I have a 2007 m6 and after installing new tires (Exact same as before) the car handles like the rear sway bars are disconnected. In fact now it activates active handling very easily in the turns. Before I put the tires on it, it handled perfectly. I checked the shocks and there are no leaks. I also increased the tire pressure to 34psi (No help). The sway bars are tight also.

Some facts:
1. the car has 109K miles on it
2. the tires are 305/30/19 and 275/35/18 hankook ventus
3. non z51 suspension
Any ideas?

 

I have a couple questions:

1. Did you put the wheels back on the car yourself? If not, did you check the torque on the lug nuts?

2. Is the car sitting at the same height as before?

3. Those are the exact same tire sizes as before? I only ask because there is only .7" difference in tire diameters between the front and rear tires.

DJ

 

The tires are exactly the same

The ride height is the same

firestone did the tire swap. I will check torque

 

New tires tend to have a film on them from time to time ..

I think it keeps the tires fresh?

Anyways....after checking to make sure all the bolts are tight on the wheels..

I would say driving a few hundred miles and the car will drive fine ..at least I remember it did for me a few times after a few hundred miles with new tires on the car..

Not all tires come with that compound to preserve them in storage before they are sold..but some are and it can be confusing on the drive home from the shop...even as much as a couple hundred miles..(or at least a hundred miles I'd say)

Hope this helps..(EDIT)

PS..I have hankook Evo's on my 08 c6 and I don't believe they are the same sizes as I have ....still if they are the same size as your previous firestones .....you had before without a problem...I'd suggest its the preservative..

I even think this most recent set of hankook Evos I have on my car which I believe are 285/35/19's and 245/40/18's (I'm not sure of the exact aspect ratios at this moment so bear with me) had that crazy @ss film on the tires...and I remember driving home thinking the same thing...I was like wtf!!! LOL pretty squirrelly on that 100 mile ride home and then the film wore off shortly and the tires were great!


It wears off shortly and then the tires should be great as long as your sizes are not setting off active handling...as they are not stock sizing..

I believe its the storage preserative.. thats probably causing your concern..

Congrats on the massive mileage of your car!!!!

let us know how it works out..

 

The wheels are at 105 ft lbs

 

You may be right about the preservative. I had them put on last week and I have noticed a little better handling (A little). I also have not changed the fronts. I will do them this week. I have decided to go to 265/35/18 rather than 275/35/18. My gass mileage went down when I went from the factory size to the 275s. Thanks for your help

 

You say you put the tire pressures up to 34psi - I assume that was with a good handheld gauge.

What pressures are displayed in the DIC???

Bob

 

Yes, with a quality guage. It really feels like the tires are low or the sway bar link is disconnected. When I push the car from side to side (By hand) i do not get hardly any side wall flex.

 

The DIC is dead accurate with the guage.

 

What does your DIC display for pressure - same as your gauge???

You did use your old wheels and tire pressure sensors, right???

Bob

 

Please make sure you maintain the proper differentiation in stock size tire height when chosing tires. I don't know all the details but I believe the difference in height between the front and rear tire height must remain constant...or within a range from the factory tire height that does NOT set off active handling..

I really do believe its the preservative..but check tire height differentials between front and rear and try and maintain the stock height differential.

I remember I almost turned around in my 100 mile trip because the car was so squirrelly... thats why I posted to your thread...

It also happened with the toyo proxi's I put on my c5 z06 when they were new and until that peservative wore off...I was like WTF!!!!

Good luck..

 

Same factory wheels and sensors. Again, the DIC reads accurate. I did not have this problem when I put the last set of tires on it.

 

Does anyone know what the ride height differential should be?

 

I am .6 taller in the front and .6 lower in the rear. I will try to adjust with tire pressure until i install new front tires. Still not understanding why it has been perfect until now.

 

1.2 inches.

 

It is not active handling that gets invoked, but traction control. I run Toyo R888's for track days and autocross. I have to drive to the tracks and the farthest away is 200 miles. All nannies on and no problem at freeway speed, say up to 75mph.

On the track right around 100mph traction control kicks in if I forget to shut it off.

 

Sounds like you got a defective tire - maybe an incorrectly made belt in one of them. I've seen it and it can make the back end feel like jelly. Almost like driving on a bias-ply drag slick on the street with standard radials in the front.

No offense, but I don't hold Hankook tires in the highest regard. Try swapping the back wheels and tires with another car if possible for testing.

 

Mine felt like I was driving on ice because they didn't compensate for ride height after I lowered it. I use the Pfadt alignment specs. (max angles for steet)

 

Yes, I recently had it aligned after the rear tires were installed. The alignment made no difference. Is it possible that one of the rear shocks are bad?

 

these are the tire specs I use when I purchased my Hankook Evo 12 tires..

Please note the height of both the front and the rear tires of the stock sized tires..

Currently Selected Tire Size(s)
Size
Service Description
Load Range UTQG Max
Load Max.
Inflation
Press. Tread
Depth Tire
Weight Rim
Width
Range Meas.
Rim
Width Sect.
Width Tread
Width Overall
Diam. Revs
Per
Mile Country
of Origin*
245/40ZR18
Load Index 97 = 1609lbs (730kg) per tire
Speed Rating “Y” = 186mph (300kph) 97Y XL Treadwear: 280
Traction: AA
Temperature: A280 AA A 1609 lbs.
50 psi
10/32"
25 lbs. 8-9.5"
8.5"
9.7"
8.4"
25.7"
808
Country of Origin "KR" = KOREA, REPUBLIC OFKR
285/35ZR19
Load Index 99 = 1709lbs (775kg) per tire
Speed Rating “Y” = 186mph (300kph) 99Y SL Treadwear: 280
Traction: AA
Temperature: A280 AA A 1709 lbs.
51 psi
10/32"
29 lbs. 9.5-11"
10"
11.4"
9.8"
26.9"
773
Country of Origin "KR" = KOREA, REPUBLIC OFKR

Please be aware the rear tire has a larger diameter than the front. I don't know the range required to NOT throw off Active handling yet I believe there is a range that needs to be adhered to.

HOpe this helps. I just ordered up a set of Hankook Evo's for installation on my 08 coupe next week...

They lasted 23k miles and I had a nail in one of the tires seen during an oil change today...so we just ordered up a set for next week..(the soonest I will be able to get back to the dealership...Just pulled the nail...and did a 2 second plug job for the week.. )

Let us know what works out best for you ..