Vibrations

[hjb981]

I am curious about what happened to the STS 98-up and DTS 2000-up sensitivity to imperfections in the tires and their balancing. Has it been cured in later models? For example, how is the DTS 06-up? There were lots of changes on the suspension parts that year.

/Jonas

[Texas Jim]

I have a 2006 DTS and have no issues with vibrations like others have talked about.

[Cadillac Jim]

I have a 1997 ETC that is on its 4th set of tires and have never had a vibration problem.

[OynxSTS]

My 2002 HAD a vibration problem...

Road Force Balanced tire/wheels with a RFB number of less then 10lbs of force per corner solved the problem.

[ted tcb]

On my 2001, RFB and new tires wouldn't eliminate the 65mph shimmy.

What worked for me was a combination of cleaning up the wheel hub and good, old

fashioned lead weights on the outside of the rim.

I believe there was no longer an issue on the newer design DTS/Lux models.

[JohnnyG]

I own a 2008 DTS, and since it is the exact same chassis as the 1998 Seville, I can't see how anything would have changed. The only difference is the absence of the electronic shocks and the road sensing suspension. I'm on the original set of factory Michelins, which were undoubtedly chosen for roundness and conformance to spec. I don't have even the slightest vibration at this time, and no wheelweights on the outside of the rim, but when I need to replace my tires, I'll certainly be very particular.

[hjb981]

I own a 2008 DTS, and since it is the exact same chassis as the 1998 Seville, I can't see how anything would have changed. The only difference is the absence of the electronic shocks and the road sensing suspension. I'm on the original set of factory Michelins, which were undoubtedly chosen for roundness and conformance to spec. I don't have even the slightest vibration at this time, and no wheelweights on the outside of the rim, but when I need to replace my tires, I'll certainly be very particular.

Do those two have the same chassis??? Does that include all the suspension parts as well (if compared to a 98 Seville without the electronic shocks and RSS)? What about 94-99 and 00-05? And by the way, the tires I got for my -97 were Michelin HydroEdge. They have worked fine. Since I moved to Sweden, I am also running Gislaved Nordfrost 3 with the dimension 215/65R16 in the winter. It's a studded tire made of soft, cold temperature rubber. The car runs smoothly with them as well. I use the slightly narrower dimension because it makes the car more stable in slush and snow. It does, however, also make it slightly more "floaty" on dry pavement.

[ted tcb]

To be fair, I don't know of any examples of the shimmy occuring on new vehicles, like an 08 DTS.

My 99 and 01 had the issue develop after experiencing 5 or 6 Canadian winters.

I've always assumed that years of suspension wear, coupled with corrosion on wheel hubs

likely contribute to an imbalance.

I guess it will be interesting to see if an 08 DTS is "shimmy free" by, say,

the year 2014?

'

'

[hjb981]

To be fair, I don't know of any examples of the shimmy occuring on new vehicles, like an 08 DTS.

My 99 and 01 had the issue develop after experiencing 5 or 6 Canadian winters.

I've always assumed that years of suspension wear, coupled with corrosion on wheel hubs

likely contribute to an imbalance.

I guess it will be interesting to see if an 08 DTS is "shimmy free" by, say,

the year 2014?

I once test drove a '99 DeVille that was so badly abused by its owner that the steering wheel had, say, 1/8 turn of play, the wheels were so unaligned that the tires looked burnt on the outsides (from excessive wear), and everything clunked and rattled when going over bumps. Still, that car ran completely vibrationless. The headliner was full of dirt marks (looked like he had used it to dry his hands on after gardening), the upholstery was worn and loose, and the engine was leaking oil badly. I was quite annoyed at the seller. He had used the word "immaculate" in his ad, and also said so when I called him. I had spent two hours on bus and train rides in each direction only to be disappointed.

Was the -99 you had an STS?

[BodybyFisher]

While we have heard about this so called vibration a few times, we dont hear about it a lot. I do believe that all cars are sensitive to out of round and tires that are heavier on one side of the tread causing an up and down imbalance.

Tires can be defective in two directions side to side where standard balancing cures the problem and an imbalance at the tread causing an up and down vibration requiring a road force balance.

Most of the time we have found that the problem is solved with a road force balance

[JohnnyG]

While we have heard about this so called vibration a few times, we dont hear about it a lot. I do believe that all cars are sensitive to out of round and tires that are heavier on one side of the tread causing an up and down imbalance.

