Swirly rear end at 120+ mph

RICAN · 02-23-2013, 01:19 AM

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?

cautupwitdm · 02-23-2013, 01:34 AM

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?

RICAN · 02-23-2013, 01:53 AM

Quote:

Originally Posted by cautupwitdm

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

iceman21_23 · 02-23-2013, 02:07 AM

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

RICAN · 02-23-2013, 02:13 AM

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

cautupwitdm · 02-23-2013, 04:17 AM

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.

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?

KngScottieV · 02-23-2013, 04:18 AM

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.

cautupwitdm · 02-23-2013, 04:20 AM

Quote:

Originally Posted by KngScottieV

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.

KamiSpeed · 02-23-2013, 06:05 AM

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

cptspeed · 02-23-2013, 06:12 AM

Quote:

Originally Posted by RICAN

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

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.

RICAN · 02-23-2013, 09:00 AM

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

m4a1mustang · 02-23-2013, 09:07 AM

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

NickTurnon · 02-23-2013, 09:54 AM

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

cossie1600 · 02-23-2013, 10:17 AM

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.

SS_Firehawk · 02-23-2013, 11:01 AM

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.

02-23-2013, 01:19 AM	#1 (permalink)
RICAN Enthusiast Member Join Date: Jan 2013 Location: fort hood, tx Posts: 345 Drives: 2012 370z m6 Rep Power: 12	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?

02-23-2013, 01:34 AM	#2 (permalink)
cautupwitdm Base Member Join Date: Feb 2012 Location: Utah Posts: 88 Drives: 10 SR M6 SPT Rep Power: 13	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? __________________ GTHaus Meisterschaft GTS Exhaust (Round) \| CNT Racing HFC \| Stillen 19 Row Oil Cooler \| Carbotech Brake Pads \| Eibach Anti-Roll Sway Bars \| K&N Drop-In Filters \| UpRev \| Clutch Helper Spring \| Password JDM Shift Knob \| GTR Push Start Button

02-23-2013, 02:07 AM	#4 (permalink)
iceman21_23 Track Member Join Date: Jan 2009 Location: league city, tx Posts: 757 Drives: 09' Solid Red 370z Rep Power: 17	well the nexens do have a speed rating of H (130 mph) __________________ Zele front bumper cf front lip, Seibon TS Hood, Work GS2, Ings+1 side skirts Takeda CAI Litespeed Exhaust

02-23-2013, 04:17 AM	#6 (permalink)
cautupwitdm Base Member Join Date: Feb 2012 Location: Utah Posts: 88 Drives: 10 SR M6 SPT Rep Power: 13	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. 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? tjlazer and Z-Girl 12 like this. __________________ GTHaus Meisterschaft GTS Exhaust (Round) \| CNT Racing HFC \| Stillen 19 Row Oil Cooler \| Carbotech Brake Pads \| Eibach Anti-Roll Sway Bars \| K&N Drop-In Filters \| UpRev \| Clutch Helper Spring \| Password JDM Shift Knob \| GTR Push Start Button

02-23-2013, 04:18 AM	#7 (permalink)
KngScottieV Base Member Join Date: Dec 2012 Location: Utah Age: 39 Posts: 155 Drives: 13 370z MagmaRed M6S Rep Power: 22	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. osbornsm, cautupwitdm and BrooklynBully like this. __________________ 2013 Nissan 370z Magma Red Base w/Sport package 6speed. AAM intakes (S-line for now, still needs tuned), Berk HFC's, ARK DT-S cat-back, CJM baffled oil pan, and FI 34 row oil cooler. Last edited by KngScottieV; 02-23-2013 at 04:24 AM. Reason: Thoughts!

02-23-2013, 02:13 AM	#5 (permalink)
RICAN Enthusiast Member Join Date: Jan 2013 Location: fort hood, tx Posts: 345 Drives: 2012 370z m6 Rep Power: 12	Sorry it's the nexen 7000 not the 5000 ..I had to double check the tires !!

02-23-2013, 06:05 AM	#9 (permalink)
KamiSpeed A True Z Fanatic Join Date: Feb 2011 Location: Orlando, FL Posts: 5,888 Drives: 09 370z Rep Power: 25	check alignment and get some more rear downforce, also hope this is on the track haha __________________ KAMISPEED \| SHOP 370Z PERFORMANCE PARTS & MODS \| SUPPORT@KAMISPEED.COM KAMI SPEED REVIEWS \| FINANCE YOUR PARTS WITH US \| MILITARY & FIRST RESPONDERS PRE-ORDER DEPOSIT PROGRAM \| HKS MASTER SELLER

02-23-2013, 09:00 AM	#11 (permalink)
RICAN Enthusiast Member Join Date: Jan 2013 Location: fort hood, tx Posts: 345 Drives: 2012 370z m6 Rep Power: 12	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

02-23-2013, 09:07 AM	#12 (permalink)
m4a1mustang A True Z Fanatic Join Date: Feb 2009 Location: Northern VA Posts: 55,385 Drives: on two wheels Rep Power: 6962	It's mis-matched tires. You need the same tire front and rear... and good ones at that. cossie1600 likes this. __________________ - Steve Zs & Coffee - Saturdays at 10AM in Fairfax, VA and Columbia, MD (Click the banner!) LIKE us on Facebook!

02-23-2013, 09:54 AM	#13 (permalink)
NickTurnon A True Z Fanatic Join Date: Jul 2011 Location: Scottsdale Age: 33 Posts: 1,636 Drives: 09 BS 7AT 370z Rep Power: 17	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 __________________ 2009 Brilliant Silver BASE 7AT \| TEIN S-Tech Springs \| K&N Drop Ins & z1 Maf Tubes \| AAM S-Line Short Tails \| 5% Tint \| 20MM Spacers \| Sport Spoiler NickTurnon's 370z Build

02-23-2013, 10:17 AM	#14 (permalink)
cossie1600 A True Z Fanatic Join Date: Jun 2009 Location: californee way Posts: 5,380 Drives: 370, Leaf Rep Power: 29	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.

02-23-2013, 11:01 AM	#15 (permalink)
SS_Firehawk Premium Member Join Date: Oct 2011 Location: Tampa Posts: 4,142 Drives: 13' Magma Red Nismo Rep Power: 7334	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. Z370Z011 likes this. __________________ Old Car:GTM TSC'd 550whp / 410lbft tq @ 11.88PSI New Car: Under Construction

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