Excessive high speed roll *Need to go Lower *

[steve shadows]

Well I want to go lower.

I learned some weak spots on the car this weekend at B-willow.

It was my first real road racing track day and the car was a handfull to control around the technical course will all that HP but was mighty fun irregardless.

Anyways...

I have AGX Adjustable shocks front and back with GC Coils kit with 400 rate front springs and 300 rear.

I love the way the car handles but I would like to get the whole car 1/2 inch lower all the way around. The rear coils are only adjusted halfway down right now, so I have more room to drop the back ( a whole nother inch!). However if I go too low in the rear the car sits like its drag launching. So the problem is only on the font suspension pieces

I followed the directions on the installation from GC for the AGX's perfectly. I don't want to buy another coilover system. I was thinking of these options.


1. Complete shave area where GC coil perch is sitting now and move it down the AGX body 1/2 inch , tack weld the mild steel part to the body and then have my room to go down in the front.

2. Try to source up two front coilover from another maufacturer, used or new that allow for more ride hieght adjustment in the front.

3. Remove the actual adjuster (gold perches) from the front GC coils completely and secure the lower milde steel perches some how, or add a large metal ring ontop of them to support the spring seating on a circular matching base. (the gold perches are like 3/4 of inch in height).

Any Advice?

Again I really liked the way the car handled this weekend (aside from needing new subframe bushings and better brakes). The springs were just stiff enough and very digressive feeling in the car overall, easy to control and linear feedback, just too much body roll over elevation change turns.

Also heard that lower engine mounts could also support a lower center of gravity? I was looking at the peak performance ones, I need to replace my blown out nismo mounts any ways next month.

Cheers and thanks to any help from anyone!

Here is how the car sits the front coils adjusted all the way down, the rears adjusted down half way.



Under hard decel




Slalom Acceration





Acclerating from Pre-Grid




The car did not seem as rigid on outside roll over, or general body roll on hard decreasing apex turns.

The other option I was considering is just purchasing some tein flex for the car.

[tacotacotaco]

lower it tuck a tad bit. Do you have any sways? I believe cusco mounts provided the lowest drop on the motor other than custom.

[steve shadows]

Peak performance engine mounts are lowest I checked it out and will be picking them up next month along with subframe spacer and possibly bushings.

I was just thinking as I was posting about my front sway. It is still stock! I think a better front sway should help with that.

During the first part of the day I ran with no front strut brace. The second half with. The second half I also reduced camber to -3 instead of -6, the car had less body roll and more response but still a little lifty.

I have no rear sway. I would die with one, the car already drifts through 2nd at half throttle and part of 3rd depending on apex.

1. sway bar.
2. modify the gc kit and perch location?

front sway bar is probably a must in this case.

[tacotacotaco]

yeah best shot is to modify the gc perch take out that huge perch for the stock springs weld it, in lower your center of gravity. You should wait till wiisas post he seems to be pretty passionate about suspension like you are motor/tuning

[mrmephistopheles]

Wait wait.

A thread from Steve talking about a *need* to go lower?

Next think you know he'll be looking for wide, low-offset wheels and stretched tires...

I mean... *cough*

Nothing to see here, move along.

[mmdb]

For high speed stability look into some aero such as a front splitter and rear wing. I'd also up the spring rates and dampening as well. If you're getting serious about road racing a guy on this forum / freshalloy.com named "nikeboy???" is developing koni yellows with gc springs setup. He should be able to get you a custom setup with the correct springrates.

*edit* Whoops my bad didn't see the pictures since they wouldn't load at work. Yeap lower the car and up the rates.

[bigOdom1]

so you want to go lower but the wheels are hitting the shocks? how much travel do you have?

[PoorMans180SX]

lowering your car will reduce body roll a little, but really your springs and anti-roll (sway) bar have a lot more to do with it.

I would say source some new coils that have adjustable bottom mounts , as your plans will reduce shock travel too much? Maybe I'm not understanding, but from what I can tell from your post, just lowering the spring perches will reduce shock travel too much and probably cause some problems. You'll either have to shorten the shocks themselves, or source new coils. Also, with new coils, you could step up your spring rate, which would help with your body roll.

post some pics of the springs/shocks.

[steve shadows]

Ok will do.

Maybe I was unclear or overwrote that.

