I have seen it advertised for less, so I'm waiting for a sale.

Rickw wrote:

Not on my end.
I had scheduled it with a shop that has a Hunter Radial Force Balancer, that is supposed to determine if the wheels and or tires or both are out of round.
Then they can try and eliminate the problem by breaking the tire from the bead and indexing the tire to the wheel for the least amount of runout while under a load.
The machine applies, I believe 1500 lbs of, pressure to the wheel tire assembly while rotating it like a normal balancer would, then it will read out various amounts of runout, etc. The pressure mimics the weight of the car to some degree and provides a much more accurate picture of what's going on. This shop gets $25.00 per tire. I have seen it advertised for less, so I'm waiting for a sale.

Thanks for the update. I'm almost positive it's got something to do with my tires at least mostly anyway. I decided to check the air pressure in the tires the other day and discovered that the two rears were in the 15 pound range and the fronts were in the 25 pound range. So I inflated them all to around 35 pounds. Since then the vibration is more pronounced and at low speeds the so called wobble is also more pronounced. I think the tires are fairly old on this car, because they have some cracks occurring from what looks like weather checking. I can't see any visual signs of damage besides that, but I suppose the cracking could do that....