This is the roll center, suspension pickup, and steering angle modification thread.
 

Disclaimer: Modifying a car's suspension in the ways discussed in this thread will always result in some compromise. Increased steering angle makes things rub, raising the subframe increases anti-squat, etc. Please read through and understand the concepts before you go hacking up your car in pursuit of performance. All of the suspension components are affected when lowering the car, especially when lowered to the extreme. Correctly modifying the suspension pick up points or knuckles to correct for these changes can reap large rewards, including better camber and toe curves, less body roll for a given spring rate/anti-roll bar, and more traction/grip.

This thread is focused mainly on the S-chassis, with some Z and R chassis thrown in for good measure. There are many more brands than mentioned in this thread, but I've tried to include the most original and functional options. Feel free to contribute more.


Part I: The Basics.

The Front Suspension:

Tension rods: These are used to adjust caster, and together with the lower control arm pivot points, determine anti-dive and anti-lift in the front suspension. Positive caster like the S and Z chassis have gives positive steering feel, and helps the steering return to center automatically from lock. The angle of the tension rod and lca (horizontal plane, front to back) determines anti-dive under braking situations and anti-lift on acceleration.

Tip: If you're using your tension rods to adjust caster more than one or two degree(s) past factory settings, there will be bind in the lower control arm's traditional rubber or urethane bushing. It's recommended that you change to an aftermarket control arm with a heim joint/spherical bearing.

Front lower control arms: Determine your roll center (basically), track width, and camber curve of the front suspension. The arc they move in is the camber curve. Together with the tension rod they form an A-arm.

Tie rods are used to adjust the toe in the front, and obviously to steer your car. Aftermarket tie rod ends can be used to adjust bump steer by spacing the tie rod and changing its relationship with the control arm.

The Rear Suspension:
In a multi-link setup, as is present on nearly all modern RWD Nissans, the control arm pivot points determine the roll center, similar to a double wishbone setup, but with some variance according to where the toe and traction rod are mounted.

Rear upper control arms: Used to adjust static camber. Together with the lower control arm form the curve which the knuckle travels in vertically, gaining increasing negative camber with suspension compression.

Toe rods:These control static toe and toe change during suspension compression. When lowered aggressively, our car's toe and camber curves are significantly changed, becoming ‘steeper’ (more change with less movement).

Traction rods: Determine caster (or thrust angle) on the rear suspension. For most of us, that doesn't mean much. What matters is that they have a large effect on the toe curve, or bumpsteer of the rear suspension. A good rule of thumb is to lengthen these just as much as you lengthen your RUCA to minimize bump steer. This also slightly reduces anti-squat, which can be beneficial or detrimental depending on your chassis and setup.

Rear lower control arms: Help determine roll center, anti-squat, and camber gain. Can be used to adjust static camber as well as the camber curve over the suspension stroke.

Anti-squat: Anti-squat is probably the single most misunderstood aspect of the rear suspension. Anti-squat by definition is the resistance to squat the rear suspension possesses by way of diverting force through the suspension links. The higher the percentage the more resistance to suspension compression. Most people incorrectly assume that squat equals weight transfer to the rear, and thus increased traction. The truth is, multi-link rear suspension is vastly different from a solid axle, and squat actually reduces rear weight transfer, and takes up time compressing the suspension, where it must be damped by the shock. It is true that in traction limited scenarios, such as gravel or snow, we do want very little anti-squat, but on dry roads or the racetrack, this is not the case.
To determine anti-squat, we must first draw a line from the overall center of gravity of the vehicle through the centerline of the rear wheel. This is called the neutral line. Then we must draw lines from the rear control arm pivot points forward. Where these lines intersect, and whether they are above or below the neutral line, determines the percent of anti-squat. If they are below the neutral line, there is a negative percentage of anti-squat (or pro-squat), and if they are above there is a positive percentage. Around 120% is ideal. Here's a nice GIF and a couple images Motary put together.:

http://i.picasion.com/pic78/180a8b6a...28e4d9f555.gif

Here's S14 anti-squat:

http://i.imgur.com/DL6YZmAh.jpg

And with GKtech rear knuckle:

http://i.imgur.com/T1k87Bwh.jpg

Unfortunately for 90's Nissans, we are stuck between two extremes. The S13 (and Z32/R32 for that matter), have a huge amount of anti-squat (somewhere around 180%), which means engine torque is very directly transferred to the tires, often shocking them into breaking traction earlier than ideal. The S14 and S15 (and R33/34), have a very small amount of anti-squat at standard height, but this quickly goes pro-squat when the car is lowered. This means the car squats excessively, changing the suspension geometry, reducing traction, and delaying the cars reaction to inputs to the throttle. Fortunately, the overwhelming aftermarket support for these vehicles have come up with some very nice solutions, which I will present below.

Roll Center:

Front roll center is determined by the angle of the lower control arms and the angle of the upper strut mounting points. These angles, drawn in space, determine the instant centers for the front suspension (instant centers are the points that the entire suspension moves around during body roll). Then take a line from each instant center to the middle of the tire tread on the opposite side, and where these lines intersect, there is your front roll center.

Rear roll center (for our cars) is determined much like a double wishbone setup. Use the angles of the upper and lower control arms to determine the instant centers of the suspension. Then, just like the front, take a line from each instant center to the middle of the tire tread on the opposite sides. The intersection is your rear roll center.

http://i.imgur.com/43UbNzH.jpg

Center of Gravity:

The center of gravity is the point at which all the weight of the car is balanced. It's roughly the crank centerline in the front, and above the differential in the back. You can find out your exact CG by using scales, but that is beyond the scope of this article.

Roll Couple:

Roll couple is the distance between your center of gravity and roll center. This is the reason that lowered cars have more body roll. The roll center moves lower (due to the change in angle of the suspension arms), while the center of gravity is only lowered as much as the body of the car. This makes the distance between the two longer, thus the roll couple longer, which gives the body more leverage on the suspension. I'm sure we all know how much of a difference leverage can make.

You actually want your roll center just under your center of gravity.

Part II: Roll Center Adjustment

Here are the things you can use to adjust roll center:

1. Use a ball joint with a shank that is longer, thereby spacing the pivot point at the knuckle farther down.

The only ball joints that I’ve seen that actually have a longer shank are Sunline Racing, Moonface, and Nagisa auto:

Nagisa:

http://i.imgur.com/gknIl76h.jpg

Beware of "Roll Center Adjusting ball joints" that just space the ball joint up. The ball joint shank needs to be longer. Nagisa has a good illustration (bad on the left, proper on the right):

http://i.imgur.com/8NPuGOn.jpg

The above method is only so effective. Due to the angle of the ball joint, using a long shank increases ackerman, and at about 20mm of correction, the lower control arm starts running into the brake rotor.

Dan at Parts Shop MAX made a nice diagram showing how the ackerman change happens:

http://i.imgur.com/rEKtKu1.jpg

2. Purchasing aftermarket lower control arms that have roll center adjusting heim joints and shanks.

There aren't a whole lot of arms that offer more than 10-15mm of correction because of brake rotor clearances. Ikeya Formula has some correction, and PSM has a 5mm fine adjustment spacer.

http://i.imgur.com/jA6QUDo.jpg

They've updated these with bent tension rods for more steering clearance:

http://i.imgur.com/BfX6e1Vh.jpg

PSM's limit break (longer) LCA:

http://i.imgur.com/DvZHFDQh.jpg

And GKTech's latest chromoly FLCA's. You can order these with 20mm longer shanks.:
(Image courtesy of swapmysilvia.com)
http://i.imgur.com/hXhWoPxh.jpg

These are some nicely engineered pieces, and they fail just as they should when running into things.

http://i.imgur.com/zeSmipJh.jpg

3. Modifying the pickup points on the knuckle (usually by creating a whole new knuckle), dropping them lower. Also, raising the hub location in the knuckle, which effectively creates a ‘drop knuckle’; a knuckle that lowers the car while keeping roll center similar. Some of the kits actually combine both ways, raising the hub, and lowering the pickup points.