This is very true. I have a friend that bought a set of tires which were "bargain basement" versions from a reputable manufacturer. They were NOT round, and caused his pickup truck to shake at speed, despite them being perfectly spin balanced. Moving them around and replacing with a known good tire eventually revealed the problem tire.....the rest were "good enough".

We expect our cars to ride EXTREMELY vibration free, which does cause us to scrutinize the ride a little more.

I believe that the use of aluminum suspension parts and wheels, in an effort to reduce not only unsprung weight (improving ride control) and overall weight (improving fuel economy), combines with suspension design and electronically controlled components to emphasize any effect out of spec tires might produce. This is more apparent on some models that others, so my '08 DTS with "dumb" suspension, would be less susceptable to say Texas Jim's performance DTS.

[ted tcb]

Was the -99 you had an STS?

Yep, I've owned 4 of them to date.

The 1999 had the vibration when I test drove it ... I was trading in a 97 STS.

I even had the dealer put my OEM 97 rims/tires on the 99, and the vibration was still there.

I bought the car anyway, because I "had to have" the newer body style.

The vibration never went away.

On my 2001 STS, I had Pirelli's. RFB did not eliminate the issue, new tires didn't help, and it was still

prevalent with my winter steelies and snow tires .... sooooo, rubber and rims weren't the issue for me.

However, cleaning the hubs and putting on "lots" of old fashioned lead weights masked the vibration to the

point where I really couldn't notice it, so I was satisfied.

Remember that "Logan" tried every fix imaginable for his converted DTS. He tried suspension pieces, RFB, you

name it. He eventually found virtually brand new take off rims and factory Michelins, and it was like driving a new

car for the first time.

His belief was that the truest "round" tires go to the the manufacturer, then the dealerships, then the largest

tire retailers, and so on. The thought was that every single tire built gets RFB'd by the manufacturer, and then the

best tires go the assembly line.

I agree with those that say these cars are very susceptible to tire/rim/suspension imperfections, which likely increase as

the car's age.

I don't have a clue as to why a beater STS still rides pure without any shimmy.

Maybe its the same reasoning as to why some neglected Northstar motors never experience a HG problem, while

some well maintained STS' suffer from pulled headbolts?

But yes, I have a compulsion for STS', especially with tint and chrome wheels.

Unfortunately, I've never had the resources to buy one brand new ... mine always come

with about 70k on them.

In the spring, I plan on picking up an 03/04 with magnaride ... there are great values to be

had, especially if gas prices go up.

[Cadillac Jim]

I got an out-of-round tire on my 1959 Chevrolet once. I ended up putting it on the rear, where the effect was not so noticeable. The Firestone dealer stonewalled me. I think that this may have been my last bias-ply tires; I already had radials on my Corvette from the week I bought it.

[Logan]

For JohnnyG...everything changed in 2006. The cradle changed..all the forward suspension parts changed..all the engine mounts change. Completely different then any '98-2005 model.

I did a paper in college about tires. Tires are just about the hardest thing to manufactor. No 2 tires come out the same.

Tires are rated. Some even have a manufactures spec #. A GM spec Deville Michelin may look the same as one from the Tire Rack, but they are in fact very different Michelins.

Cadillac does sell GM part # tires. These tires are different then those available from Tire Rack.

Tires are RFB at the tire plant. All the car manufactures are very sensitive to RFB. The best tires go to the OEMs. GM, Ford, Honda, etc plants etc...the next so-so go to the tire stores..the next go to Tire Rack.

In a what used to be 17 million new car market. Your talking about the best first batch of 60 million tires are going directly to the OEMs. The scraps left over are being sold thru tire stores.

Tire mounting and balancing praticies also weigh in. You can ruin a tire in seconds if you do not mount it correctly. You will never see the damage. What? They pay tire techs what $9 bucks an hour...lots of turnover at those rates.

Hunter Road Force balance is only as good as the tech doing the work.

Be sure to see the posted Tire picture.

This is a 2007 OEM Cadillac DTS wheel with factory mounted Michelin. These wheels / tires were 5 mile take offs. Note! Only 2 small weights on the wheel. Try that on a set from Tire Rack.

[Logan]

Part 2: Motor Trend had a short article about 'reading' tires. It discussed the GM IPC spec and the BMW 5 star molding in the tires. It's at work. I will try to grab it back..

Anyway. Deville /Seville were set up just like mid '90 Ford Taruas in the engine mount design. Hydro mounts no dogbones.

These Cadillacs feel exactly like the Fords.

Freaking bean counters.

Here is a pic on my 2001 Deville using modified using 2001 Edlo dogbone mounts. This conversion makes a big difference...ausuming you also have good OEM tires

[ted tcb]

Nice post, Logan.

