Need help eliminating oversteer

robertkroll · 08-05-2018, 09:45 AM

Quote:

Originally Posted by Hotrodz

I reduced mine back to -1.8 from -2.0 but I got to sort things out again as my whole rear setup has changed again. I now have true coilovers and higher spring rate and the car sits lower. I have not been to the track since I changed things up, but she felt a lot more balanced on the dragon. I also softened the damping in the rear quite a bit. Out of 24 clicks I went with 10 in the rear and 12 in the front. Before the change on a slightly softer rear spring, 11k and a less aggressive damper, it was set at 18 clicks.

Mr. Kroll, are you on true coilovers?

Yes. JRZ RS Pro 2 way

Rusty · 08-05-2018, 01:43 PM

Quote:

Originally Posted by robertkroll

The problem is that with a lowered car, the camber is set at a point in the suspension travel that is typically reserved for a “compressed” state. This leads to rapid and noticeable change in kenimatics when compressed further. This keads many people to over “spring” the car to prevent further geometric progression and loss of grip. This car is NOT designed to be lowered to this degree. I’m thinking of raising the ride height, installing spacers (or even the WiseFab kit). To change the kinematics to favor a bit of squat and body roll.

I didn't see mention if you had a SPL rear sub-frame bushing kit. If you do. you can add and subtract spacers to change some handling characteristics.

Hotrodz · 08-05-2018, 05:48 PM

From the list on SPL parts on that are list on the add that the car was posted for sale you are still missing some really good an necessary suspension parts as Rusty is eluding too. I and Rusty have all of their front and rear suspension parts installed. I am really interested to see how the Z behaves on the true coilovers and running on stiffer springs but not as much dampening.

I don't know if Eagle is lurking around as he has his car dialed in and might be able to provide some input. I do know BILSTEIN coilovers and has SPL suspension products.

cv129 · 08-05-2018, 06:17 PM

I am surprised BGTV8 hasn't chimed in yet.

BGTV8 · 08-06-2018, 02:36 AM

Been busy .............. still traveling 2000km to work each week(by air - not driving) and trying to keep SWMBO happy leaves me with almost zero time.

In terms of rear suspension setup, I have deliberately used lower diameter tyres to drop the CoG rather than over-lowering on the spring perches which as several have surmised leads to excessive camber gain in the rear in bump and camber-reversal in pitch under braking being the cause of rear instability.

Over springing the car will kill rear grip - which some folks counter with a really fat tyre (needed perhaps for FI cars but not IMHO a NA car). I reckon that a 275 wide tyre in 35 profile on square setup to be ideal for me although others clearly prefer a bigger tyre.

I am happy with the balance on 265/35R18 (Yoki A050) or 275/35R18 (NT01) and will be running either Dunlop 280/650R18 slick or perhaps a Pirelli 285/645R18 and therefore following the pattern of lower diameter tyre to drop the car rather than lowering it on the spring which stuffs-up suspension angles and compromises rear camber control in bump as well as getting some weird angles in droop as the car pitches under braking which can affect your ability to rotate the car as you come off the brakes. Somewhere I have the SusProg details of the Z34 rear suspension and I was surprised at some of the changes in droop - which is something to remember - camber gain in bump is one factor to look at, but so is camber and toe change under droop as the car pitches under heavy braking. Remember that the rate of pitch is affected by rebound in the rear shocks and bump in the fronts and the recovery is governed by rebound at the front and bump at the rear so a hard turn-in can be affected by rear toe/camber recovery as you come out of the brake, depending on these settings

I have a 3.9:1 diff with Quaife LSD and a 4.08:1 with KAAZ LSD for fast and slow circuits respectively.

I go back to the settings that Doran Racing used in Grand Am and took my initial lead from them.

I've limited my drop on the springs and added 5mm of rake by dropping only 15mm at the rear and 20mm at the rear as my absolute lowering limit, which still does get played with from time to time.