Driftworks makes drop knuckles, 45mm in the front, and 50mm in the rear. The rears have urethane bushings for the control arms:

http://i.imgur.com/O02an4D.jpg

Stock knuckle:

http://i.imgur.com/eqvZy3G.jpg

Driftworks knuckle:

http://i.imgur.com/itWWEqv.jpg

R-chassis front Driftworks with 20mm correction:

http://i.imgur.com/lmJ3RcRh.jpg

They just released their new Geomaster V3, which was collaborated on with Wisefab. Now with 50mm of front correction and revised steering geometry. Front knuckle has drift and grip settings and the rear now has sphericals.

https://i.imgur.com/SDGKLLqh.jpg

https://i.imgur.com/YXRf8khh.jpg

http://i.imgur.com/8tBKroqh.jpg

Parts Shop MAX forged pro knuckle:

http://i.imgur.com/UtBLqJD.jpg

http://i.imgur.com/q39Rxb0.jpg

And their new ‘trailing knuckle’ with increased caster trail and adjustable ackerman:

http://i.imgur.com/npTJocTh.jpg

http://i.imgur.com/9lpH0kqh.jpg

Parts Shop MAX latest forged 25mm drop knuckle with spherical bushings:

http://i.imgur.com/RDquZbMh.jpg

And their ‘toe control’ brackets, which allow you to dial in different levels of bump steer:

http://i.imgur.com/6S6EpYbh.jpg

Here's a comparo shot between the Driftworks and PSM:

http://i.imgur.com/CD3V90E.jpg

Wisefab now has their s-chassis V2 kit out, packed with features. Double shear pickups for LCA and tie rod, camber/caster top hats, 56+mm of roll center correction, trailing knuckle design, adjustable ackerman, and a rack relocation kit that moves your rack 46mm forward.

https://i.imgur.com/HI5SWZ1h.jpg

https://i.imgur.com/5OnpxOZh.jpg

Wisefab's rear kit, with all new geometry for better rear grip:

https://i.imgur.com/jnCiMsRh.jpg

http://i.imgur.com/Eb0GpVR.jpg

GKTech now has three different variants of their front knuckle with 50mm of correction. They have grip, grip/drift, and pro drift versions, each with their own characteristics:

https://i.imgur.com/uKLRIqoh.jpg

http://i.imgur.com/ntkGBJjh.jpg

https://i.imgur.com/F0YLQbqh.jpg

They also have this cool diagram of the different steering geometries of their knuckles/kits:

https://i.imgur.com/6yZUQFyh.jpg

And this very informative link about all the geometry associated with their knuckle and why they designed it the way they did.

https://au.gktech.com/news/gktech-s-...eering-knuckle

GKtech also offers R-chassis knuckles which can be used on the Z32.

http://i.imgur.com/lotcx0Wh.jpg

Photo courtesy of Chris York:

http://i.imgur.com/1RF83HIh.jpg

http://i.imgur.com/lqAEaroh.jpg

And their rear 40mm rear knuckle with new kinematics for better camber and to curves and corrected anti-squat. This knuckle is also significantly lighter than stock:

https://i.imgur.com/7d7aXY2h.jpg

https://i.imgur.com/jIH5f0Ih.jpg

http://i.imgur.com/EMttkf7.jpg

And GKtechs bolt on knuckle adapter with 40mm of correction (now in forged steel instead of aluminum):

https://i.imgur.com/RQNs2m5h.jpg

https://i.imgur.com/KMgG2vdh.jpg

Track Day Performance has a billet aluminum front suspension kit with 70 or 100mm of correction (No longer available).