As I recall, you went to extreme lengths to cure your shimmy, until you found

a perfect OEM tire/rim combo.

I believe you mentioned that you could finally feel what a new Cadillac should feel

like, before you even exited your driveway!!

Has your car remained vibration free since the switch?

[Logan]

Car is driving the best it ever has. That said, someday I will have to get the tires balanced. All the current OEM weight locations will be marked.

The other trick will be finding someone with a Hunter that knows what they are doing. I think a good Hunter job should be about 20 minutes per wheel.

As for the OEM tire markings..Car And Driver, October 2009 issue, page 26.

"Original Equipment (OE) Marking: These letters- or a symbol- indicates that this is the automaker -specified version of a tire that came as a car's original equipment. These tires can often be a very different blend of rubber compound compared with the-off-the-shelf variety of the same tire, even though the tread pattern is identical. Examples of OE markings: General Motors- all have a TPC SPEC number; BMW -most have a five-pointed-star symbol; Mercedes- some are emblazoned with 'MO'; Porsche- all have the letter "N" followed by a number, i.e., N1, N2, etc."

[hjb981]

Lots of interesting reading! Especially about the conversion to give an '01 DeVille dogbones. I have a couple of questions for Logan regarding that: how easy would you say such a conversion is? And would you say that an '01 DeVille with the conversion gets to be as smooth as a '99 or earlier DeVille? Actually, the dogbones was the first thing I ever replaced on my car (since they were completely worn out when I bought it), but the car ran smoothly also before getting the new dogbones.

[OynxSTS]

Hunter Road Force balance is only as good as the tech doing the work.

I'll repeat the most important part of that post...

Way to often we will get people who say "I had the RFB procedure done and it did't solve my problem"

But when asked what the RFB numbers were on their RFB report... we get "What report?", or "There was a report?", or "The guy said they were 'really' good" or when they actually have the report we get RF 15# LF 20# RR 29# LR 35#... Yes those numbers are TERRIBLE AND you will feel them.

If you take the time and expense to get the RFB done you should leave the shop with a computer report that tells you what the tire/wheel road force was before and after the balance... Unlike a spin balance, RFB will not always result in a PERFECT balance... it will be the best they can do...

If the tire is a POS then it is very possible that a tire/wheel combo can still generate 15-20 pounds of force AFTER the RFB has been done.

And you will FEEL that in these cars... You need the report! And you need to have numbers LESS then 10 pounds... You will feel any tire over 15 pounds and most can feel a tire over 12 pounds.

Demand single digit RFB... Simple as that.

[JohnnyG]

For JohnnyG...everything changed in 2006. The cradle changed..all the forward suspension parts changed..all the engine mounts change. Completely different then any '98-2005 model.

The only visible difference is the engine mount, which we have discussed here before. I do know sometimes the vibration has been traced back to the mounts, but I didn't know it was a redesign, thanks for that. I DO know acceleration is a lot smoother (in the suspension) on the DTS, but the rear road noise is about the same as the '99 STS.

While we're at it, I saw a 2009 DTS at the dealership the other day. The sticker had about an $800.00 add on from the dealer which they called sound deadening and appearance package. Does anybody know exactly what they might do to make these cars quieter? I didn't really check, but I think I can rule out undercoating. What do you think?

[Wildcard]

hmmm i wounder if this is the problem im having. what im exping is this. at 60 or 65mph i start getting a vibration in the front end. it will vibrate for a couple seconds then it will smooth out for a few seconds then repeat. it gets worse at 70+. how ever its evens out when i accelarate but soon as i take my foot off the gas it starts wobbling again. do u guys think this is my problem?

[JohnnyG]

it will vibrate for a couple seconds then it will smooth out for a few seconds then repeat. it gets worse at 70+. how ever its evens out when i accelarate but soon as i take my foot off the gas it starts wobbling again. do u guys think this is my problem?

A tire with a road force issue is very hard to pinpoint, it feels like it moves around the car, especially if more than one tire is out, since the phasing of the vibrations differ as the tires warm up or cool down.

I doubt that road force ever made the archives, it is just too elusive to fix and none of us have ever reached a consensus on what is exactly needed to fix it. Some never succeed, just make it acceptable and live with it.

If your problem is DIRECTLY related to lifting the accelerator and not the CHANGING SPEED of the car, I'd look at CV joints or bearings first.