I have just measured from bottom edge of the rim to the under-edge of the wheel arch which are 610mm all round on my DD wheels (245/45R18 fronts and 275/40R18 rears) - these tyres are Falken FK453 at 677.7mm dia front and 677.2mm rear. My track Enkei's RUN 275/35R18 NT01 at present and these are 650mm tall - so tyre height accounts for around 13mm CoG overall drop. I run KWv3 shocks (front rate is 425lb/in and rear is 450lb/in) but have Penske double adjustables to go into the car when I take it off the road. Spring rates will rise to ~550 front and ~650+ at the rear on proper coil-overs as a starting point but there will be a lot of testing to get it right.

I am running quite a soft setup (Whiteline front bar, full stiff and Whiteline rear bar fitted but currently disconnected - sometimes I run it on softest setting if I need to shift balance to the front depending on track and/or track grip).

I have the yaw-sensor DIY installed as the standard electronics are dangerous on the track - even with VDC off, there are sufficient electronic nannies left to cause problems which I reckon is dangerous.

I also have the SPL FUCA installed and the balance of SPL bits for both front and rear suspension/subframe but not yet installed as the car is still my sometime/weekend drive (I have a Ford Ranger ute as my actual DD) and not a dedicated track car.

As soon as the car comes off the road (it has 160K kms on it now) it will get the complete SPL suspension upgrade and Penske shocks installed as well as 4-litre forged engine, Motec M150 and QBE69G gearbox which is when suspension tuning really starts. I also have AP brakes to go onto it and if I can persuade one of my suppliers to part with his old-spec Bosch MotorSport ABS - I'll have that as well. The Motec can also support launch and tunable traction control but that will be a bit down the track I think

robertkroll · 08-06-2018, 06:09 AM

Quote:

Originally Posted by BGTV8

Been busy .............. still traveling 2000km to work each week(by air - not driving) and trying to keep SWMBO happy leaves me with almost zero time.

In terms of rear suspension setup, I have deliberately used lower diameter tyres to drop the CoG rather than over-lowering on the spring perches which as several have surmised leads to excessive camber gain in the rear in bump and camber-reversal in pitch under braking being the cause of rear instability.

Over springing the car will kill rear grip - which some folks counter with a really fat tyre (needed perhaps for FI cars but not IMHO a NA car). I reckon that a 275 wide tyre in 35 profile on square setup to be ideal for me although others clearly prefer a bigger tyre.

I am happy with the balance on 265/35R18 (Yoki A050) or 275/35R18 (NT01) and will be running either Dunlop 280/650R18 slick or perhaps a Pirelli 285/645R18 and therefore following the pattern of lower diameter tyre to drop the car rather than lowering it on the spring which stuffs-up suspension angles and compromises rear camber control in bump as well as getting some weird angles in droop as the car pitches under braking which can affect your ability to rotate the car as you come off the brakes. Somewhere I have the SusProg details of the Z34 rear suspension and I was surprised at some of the changes in droop - which is something to remember - camber gain in bump is one factor to look at, but so is camber and toe change under droop as the car pitches under heavy braking. Remember that the rate of pitch is affected by rebound in the rear shocks and bump in the fronts and the recovery is governed by rebound at the front and bump at the rear so a hard turn-in can be affected by rear toe/camber recovery as you come out of the brake, depending on these settings

I have a 3.9:1 diff with Quaife LSD and a 4.08:1 with KAAZ LSD for fast and slow circuits respectively.

I go back to the settings that Doran Racing used in Grand Am and took my initial lead from them.

I've limited my drop on the springs and added 5mm of rake by dropping only 15mm at the rear and 20mm at the rear as my absolute lowering limit, which still does get played with from time to time.

I have just measured from bottom edge of the rim to the under-edge of the wheel arch which are 610mm all round on my DD wheels (245/45R18 fronts and 275/40R18 rears) - these tyres are Falken FK453 at 677.7mm dia front and 677.2mm rear. My track Enkei's RUN 275/35R18 NT01 at present and these are 650mm tall - so tyre height accounts for around 13mm CoG overall drop. I run KWv3 shocks (front rate is 425lb/in and rear is 450lb/in) but have Penske double adjustables to go into the car when I take it off the road. Spring rates will rise to ~550 front and ~650+ at the rear on proper coil-overs as a starting point but there will be a lot of testing to get it right.

