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DEMonte1997
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Nov 16, 2010 6:37 pm

Not perfect and I echo AA's comments about the vibration going away with aftermarket wheels. I'm sure the control arms on my car aren't perfect and it will eventually need struts but for now the vibration isn't that bad.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Nov 16, 2010 7:05 pm

DEMonte1997 wrote:
Not perfect and I echo AA's comments about the vibration going away with aftermarket wheels. I'm sure the control arms on my car aren't perfect and it will eventually need struts but for now the vibration isn't that bad.
And you have changed wheels on your car, haven't you.? I'm just frustrated at what this car, the Riviera, takes to remove the inherent vibration.
It isn't just one car or even the minority of cars, it seems to be the majority, but not all of them.
Maybe I'm experiencing a worse vibration than some, because as far as I'm concerned, what I have to deal with is not acceptable.

So, being unemployed and essentially broke, I am now officially lowering myself to accept donations.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Nov 16, 2010 8:13 pm

Rick I just got in the BL Shoe for my tire machine, and we should have our balancer running by T-day. Hopefully we can start doing some more extensive tire/wheel inspections and figure out the problem you are having. My brother might even be willing to swap wheels/tires with you until we find your bad wheel/tire.

I had similar problems on a Park Avenue and Regal, and have solved them both. PA turned out to have two bad tires, Regal had a bent rim. We should be able to find it.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Nov 16, 2010 8:21 pm

That sure does piss you off,if she ain't tight,she ain't right!!!
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Nov 16, 2010 8:23 pm

Can you plan some tuning on my pig of an engine. I have lost all noticeable torque below 4,000 RPM and rarely go up there in the power band, but finding I need to just to pass a car.
It's become pathetic.
Rick
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Nov 16, 2010 10:36 pm

...hmmm interesting...very.It`s not the shocks i think.I have a 99 s/c with 31K miles in brand new condition with 7 spoke chrome- all factory and still have the shimmy @ 65-70 mph.The thing with me is sometimes i get it sometimes it`s barely noticeable almost not there.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Nov 16, 2010 10:54 pm

stan wrote:
...hmmm interesting...very.It`s not the shocks i think.I have a 99 s/c with 31K miles in brand new condition with 7 spoke chrome- all factory and still have the shimmy @ 65-70 mph.The thing with me is sometimes i get it sometimes it`s barely noticeable almost not there.
Stan,
Mine is the same way, it is strange, isn't it. But mine has gotten worse with time and also seems to be worse in the winter on a clean highway. Just colder out. Very odd.
Rick
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Nov 16, 2010 11:19 pm

its my uneducated opinion that the way too soft oem bushings are to blame. i believe that if you replace all the oem rubber bushings,all the high speed shimmies will disappear..
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Wed Nov 17, 2010 11:44 am

AA wrote:
For me, aftermarket wheels cured the problem for the 6 months I had them on. The tires that came with the wheels were used, and are now bald, and still no vibration.

When I put the OEMs back on for winter last week (w/ almost new Firehawk WO tires, mounted & balanced), the vibration came back immediately. It's obvious what's wrong, imo.

Firestone tires, in my experience, are not necessarily round enough for a Riv.

Albertj
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Wed Nov 17, 2010 11:50 am

robotennis61 wrote:
its my uneducated opinion that the way too soft oem bushings are to blame. i believe that if you replace all the oem rubber bushings,all the high speed shimmies will disappear..

This makes a LOT of sense, if only beacuse it would move the period of the suspension in a way that would probably quit amplifying natural vibrations. The cradle mounts perhaps could be modified to deal with blocking what would be transmitted as a result. Not sure how practical it is to modify the strut mounts, but someone with expertise may be able to identify mounts form the GM parts bin or aftermarket replacements that would do it. For instance, do the concurrent model Bonneville mounts fit and are they stiffer? Was there a Park Ave Ultra mount for the FE2 option that was stiffer? Dunno. But wish I'd thought of that. Any comments?