If you want to go the Road Force balance route, find somebody with a Hunter road force balancing machine that knows how to use it and is WILLING to do the needed work. For practicality sake, I recommend getting the tires under 10 pounds of road force, some will tell you that under 5 is required to remove all vibration.....this is very hard to achive. I always say to make sure your tires are warm before starting the process, pulling a car into the tire bay that has been sitting overnight will give false readings.

[Logan]

JohnnyG....we were really interested in when the 2006's came out. Cradle is different design..solid mounted to the car rather then float style. Front lower control arms completly different style. Engine mounts all over the car are different. I think the only one that remains the same is the front lower mount. There is a interesting lower trans to cradle mount on the passenger side. I'll try to get a pic.

As for the 2001 Eldo dogbones. Very worthty upgrade. The passenger side cylinder head bracket needs to be slightly modified. The Eldo uses different alternator mounting point..go figure. The driver side bracket is rare. Maybe 10 new brackets left thru the GM dealer / vintage parts source.

The actual dogbones are cheap AutoZone parts. Forward radiator mounts are actual modified chunks of barn door hardware from Tractor Supply. Pretty easy mod.

The dogbones really help cure the engine 'flop' you feel in these cars.

As for tires. Here again we hearing about 'phase in' and 'phase out'. Tire balance /bad tires. Hunter Road Force will not fix a bad tire. Hunter RF is only as good as the tech willing to spend the 20-30 minutes per tire to do it right. We just have to find that tech...

Every roational vehicle will have some measurable vibrations.

Roads: In our case...25% of the problem is the roads where I live. In TN, we have very heavy truck traffic on hot black summer asphalt. This leaves a pattern in the road. If you look at some of these truck/trailer tires. They are so sprung with tire wear you wonder if they are legal. Real bad. Plus most are recaps. No wonder the asphalt has pattern issues.

JohnnyG has a good point. GM has a bulletin about driving the vehicle about 20 miles before road force balancing. This gets the flat spots out of the tires. That said, I live 14 miles from work. So technically, my flat spots never go away before I get home.

Most GM products, the engine mounts are designed to reduce the torque axis of the engine. The 1998-2005 design seems to throw this idea out the window.

For JohnnyG. Here is a pic of one of the new 2006 mounts. This one is located behind the rear, lower, passenger side, outboard side of the trans and the cradle. This and the huge upper passenger side dogbone on the 2006 is really the same idea as the 2001 Eldorado dogbones.

The rear mount lower shown should work on 1998-2005 models with some mods. The upper huge dogbone will not. It's where all the AC lines are.

The 2001 Eldo dogbones are easier and cheaper to do.

[Wildcard]

it will vibrate for a couple seconds then it will smooth out for a few seconds then repeat. it gets worse at 70+. how ever its evens out when i accelarate but soon as i take my foot off the gas it starts wobbling again. do u guys think this is my problem?

A tire with a road force issue is very hard to pinpoint, it feels like it moves around the car, especially if more than one tire is out, since the phasing of the vibrations differ as the tires warm up or cool down.

I doubt that road force ever made the archives, it is just too elusive to fix and none of us have ever reached a consensus on what is exactly needed to fix it. Some never succeed, just make it acceptable and live with it.

If your problem is DIRECTLY related to lifting the accelerator and not the CHANGING SPEED of the car, I'd look at CV joints or bearings first.

If you want to go the Road Force balance route, find somebody with a Hunter road force balancing machine that knows how to use it and is WILLING to do the needed work. For practicality sake, I recommend getting the tires under 10 pounds of road force, some will tell you that under 5 is required to remove all vibration.....this is very hard to achive. I always say to make sure your tires are warm before starting the process, pulling a car into the tire bay that has been sitting overnight will give false readings.

Thank you for the reply.It def changes as the speed of the car goes up or down. I first notice the vibration at 60MPH but it gets worse the faster i go. Just that if i give it heavy excelaration it stops. and like i said it it will vibrate for a few seconds then stop for a few seconds the start again. the tires on the car are some name brand iv never heard of called blue streak or blue something lol. They were on the car when i got it.

[hjb981]

JohnnyG....we were really interested in when the 2006's came out. Cradle is different design..solid mounted to the car rather then float style. Front lower control arms completly different style. Engine mounts all over the car are different. I think the only one that remains the same is the front lower mount. There is a interesting lower trans to cradle mount on the passenger side. I'll try to get a pic.

...

"Solid mounted to the car" - does it mean that it does not have the rubber bushings between the cradle and frame as my '97 does? Doesn't that affect noise and (other) vibrations in a negative way? One less bushing to go through... Or has it been compensated for? Or am I misunderstanding it?