I want the location of where the coil seats on the shock body lower in the front, so I can lower the car more in the front. Its all way to the threaded base right now and the perch is in the location per GC's instructions.

I also have a stock front Sway do you think this is a bigger contributor than spring rates?

My spring rates are basically the same as 7.8 front 5.8 rear to JDM spec.

I know an instructor was making comments on another car at the event with 8 front and 6 rear mentioning the ride hieght was good but the spring rate was too stiff!

Just food for thought.

[rps13drift]

Car looks great steve! and + rep for autocrossing the beast! Not to be off topic about you suspension dilema but how did the 3076r perform on the track? Im still dying to drive my car but unfortunetly we have 7 inches of snow in my area

[steve shadows]

It was a handful but once I got the hang of the course layout a little bit- everytime there was a straight I passed at least 1 car in my group

I think the end plates on the spoiler were doing anything but good as well.

Not sure if this could effect outside roll over at all under accleration but It felt different than when I had no endplates at all messing around in turns back home at sea level.

[PoorMans180SX]

Originally Posted by steve shadows

Ok will do.

Maybe I was unclear or overwrote that.

I want the location of where the coil seats on the shock body lower in the front, so I can lower the car more in the front. Its all way to the threaded base right now and the perch is in the location per GC's instructions.

I also have a stock front Sway do you think this is a bigger contributor than spring rates?

My spring rates are basically the same as 7.8 front 5.8 rear to JDM spec.

Actually 400 and 300 are roughly 7.15 kg/mm and 5.35 kg/mm respectively.

I do think your front sway is having an effect. Definitely should consider an upgrade.

BUT, you are talking about making the spring sit lower on the shock. Unless you reduce the height of the shock itself, this will limit shock travel, and not be a good thing for the sudden transitions in an autocross, or anything else for that matter.

[steve shadows]

ok good to know.

I'm still learning all the dynamics of suspension and I am totally willing to admit when I am unclear right now.

I'm an engine guy.

I will try the front sway for regitiy (I am also getting a 4 point in the next batch of parts to buy). If that still doesnt support it I will go with a coil that allows dual hieght adjustment and the right spring rate (probably tein flex) Dave (mehsilvia) loves them for that style of course.

Would a helical diff help with outside tire power transistion? Maybe the wrong tire is getting more power affecting the feeling of how power is being applyed, It feels like I am getting pushed to the outside line a lot.

[veilside180sx]

You should not be welding on a sealed strut.

The lower you go...the less shaft travel you'll have. Steve you really should be running shortened struts if you want to go any lower.

[PoorMans180SX]

I don't know, I haven't heard the greatest stuff about Tein dampers, but whatever, your car is track only right?

I take it you have a VLSD?

Probably the combination of no rear bar and stock front bar is what's making you push. It doesn't feel like the front tires are losing grip before the back ones (in a steady state turn)?

[McRussellPants]

It all depends on what you want.

I wouldn't go over 8/6 in a car without a cage. S-chassis are flexy 5000. I don't know why everyone always tries to claim like theres one S-chassis spring rate to rule them all. 16/16 is right on a car with hoosiers and billion point cage, 6/5 is fair enough for doodlin around town on the way to the grocery store.

Sway bars will help.
Solid Endlinks will help
upping spring rate would help.

There is a school of thought that you don't want a rear bar and you need to control rear roll and overall balance with spring rate. In return you get more exit grip. I kinda think thats dicks though. Particularly if you're just dicking around with off the shelf GCs and weak springs. keep the rear bars from the same manufacturer and hopefully it will come out neutral.

Shut up about engine CG. you don't have a cage, you won't feel it. Your car won't handle better if you slump in your seat. although, super low seats are cool because it forces you to look further ahead.

Helicals are ass. Racecars can use helicals because they build their own to handle the HP. A Nissan Helical will flip out with 400whp and 255 R comps.

It looks like your searching for rear grip to put the power down, but building a understeer biased car by taking away front grip and confusing it for more rear grip.

Why you haven't gone for 9/10 FN01s with 255/275 already is beyond me. Get a real cage, 4pt is a waste of money imo.

noone can tell you how much to lower your car, lower it to where it barely rubs but never does. You'll like the consistancy more than any sort of jerk off pride about calculating roll center and posting it ony line.

/too much to talk about.

