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.