the shakes

[joeydax]

So, new tires, new hubs, alignment, and she still shakes. My struts are good, my wheels aren't bent. What else could it be? And could I fix it? Thanks guys.

-Joey

[Ranger]

Road force balance

[BodybyFisher]

Check for bent wheel studs, out of round bolt holes in the wheel, lugs that bottom out before they tighten the wheel. Check for an out of round tire and have the wheel road force balanced. Check your inner and outer tie rods and look for a loose rack.

What make of tire?

Stock OEM wheels?

Check for run out with a dial indicator

Check for debris on the hub flange and wheel seat

Make sure the lugs are torqued evenly

[ted tcb]

Good point on checking for debris.

On my new tires, one front wheel hub needed to be cleaned up, as well as the studs.

Also, the inside of my rim had some oxidation.

A thorough cleaning and a second wheel balance definitely quieted down any shaking for me.

[Dadillac]

I think that it has to do with the front end alignment. Anytime I install new tires, or rotate my tires, the shimmy almost disappears. That is until the tires have a few miles on them. The alignment specs are fairly broad, and I would love to have someone who has a Seville, that doesn't have the shimmy, post thier alignment numbers. My alignment checks out within spec. But side to side there are great differences. I am wondering if this is the issue.

Don

[Ranger]

Funny you should mention that Don. I had an alignment last fall and was just comparing the numbers to the FSM specs an hour ago. There is a max cross camber and caster allowable differential. Not sure what it is on the Seville, but I think it was something like 0.50 degrees on the Deville.

[JimD]

.... and I would love to have someone who has a Seville, that doesn't have the shimmy, post thier alignment numbers. My alignment checks out within spec. But side to side there are great differences. I am wondering if this is the issue.

Don

Yes the spec's. are very broad. Generally speaking, for a street vehicle, it is nice to be in the middle of the range but it's not that important. In order to "adjust" camber or caster, it is necessary to enlarge the bottom mounting holes in the strut, or the top mounting holes for the strut bearing. And that should not be necessary unless there has been collision damage. The first time you have the front end apart to change a strut assembly, you will see what I mean.

I cannot tell you my numbers because my '98 has not been on an alignment rack. Not even after I replaced the OEM struts at 146,000 miles.

The issue is vibration in the rotating mass. Wheels, tires, lug nut torque procedure, brake rotors, steering knuckle bearing, axle shaft.

[joeydax]

Well it is mainly on the highway. The studs are new on hub, and everything around the hub looks good. Some of the stuff you guys suggested is a little over my head. I just don't want to take it to the dealership for it.

[Dadillac]

.... and I would love to have someone who has a Seville, that doesn't have the shimmy, post thier alignment numbers. My alignment checks out within spec. But side to side there are great differences. I am wondering if this is the issue.

Don

Yes the spec's. are very broad. Generally speaking, for a street vehicle, it is nice to be in the middle of the range but it's not that important. In order to "adjust" camber or caster, it is necessary to enlarge the bottom mounting holes in the strut, or the top mounting holes for the strut bearing. And that should not be necessary unless there has been collision damage. The first time you have the front end apart to change a strut assembly, you will see what I mean.

I cannot tell you my numbers because my '98 has not been on an alignment rack. Not even after I replaced the OEM struts at 146,000 miles.

The issue is vibration in the rotating mass. Wheels, tires, lug nut torque procedure, brake rotors, steering knuckle bearing, axle shaft.

Jim, that would not explain why my car shimmies, but after rotating the rear tires to the front, the shimmy almost disappears. Then after some miles, it reappears. That leads me to believe that the front end is wearing the tires funny, and when switched to the rear, the tires become corrected again. I know all about the non adjustable front end on our Seville's. But I also remember getting an alignment (before I knew about this) that the numbers were within spec, but very different from left to right. I am very eager to find out what the numbers are for a Seville that does not shimmy. That may be the answer to this problem.

Don

[joeydax]

so is this just an issue with the sevilles? I was going through my car history, and the pervious owner had some work done. it says the replaced the the lower steering shaft, lubed it, rplaced a bearing and retainer. not knowing if any of that would have to do with anything.