[ak_slick]

What engine do you have? Stripped interior? a 7k/5k setup is what of the guys I am around seem to really like for an all around good handling setup in stripped cars, 8k/6k for full interiors.

Remember, not to go to stiff without stitch welding or a cage, as you will really start to feel the chassis flexing. I agree that engine CG depending on your engine(rb) makes a difference. More noticeable once you stiffen things up though.

I don;t know about modifying your current setup like that... welding shocks = bad.

You should really spring for coil overs.

Course of action:
-Set of coil overs 7/5 or 8/6 you can always change the springs later and adjust the valving to your hearts content.

-After that if you still need sway bars go for it. I think you will be surprised at what a difference a properly setup set of coils will do for you though.

[cdlong]

Originally Posted by McRussellPants

You'll like the consistancy more than any sort of jerk off pride about calculating roll center and posting it on line.

and i was going to post something about roll centers, now i'll sound like a jackass. oh well, i'm not calculating shit.

when you lower a car the roll center drops more than the CG. since the car rotates around the roll center that gives the mass of the car a longer lever arm to act on during cornering. there's a good diagram here since you're an engine guy. http://e46m3performance.com/tech/transfer/pg-2.htm

you can get the geometry back into shape by using modified lower ball joints. you can either get full arms like SPL's or some other company (orange someting or battle version maybe) or using replacement ball joints from moonface or hardrace. i haven't seen any proof that the replacement ball joints are setup properly to fix the problem, so be careful.

fixing the roll center will limit body roll without affecting the suspension travel or ride like stiffer springs would. stiffer anti-roll bars would help to but that was already covered so i'll leave that alone.

[OBEEWON]

The ammount you would have to lower the car to affect roll without changing anything else is going to cause clearance issues with your current setup. Welding on a sealed strut = no good like everyone said. Go for overs with similar spring rates and udjustable dampening.

[steve shadows]

I was thinking of using a shorter spring in the same spring rate for the front to get th extra 1/2 inch I am looking for.

I think my spring rate is fine. I don't want a full cage yet, but when it becomes a full race car I will go that route as well as beef up the dampers with Koni and a higher spring rate. I still tool around on the street from time to time. The roll bar will be more for saftey than performance (obviously).

The car does losses rear traction before it understeers in pretty much any scenario right now.

In fact I don't remeber understeering ever during Sunday (maybe a little around mazda star, it's a very hard right hander with decreasing apex).

FN01Rs in a bigger width were planned after I sorted lowering the car a tad bit more and getting the saftey equipment and brake pads I mentioned in.

[PoorMans180SX]

Shorter springs won't solve your problem either. You'll still be reducing shock travel.

I think McRussellPants is pretty right on with your situation. Just because the car loses rear traction from overpowering the tires doesn't mean you should set the car up to understeer. However, guys that do autocross have problems with inside tire lift with a rear bar installed. I really think your first priorities should be a nice set of coils (or a nice shortened Koni/GC setup) and some bigger tires. Then maybe bigger bar(s) and 2- or 1.5-way LSD.

You could probably PM AceInHole about this stuff too. HA, he and Wissass are where I've gotten a lot of my knowledge from.

[steve shadows]

2 way?

If I invest in an aftermarket rear diff it will be a Quaiffe Helical or 1 way Clutch Type.

Shock travel right now is at 2 inches in the front. I still have a little room to play.

Bigger front bar yes.

Bigger Wheels yes.

The only thing I could think of doing is going with the Koni Inserts in the front in the future. Someone on FA offered to fabricate them and have them pre-made for install with my gc's for 900 bucks IIRC. Or I could just install them into some stock nissan shock bodies myself. It doesnt look that hard.

I should tap Ace for this thread, but he does auto-x not big track stuff. I am seeing 120 mph on the back sweeper at bwillow without pushing the car. I was seeing 135 mph on the straight when people got out of my damn way, and was in top of 3rd on every line with a coner with a degree less than 20% grade

I am not setting the car up to understeer, right now the car is very neutral and if anything oversteers. Rear traction is not a big issue, but with Azenis it's a bigger one than some warmed up R-comps, I am sure. I just have to feather 2nd gear exits and the car sling shots up to the next corner like a missle.

Once the Azenis get hot they grip just fine in any 3rd or higher gear situation. The turbo lag before 4 is actually a good thing in my case.

