G8 Handling Questions

[LVGoat]

Appreciate some help on the handling of my ’09 G8 GT with 45,000 miles. The performance has been awesome, but I have some “twitchiness” in straight line handling. It kind of feels like the wandering you get from tramlining, but it happens on all road surfaces at speeds 30-80 mph. I’m constantly making small steering corrections to keep it tracking straight. I also sense slight yawing or rocking side to side at times. It did this with the prior Bridgestones as well as my new Michelin Pilot Super Sports and my winter Blizzaks. The car is completely stock, with original suspension parts, and never damaged. I and my alignment guy both feel there is no play in any links including the LCAs. Caster, camber and toe are all in spec and even side to side. I run 36 psi front and back.

Before I start trying things, has anyone had this same experience with stock G8 and what did you find? Are certain things (shocks?) simply worn out on any G8s with this many miles? With these symptoms should I check for wear or looseness in particular parts? Are there common upgrades or adjustments I should make? Is this “the way stock G8s are?” I will say at 80-120 mph it tracks well so maybe it is just set up for high speed? I’d like to keep it close to stock if I can. Thanks much.

 

[melsg5]

There is a TSB, technical service bulletin, on the topic of "tire wander" have your shop look up the specifics. The GM/Pontiac number is 3144 and the NHTSA number is 10010180.
Is 36 PSI the cold tire pressure number listed on the drivers side door pillar?

 

[LVGoat]

Thanks Mel. It says 36F/39R. I used to run higher rear tire pressures, but my car is always lightly loaded and rears were wearing faster in the middle, so I backed them off to 36psi.

Spent 30 minutes trying to download and read TSB 3144/NHTSA 10010180 online. No luck... just get to websites that want to charge $26/year or $50/hour. Surprised these are not made easily available and free, considering many are safety related! Guess I may need to call the dealership to find out...

 

[melsg5]

if the alignment shop has a subscription to www.Alldata.com they can look it up for you

______________________________

 

[LVGoat]

For Mel and anyone with a similar "wandering" feeling, I spoke with my local GM service man and he read me the TSB 3144. I'm paraphrasing but here is what's in it:
- Can be caused by non-standard aftermarket wheels, tires or suspension
- Can be caused by non-standard tire pressure... particularly running higher than spec can stiffen the sidewalls and cause more of the wandering feeling
- Generally not something related to wheel alignment
- Tramlining is experienced in cars with larger diameter wheels and low profile performance tires

Since my G8 is stock, my tire pressures are not high at 36/36 (vs door sticker 36/39), my miles are low, my alignment is spot-on, and it's been doing this with two sets of tires, my conclusion is "this is the way they are," consistent with dealer's last comment from the TSB.

For fun, I might try lower tire pressures like 34/37, maybe 34/34, etc to see if that makes it track more easily.

 

[melsg5]

thanks for the update on the TSB.

 

[cammerjeff]

Our 2009 G8GT does not have the issue and we ran the stock Goodyears, Bidgestone Blizzaks , and sense last spring new Michelin Pilots. We did have an issue with the LCA Bushings and both the Bushings and Bolts were replaced under warrenty. But that was causing a clunking noise when going over rough road surfaces.