I am running quite a soft setup (Whiteline front bar, full stiff and Whiteline rear bar fitted but currently disconnected - sometimes I run it on softest setting if I need to shift balance to the front depending on track and/or track grip).

I have the yaw-sensor DIY installed as the standard electronics are dangerous on the track - even with VDC off, there are sufficient electronic nannies left to cause problems which I reckon is dangerous.

I also have the SPL FUCA installed and the balance of SPL bits for both front and rear suspension/subframe but not yet installed as the car is still my sometime/weekend drive (I have a Ford Ranger ute as my actual DD) and not a dedicated track car.

As soon as the car comes off the road (it has 160K kms on it now) it will get the complete SPL suspension upgrade and Penske shocks installed as well as 4-litre forged engine, Motec M150 and QBE69G gearbox which is when suspension tuning really starts. I also have AP brakes to go onto it and if I can persuade one of my suppliers to part with his old-spec Bosch MotorSport ABS - I'll have that as well. The Motec can also support launch and tunable traction control but that will be a bit down the track I think

Do you still have the Doran Racing specs?

Hotrodz · 08-06-2018, 09:43 AM

I have been thinking of reaching out to Rearden to see if they might be willing to share some information as well. They have been kicking butt in the PWC.

2011 Nismo#91 · 08-06-2018, 02:13 PM

Andrew from Tachterion Driver Development | Making you faster one lap at a time! is an excellent driver who could defiantly find the culprit here. Your car is very different from what most people have and at least for me would be hard to diagnose. The only thing I notice, your spring rate is fairly "standard" and you should be looking at changing the rates to less in the back and maybe even more in the front but I'm not the best at this by far. Mine (full interior) is 1000/450.

I wish I had my current settings handy, I almost have it right but the rear needs more work.

AlWakRa · 08-07-2018, 07:03 AM

I am not that expert as most people here, but I will give my 0.02$

A lot of informative replies, I didn't read all of it, but I have nearly the same issue right now, and it appeared when my friend drove it, he couldn't complete an AutoX run in it as he spinned all the time

mainly due to his early throttle input. I didn't have this problem before, what have changed from my last setup which was very balanced with slight oversteer.

Tires: from RE71R 275/35-285/35 combo to R888R 265/30-295/30
LSD: Installed OS LSD
ALIGNMENT: it was around Front camber -2.4 caster 6.0 toe 0 Rear camber -1.8 toe 0.12 (total 0.24) to front camber -2.8 caster 6.5 toe 0 rear camber -2.7 toe 0.32 (total 0.64 !!!! - couldn't dial it as I skipped ML as I was planning to change suspension and Truetype could be on the card) my front grip was very good, but rear isn't, even with an added downforce, it didn't improve. I don't know about hoosier recommended alignment, but I can say the first culprit could be excessive camber-toe.
Then, it may be the hard springs at rear, as it is true-type, I saw most TT setups are a lot softer than oem style at rear, I reached out to MCA for new coilovers, they suggested 22kg front and 8kg rear.

ValidusVentus · 09-15-2018, 02:47 AM

OP, your car does sounds well setup (aka badass). Our cars are actually very similar minus your custom fuel cell and abs (nice). Any pics of your brake cooling setup?

Ideas:
-Ride height (and effects)
-Front vs. rear tire temps off, perhaps exacerbated by the amount of rear toe? (And dynamic toe?)
-I also run 1000lb fronts but run a 550lb rear spring on my true type AST 5200s (with JRZ top hats

).

I'd bet a nickel, though, that its due to the rear loaded tire operating in an unfavorable kinematic situation, as you said. I've noticed a big change in rear grip from ride height changes. Also keep in mind that rear toe changes with suspension position as well, so perhaps not just a camber curve issue. After making a rear rideheight change before my last track day -to help combat inside rear wheel lift on some offcamber corner exits- I was battling a lot of oversteer everywhere. I tried softening the rear ARB but absolutely hated the rear roll amount that introduced and just went back to the mid setting on my whiteline rear, made a small tire pressure change and just drove around the oversteer. Discovered one of my damper adjusters was broken and I had forgotten my spring perch wrench at home

From looking at your car pics sort of looks like you have SPL solid rear subframe bushings? I have those as well with the OEM'ish spacer setup at the moment.