http://i.imgur.com/0Er0Q4Ah.jpg

http://i.imgur.com/Nt7P9lJ.jpg

And their rear kit (I don't have shots of the arms that come with :()

http://i.imgur.com/FiHl3Mgh.jpg

Heatmaker knuckles offer 60mm of correction:

http://i.imgur.com/1Of94VFh.png

http://i.imgur.com/wJUJXhZh.jpg


6. You can move the whole subframe up, correcting the suspension geometry much like the modified knuckles.

SPL’s subframe adjusters (which can be either set for stock, or raised for ride height correction). These also can be ordered in an offset pattern, so you can mount a S14/15 subframe in your S13:

http://i.imgur.com/Ae4qunY.jpg

PSM's slip fit risers (Installing these was cake):

http://i.imgur.com/VGTGHNrh.jpg

NOTE: Raising the subframe also increases anti-squat. SPL provides a very good link on how pushing the Subframe affects anti-squat and roll center:

http://splparts.com/instructions/SPL_SSB_S13C.pdf

This is the roll center, suspension pickup, and steering angle modification thread.
 

Part III: Steering Angle Modification

Let's talk about steering geometry for a bit. There's a lot to consider when you're picking out parts for steering angle. We now have tons of options. When I first made this thread, it was pretty much cut n' shut knuckles or Driftworks.

Ackerman in the steering:

In layman's terms, ackerman is the steering angle difference between the right and left front wheels when turned. This has important implications in drifting and in road course work. When turning normally, the wheel to the inside of the corner turns a smaller circle than the outside one. This makes the ideal angle between the two different. In long sweeping corners, low ackerman is advantageous, while tight hairpins require more positive ackerman. Drifting has the same requirements, except there are situations where you are turning much farther than a road course car would be. Too much ackerman in high speed corners (or at high steering angles) means that the wheel with less angle is scrubbing, which slows the car down and increases tire wear. Too little ackerman in tight corners means the opposite, while turn-in speed is reduced and more input required.

Basic image of ackerman reduction:

https://i.imgur.com/6pTVip1.jpg

Now let's talk about steering axis inclination (SAI). This is also known as kingpin inclination or kpi, but since cars haven't had kingpins since the 30's, I feel like we should use the proper term. This is another thing that is very easily misunderstood, as the kinematics are quite dynamic throughout the steering range.
For the purpose of our discussion, I'm going to talk about SAI as if it includes caster. By definition SAI is the angle of the suspension from the top mount of the shock through the ball joint when viewed from the front only, but since our cars are always going to have positive caster and our goal is to understand how the suspension angle effects the geometry throughout steering lock, it's easier to condense the two.
Let's start with a car going around a track in standard racing fashion. Front camber while steering is determined by the SAI, and with positive caster, this means the outside wheel gains negative camber and the inside one positive. This is very beneficial in typical racing, as the outside wheel needs negative camber to offset body roll and tire deflection. This can obviously be adjusted so as to be optimal per setup. In drifting, quite the opposite is true. Countersteering into a corner means the lead wheel gains positive camber and the trailing negative, leaning the tires up on their edges and reducing contact patch. This effect also makes the steering want to self-center, as the car lifts in the front and the weight of the car wants to push the steering back to center. There is a balance to be struck here, and it largely depends on how the driver likes it. Professional drifting has moved towards reduced caster and therefore flatter contact patch at big steering angles. This increases controllability at speed and allows for effective braking. A large number of grassroots drivers prefer standard or even increased caster though, this makes the car self-steer more aggressively, and can help with hucking big backwards entries. The front tires will start to slide and then smoothly return when correcting, which makes the entry look much smoother.

