Need help eliminating oversteer

Hotrodz · 08-03-2018, 11:53 PM

Quote:

Originally Posted by robertkroll

The bite at the front is good, the oversteer is the issue. I am researching suspension alternatives for the rear that can improve the grip with new geometric angles since the car is lowered.

Copy that, my setup is somewhat close to yours. I have pretty much the same suspension up grades except for one way coilovers 14k front and 11k rear. I run no bar in the back as well. I run square but not on slicks, nt01's 315 30. I am lowered as well and have just a slight oversteer.

I mentioned this in another thread but in talking with a Nissan employee while looking at some Nissan race cars in their heritage collection he said you might want add some weight over your axles. He went on to say that every z back in the day had added weight in the rear. He the showed me a few cars with post over the rear tire well were they added the weight help the car with traction.

Sent from my SM-G965U using Tapatalk

cv129 · 08-03-2018, 10:27 PM

Wow standalone ABS. You weren't kidding when you said a full race car.

Could you describe the oversteer? Was it entry, mid corner, exit, or left to right transition?

When you've gone into thinking changing rear suspension geometry, I am sure you have already tried the usual suspects, like toe, downforce, rebound and compression settings, brake bias....It'll be great if you can share the different adjustments you've made and your conclusions on them.

And the SPC front camber arms...typo?

Rusty · 08-03-2018, 11:46 PM

Quote:

Originally Posted by cv129

Wow standalone ABS. You weren't kidding when you said a full race car.

Could you describe the oversteer? Was it entry, mid corner, exit, or left to right transition?

When you've gone into thinking changing rear suspension geometry, I am sure you have already tried the usual suspects, like toe, downforce, rebound and compression settings, brake bias....It'll be great if you can share the different adjustments you've made and your conclusions on them.

And the SPC front camber arms...typo?

Too add to that question. Is it tail happy all the time? Or at different corner speeds? What's your tire temps across the tires. What's your fuel level when it happens? How many heat cycles on the tires?

robertkroll · 08-04-2018, 05:46 AM

Quote:

Originally Posted by Rusty

Too add to that question. Is it tail happy all the time? Or at different corner speeds? What's your tire temps across the tires. What's your fuel level when it happens? How many heat cycles on the tires?

The car is tame in the straight braking zone and becomes slightly lose as you trail into the turn. You have to be careful not to carry too much speed or the back will start to wash out and this will destroy your turn. It's predictable for rotation at the apex which is helpful, but I would rather have the added grip. Once through the apex, the car doesn't let you go back to power without the back pushing out. You have to very gently add power through the track out without getting too excided, but as you get closer to a straight wheel, you can go back to power. I can hear the E46's get back to full power ahead of me. The crappy part is that I have the power on the straight, so I can reel them back in, but lose the distance again at the next corner.

The WORST thing about this is that we rent seats out for endurance racing and we use the car for instruction and when we put somebody in the seat with slightly less experience, it becomes a dangerous situation.

Hotrodz · 08-04-2018, 01:11 PM

Quote:

Originally Posted by robertkroll

The car is tame in the straight braking zone and becomes slightly lose as you trail into the turn. You have to be careful not to carry too much speed or the back will start to wash out and this will destroy your turn. It's predictable for rotation at the apex which is helpful, but I would rather have the added grip. Once through the apex, the car doesn't let you go back to power without the back pushing out. You have to very gently add power through the track out without getting too excided, but as you get closer to a straight wheel, you can go back to power. I can hear the E46's get back to full power ahead of me. The crappy part is that I have the power on the straight, so I can reel them back in, but lose the distance again at the next corner.

The WORST thing about this is that we rent seats out for endurance racing and we use the car for instruction and when we put somebody in the seat with slightly less experience, it becomes a dangerous situation.

Thank you for providing detail on what you are experiencing. It is obvious you have a lot more track experience than I do and I hopefully we can find some solution to what you are describing. Although I might not be driving as aggressively as you are I know exactly what you are talking about when accelerating out of low to medium speed turns. I have thought it was and still maybe to a degree my inexperience and driving technique along with boost (torque) coming on strong and early. That said, if I must go to second gear I have to really be light on the throttle or allow the car to totally rotate beyond the apex to apply throttle many times I simply stay in third gear for risk of loosing to much time or spinning out. It is definitely annoying to run away from most in my run group only to be caught in the corners because of poor exit speed. I am not a fan of short twisty tracks because of this.

You said you were researching some geometric suspension alternatives, care to share what you have found so far? I know some of the folks that are doing the quarter mile and half mile thing are making strides in this area and it is very much on the down low as records continue to be broken in the straight line game.