Albertj
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Wed Nov 17, 2010 11:53 am

stan wrote:
...hmmm interesting...very.It`s not the shocks i think.I have a 99 s/c with 31K miles in brand new condition with 7 spoke chrome- all factory and still have the shimmy @ 65-70 mph.The thing with me is sometimes i get it sometimes it`s barely noticeable almost not there.

this could be flatspotting on your tires when parked, or enough dirt/mud in the rim.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Wed Nov 17, 2010 12:02 pm

i can take a big pry bar and wedge it in between the front cradle and the chassis and torque the cradle around. side to side and up and down. at speed and under load i can only imagine the stresses the suspension has to deal with? it must somehow translate into shimmies and shakes.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Wed Nov 17, 2010 12:29 pm

robotennis61 wrote:
i can take a big pry bar and wedge it in between the front cradle and the chassis and torque the cradle around. side to side and up and down. at speed and under load i can only imagine the stresses the suspension has to deal with? it must somehow translate into shimmies and shakes.

it's an interesting problem. Seems to me all this road shimmy isolation needs to be done at the strut, control arm and sway bar mounts.

It is instructive to see how other cars are set up. Had an Audi and a Subaru, they were quite different in their own ways. Audi (99 A6 Avant) has a trick multilink suspension that is really hard on its own bushings. Subaru has a fairly simple MacPherson strut and control arm setup

Hmmm...


Last edited by albertj on Thu Nov 24, 2011 2:29 pm; edited 1 time in total
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Wed Nov 17, 2010 12:49 pm

Quote :
Firestone tires, in my experience, are not necessarily round enough for a Riv.

Albertj
Here's what Corvette/Z06 owners are saying about Firehawk Wide Ovals, the Firestone tires I run on my Riv (corvetteforum):

"Ride smooth no problems"

"They are much quieter than the GY SuperCar F1's."

"The GY have a harmonic noise that my wife and I were both bothered by. She used the term "sing" to describe the sound. I DynaMatted the rear and that killed most of the road noise and "singing" from the rear but it was very much present up front (before and after installing the new front tires) so I can only conclude it's a design trait of the GY's. The FSWO's make NO such noise. Second the FSWO are silky smooth. They are much smoother than the GY in any state."

"I was and never been a fan of Firestone tires. I grew up a "GOODYEAR" man. But I have to admit that Firestone seems to have come up with a great high performance tire that should be on any one's short list when it comes time for new tires."

"These are actually Bridgestone RE750 with the exact same spec's renamed as the Wide Oval"

"I have my wide ovals on my Z around 4 months now and they are GREAT!!!!!!!!!!!!!!!!"

"Those FS's are the best bang for the buck that you can get. For just casual open track events at Spring Mtn., I run the FS's and can turn 1:54 lap times compared to 1:51's with the GY's. When I need to pick up the pace, the R-compounds go on, but those FS's are really hard to beat for a nice balance between durability and traction! I'll buy them again."

"They work great at high speeds in the rain and handle greasy track conditions very well. The GYs couldn't come close."

"Definitely the best set of tires i have ever owned for the money"

"I would say they are some of the best tires I have driven on."



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'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
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EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


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albertj
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Wed Nov 17, 2010 1:37 pm

AA wrote:
Quote :
Firestone tires, in my experience, are not necessarily round enough for a Riv.

Albertj
Here's what Corvette/Z06 owners are saying about Firehawk Wide Ovals, the Firestone tires I run on my Riv (corvetteforum):

"Ride smooth no problems"

"They are much quieter than the GY SuperCar F1's."

"The GY have a harmonic noise that my wife and I were both bothered by. She used the term "sing" to describe the sound. I DynaMatted the rear and that killed most of the road noise and "singing" from the rear but it was very much present up front (before and after installing the new front tires) so I can only conclude it's a design trait of the GY's. The FSWO's make NO such noise. Second the FSWO are silky smooth. They are much smoother than the GY in any state."

