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Discussion Starter #1
I have 96k on my '08 and I have started to notice some shake through the steering wheel. It happens during moderate or heavy breaking from highway speed to a crawl. I'm in San Diego so 70mph to 10mph happens regularly. I replace my rotors and pads just over a year ago and they only have 15k on them so figured it's not them.

Either way, I performed most of the checks at the following post:
http://www.g8board.com/forums/showthread.php?t=90746

The "rear most Ball Joint in the Control Arm" and "Checking the Tie Rods" both exhibit play. How can I tell which needs to be replaced? Or do I just need to replace both?
 

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I have a similar issue as yours, but I'm pretty sure mine is due to rotors. When I ease on the brake pedal the steering wheel can and often shakes pretty violently and lately I've even heard/felt movement and knocking up front during that time. If I press the brakes hard or let off the shake and other issues go away. I have Rotors in the mailbox at the moment and I plan on putting them on this weekend. I'll keep up with you in case my problem doesn't get fixed. Otherwise I'm not really sure about yours being the tie rods or control arm. I just replaced my control arms not to long ago actually, to get rid of the dreaded clunking (which didn't fix it), and end links more than a year ago. Best of luck with yours.
 

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Discussion Starter #3
Thanks for the response. My brother and I checked out my rotors and all four showed signs of grooving after only a year so I replace the fronts with 2004-2007 CTS-V Brembos and the rears with the stock setup. I was hoping that would resolve it and it pretty much did. But since I added the Brembo's I had to add a 15mm spacer and I have some general steering wheel shake between 40-60 whether accelerating or braking. When I did the brakes I also did the struts so I got an alignment, and also balanced and rotated the tires. The shop checked the tie rods, controls arms, and bushings and said everything looked fine. So my only assumption at this point is either the steering rack or the spacers. It's not a bad shake though, if I strongly grip the wheel the shake goes away, not sure what that means. Either way, I'm probably going to switch to Camaro 20's at some point so who knows.

Side note, big Chiefs and Joe's Kansas City Bar-B-Que Fan!
 

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If you haven't already, road force balance the tires. You might have thrown a weight. Or if you recently had the tires rotated after your brake job, have them rotated again. My G8 is very sensitive to front wheel/tire balance and many other G8 owners have had the same issue. It leads to steering wheel shake/wobble and there is no single solution. But starting with rotating tires and/or road force balance is generally the first step with G8 steering wheel shake if you are *sure* that your rotors are in good shape.

That said, if you had the rotors turned 15000 miles ago maybe they warped out already. I had a set of rotors warp almost immediately after turning (a few thousand miles later) so don't count that out. Doesn't cost much to pull the rotors and check for warping.
 

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Discussion Starter #5
I had never heard of road force balancing, thanks for info! (Link for others: http://www.motorweek.org/features/goss_garage/road_force_balancing)

I'll rotate them tonight and see what that does. Otherwise, i'll have to check with the shop who did the alignment and balance last week and see if they have that system. I doubt it so I' may on the search for a shop that does.
 

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If the shop says that 2 of the wheels/tires are "better" than the other 2, have them put the best 2 on front. Sometimes that makes a big difference.

Since your shaking is mostly under braking though, I'm almost leaning towards suspecting one of these 3 things:
1. Brakes went bad early (uneven pad wear or rotors warped)
2. Something is put put on straight. Rust or debris on the rotor or hub can cause the rotor to be re-mounted slightly off-center. Also if it was resurfaced with a little rust on the mounting surface, it'll be perfectly wobbly :)
3. The wheels/tires aren't balanced or they torqued them down off center or unevenly
 

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Discussion Starter #7
1) Yup, replaced fronts with Brembo and rear with stock
2) Shouldn't be the cause, everything replaced is new and/or clearned
3) Looking into rotating and the road force balance (still love that they are now doing this)

Thanks again!
 

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Shocker...another shaky G8. I have been chasing this down for quite some time with no success. Best of luck.
 

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Discussion Starter #9
Shocker...another shaky G8. I have been chasing this down for quite some time with no success. Best of luck.
Do you have a post that talks about what you've done? Just curious.

My tires have about 50k on them and between that and the spacers for the CTS-V brakes I'm sure that all doesn't help. Luckily the shaking under braking has disappeared but that 40-60 steady driving is annoying.

I've been thinking about upgrading to 19's anyway so this might just be the kick in the butt but curious what others have done. Thanks.
 

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http://www.g8board.com/forums/showthread.php?t=173898
I cannot just accept that this is how it has to be. The car drove perfect for years. Something has to be loose, and I cannot track it down. Frustration!
You replaced the rotors and calipers, right? Maybe put the old parts back on or buy some cheapo OEM style rotors to see if that changes things.

Also, small alignment changes can change the pre-load steady state forces on the wheels. They might be happier with a little toe in or out to put some load on them while driving straight, or may prefer more or less camber and/or caster.

My brother had a car that had un-fixable front end shimmy when he used wider aftermarket wheels. The car was an old econobox and ran just fine with stock parts, but when he put on wider wheels the geometry and force balances all changed to where the tires would wobble badly at several different speeds. Nothing can possibly fix that except radically changing the geometry to make it stable again. Maybe a different offset, or different weight wheels/tires. Maybe adding a 10 lb weight to the steering arms would have done it. Regardless, something made it dynamically unstable.