Rusty · 08-04-2018, 01:32 PM

Because of the camber curve being what it is on the Z. Steep. Sometimes I wonder if we are running too much in the rear.

andy_meng1024 · 08-04-2018, 06:37 AM

I think this is your car. Nice mods.

http://www.zcarblog.com/for-sale-1/2...-370z-race-car

robertkroll · 08-05-2018, 08:36 AM

Quote:

Originally Posted by andy_meng1024

I think this is your car. Nice mods.

http://www.zcarblog.com/for-sale-1/2...-370z-race-car

That’s her!

Spooler · 08-04-2018, 11:46 AM

What are your spring rates in? Pounds per square inch or Kilograms per mm.
Most folks on this board use Kg/mm. The hard core autocrossers and racers use Lb/in.
It's sounds like you have the suspension adjusted all whacky causing the oversteering issue.

cv129 · 08-04-2018, 03:12 PM

I believe JRZ only has true type for the Z34

Hotrodz · 08-04-2018, 03:18 PM

Quote:

Originally Posted by cv129

I believe JRZ only has true type for the Z34

I thought so, but didn't want to assume. Thanks....

Hotrodz · 08-05-2018, 04:48 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, 05:17 PM

I am surprised BGTV8 hasn't chimed in yet.

BGTV8 · 08-06-2018, 01:36 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, 05:09 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?

08-03-2018, 10:27 PM	#2 (permalink)
cv129 A True Z Fanatic Join Date: Jul 2011 Location: Dallas, TX Posts: 3,265 Drives: 09 Nismo, 16 Nismo Rep Power: 163995	Wow standalone ABS. You weren't kidding when you said a full race car. Could you describe the oversteer? Was it entry, mid corner, exit, or left to right transition? When you've gone into thinking changing rear suspension geometry, I am sure you have already tried the usual suspects, like toe, downforce, rebound and compression settings, brake bias....It'll be great if you can share the different adjustments you've made and your conclusions on them. And the SPC front camber arms...typo? DarkJak and Hotrodz like this. __________________ Setrab \| RE-71 \| SPL \| JRZ \| Nismo \| ARK \| Whiteline \| RacingBrake \| CJM Oil Pan \| Ti shield

08-04-2018, 01:32 PM	#6 (permalink)
Rusty Ronin Samurai - Assassin Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 69 Posts: 35,441 Drives: 2011 Nismo GM 6M Rep Power: 2684438	Because of the camber curve being what it is on the Z. Steep. Sometimes I wonder if we are running too much in the rear. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html

08-04-2018, 06:37 AM	#7 (permalink)
andy_meng1024 Premium Member Join Date: Nov 2009 Location: Taipei Posts: 233 Drives: 2012 370z Rep Power: 3382	I think this is your car. Nice mods. http://www.zcarblog.com/for-sale-1/2...-370z-race-car __________________ Current: 2015 C200 / 2018 Cayenne / 2012 370z / 2012 C250 Coupe Gone: 2013 Cayenne / 2004 Cayenne S / 2003 SL55 AMG / 2008 C300 / 2006 350z / 2006 C280 4Matic

08-04-2018, 03:12 PM	#10 (permalink)
cv129 A True Z Fanatic Join Date: Jul 2011 Location: Dallas, TX Posts: 3,265 Drives: 09 Nismo, 16 Nismo Rep Power: 163995	I believe JRZ only has true type for the Z34 Hotrodz likes this. __________________ Setrab \| RE-71 \| SPL \| JRZ \| Nismo \| ARK \| Whiteline \| RacingBrake \| CJM Oil Pan \| Ti shield

08-05-2018, 04:48 PM	#12 (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\|

08-04-2018, 11:46 AM	#9 (permalink)
Spooler A True Z Fanatic Join Date: Jun 2014 Location: Ga Posts: 14,061 Drives: 2013 Nismo 370z Rep Power: 2684393	What are your spring rates in? Pounds per square inch or Kilograms per mm. Most folks on this board use Kg/mm. The hard core autocrossers and racers use Lb/in. It's sounds like you have the suspension adjusted all whacky causing the oversteering issue.

08-05-2018, 05:17 PM	#13 (permalink)
cv129 A True Z Fanatic Join Date: Jul 2011 Location: Dallas, TX Posts: 3,265 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, 01:36 AM	#14 (permalink)
BGTV8 A True Z Fanatic Join Date: Dec 2009 Location: 03350 Australia Posts: 1,515 Drives: 09 Nissan 370Z M6 Rep Power: 39974	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 02:09 AM. Reason: Add more detail

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