"I was and never been a fan of Firestone tires. I grew up a "GOODYEAR" man. But I have to admit that Firestone seems to have come up with a great high performance tire that should be on any one's short list when it comes time for new tires."

"These are actually Bridgestone RE750 with the exact same spec's renamed as the Wide Oval"

"I have my wide ovals on my Z around 4 months now and they are GREAT!!!!!!!!!!!!!!!!"

"Those FS's are the best bang for the buck that you can get. For just casual open track events at Spring Mtn., I run the FS's and can turn 1:54 lap times compared to 1:51's with the GY's. When I need to pick up the pace, the R-compounds go on, but those FS's are really hard to beat for a nice balance between durability and traction! I'll buy them again."

"They work great at high speeds in the rain and handle greasy track conditions very well. The GYs couldn't come close."

"Definitely the best set of tires i have ever owned for the money"

"I would say they are some of the best tires I have driven on."



Then explain why yours vibrate. None of those posters had the privilege of rolling on the 4 tires you bought.

As for the generalization about Firestone tires I admit I was being sarcastic - permissible, but not necessarily nice. Apologize if anyone's offended, and here is some perspective: truth is, pretty much no tire is perfectly round. Depends on what runout limit you want to set for roundness.

As earlier discussed on this board, another factor in roundness is "radial force variation." The place where the belts are connected has a different stiffness than the rest of the tire. Michelins don't generally have this problem but they have a trick way around it. I do not really know what it is but I bet it involves making tubes and slicing them for belts instead of wrapping material linearly around a circumference. They have also invented new ways to reduce radial force variation, as shown in the recenlty published patent (it's an easy read)

http://www.wipo.int/pctdb/en/wo.jsp?WO=2010126507

Goodyear research has worked with the Jet Propulsion Laboratory on finite element models for tire construction. Their work resulted at first in the first "Assurance" tires, which were very smooth rolling. Those tires have different rubber in different zones (not different *layers*) on the tread.

At teh global level, tire manufacturers compete in coming up with cost effective ways to hit roundness quality targets. Within country by country though, there's not all that much competition anymore. As for the FIrestones, it's no surprise that Bridgestone has started rebadging Bridgestones as Firestones. Firestone has a loyal following. I tried Affinity LH's for a few days and although I allowed the Firestone store to have my car for most of that time in order t make the tires roll smooth they just could not. Might have been just that shop, but the bottom line was I returned them under the Customer Satisfaction guarantee, and they resold them to someone else who I imagine does little to no highway driving and was happy enough about the "used tire" discount. That is, those tires would probably be perfectly fine on a different car.

PS - article about radials:

http://www.itec-tireshow.com/history/Radial%20tire%20spawned%20industry%20revolution.pdf

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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Wed Nov 17, 2010 1:52 pm

Quote :
Then explain why yours vibrate. None of those posters had the privilege of rolling on the 4 tires you bought.

I've gone through at least 16 of these exact tires since I've owned the car. The result is consistent - always the same, slight shimmy. I've run Michelins, too - same thing. The tires are not the problem. It's the wheels. Suspension parts help, but it originates at the wheels, and cannot always be balanced out.

My new wheels came with a worn set of Bridgestone Potenzas, much the same as Firestone. No vibration at all.

Quote :
As for the generalization about Firestone tires I admit I was being sarcastic - permissible, but not necessarily nice. Apologize if anyone's offended, and here is some perspective: truth is, pretty much no tire is perfectly round. Depends on what runout limit you want to set for roundness.
Then we agree that Firestone tires are no more out of round than any other brand. I was not offended by your sarcasm, just clarifying, as someone could take it literally, since your statement was embedded within more serious discussion.