And that's the point I'm making with swapping parts. If you just swap existing parts for newer stock-shape/weight parts with better bushings, you're not changing the inherent dynamic instability. You're just dampening it out with stiffer bushings. You need to change the dynamic system with geometry (alignment or wheel size/offset) or weight. Geometry changes can eliminate the vibration, weight changes will probably only shift the vibration issue to a different speed range.

Lighter wheels and even lighter or heavier brake rotors/calipers will affect that. Same goes for alignment changes or wheel size/offset changes. I suspect that the entire front end was only marginally stable to begin with and they pushed it out the door for sale without solving it in the first place. They just picked the best of what they had and hoped it would be good enough that people wouldn't notice.

It could be *anything*, even those stupid dangly weights in the back of the car that many people remove, if it changes the dynamic harmonic vibrations in parts of the car. A tiny vibration in one spot can be amplified through suspension components and if they end up focused on the steering components, you bet we'll feel them through the steering wheel.

Heck, you've seen this yourself while pushing around shopping carts. Most go just fine but sometimes one of the front castered wheels on a shopping cart will freak out and vibrate like crazy, right? Why does only that one cart do it and not other identical carts? Put a 24 pak of soda in the cart, and suddenly that front wheel doesn't do that anymore. Why did just increasing the load stop the vibration? Same thing with our cars. And GM doesn't seem interested in engineering a solution or sharing what they know about it, so EF them and the horse they rode in on. :whine:
 

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Even a different tire tread depth can change things. My stock OEM RSA tires wobbled badly and I had them road force balanced by the dealer about 5 times. But at 25000ish miles suddenly they didn't get worse again over time after a balancing, like they did before. As the tires got old/hard for some reason they didn't wobble nearly as much.

And my new tires don't wobble at all. Nothing changed with the car but the new tires, and that eliminated 99% of the wobble. Weird.
 

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I certainly appreciate all of your input. It seems odd that it would start out of nowhere. I have brand new rims/tires, all rf balanced. I struggle with "changing the geometry" as the current geometry worked just fine for 43000 miles. I feel I have to have a bad part somewhere, I just cannot seem to locate it. Wheel bearing? Steering rack? All spendy parts to just throw at the car. That is just my simple thinking.
 

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I had this same exact problem on another car, it was the front upper control arms and it took a very long time to figure it out. Only happened while braking, it would get worse stopping at certain speeds. Sometimes it would shake the steering wheel so bad it would be dangerous to drive. Finally changed the front upper control arms After researching online and making sure it wasn't the brakes, rotors or wheels(which were all replaced and fairly new) and it went away. Even after taking it to several shops they couldn't find the problem, and of course I checked everything myself too.
 

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GTP maybe try swapping front wheels/tires with someone else for a day or two?
 

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I have 96k on my '08 and I have started to notice some shake through the steering wheel. It happens during moderate or heavy breaking from highway speed to a crawl. I'm in San Diego so 70mph to 10mph happens regularly. I replace my rotors and pads just over a year ago and they only have 15k on them so figured it's not them.

Either way, I performed most of the checks at the following post:
http://www.g8board.com/forums/showthread.php?t=90746

The "rear most Ball Joint in the Control Arm" and "Checking the Tie Rods" both exhibit play. How can I tell which needs to be replaced? Or do I just need to replace both?
Did you check lug nut torque? Over torqueing can cause warping. 125 ft lbs.
 

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Discussion Starter #17
So I ended up removing the wheels, rotors and calipers, then got a wire brush for my drill and scrubbed the world out of the hubs until they shined. I also cleaned the inside of my wheel where there was some rust build up.

Initial drive on Friday night was pretty good. Saturday I noticed a minor shake at one spot during a turn for such a fraction of a second that I'm not even sure it was related. Sunday was kind of the same story. The roads in SD are pretty crummy so I couldn't tell based on the conditions. Today it seems it is slowly coming back into play. I'm going to re-torque the wheels to 125 tonight just to be sure, but yea looks like I'm seeing the same as everyone else.
 

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Regarding the 125lb torque for the wheels, I pulled of my snows and put on the summers this weekend, my son as well as a neighbour are GM wrench's.
According to them wheels should only be torqued to 100lbs as 125lbs put to much pressure on the bearing and hub assembly. Possibly your bearing/hub is on its way out due over-torqueing.
I am certainly no mechanic but this was my experience this weekend, I am sure there must be some other GM wrenches on the board who can add there two cents.
 

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Regarding the 125lb torque for the wheels, I pulled of my snows and put on the summers this weekend, my son as well as a neighbour are GM wrench's.
According to them wheels should only be torqued to 100lbs as 125lbs put to much pressure on the bearing and hub assembly. Possibly your bearing/hub is on its way out due over-torqueing.
I am certainly no mechanic but this was my experience this weekend, I am sure there must be some other GM wrenches on the board who can add there two cents.
125 is what GM says to use.
 

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Discussion Starter #20
Agreed, everything I've seen says 125. Even so, just curious if 5lbs would even make that much of a difference?
 
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