Caster trail:

There is also ‘caster trail’ to consider. With the need for larger front contact patches and less static caster, the steering can lack feel and lead to a driver having to steer excessively, pulling the wheels away from lock and manually returning the wheels to center. By setting the hub farther back in the knuckle (front to rear), the caster trail can be increased, meaning that the steering still wants to return to center even at low static caster angles. I borrowed this image from interia-ms.com as it illustrates it nicely:

http://i.imgur.com/uKYntcYh.jpg

PSM, Wisefab, and TDP, and Driftworks all have knuckles with increased caster trail available. GKtech has one in development. PSM has a good side-by-side so you can see the difference. Trailing knuckle on the left and standard on the right.

http://i.imgur.com/GrgfMRUh.jpg

With the increased prevalence of reducing static caster angles, companies have developed offset strut tops. This allows the tension rod to be used as a fine adjustment, and keeps the wheel more centered in the well.

GKtech has two versions, one that you need to cut the top of the tower to fully utilize, and another thicker one that bolts in with no modification:

http://i.imgur.com/M66xa1Dh.jpg

http://i.imgur.com/shUKHbJh.jpg

TDP's is similar to the second GKtech:

http://i.imgur.com/UjWJYEzh.jpg

PSM has one available for their coilovers specifically:

http://i.imgur.com/dcuWD92h.jpg

Wisefab was pretty much the originator of the idea, first with their fixed position "non-FD legal" tops, and then with their adjustable "FD legal" variant. Fixed position is pictured above in the picture of the full kit.

http://i.imgur.com/WPjR540h.jpg

There are several ways to go about getting more steering angle; like tie rod spacers, steering rack spacers, and obviously modified or new knuckles.

Classic steering angle spacer:

https://i.imgur.com/tByWkxb.jpg

Big steering angle spacer:

https://i.imgur.com/eJJEeOF.jpg


There have been plenty of companies that have come and gone over the years, making their own version of modified or new knuckles for the s-chassis:


Naoki Nakamura's now infamous B-knuckle:

https://i.imgur.com/vUQSu2kh.jpg

https://i.imgur.com/3qvz7q9h.jpg


MA-Motorsports modded (no longer available):

https://i.imgur.com/5mt8vKh.jpg

Billspeer 555 Knuckle (no longer available):

http://i.imgur.com/maPJBZgh.jpg

Abercrombie (no longer available):

http://i.imgur.com/KoHMLz2h.jpg

http://i.imgur.com/3NM6TSnh.jpg

Driftworks claims 65 degrees of steering lock on their V2 Geomasters:

http://i.imgur.com/lhMRWPUh.jpg

http://i.imgur.com/COcRIAuh.jpg

Parts Shop MAX has 65+ degrees of steering lock:

http://i.imgur.com/v3PisZmh.jpg

http://i.imgur.com/6IO9NKMh.jpg

Wisefab also claims 65 degrees of lock:

http://i.imgur.com/glU5O6Wh.jpg

And their ackerman adjustment spacers:

http://i.imgur.com/K1Qw7xNh.jpg

Track Day Performance claims up to 70 degrees of lock (No longer available):

http://i.imgur.com/zqjDCVbh.jpg

GKtech claims 70 degrees of lock with their V3 knuckles and LCA combo:

http://i.imgur.com/b73LG1vh.jpg

Overcentering:

Another thing that's rarely mentioned when talking about all this increased angle, is the tendency of the steering rack to go "over center". This is where the angle of the tie moves farther than parallel with the steering arm of the knuckle Image borrowed from interia-ms.com

http://i.imgur.com/5VJoEzsh.jpg

This can be alleviated a couple ways:

1. Moving the steering rack forward:



https://i.imgur.com/B9Wm400.jpg

https://i.imgur.com/qB0K1dW.jpg

2. Spacing the tie rods farther forward, using spacers like these Driftworks ones:

Version 2:

https://i.imgur.com/OQfOEJQ.jpg

Or the Parts Shop MAX version:

https://i.imgur.com/0jynKz0.jpg

and GKTech:

https://i.imgur.com/5vXBK1v.jpg

These do the same thing as the eccentric bushings, but have more correction. And there have been talks of solid steering rack bushings warping and becoming loose.

