Horrible handling
 

Went to the track yesterday and only ran one session due to other minor issues. But even if that wasn't the cause the handling would of made me stop.

Normally I run -2.5 camber -.02 toe on front and -1.8 camber 0 toe. Well I was telling my alignment guy about the mild bump steer our cars have and he felt running some toe in would help this cause and give more rear traction. First let me say the guy knows his stuff in this area. Wouldn't trust no one else so let's not go there. So he added .08 toe in which at the time I really didn't want that much but let it ride. Well come yesterday on the track it was the most horriable rear handling car I ever felt. I did not feel like going over 40mph around turns for it was that bad. The front was planted but felt as the rear was on ice the hole time. Very loose. The rear was steering the car bad IMO. Nothing else was changed on the car besides the traction arms but I dont see where's that's a issue. Maybe I should take the sways off full stiff in the rear. But there's no doubt I'm going back to the alignment shop and get this undone ASAP.

I talk to my guy today and he doesn't feel that should of been the case at all. He feels there should of been more traction added. So any input guys? I know our cars are far different from other. I don't want no slander on my guy. I trust him. It was definitely a trail and error. I also have always run a true type coilovers no issues. I now have SPL traction arms going on the week to help with bump steer by eliminating the crappy rubber bushings.

Probably takes some time to get use to... Toe-in in the rear is generally the standard for RWD and helps with high speed stability. Heck toe-in in the back comes stock.

This is not a getting used to situation. I know how my car was handling and I know how one should handle and this was nasty. It was pushing in the rear while the front was behaving perfect.

Chris you think it could have anything to do with the crash at Road Atlanta? I know you took allot of damage to the read of the car.
I don't feel .08 of toe is going to cause that issue, but you never know. Just set it back to zero an give it another try buddy.

The frame machine came back dead on so there was no pulls made to the sub frame/ unibody area. The alignment was hardly off. I haven't been on the tack in close to four months. I am running on new tires with about 800 miles on them. Maybe it's me. My nerves were shot trying to get back into the feel of it all. But even then I didn't feel right.

I talk to my buddy Mike and he feels also the toe maybe the issue along with the sway being to stiff. The turn in felt great but the exit of all turns felt slick. Maybe the tires need more time. Just trying to get different views here.

I highly doubt the toe-in was the issue unless he accidentally went toe-out. You say you did or did not change the traction arms prior to the event? If you did, that's likely the issue as they can affect bump steer. Where exactly was it loose? Entry? Mid-corner? Braking? Exit? All of the above? If you answered all of the above its most likely a toe situation unless there is something mechanically wrong/broken that you didn't notice.

Most felt mid corner and exit. Maybe the tires need more time on them? The spring percent got missed up pretty bad but it seems correct. The thrust angle is good also. I'll have someone else drive it to see its it's in my head. I changed the the camber arms and toe arms before last alignment. This week I'm installing new traction arms. All through SPL. Maybe it's me. The tires are hardly broke in. The hole course was a off camber track. Never done that much. So I'll keep a open mind. Maybe my accident has me mind boggled.

Way too much toe in up front. Not enough in the rear. .010 toe out in front, (.020 total) .025 in on the rear. (.050) Camber seems about right for the front, consider less in the rear, these things go negative camber very fast in back once the compression starts, I actually dial some camber out so when I'm fully compressed they're around 3 degrees neg. and wear patterns are near perfect.

Oh, and definitely soften up the rear camber.

Now- how was the Fuel Starve fix?

You just changed rear tires? Street tires or race tires? Same brand/model/compound as the front? That could be the case. Was it only when turning a certain direction? When the rear broke loose was it snap oversteer or gradual/controllable? Was the turn-in good because the rear rotated easily or because the front was sharp? How was it under braking?

If it was indeed driver error it was likely a case of going too slow in and getting on the gas too early/hard. Without messing with the traction arms/toe curve I am going to say it's likely not due to the small toe-in.

Same tires front and back. AD08's. It was gradual and controllable. The turn is was what seem sharp and rear rotated easly. I was running a 265 up front went to a 275. Braking was more than fine. Maybe it's such a dramatic change on all levels that made it feel wild. I was definitely slow in a trying to push it out hard. I guess my nervous are a wreak from my incident. I've been beating myself up for months about it so........

I am going to go ahead and guess that its a combo of getting on the the gas too hard/early and rear sway was too stiff for the new setup. Toe issues usually end in a more snap-oversteer or unpredictable feeling. I don't think it was the tires. The AD08s are actually best on their first heat cycle. Race slicks when cold/brand new can be a handful but usually not true for street tires.

Sways are on full stiff now. I'll back them down check my alignment again in case and grows some balls. Lol. Thanks for the advice Mike.

I also assume that going with the SPL arms and how they do away with the stock rubber bushings and going with solid mounts had to create more stiffness and teamed up with all my other suspension parts I already have on top of all the weight I've removed back there has pushed it all passed it limits.

Let's just be clear that toe IN tends to make the rear more stable. Toe OUT allows the wheel's slip angle to describe a turn and increases turn in grip (weight transfer will scrub some of this out). See DG's "autocross to win" link Jordo recently posted.

I think there might be something else to consider at play also. Didn't think about it till later. I don't really wan't to go all into it. But may have something to do with fluid getting on my tires. More details tomorrow.

the obvious first comment is the new tires...you sure mold release, etc was good?