[RJSUS]

so is this just an issue with the sevilles? I was going through my car history, and the pervious owner had some work done. it says the replaced the the lower steering shaft, lubed it, rplaced a bearing and retainer. not knowing if any of that would have to do with anything.

IS it a constant thing or does it let up under acceleration? If it seems to get a bit worse after letting up on the gas, I'd bet it was a tie rod or bushings

[Logan]

This issue has been around for years. I think everyone understands the tires need to be good road force wise. Also GM has updated a TSB that the car should be driven 10-20 miles before road force balance.

Anyway, todays development...

Dcadillac will be happy to hear this. I just did an experiment 20 minutes ago and the car drove like a differnet beast...I loosened the front stabilier links. Loose enough I can rotate the inner shaft. Make sense?

The theroy is if the links are too tight...it creates a second suspension system. It is human nature to snug the links up as far as they will go. That creates a 70 mph quiver.

[tjtjwdad]

A question for all of those with the 70 MPH shakes?

Have you folks ever noticed if the shakes/vibration occurs at the same place on the highway, in other words have you considered it to be the road itself?

The reason I ask, is because my 01 sees a lot of I-5 between Portland, OR and Seattle, WA. For the most part the ride is like glass. But there are spots where the vibration is present. When I first detected it, I would chage lanes and when I got out of the normal wear sports (ruts if you will) the vubration would subside considerably and in most cases go away all together. I've also noticed this as well when using US-30 instead of I-5 but the speed is reduced considerably, so its not as noticible.

Jim

[Dadillac]

A question for all of those with the 70 MPH shakes?

Have you folks ever noticed if the shakes/vibration occurs at the same place on the highway, in other words have you considered it to be the road itself?

The reason I ask, is because my 01 sees a lot of I-5 between Portland, OR and Seattle, WA. For the most part the ride is like glass. But there are spots where the vibration is present. When I first detected it, I would chage lanes and when I got out of the normal wear sports (ruts if you will) the vubration would subside considerably and in most cases go away all together. I've also noticed this as well when using US-30 instead of I-5 but the speed is reduced considerably, so its not as noticible.

Jim

With my car, I do not attribute the shimmy to road conditions. My front tires seem to be wearing funny. I can do a tire rotation right now, by bringing the rear tires to the front, and the shimmy will almost disappear. So that leads me to believe that the frontend is causing the issue, not the road itself. By putting the front tires on the rear, it gives them some miles to "repair" themselves. Then on the next rotation, all is well again. That is until a few miles are driven, and the tires start wearing funny again.

Don

[Dadillac]

This issue has been around for years. I think everyone understands the tires need to be good road force wise. Also GM has updated a TSB that the car should be driven 10-20 miles before road force balance.

Anyway, todays development...

Dcadillac will be happy to hear this. I just did an experiment 20 minutes ago and the car drove like a differnet beast...I loosened the front stabilier links. Loose enough I can rotate the inner shaft. Make sense?

The theroy is if the links are too tight...it creates a second suspension system. It is human nature to snug the links up as far as they will go. That creates a 70 mph quiver.

Logan, please man, update this thread around the end of July, to inform us if your fix continued to work. If it doesn't, please update as soon as you can. Inquiring minds are interested. Thanks

Don

[JohnnyG]

With my car, I do not attribute the shimmy to road conditions. My front tires seem to be wearing funny. I can do a tire rotation right now, by bringing the rear tires to the front, and the shimmy will almost disappear. So that leads me to believe that the frontend is causing the issue, not the road itself. By putting the front tires on the rear, it gives them some miles to "repair" themselves. Then on the next rotation, all is well again. That is until a few miles are driven, and the tires start wearing funny again.

Don

So, did you have the tires road force balanced or not? I cured mine on the '99 with a road force balance of under 10 -15# on all 4 tires. I think one other person here has done the same thing. No loosening of the front stabilizer links, nothing mechanical, just the tires.