NOTE: These could put stress on your rack that it was not designed for.


3. Using Parts Shop MAX steering rack eccentric bushings:

https://i.imgur.com/O9XRLv0.jpg


https://i.imgur.com/M0ZxPPC.jpg


Dan gathered some interesting information about how moving the rack forward effects ackerman angle:

https://i.imgur.com/dWWwvBr.jpg


4. Once you're using high-clearance tension rods/control arms, you'll need to worry about your trailing wheel hitting your sway bar. There are two solutions for this:

The GKTech high clearance sway bar:

https://i.imgur.com/nzDXLxmh.jpg

https://i.imgur.com/Eka1Auvh.png

https://i.imgur.com/KlFpaMah.jpg

And the Bink Industries high clearance bar, available in street and Pro versions, and residing on quite a few Pro and Pro-am cars. These come with endlinks, D-bushes, and brackets.

Street:

https://i.imgur.com/rgmNkORh.jpg

https://i.imgur.com/W4iFOlYh.jpg

https://i.imgur.com/FA27LpGh.jpg

Pro:

https://i.imgur.com/lVLvKOYh.jpg

https://i.imgur.com/Jy9QEKbh.jpg

https://i.imgur.com/W0HAji7h.jpg

Parts Shop Max has a high-angle sway bar as well. Comes with brackets, bushings, and locks.

https://i.imgur.com/xBvBZpih.jpg

https://i.imgur.com/OR1Y89xh.jpg

Depending on your knuckle/LCA/tie rod end combo, you're probably going to need longer tie rods. Here's a nice list of lengths:


Inner:
M12x1.25:
11.10" - '89-'94 240sx (S13)
M14x1.5:
11.37" - '95-'98 240sx (S14)
11.42" - '94-'99 Maxima (A32)
11.42" - '96-'99 I30 (A32)
12.00" - '97-'01 Q45 (FY33)
12.00" - '01-'06 Q45 (F50)
12.91" - '99-'03 Maxima (A33)
12.91" - '00-'04 I30 (A33)
13.30" - '03-'08 Maxima (A34)
9.25" - PSM Short
11.73" - PSM Medium
13.93" - PSM Long
14.50" - GKTech

Outer:
M12x1.25:
3.88" - '89-'94 240sx (S13)
M14x1.5:
3.63" - '95-'98 240sx (S14)
5.00" - '88-'94 Maxima (J30)
x.xx" - '94-'99 Maxima (A32)


Let's discuss.

wow looks like you put a lot of work into getting this thread started. very informative. good job imo

In for info and updates I like where this thread is going

Great job and good info, thanks for taking the time to do this.

Awesome info!!! Thanks!!

You're welcome guys. This is something I kind of geek out on, so I thought I would contribute to the community.

Here's a question I have.

It seems like if you did all the roll center adjustment you possibly could, you could actually put the roll center above stock, even on a slammed car. Anyone know if this is detrimental to suspension performance or not? Maybe it's advantageous?

There various thread on NRR already dealing with these topics
one of the more extensive ones:

Roll Center.....again - Nissan Road Racing Forums

good topic, I've seen the suspension set up of a Porsche GT3 Cup car and it floored me
just like our cars they're McPherson struts up front with a independent arms in the rear
I want that in my car

i <3 this thread :D

i own the PSM subframe risers and knuckle/LCA kit. complimented by the rest of their GEN1 catalog lol....

i want MOAR now

im really sure there is a ton of info here but im an uber noob on suspension and dont really nkow whats going on in some of these pictures. maybe a introductory thread that leads up to this one would be sweet!!

That's nice, but THIS IS ZILVIAAAAA!!! haha. I wanted a thread on here, and I want to update it with the latest products and such, not just "this is how you could possibly do it". Thanks for a solid link though, I might steal some of their pics to make this thread better.