If we are staying on the topic of toe, you dialed in .08 of toe in, when the 370Z has an issue of too much toe when in on-throttle corner exits. If you were noticing it while on the gas, that really doesn't surprise me much...you were probably seeing an excessive amount of toe-in.

It was definitely when on throttle or applying throttle.

I think the toe explanation is pretty reasonable then.

I definitely saw gain of > 1/32 when on throttle exit, and starting at .08 means you are probably seeing some crazy numbers.

chris, you ever get a chance to tweak the toe and see how it felt?

Not yet. Changing traction arms tomorrow. Alignment next Friday. Been crazy busy with life lately.

Thats what chicks will do to you.:icon18:

Some much more experienced folks have chimed in already but the first thing I would have done in that instance was soften the rear sway bar.

My first event of the year was my first on coilovers and with the rear bar at full stiff the car was very unpredictable and liked to step out mid-corner. (It put me 4 off twice! in one session) Dropped it to the middle setting and the car was much more predictable.

I'm going to make a handful of adjustments. With as much weight out of the rear and the roll cage added its definitely light and stiff back there.

I wouldn't put the rear sway on full stiff. I'm looking at the Whitelines and even on the softest setting, they are something like 30% stiffer. With the sways super stiff, you leave a lot up to the traction of the outside tire.

I would have rechecked the toe.
Toe in will not do what you were experiencing. There are sooooo many things it could be.
Just as an FYI... Our front bar is 1.75" and our rear bar rates just a bit stiffer than stock ;)
Again.... Without knowing everything.... It could be anything.

I feel now it's the sway bar. I'm changing traction arm tomorrow and will recheck alignment after. Do you guys feel I should keep the toe at .08 in?

I think I might had another issue. The same day I had a small fuel leak from the stock fuel side. A single screw was missing that holds the pump in and the O ring expanded allowing fuel to come out. So it ended up being a good bit coming out under track conditions. I wonder being the tank is on the outside of the car if the fuel was spilling onto the tire. Some fuel ended up in the passenger side floor board also. I had been testing the handling of the car on the street with no issues till that day.

SPOHN, what you describe is exactly how I felt when running with my hotchkis sway bar set to full stiff at rear, I'll loosen it up to lowest if I were you.

That's what I was running (full stiff). Worked super great for me. But I believe the roll cage stiffened up the rear a lot. Never got to fully test my car after for the day I went to the track it was raining. definitely going softer setting. I'll get it right. It's definitely not the toe.

In for updates!
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I agree sounds more like toe out issue or something that is not right after accident. Too much rear bar can be problem too.

Pretty sure there's nothing wrong from the accident. Been driving perfect on the street even when pushing it. I feel the sway is goingto be the biggest thing. Toe will be check next Friday to ensure. Thanks for everyones help.

I told you sway bar from the get-go. Unfortunately, there really is no way of safely testing other than the track.

If you merely pulled car back to factory specs and didn't reinforce rear pickup points you may have some fatigued metal that allows rear suspension to deflect when under loads at the track. I have seen this too. That might explain feels fine on street but then gets funky on track, but too much rear bar is rarely a good thing for a track car. I run stock nismo rear bar with soft springs in rear to keep power down.

Also are bar mounting points all in stock spec? If something was moved in accident you may be getting strange loading of the bar.

Shock settings can also cause this problem for sure...or a busted shock maybe.

Check and record all your shocks settings....

I hope you are on the solution trail. I am surprised you do not have video though.

I suggested the bar because when I went from a street to track only alignment from the same shop, I had to soften my rear bar for the same symptoms.

Yep, a full hard rear bar is almost always TOO MUCH rear roll stiffness...that is for Autocross where you need to kick the rear end around to rotate the car. You don't want that to happen at a high speed track like Road Atlanta/Roebling/etc :-(

I "ain't no" Engineer, but sway bars are used to fine-tune a suspension that is already setup correctly. So if you are running a full hard rear bar, you are overcoming a another setup/tuning issue.

My humble recommendation is to start out very soft on all adjustments (shocks/ASB) and them work your way towards a more firm setting. And tire pressures play a part in this adjustment as well. To start go with the manufacturers hot pressure recommendation and then work from there to fine tune feel and total grip. Adjusting tire pressure has the same effect as changing spring rates...higher pressure is like adding higher spring rates...CHECK TIRE PRESSURES ALL DAY LONG...THEY MATTER.

I autocross all the time and dont need anything more than stock nismo rear bar to rotate easily. The Grand Am cars were using small rear bar as well. These cars have no issues with turning if they are setup properly. Honestly a larger rear bar on full firm is disater waiting to happen. No wonder this car spun like a top originally.

Only car I would use large rear bar might be a FWD car.

I run stiff up front and softest in the rear for whiteline, car handles great....

There's no standard sway bar setting for every car. There's a whole list of things that can affect where your sway bars should be set. The track alone is a major one, I have completely different sway settings for different tracks. What you have done to the rest of your car is also a huge factor: spring rates, dampening settings, tire size, tire compound, alignment settings, suspension geometry, aero, diff settings, and all of that put together and how they react with one another. I guess my point is, there's no way any of us can say that having your rear sway on full stiff is always bad. There's just too many other pieces of the puzzle we don't have.