Swirly rear end at 120+ mph
 

Ok so my rear end gets real swirly when ever I got over 120 and start applying brakes ....my car is lower on H&R springs and eibach sway bars front and rear!!......I really don't like to take the car fast because it feels like is gliding side to side!!...can anyone help me with this?

A few questions first. What kind of tires do you have? Do you have the sport or non-sport brakes or upgraded pads? Any change in brake fluid?

Base model, no upgrades on brakes!!and using oem fluid!!.the guy that had the car before put nexens 5000 on the back

well the nexens do have a speed rating of H (130 mph)

Sorry it's the nexen 7000 not the 5000 ..I had to double check the tires !!

Your tires seem decent. They aren't tires that are used much on our cars that I've seen but probably not the main cause. My best guess is the surface of the road you are driving on. If you are going 120+ on a rough surfaced (public) road most people will experience some instability unless suspension, tire pressure etc. has been fine tuned. Please stop doing 120+ on public road if this be the case for your safety and others. Public roads were not constructed for high speeds. :shakes head:
On the other hand if you are experiencing instability on a very smooth track then it might be your tires or something off in your setup. It is kind of hard to pinpoint with so many variables involved. Anyone else got some input?

Well at 120+ if you have the base without the rear spoiler the lack of extra downforce could be allowing the rear-end to lift, or roads/tire pressure. Just a guess.

Edit:Thought of something else, if the H&R springs lowered the car the camber for your tires may not be correct toe-out/in causing not enough of a contact patch.

:iagree:

check alignment and get some more rear downforce, also hope this is on the track haha

I noticed you said nexens on the back. I had the same problems with mismatched tires. After installing new fronts that matched the rear, the problem went away. Hope this helps.

Thanks for all ur help guys !!...I'm goin to install my camber kit today and start from there..if that doesn't fix it il put new tires

It's mis-matched tires. You need the same tire front and rear... and good ones at that.

Honestly, coming from the base model, with base brakes, and big perfect tires. Tires aren't the solution to this...

When I was at the track, I would end the quarter mile at 105 or something and kept going til 120 or so. At that speed, I had to consistently go to the FAR turn around point because my car felt like it wasn't able to brake fast enough to turn around in the first turn around area (or I didn't want to waste my brakes that much).

I get scared when I apply my brakes at high speeds. I have this video playing in my head the whole time...

http://youtu.be/OQPumIh6CY8

Big tire doesn't mean it is a good tire. My Prius tires are 225, doesn't mean it grips better than my 205 slicks. My car is stock, never had a problem stopping except ice mode. It can hit 1G+ under braking almost all the time.

mismatched tires is definitely plausable. Alignment after drop definitely also. Checking the alignment is cheaper. I woul start there first. Also if your sway bar is adjustable, set the rear to the softest setting for now to allow the body to roll a bit more if it feels like your tires are sliding, at least until you can figure out what it is. Z's should be rock solid, even at 120 mph without a spoiler.

If the road surface is uneven (crowning) or you are turning even the slightest bit - the reason is that there is weight transfer from the rear to the front tires during braking. The rear end is lightening up when you begin to apply the brakes... so naturally, it will get light and 'swirly'..

Other factors might hurt or help the situation.. alignment, tires, tire wear, suspension, brake pads..etc.. but definitely keep your weight transfer in mind.

Ok so I install the camber kit that was in the back of the car when I got it!!...i just drop it off to get a alligment on all the tires ...il give more update later when I get the car back !!..

Oye Loco Stay safe...the roads around Hood aren't the best. Also, don't overlook anything small, PMCS your ride, check the brakes, pads, and tire wear.

Well I just got the car back!!..and it fix it was alignment!...

Lol...are you from around here?...I'm a mechanic but I never owe a rear wheel drive car !!i had a caliber srt4 with 390 whp!...it was fwd and I had no traction at all...I couldn't even do a 65 mph pull with out loosing traction!!....that's why I decided to get the Z...I'm getting it right before I leave to Afghanistan!!..and when I get back I'm boosting it

Get it when you get back so it isnt in storage for so long. Z's are not going to disappear any time soon.

These cars do not have the best weight distribution. I have weighed mine, and static is about 54/46. With a driver and fuel, that shifts to 55/45. Apply the brakes hard, and yeah, it's going to feel floaty in the back.

Weight distro isn't bad on the car. Driver sits at the axis point of the vehicle and the gas tank is right in the middle of the car, so regardless if it's full or empty, weight distribution doesn't change.

I know what the problem is. You're using way too many exclamation points. You sound like you're freaking out, and it's freaking your Z out. It's basically like spooking a horse, she's really nervous right now and is considering throwing you. You need to relax, talk calmly to her, and give her a good wash. Then try again.


!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!


Sent from my iPizzle using magic and new-fangled science stuff

My parents live in the area. Hood my be my next duty station. I had a 400+ whp Neon SRT4 and the back end would get way more squirley than the Z. There's hardly any weight on the back of those. Never had an issue though aside from the torque steer.

Car has freaking ABS and EBD, it shouldn't get sideways unless you f things up

The only time I've noticed this on my car is if I've unsettled it prior to heavy breaking or if I'm not breaking in a straight line at the start of braking.

But thats never a problem for me in Need for Speed?! :confused:

:stirthepot:

Lol...I forgot to update you guys ...sorry for that!.....I already fix the problem...after installing the camber kits all around .. I took it to get a alignment and since the I haven't got any problem.thank you for all your inputs

Glad you got it fixed, but you should still consider a few brake upgrades. Pads, SS lines and a good quality brake fluid at the very minimum. You'll feel quite a difference.