Anyone feel like measuring hub centerline to rear wheel arch distance and alignment settings and collaborating on establishing an optimum rear ride height range?

Also: Get on the "370z Top Ten Track Records - Road Courses II" thread! The only times I've got up there, with the car as set up as it currently is, are from the Ridge MSP unfortunately.

08-05-2018, 05:48 PM	#33 (permalink)
Hotrodz A True Z Fanatic Join Date: Aug 2012 Location: NW, AZ Posts: 9,330 Drives: 10 Nissan 370z Nismo Rep Power: 2684385	From the list on SPL parts on that are list on the add that the car was posted for sale you are still missing some really good an necessary suspension parts as Rusty is eluding too. I and Rusty have all of their front and rear suspension parts installed. I am really interested to see how the Z behaves on the true coilovers and running on stiffer springs but not as much dampening. I don't know if Eagle is lurking around as he has his car dialed in and might be able to provide some input. I do know BILSTEIN coilovers and has SPL suspension products. Rusty likes this. __________________ *Fast Intentions TT Installed and Tuned by Seb at SpecialtyZ 610whp 560tq:\|Fast Intentions 3" TT-TDX*\|SpecialtyZ/Fast Intentions 72 Row Oil Cooler\|SZ 6 Puck Clutch & Flywheel\|3GsCustoms\|Z1\|Wavetrac\|Hotchkis\|Whiteline \|Blitz\|Fortune Auto 500\|Fujimura\|SPL\|H&R\|TK\|TWM\|RPM Rollbar\|Sparco\|Next Level Performance\|TrackSpec\|AeroFlow Dynamics\|Pioneer\|

08-05-2018, 06:17 PM	#34 (permalink)
cv129 A True Z Fanatic Join Date: Jul 2011 Location: Dallas, TX Posts: 3,222 Drives: 09 Nismo, 16 Nismo Rep Power: 163995	I am surprised BGTV8 hasn't chimed in yet. Rusty, Hotrodz and Spooler like this. __________________ Setrab \| RE-71 \| SPL \| JRZ \| Nismo \| ARK \| Whiteline \| RacingBrake \| CJM Oil Pan \| Ti shield

