AutoX stock class, rear bar instead of front?
 

Ok, I just attended my first event with the Z running RTR. Have square 285 Re11 and eibach front bar on full stiff. Car pushes like a pig. Yes I know slow down, brake earlier and all that technique. I came from a Solstice and STR S2000 and find the same driving style does not work very well. Car mainly understeers on steady state (sweepers). Car feels floaty on stock shocks but got Koni in the garage already.


My question is has anyone tried running a big rear bar and keep the stock bar on front to losen the car some? I ran around 45 front and 42 rear tire pressure. RE11 IMO does not mind high pressure and help with roll over. Also a little hesitant because i dont want to kill the front tire cause the lack of camber if I run the stock front bar. I have not ran A6 on the Z and do not know if the tires make a difference in handling compare to street tire. Any input would be appreciated.


What toe are you guys running?

Sure many gonna say soften the front if anything first...that should slow down the understeer.

Yeah that would be my first experiment in your boat. You say the front sway is set full stiff and you're getting understeer, so try reducing the front bar stiffness setting on that. If that helps then at least you have an idea what's going on and decide on more radical changes that would keep it sane with the front bar full stiff.

Try lowering your tire pressure, I have the same setup and I run in the high 30s cold. I don't have the sway bar, I run 38F and 38.5R. There is always going to be some plow, especially at the slower corners. That's pretty much what you get with a car that is nose heavy and on street tires

zero toe here

You run a big rear bar, the car is going to have even more wheelspin

One word .....no

I run 1/8 to 1/4 toe out up front and 0 in back. What mods does your class allow?

On street tires with a stiff front bar only the plow is pretty bad, worse than stock IMO. You have to run race tires to make that setup work.

You're pressures do seem really high.

Rear bar bumps you out of stock class into Street Prepared.

you can change front or rear under he new rule

Ah, that's right. Hmm, I would probably still do the front on this car since that is where the weight is but perhaps not as aggressive if on street tires.

I'm running 285 on a 9" rim in front and is definitely pinched. I'm afraid if I run lower pressure the roll over will kill the tire, especially if i go back to a stock front bar. The tire wear is currently acceptable considering how I drove it like a tank. Haha.

Rules are 140 tire rating and above, any size you can squeeze on a stock size rim with 1/4" allowance in offset. Change front or rear bar not both. Two external adjustment on shocks but can't change springs.

I am on run # 151 with the same tire and setup. I have never run it above 40 psi...

got almost 10k miles on it

Thanks for the advice, I'll try those pressure. So you are running stock front and rear bar?

stock everything except tires and a backup camera

I'd get some good gas shocks and custom valve to get more compression dampening (artificial spring rate) in rear.

Monotube shocks then. Koni are twin tube, but can be converted to double. Any experience on how they are when converted to double?

Never converted them but Koni North America has great technical support staff. Also Koni, Ohlins, Moton, Penske, Hypercoils, Your Racing Shocks Shop! is awesome to speak with.

I've actually thought a lot about switching to a rear bar and compensating by increasing the bump stop rate to get the front stiff enough. Not going to make the jump this year but may play around a little after nationals this year and see if I can get it to work.

Are you not allowed front control arms for camber?
If your not running a LSD and go with just a rear bar... Def creeping in on inside wheels spin which will kill any forward bite out of a corner.
There is always a couple ways to skin the cat as they say.
Again .... Not sure exactly what your rules are.

Rules are alignment adjustment using OEM equipment only (no camber arms, crash bolts, etc.), shocks (not springs), bump stops, and front OR rear bar. Aside from tire pressures that's all you get to tweak the set-up of the car.

Nope SCCA solo rules suck. You are pretty much stuck with max of stock alignment specs. You have to be real careful in Solo it's not like track. Slow turns in second gear will induce wheel spin. They are also stuck with crappy VLSD not a real LSD like we are used to so inside wheel spin is huge consideration.

A good driver can drive around slight understeer but it's real tough to overcome inside wheel spin if your rear bar is too big.

But I'm biased I have no patience for goofy stock classes in SCCA I want a car that allows me flexibility in setup. I dont want to be a slave to restrictive AX rules. At minim street mod if not prepared are where my cars always end up with SCCA. I couldn't even live with Street prepared. Winning isn't everything for me in amatuer motorsports having a car I can tune and play with is where it's at. It's growing sentiment in my region where we have growing non SCCA clubs that attract 200 plus attendees at each event. Most not running stock classes. sCCA needs to be mindful they are losing mindshare with folks like me and others. I'm petitioning for differnt set of street modified and prepared rules that allow heavier street going cars to be comptitve.

I don't think it's just your region. Personally, I could care less about competing with anyone but myself. I just go to events to try to get better at driving, and the last thing I want is to add complexity to managing the car/build to fit into some specific rules-lawyered competition classification.

What are your current camber settings?
Back in the 350z T2 SCCA days... We would put the front control arms in a press an tweak them a bit for camber.
:)

That's illegal in SCCA Solo II stock classes. But I can assure you there are people at a national level with slightly tweeked control arms. Im not much for cheating to win an auto cross competition but if goal is to win at all costs certainly that's an option for person willing to take risk of being protested.

I think provided your numbers are at the limit of stock specs there isn't much they can say. If you go beyond stock spec then there is certainly grounds for a protest.

a lot of people cheat.....