[McRussellPants]

Originally Posted by steve shadows

2 way?

If I invest in an aftermarket rear diff it will be a Quaiffe Helical or 1 way Clutch Type.

lol one way. you know you want some lock up under braking for stability? even helicals will have it? you know there are alot of race cars that run straight weldeds right? Seriously, going to zero lock up off power would be weird feeling as hell.

i bet the no rear bar helps as is because the VLSD would shit its drawers if it had to deal with a big amount of weight transfer. get a better diff and you'll probably be able to run stiffer in the back and still have enough grip.

Originally Posted by steve shadows

Shock travel right now is at 2 inches in the front. I still have a little room to play.

2in of bump is about what you need on a soft spring, don't go less than that when you do adjust it.

As for the spring, shorter springs don't really lower your car unless you droop them and run helpers. blah blah, you should run the tallest spring you can fit closer to the bump stop ect.


Get some KW V3 or Competitions. V3s can be had for less than flexes and probably have better dampening.

[PoorMans180SX]

Veilside180SX can fab you new shock holders or whatever the name is. He posted above and he does excellent work.

But...what McRussell said. I don't think a rear bar would hurt on a big track like Buttonwillow, since the weight transfer isn't as sudden as autocross and our cars don't tend to lift the rear tire on big tracks. I apologize, I wasn't saying you were purposely setting up the car for understeer.

It's really all about balance. Spring rates that go with shock damping that go with anti-roll bars that go with chassis stiffness that go with tires. I think what you're looking at right now is the next stage of upgrades in these areas, and I don't think one or two parts are going to get you what you want.

[MrChow]

Originally Posted by steve shadows

Peak performance engine mounts are lowest I checked it out and will be picking them up next month along with subframe spacer and possibly bushings.

My friend has these didn't like it. There really sniff. It vibrated whole car. Only time if wasn't when he was rev at like aroun 4.5 5 rpm. Not something for the street. But there very pretty mounts.

Originally Posted by steve shadows

During the first part of the day I ran with no front strut brace. The second half with. The second half I also reduced camber to -3 instead of -6, the car had less body roll and more response but still a little lifty.

-3 camber!! What tires do you have on there?? I think 2.5 is max.

Originally Posted by steve shadows

I have no rear sway. I would die with one, the car already drifts through 2nd at half throttle and part of 3rd depending on apex.

I still don't understand why not. My S14 did fine at Laguna Sage with coils, stock front sway bar and a 22mm in the rear just fine. I wasn't driving it.. But it was going fasssttt.
I believe a lot of it was drivers control. The driver said that my suspension setup was good but there was a lot of flex in my chassis. He also said that I need to redo my alignment. Which I knew was F-- up. I need suspension arms and bushings.
There's .02 cents for you.

[steve shadows]

Originally Posted by MrChow

My friend has these didn't like it. There really sniff. It vibrated whole car. Only time if wasn't when he was rev at like aroun 4.5 5 rpm. Not something for the street. But there very pretty mounts.

Yeah then that is not what I want haha.

I hate to start talking about engine mounts in this thread but I have always used Nismo style mounts.

What is a compromise between those and the peak perf?

also could excessive front tow angle contribute to this at all? (outside line) ( I need an alignment also).

I am trying to effect handling on the best budget possible for now after April- May I will be able to splurge a bit more on car parts.

[tknbkthrsdy4anfg]

Steve in all seriousness, just lower your car so the frame rails drag in corners. Infinite spring rate will keep your car from rollin'.
Also if I am reading this right, you have a stock VLSD?
omg get rid of that shit box.
I ran buttonwillow with a welded and was super happy with the off throttle rotation to point in and when putting the power down it over steered a little but planted that shit.

[steve shadows]

no thanks on the welded.

Ill be saving up for a 1 or 1.5 way clutch type or maybe evena quaiffe. I would much rather have a more predictable VLSD "shit box" with my HP level than a welded ghetto diff. At least the crap box vlsd is more predicatable and I know exaclty how the car is going to react.

[tknbkthrsdy4anfg]

I'm not saying get a welded, but it wayyyy better then a VLSD.

[steve shadows]

no it's not. It's good for parking lot drifting. Not exiting a corner at 100+ mph with 440 whp on tap on street tires