Looking for any possible insight into issue I've been chasing for last few months. Looked through some old forum posts and saw some with similar issues, but many were wheel and tire balance related. And I have ruled out wheel / tire balance as my issue.

Here's the problem. Noticed initially that at speed...around 110-120 km/h range....60-70mph for you US guys....that I was getting a shudder in my steering....going straight, my steering wheel would be rocking back and forwards quickly by a little bit. I had only just bought the car (2010 GrandSport with 17,000 kms on it), and first things I did was put some Doug Rippie shocks on the car and a set of forged wheels with new Michelin pilot sport 4S tires. Had the wheels / tires roadforce balanced multiple times, found that one front tire wouldn't road force balance out. Was out by 28 lbs. Had to wait for almost 3 months to get a new tire. Put on the new one...it balanced out to within 1lb. Wheels and tires balanced as they can be. And still experiencing the issue.

Took car out to try and really diagnose when and what is happening. At slower speeds...30-50 km/h sort of thing...if I gently turn the steering off center to the left and right, feel a bit of a shudder or resistance each way. Steering is super tight, but just feels like the steering isn't completely smooth off center. Then at speed...60-70 mph and above....the steering wheel can be rocking back and forth by let's say an inch or so going straight. But then I can drive a bit more, turn a bit, etc....and hit that same speed and the steering wheel is dead straight with no rocking.

Losing my mind with this. Took car to local mechanic I trust. Only thing he could really suggest, without being able to specifically diagnose....is being steering rack and / or power steering pump. I was coming to that possible conclusion myself after diagnosing myself. And based upon couple people mentioning steering rack being issue with similar sounding problems on old forum posts. From leaking steering rack (which mine doesn't appear to be leaking), to mentioning magnets inside steering rack shifting or falling off or something?

Just want to get this issue fixed. Beyond annoying that I'm dealing with this on car that should be dead smooth to high speeds...and on such a low mileage car. I would normally just throw the new parts at the car to see if fixes problem. But the issue is this. Was told only could get a new OEM pump from GM (think said OEM)....at cost of $700-800 Cdn. And can't get an OEM steering rack new...just a reman (which mechanic wasn't too hot on)....for $1000 Cdn!!! Wtf. And mechanic told me probably 3-4 hours labour for steering rack as not that easy, and then less time for steering pump. So looking at over $3K Cdn if I try throwing in both steering rack (which could be **** from what he's saying as no new OEM) and pump.

So just seeing if anyone could possibly confirm this as the actual issue, and fixed similar problem with replacing. Or if any other possible cause of issues I'm experiencing. But when having ruled out suspension components, and wheels / tires....I just don't know what else it could be but actual steering system. I've just never heard of or experienced a steering rack or power steering pump to cause similar issues to an out of balance tire / wheel combo. But I have to have ruled out wheel / tire balance....and even then, that would always happen at certain speeds consistently. Whereas my problem is randomly intermittent.

HELP!

 

Sorry I don't know what your issue is but I do know that GM does not have new steering racks and that goes all the way back to 2013. That has been a known issue. Back in 2013 when I bough my GS new it had a bad rack right off the showroom floor. The dealer replaced it but told me right there it would be a reman as no new racks were available at the time and I think none never were.

 

Yeah...ridiculous how there is so little support on parts for the C6 overall. Given how many are on the roads.

 

If you replaced the OEM wheels with aftermarket, then check that the factory clip washers that were used to keep the rotors on the hubs during the assembly process have been removed. They aren't needed. There was 1 per hub, and the OEM wheels had a relief cast in the mating area so that the wheel could fit flush around the washer. None OEM wheels may not have the relief, so the wheel ends up having a wobble if the 1 washer is still there. You'd feel that through the steering wheel for sure.

 

Yeah...I took those off. Not the issue.

 

Did you have this problem before you got the new wheels & tires?

 

My thought exactly, also wondering if the alignment has been checked, could be a bad tie rod end or loose wheel bearing. Can't belive a mechanic can't find the issue.

 

Could there be a need for wheel hub centrics?

 

 

Could the amount of "castor" in the wheels affect the wheel vibration??

( I'm thinking of a grocery cart with a wheel wobble, )

 

Remove the rotors and check that the mating surface between the hub and rotor is clean and free of any rust. Use a wire brush or wire wheel. It’s amazing how little it takes to introduce a wobble in the wheel assembly. The same is true for the contact area between the rotor and wheel.