08-06-2018, 02:36 AM	#35 (permalink)
BGTV8 A True Z Fanatic Join Date: Dec 2009 Location: 03350 Australia Posts: 1,514 Drives: 09 Nissan 370Z M6 Rep Power: 39973	Been busy .............. still traveling 2000km to work each week(by air - not driving) and trying to keep SWMBO happy leaves me with almost zero time. In terms of rear suspension setup, I have deliberately used lower diameter tyres to drop the CoG rather than over-lowering on the spring perches which as several have surmised leads to excessive camber gain in the rear in bump and camber-reversal in pitch under braking being the cause of rear instability. Over springing the car will kill rear grip - which some folks counter with a really fat tyre (needed perhaps for FI cars but not IMHO a NA car). I reckon that a 275 wide tyre in 35 profile on square setup to be ideal for me although others clearly prefer a bigger tyre. I am happy with the balance on 265/35R18 (Yoki A050) or 275/35R18 (NT01) and will be running either Dunlop 280/650R18 slick or perhaps a Pirelli 285/645R18 and therefore following the pattern of lower diameter tyre to drop the car rather than lowering it on the spring which stuffs-up suspension angles and compromises rear camber control in bump as well as getting some weird angles in droop as the car pitches under braking which can affect your ability to rotate the car as you come off the brakes. Somewhere I have the SusProg details of the Z34 rear suspension and I was surprised at some of the changes in droop - which is something to remember - camber gain in bump is one factor to look at, but so is camber and toe change under droop as the car pitches under heavy braking. Remember that the rate of pitch is affected by rebound in the rear shocks and bump in the fronts and the recovery is governed by rebound at the front and bump at the rear so a hard turn-in can be affected by rear toe/camber recovery as you come out of the brake, depending on these settings I have a 3.9:1 diff with Quaife LSD and a 4.08:1 with KAAZ LSD for fast and slow circuits respectively. I go back to the settings that Doran Racing used in Grand Am and took my initial lead from them. I've limited my drop on the springs and added 5mm of rake by dropping only 15mm at the rear and 20mm at the rear as my absolute lowering limit, which still does get played with from time to time. I have just measured from bottom edge of the rim to the under-edge of the wheel arch which are 610mm all round on my DD wheels (245/45R18 fronts and 275/40R18 rears) - these tyres are Falken FK453 at 677.7mm dia front and 677.2mm rear. My track Enkei's RUN 275/35R18 NT01 at present and these are 650mm tall - so tyre height accounts for around 13mm CoG overall drop. I run KWv3 shocks (front rate is 425lb/in and rear is 450lb/in) but have Penske double adjustables to go into the car when I take it off the road. Spring rates will rise to ~550 front and ~650+ at the rear on proper coil-overs as a starting point but there will be a lot of testing to get it right. I am running quite a soft setup (Whiteline front bar, full stiff and Whiteline rear bar fitted but currently disconnected - sometimes I run it on softest setting if I need to shift balance to the front depending on track and/or track grip). I have the yaw-sensor DIY installed as the standard electronics are dangerous on the track - even with VDC off, there are sufficient electronic nannies left to cause problems which I reckon is dangerous. I also have the SPL FUCA installed and the balance of SPL bits for both front and rear suspension/subframe but not yet installed as the car is still my sometime/weekend drive (I have a Ford Ranger ute as my actual DD) and not a dedicated track car. As soon as the car comes off the road (it has 160K kms on it now) it will get the complete SPL suspension upgrade and Penske shocks installed as well as 4-litre forged engine, Motec M150 and QBE69G gearbox which is when suspension tuning really starts. I also have AP brakes to go onto it and if I can persuade one of my suppliers to part with his old-spec Bosch MotorSport ABS - I'll have that as well. The Motec can also support launch and tunable traction control but that will be a bit down the track I think DarkJak, cv129, Rusty and 3 others like this. Last edited by BGTV8; 08-06-2018 at 03:09 AM. Reason: Add more detail

08-06-2018, 09:43 AM	#37 (permalink)
Hotrodz A True Z Fanatic Join Date: Aug 2012 Location: NW, AZ Posts: 9,330 Drives: 10 Nissan 370z Nismo Rep Power: 2684385	I have been thinking of reaching out to Rearden to see if they might be willing to share some information as well. They have been kicking butt in the PWC. Rusty likes this. __________________ *Fast Intentions TT Installed and Tuned by Seb at SpecialtyZ 610whp 560tq:\|Fast Intentions 3" TT-TDX*\|SpecialtyZ/Fast Intentions 72 Row Oil Cooler\|SZ 6 Puck Clutch & Flywheel\|3GsCustoms\|Z1\|Wavetrac\|Hotchkis\|Whiteline \|Blitz\|Fortune Auto 500\|Fujimura\|SPL\|H&R\|TK\|TWM\|RPM Rollbar\|Sparco\|Next Level Performance\|TrackSpec\|AeroFlow Dynamics\|Pioneer\|

08-06-2018, 02:13 PM	#38 (permalink)
2011 Nismo#91 A True Z Fanatic Join Date: Mar 2011 Location: NJ Posts: 2,400 Drives: slowly Rep Power: 40569	Andrew from Tachterion Driver Development \| Making you faster one lap at a time! is an excellent driver who could defiantly find the culprit here. Your car is very different from what most people have and at least for me would be hard to diagnose. The only thing I notice, your spring rate is fairly "standard" and you should be looking at changing the rates to less in the back and maybe even more in the front but I'm not the best at this by far. Mine (full interior) is 1000/450. I wish I had my current settings handy, I almost have it right but the rear needs more work. Elmo370z likes this. __________________ GTR TT 493Whp/431lbft, Ecutek, Southbend 6puck,Quaife, RPM RollBar 4Point, R888R, JRZ RSPro F(10R/10C) R(10R/6C) 1000f500r inlbs+150inlbs Tender, SPL everywhere.Full Specs Last edited by 2011 Nismo#91; 08-06-2018 at 02:16 PM.

