Need help eliminating oversteer

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.

Hotrodz · 08-04-2018, 01:48 PM

Quote:

Originally Posted by Rusty

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.

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?

robertkroll · 08-05-2018, 08:45 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

robertkroll · 08-05-2018, 08:43 AM

Quote:

Originally Posted by Rusty

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.

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.

Rusty · 08-05-2018, 12:43 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.

xavier · 06-15-2025, 12:29 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.

"... This leads to rapid and noticeable changes in kinematics when compressed further. ...This car is NOT designed to be lowered to this degree. ...to change the kinematics to favor a bit of squat and body roll.".

what you means by changes in kinematics ?
without going back to functional dynamics with compensation arms?
or what arms ?

For the camber associated with lowering, there are solutions to add positive camber, to make the wheels vertical, like oem for extrem street use.

For example, I'm thinking of lowering between -36mm and lower... -50mm, with original tires 245/275. approaching a camber of -1.8° to -2° (with ou add positive camber) or more...-2.4. there are solutions to add positive camber. not trackday. 12k or less rear. 14k front. with add positive camber, i will like to obtain 1.2° front, 1.6° rear.

Does your knowledge of the maximum lowering impacting kenimatics permeit this to be resolved with more add positive camber ?

what would you estimate as the maximum lowering to save the kinematics?

with all alignment problem solved, to original alignment, will the kinematics no longer be functional in dynamics?
or.
with or without to add positive camber, what is the maximum lowering limited by functional in dynamics ?

Thanks
Best regards
Xavier

OptionZero · 06-16-2025, 02:16 PM

Quote:

Originally Posted by xavier

"... This leads to rapid and noticeable changes in kinematics when compressed further. ...This car is NOT designed to be lowered to this degree. ...to change the kinematics to favor a bit of squat and body roll.".

what you means by changes in kinematics ?
without going back to functional dynamics with compensation arms?
or what arms ?

For the camber associated with lowering, there are solutions to add positive camber, to make the wheels vertical, like oem for extrem street use.

For example, I'm thinking of lowering between -36mm and lower... -50mm, with original tires 245/275. approaching a camber of -1.8° to -2° (with ou add positive camber) or more...-2.4. there are solutions to add positive camber. not trackday. 12k or less rear. 14k front. with add positive camber, i will like to obtain 1.2° front, 1.6° rear.

Does your knowledge of the maximum lowering impacting kenimatics permeit this to be resolved with more add positive camber ?

what would you estimate as the maximum lowering to save the kinematics?

with all alignment problem solved, to original alignment, will the kinematics no longer be functional in dynamics?
or.
with or without to add positive camber, what is the maximum lowering limited by functional in dynamics ?

Thanks
Best regards
Xavier

is this a street car or a track car?

08-04-2018, 01:32 PM	#4 (permalink)
Rusty A True Z Fanatic Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 70 Posts: 35,571 Drives: 2011 Nismo GM 6M Rep Power: 2684440	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

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