_________________
'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


'05 GTO 49k miles 0-60: 4.8s 16.9 avg MPG Nelson Ledges Lap: 1:26
Because fun
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PostSubject: vibration in front end...   Mon Nov 21, 2011 2:05 pm

not sure what it is i just got the car i came with new brakes and rotors, I purchased new tires had them balanced 2 times and rotated them from fron to back. car has 110k on it (97) i can feel the vibration a litle bit in the steering wheel around 40 and up the faster the worse it gets . Its not always there but i can feel it slowing down but more durring acceleration. I was going to try and get a allignment on it. The wheel bearing seem to be fine. the tires dont go up and down when i press on them with the car in the air. tie rod boots are cracked but when i shook them and tried to move them their was no slop..... im at a loss for figuring out what it is CV or rack maybe ??
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Mon Nov 21, 2011 2:48 pm

Those things won't cause vibration. You are dealing with a tire/rim issue, or possibly a bent/unbalanced half shaft, although those are not common.

When you rotated the tires did the vibration move from the steering wheel to the seat? Do you know anyone with a similar car you can try swapping wheels with for a test drive?
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Mon Nov 21, 2011 4:45 pm

i did notice one of the rims had a bit of a scuff on the outside edge they ae farly new.. the vibration was a little different but it was still in the steering wheel for me. i took all the rims and tires off the car and washed the inside of the rims like brand new before i had them balanced the second time. I noticed that they didnt take the old wheel weights off 2 of the rims when they balanced them the first time and they did remove all of the wheel weights the second time ( changed all the brake fluid at each wheel)
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Mon Nov 21, 2011 5:13 pm

One thing to have them do is remove the tires from the rims, then spin the rims on the balancing machine. You will be able to see runout or if a rim is particularly bent (curb bump or pothole dent).

Are these OEM wheels? What size tires?

I highly recommend finding someone with a similar vehicle that doesn't vibrate for a test exchange. 98% of the time it's tires or a bent rim.

A tire can have a belt shifted or manufacturing defect causing a vibration that won't show up on a balancing machine. Generally out of balance issues arise over 60, you are feeling it at 40 which makes me think it's more of a physical issue with the tire (or a dent in the rim).
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Mon Nov 21, 2011 8:39 pm

2000ws6transam wrote:
i did notice one of the rims had a bit of a scuff on the outside edge they ae farly new.. the vibration was a little different but it was still in the steering wheel for me. i took all the rims and tires off the car and washed the inside of the rims like brand new before i had them balanced the second time. I noticed that they didnt take the old wheel weights off 2 of the rims when they balanced them the first time and they did remove all of the wheel weights the second time ( changed all the brake fluid at each wheel)

if you can find a place with a Hunter 9700 (it measures radial force variation) and they have a good tech you might find the problem much quicker.

You have a scuffed rim? Might want to check the axle(s).

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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Mon Nov 21, 2011 9:18 pm

albertj wrote:
[You have a scuffed rim? Might want to check the axle(s).

Good point - I missed that clue. A curb strike could have knocked a hub funny as well, although that would take an awfully strong hit.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Mon Nov 28, 2011 11:53 pm

no missing parts of the rim just the paint. I did get a chance to swap rims and tires (front) with a known set of good rims and tires and found most of the vibration to go away. around 70 or so i feel a 3 sec on / 3 sec of minor vibration still so i might save up for some ZZP Axles... going tomm. to get the rims rebalanced in the front and see if the tech can check the rim while it spins for me.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Tue Nov 29, 2011 12:14 am

Tires can even play a large part in vibration at speed. I had some really cruddy tires on a previous car and they could only be road force balanced with one of the hunter machines. Otherwise, the wheels would just shuck off the weights and the vibration was bad. Worn suspension parts play a part but the wheel balance is usually key. Hope you get it figured out.
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PostSubject: Re: Vibration / Shimmy at Cruising Speed   Sun Dec 04, 2011 1:43 am

yeah had all the tires re-balanced and it got rid of most of it going to try and goto my old college and get a free alignment.. then ZZP for some axles if the alignment doesnt fix it. somone put a vent tube or maybe a suction tube on the PS cap and that made the seering a little sloppy too maybe somoone was bleeding the system and forgot to put the cap on or did a crappy job and just left it lol
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