I would call the front control arms being tweaked a bit cheating.... espc if the rules allow for some alignment changes. So if there is a max negative camber number... Going over that is cheating .... But getting some additional negative camber could be had with some arms that had a casting defect or were that way after hitting some curbing.
:)
There are other ways of getting camber on the front end of the Z.

Yes and in stock SCCA Solo classes most of those ways are likely illegal. Likelihood of being protested at local level is low. Likelihood of being protested at national level is higher, but I know of cars that have won nationals with illegal items. ...just tells you something about someones character if they are willing to cheat in an amateur sport that is supposed to be self regulated. Plenty of cheater motors, cheater flywheels, cheater bushings, etc out there. SCCA Solo rules are pretty explicit about not manipulating stock suspension parts. Is someone going to take measurements of your suspension arms? Unlikely but you have to live with fact your cheating as rules dont allow that. Changing bushing position to gain more camber is not legal in stock Solo class either. You're limited to un molested stock parts and connecting locations unfortunately.

So I wonder what best setup is? Big front bar with more bump in rear or bigger bar in rear with more bump up front for poor stock class guys? I havent seen this discussed before. I never had this issue with Nismo but base and sport model guys have sucky bars and springs and can only modify one swaybar with choice of front or rear.

those scca solo guys are weird. there was a guy that forged bunch of fake Honda docs to get some stiffer springs or something. got caught, suspended and now back writing articles. bunch of crazy middle age guys

Sorry... The above post should have read "I WOULD NOT"
There isn't a successful team in racing that hasn't pushed one grey area or another.
Again... If you tweak the arms a little bit and get -.5 more neg camber vs flat out bend them to extremes and get -1.5.... The later you are asking for it.
Get creative and find a really good machine shop.
;)

Yeah I have a hard time taking the sport seriously. But some of top Solo people have crazy driving skills. I like it for that aspect alone. The whole class thing is screwy. The things you can and cannot do arent practical for real world. You essentially have to build a dedicated nerdy autocross car to compete at high levels. Not much cross over with track driving or hillclimbing so I just drive AX for fun in 3050 lb XP car. It is fun to drive up in a street legal XP car and beat trailered cars weighing more than 100 lbs less on race slicks

Ok, I just ordered an eibach rear bar just to try it out. I have new set of Koni yellow and was thinking about sending them in to be revalved with the intension of running stiffer bump stop. How stiff I have no clue, bump stop are relatively cheap. I seen some Penske bump stop that's I believe 400 lb when compressed an inch, would be more trail and error. I would have to get the front of the Koni's revalved with high rebound to keep it on the bump stop, like NASCAR.

Oh yeah, there are some amazing drivers out there. At the same time, there are many average drivers out there who thinks they are good and tons of people who are into it a little too much. It's racing around a bunch of cones, big f-ing deal. Stock class is not really stock given most of the cars are trailered to and from the events, some of the shocks are so hard that they work almost like a spring. It's just weird rule/politics. I am happy running my local event, the days of sitting out in the sun for 2 hours for a stupid work assignment makes me want to puke. 5-10 minutes of run, 2 hours of work assignment? Screw that

getting more steering
 

I am not sure if your car is pushing on corner entry, middle exit or all three?

It's strange that you can change swaybars and not add an adjustable front upper arm for camber.


Here are some things you can do to free up the rear end:

If you are running any spacers on the rear rims, taking them off would free up the rear end a little.

If you have adjustable dampening, if you reduce the compression resistance a couple of clicks this will allow the rear to roll more causing an increased difference in vertical load on the rear tires...reducing rear grip mid corner and exit.

I am not sure what the limits are on your rear toe, but you could push to the limit and run either zero rear toe or even rear toe out if that is allowed, to free up the rear end.

You can also reduce the rear camber on the car to something like 1 degree to free up the rear end.


Certainly finding the optimal tire pressure for grip on the front and allowing the rear to be sub optimal will also give you more steering

To get some more steering on the front end:

You could start with zero toe or even some toe out. The Toe out will give you better initial turn in but depending the tires you run, will likely give you some more push in the middle of the corner due to the increased slip angle of the inside tire. Some tires like more or less slip angle to optimize their grip, so you will just need to experiment.

Also remember if you run toe out in the front and zero toe or toe out in the rear your car will feel very twitchy in a straight line. On the highway to the events you will need to be very careful as the crowns in the road will want to make the car change direction without warning on you. So be careful.

If you are allowed to change swaybars in your class, are you allowed to add some lowering springs? this would give you some much needed front camber due to the camber gain resulting from suspension compression. Since the rear has adjustments for camber you can reduce the rear camber to something like 1.5 to help with the steer.


Hopefully this helps...but in summary here's what you might want to start with

zero front toe
zero rear toe
rear camber: -1 deg
remove any rear spacers you might have on the hub
reduce rear compression resistance on rear shocks by a couple of clicks
Put your front sway bar on full soft or go back to the stock bar.

I did not comment on the rear sway bar...but as others have already pointed out, it can hurt your forward bite with the inside tire spinning especially with the stock lsd. Even the quaife diff will spin too much. I have not tried the 1.5 way or 2 way rear diffs, but they would likely fix that issue, but require more maintenance.

Cheers