This is not a problem specific to the Seville, but it is most prevelant in this and other models that share the same platform, ie Buick. It has a lot to do with the reduction of unsprung weight and the front drive design.

If the tires are "wearing funny" you need to get that fixed first. After that, you can buy new tires armed with the knowledge that they need to RFB below 10# or you will not buy them. I'd take it to a Caddy dealer that has experience with alignment on these cars. They do get special "Goodwrench" patch for alignment expertise, after all.

[JohnnyG]

Logan, happy to hear that Caddy amended the TSB. I think I suggested that to members of this board a year or two ago. The intent is to avoid tires that are "flat spotted" from sitting overnight in cool weather. This condition gives false indications to the Hunter RFB machine, and induces errors into the process. Get the tires warm before getting a road force balance done.

[Dadillac]

With my car, I do not attribute the shimmy to road conditions. My front tires seem to be wearing funny. I can do a tire rotation right now, by bringing the rear tires to the front, and the shimmy will almost disappear. So that leads me to believe that the frontend is causing the issue, not the road itself. By putting the front tires on the rear, it gives them some miles to "repair" themselves. Then on the next rotation, all is well again. That is until a few miles are driven, and the tires start wearing funny again.

Don

So, did you have the tires road force balanced or not? I cured mine on the '99 with a road force balance of under 10 -15# on all 4 tires. I think one other person here has done the same thing. No loosening of the front stabilizer links, nothing mechanical, just the tires.

This is not a problem specific to the Seville, but it is most prevelant in this and other models that share the same platform, ie Buick. It has a lot to do with the reduction of unsprung weight and the front drive design.

If the tires are "wearing funny" you need to get that fixed first. After that, you can buy new tires armed with the knowledge that they need to RFB below 10# or you will not buy them. I'd take it to a Caddy dealer that has experience with alignment on these cars. They do get special "Goodwrench" patch for alignment expertise, after all.

No I have not had this set of tires RFB. Since I bought the car in Nov '04, I have had 4 brand new sets of tires on this car, and four sets of wheels. I had set number two RFB, and my shimmy actually had gotten worse. I will not have another set RFB. It is impossible to think that 16 brand new tires would all need to be RFB. This is something deeper.

Don

[Dadillac]

Double post.

Don

[tommysls]

.... and I would love to have someone who has a Seville, that doesn't have the shimmy, post thier alignment numbers. My alignment checks out within spec. But side to side there are great differences. I am wondering if this is the issue.

Don

Yes the spec's. are very broad. Generally speaking, for a street vehicle, it is nice to be in the middle of the range but it's not that important. In order to "adjust" camber or caster, it is necessary to enlarge the bottom mounting holes in the strut, or the top mounting holes for the strut bearing. And that should not be necessary unless there has been collision damage. The first time you have the front end apart to change a strut assembly, you will see what I mean.

I cannot tell you my numbers because my '98 has not been on an alignment rack. Not even after I replaced the OEM struts at 146,000 miles.

The issue is vibration in the rotating mass. Wheels, tires, lug nut torque procedure, brake rotors, steering knuckle bearing, axle shaft.

[tommysls]

When I got my 98sls many years ago I also experience the shakes. Not allignment, balance, tires, then I went to a mechanic at a dealership who was an eperienced oldtimer. He immediately explained that it was the rear rotors. Make repair and the shakes were gone.

Ever since it has been the case with my sls.

[OynxSTS]

So, did you have the tires road force balanced or not? I cured mine on the '99 with a road force balance of under 10 -15# on all 4 tires. I think one other person here has done the same thing. No loosening of the front stabilizer links, nothing mechanical, just the tires.

If the tires are "wearing funny" you need to get that fixed first. After that, you can buy new tires armed with the knowledge that they need to RFB below 10# or you will not buy them. I'd take it to a Caddy dealer that has experience with alignment on these cars. They do get special "Goodwrench" patch for alignment expertise, after all.

Ya that was me... My 2002 would shake at 68 MPH like a vibrator in the seat..

You need three things to fix this...