08-07-2018, 07:03 AM	#39 (permalink)
AlWakRa Track Member Join Date: Oct 2010 Location: Qatar Posts: 600 Drives: 10 370Z PW 6MT Rep Power: 13450	I am not that expert as most people here, but I will give my 0.02$ A lot of informative replies, I didn't read all of it, but I have nearly the same issue right now, and it appeared when my friend drove it, he couldn't complete an AutoX run in it as he spinned all the time mainly due to his early throttle input. I didn't have this problem before, what have changed from my last setup which was very balanced with slight oversteer. Tires: from RE71R 275/35-285/35 combo to R888R 265/30-295/30 LSD: Installed OS LSD ALIGNMENT: it was around Front camber -2.4 caster 6.0 toe 0 Rear camber -1.8 toe 0.12 (total 0.24) to front camber -2.8 caster 6.5 toe 0 rear camber -2.7 toe 0.32 (total 0.64 !!!! - couldn't dial it as I skipped ML as I was planning to change suspension and Truetype could be on the card) my front grip was very good, but rear isn't, even with an added downforce, it didn't improve. I don't know about hoosier recommended alignment, but I can say the first culprit could be excessive camber-toe. Then, it may be the hard springs at rear, as it is true-type, I saw most TT setups are a lot softer than oem style at rear, I reached out to MCA for new coilovers, they suggested 22kg front and 8kg rear. __________________ 2010 370Z Touring Sport Pearl White 6MT Powered by: Fast Intentions - Motordyne - Stillen - OS Giken - CJ Motorsports - Mishimoto - MCA Suspension - SPL - SuperPRO - RJM - Z1 Motorsport - Zspeed - Volk My Humble Journals

09-15-2018, 02:47 AM	#40 (permalink)
ValidusVentus Enthusiast Member Join Date: Jun 2011 Location: Washington State Posts: 400 Drives: #18 Z34 Rep Power: 23	OP, your car does sounds well setup (aka badass). Our cars are actually very similar minus your custom fuel cell and abs (nice). Any pics of your brake cooling setup? Ideas: -Ride height (and effects) -Front vs. rear tire temps off, perhaps exacerbated by the amount of rear toe? (And dynamic toe?) -I also run 1000lb fronts but run a 550lb rear spring on my true type AST 5200s (with JRZ top hats ). I'd bet a nickel, though, that its due to the rear loaded tire operating in an unfavorable kinematic situation, as you said. I've noticed a big change in rear grip from ride height changes. Also keep in mind that rear toe changes with suspension position as well, so perhaps not just a camber curve issue. After making a rear rideheight change before my last track day -to help combat inside rear wheel lift on some offcamber corner exits- I was battling a lot of oversteer everywhere. I tried softening the rear ARB but absolutely hated the rear roll amount that introduced and just went back to the mid setting on my whiteline rear, made a small tire pressure change and just drove around the oversteer. Discovered one of my damper adjusters was broken and I had forgotten my spring perch wrench at home From looking at your car pics sort of looks like you have SPL solid rear subframe bushings? I have those as well with the OEM'ish spacer setup at the moment. Anyone feel like measuring hub centerline to rear wheel arch distance and alignment settings and collaborating on establishing an optimum rear ride height range? Also: Get on the "370z Top Ten Track Records - Road Courses II" thread! The only times I've got up there, with the car as set up as it currently is, are from the Ridge MSP unfortunately. __________________ Mods: Dedicated caged track car, lots of things. \|\|\| Valkyrie Autosport \|\|\| Last edited by ValidusVentus; 09-15-2018 at 04:06 AM.

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