Car handles like crap.
 

Ok so my car has started to handle like crap. Last fall I went on a very spirited run and was absolutely amazed by the stability and handeling of the car through the curves. It inspired confidence and never once was I worried that it would not do what I asked it to. I have never driven a better handling car. This year I had not pushed it until this last week and now it is a completely different animal. In a straight line when I get into it hard starting around 70 mph it starts to get squirrelly. It feels very unstable. Tonight I took it on a curvy run and tried to push it a little. The thing was scary. It felt very loose and the traction control kept kicking in causing the front brake to engage a couple of times. I'm not a mechanic so I thought I would bring it to the forum to see if any of you have any input.

Three variables to consider:

1. The most likely reason in my opinion is that I just put new hankook v12 tires on the rear only. I was cheap and left the front tires on as they still had some tread left although not as much as I originally thought. They are the original tires and now have 27k.

2. At the same time I had new hawk hps pads installed

3. This winter, I put the car up on wheel dollies. In the process of doing so I had more than one wheel off the ground trying to get each wheel high enough to get it on the dollie. I doubt that had anything to do with it but I thought I would bring it up.

Any ideas?

Your new tires are not fully broken in yet, maybe. Also, they are not as sticky as the stockers.

Hit any weird bumps or anything out of the ordinary that might through the alignment out of wack?

I bought just rear tires like you did on my old car and had the same problem... Now I replace all four all at once or not at all

The Ventus V12 has a completely different traction level to the stock tires, you have unbalanced the car.

Any time you are changing tire class, i.e. in this case going from 140TW class tire to 280TW, you need to change all 4 at the same time. Even changing all 4 you would of had less grip since the new tire has less maximum grip but it would have been more predictable.

Thanks guys, that makes sense and makes me feel much better...I am going to have to get the fronts replaced ASAP. Is there really that much traction difference between the stock Potenza's and the Hankooks?

Treadwear (UTQG) is your general benchmark indicator. You went from a 140 tire to a 280 tire, so the tire will last theoretically twice as long and by definition have less grip, certainly not 50% less, but probably in the 10 to 15% range.

Thanks for the info! Rep added

OP: This is my exact same experience. Only difference is I put 4 brand new V12 tires on the car, not just two. I'm now 400 miles into that tire change. My conclusion? The Hankook V12 Ventus tire (275/40 rear, 245/45 front) is simply not as grippy as I'd hoped for. I will be investing more in tires next time around.

I went the opposite way and put yoko ADVAN ad08 neovas and my handling has improved over stock quite a bit.

Its not just the traction difference at the limit: you have tires of different compounds in a high performance vehicle. Nissan designed the stock tire setup for a reason, including incorporating staggered sizing with the stock camber/caster/toe setup.

Driving strait and < 70% you won't notice the difference...push the car and you will (and have) notice as others have pointed out.

Never do this on any car: its just a bad idea. Use tires of the same compound on all 4 corners at all times.

- b

Yeah, lesson definitely learned on my part. New fronts going on Wednesday so hopefully that will take care of it. I will update at soon as I get a chance to hit the twisties.

OP, I know you've gotten a lot of info, but just wanted to let you know- I did the same as you- upgraded to some Hankook v12's in the rear and left the OEM's on the front. The very minute I took it out on the road it felt much more squirrely compared to before.

I thought it was just the new tires breaking in, but it wasn't. The car is unbalanced, as others have said above, with the different grip in front and rear.

I had an alignment which helped but it has always felt squirrely compared to stock. Very hard to keep it pointing in a straight line.

I suggest grabbing some v12's for the front. You'll find it a world of difference. Tirerack has them for around $220/ea w/shipping for (I think) 265/35s.

Did it straighten up after you replaced the fronts?

Yep. Night and day difference. Couldn't believe how much worse the handling was when I put on those rears... then how much it cleared up when I put on the matching front.

Now when I drive around (Espcially at highway speeds), I don't have to fight the car and keep correcting it. It's much easier to drive.

Can't wait for tomorrow!

Planning to upgrade the rear to Continental Extreme 285/35 19's and keep the OEM bridgestone front tires. Would I encounter the same problem of car being unbalanced?

The v12's have as much grip as the stockers, the main difference is their sidewalls are extremely soft. you have to run a pretty decent amount of air pressure to compensate. I run 40psi and i still get the walls to roll. thats why it feels unstable.

Yes.

Can proper alignment and balancing of the tire would correct it? When do you actually experience the unsteadiness during hard cornering or at certain straight line speed?

Both

As plumber mentioned- you experience it at all times. IMO, the faster you are going the more noticable it is.

An alignment helps steady the car but it doesn't counteract anything caused by this tire imbalance.

The new tires are on and I picked her up last night...from what I can tell so far it is like a night and day difference. I took her up to about 85 and it feels very nice and stable again. There is a nice set of twisties not far from work here that I plan to hit at lunch time and see how the cornering is. The way this week has been going, I could use a little bit of flogging time :)

It'll feel even better once you wear the tires in a bit. Glad the car is back to feeling good. :)