1) you need to find a shop with a RFB machine and

2) you need to find a shop that knows how to use it, last and most important

3) you need to leave the shop with the RFB report that tells you how many pounds of force each tire is generating...

IMO 15 pounds is way too much... you will be able to feel 15 pounds... I can feel road force of 12 pounds on my car...

Once all of my tires were in the single digits of Road Force (the worst one is 8 pounds the other three are 5# or less) the vibration was GONE. She rides like a magic carpet now :)

On my car, NO other repairs were required.

Get the RFB done again and this time have them report the BEFORE and AFTER road force readings...

For new tires REFUSE any tire with RFB numbers greater then 10 pounds...

Make sure they do it right... Watch them use the machine... it is kinda cool to watch..

Good Luck...

Edit: BTW very few if any 2004's have this problem... GM switch from the BadYear RSAs to a better Micheline tire...

[JohnnyG]

IMO 15 pounds is way too much... you will be able to feel 15 pounds... I can feel road force of 12 pounds on my car...

I agree wholeheartedly! However, for the sake of practicality, I generally quote 15# to be acceptable. I undersand that you can still feel 15#, even 12#, but sometimes that evens out with wear. Mine rides like glass right now, and I'm not touching the tires until I absolutely need to. Single numbers are best, but hard to achieve.

It is very difficult and time consuming to teach a tire shop how to deal with this problem. They will very rarely admit that they are selling a tire that is not suitable for your car. Most, even though they have a Hunter machine, still don't know EXACTLY how to use it. Not from an "instruction manual" point of view, but in how it relates to the real world. It took GM SEVERAL years to say that the tires need to be warm (or just off the rack) so how long would it take a tire shop to understand exactly what is happening?

Well Dadillac, I think you can rule out wheels, studs, tightness of the lug bolts, mud, corrosion, suspension modifications, and the like. I'd look for worn parts, bad CV joints, HORRIBLE alignment, bad wheel bearings, and finally just plain junky tires if I were you. You never did say exactly when the shaking begins, did you? At what speed and under what conditions does this happen?

[Dadillac]

IMO 15 pounds is way too much... you will be able to feel 15 pounds... I can feel road force of 12 pounds on my car...

I agree wholeheartedly! However, for the sake of practicality, I generally quote 15# to be acceptable. I undersand that you can still feel 15#, even 12#, but sometimes that evens out with wear. Mine rides like glass right now, and I'm not touching the tires until I absolutely need to. Single numbers are best, but hard to achieve.

It is very difficult and time consuming to teach a tire shop how to deal with this problem. They will very rarely admit that they are selling a tire that is not suitable for your car. Most, even though they have a Hunter machine, still don't know EXACTLY how to use it. Not from an "instruction manual" point of view, but in how it relates to the real world. It took GM SEVERAL years to say that the tires need to be warm (or just off the rack) so how long would it take a tire shop to understand exactly what is happening?

Well Dadillac, I think you can rule out wheels, studs, tightness of the lug bolts, mud, corrosion, suspension modifications, and the like. I'd look for worn parts, bad CV joints, HORRIBLE alignment, bad wheel bearings, and finally just plain junky tires if I were you. You never did say exactly when the shaking begins, did you? At what speed and under what conditions does this happen?

I have the "Classic Shimmy" between 60 and 75 mph. I have installed new struts, shocks, wheel bearings (all 4 wheels), tie rod ends, brakes (several times), many wheels and tires. I get no shimmy before 60 mph, and it disappears after 75 mph. The shimmy did not feel any different with any of the sets of tires that I had on the car. This makes me rule out a RFB as being a fix. It doesn't appear to be tire related, as much as it seems to be vehicle related. I am holding off on getting the control arms replaced as they are quite expensive, and many have stated that it did not fix the problem. But it would seem that the only things left are the ball joints or the control arm bushings. Unless like I siad in a previous post, it has something to do with the front end not being synced side to side.

Don

[JohnnyG]

That's the "classic" RFB shake if you ask me. When you had the tires rfb'd, what kind of numbers did you end up with? I suppose a very bad alignment might cause this, but my money's still on the tires.