Yeah, I might do that, but most of the general stuff is readily available and easy to find. This is the hardcore stuff.

That's my thread on NRR - lots of ideas got shot down in there, haha.

One of them was modifying the inner pick up point. You affect a lot more then just the roll center when you do it. There is more then enough room to drill a hole above the stock location and move the arm up a good inch. I was steered away from that by the guys on NRR though so I would listen to them.


Also, my rear arms are corrected more then stock, I just don't have any spacers on them yet. You can see the slight angle difference from my toe arm and LCA. I should be able to get it mostly flat, but I've got to track down the proper spacers.


Also, you don't necessarily want the roll center back to the factory location. The 240 wasn't exactly a performance monster from the factory. I haven't done enough research to say what might be optimal...so going for straight LCAs is a good goal for now. I'll be able to fine tune it as I drive it.

Oh wow this thread has definitely been one ive been waiting for/ planning to make. Ive been researching this stuff forever too but it seems like you have covered a lot of it! NICE JOB!

I did all the mods to 95KA-turbo's suspension. Let me tell you that this wont be an easy install. All the parts that where ordered had very close tolerences. I had to grind down/sand a few things to get it to work. We dont now how its all gonna work out because we are in the R&D mode right now. Once we get it set the way we want it we will report back here with updates. Hope fully in about 2 months when the car is rolling under its own power.

Danny

Very informative! Thank you very much for putting this together.
I am interested to see how these mods are affected by the sactioning bodies. Last I read is that you could only move your pick up points 1" in any given direction.

nice, I keep going back to that thread for inspiration from time to time
the griggs stuff that was posted there haunts me, specially their 3 piece knuckle.

http://image.mustangandfords.com/f/9...g_products.jpg

http://www.griggsracing.com/images/MDS4000.jpg

http://www.griggsracing.com/images/AlumSpindl2.jpg

I modified the stock lowers (rear and front) to acccept 3/4" spherical bearings and monoball studs for roll center adjustment. No pics of the fronts yet. But I had to ream the uprights to a 7° GM taper for the studs to work.

http://otto-fab.com/pics/IMG00080-20...46RCA_mod2.jpg

http://otto-fab.com/pics/IMG00106-20...44_rolladj.jpg

Tension arms control caster, unless you are talking about the tie rods.

I am sure it was a simple slip up in typing, but yes that's important to point out, haha.

I personally do not 100% understand how moving the inner point up effects the motion of the tension rod - I mean it should technically do the same thing as lowering the outside out point. I was assured that it would put some unforeseen forces on the arm that would screw up everything. I am not an engineer - perhaps Def will come in and explain. It is stated in that NRR thread. I got mad because no one would explain it to me at first, then I got a kind of half-ass explanation from a few people.

That is correct.

And therein lies the problem, if you move the FLCA pickup points up, because the rack would also need to go up along with the FLCA pickup points so that the tie rods' arc and the FLCAs' arc will stay in sync.

If not, the car will get some nasty bumpsteer. that pretty much cannot be corrected due to the 2 having totally different arcs.

Edit - if you move the FLCAs' pickup point, then the T/C rods' pickup points will have to move up the same amount as well.

Think about it.

If you moved the FLCAs' pickup points by an inch, and if you flattened it, the T/C rods will no longer be parallel to the FLCAs anymore. They'd be pointing up in order to meet the FLCAs, and probably no way for them to bolt up to the FLCAs because of the angle that they're in, so they will need to be moved up an inch as well.

Well corrected to a point with a bumpsteer kit but they can only correct so much before moving the whole rack up is the next option. Which in my case with the LSx is a no go, there is about 1/16" between the rack and the oilpan.

Exactly, I liked the solution on the Porsche cup car
the traction rod connects to a perpendicular brackets and it's position can be adjusted with round spacers of various lengths held with a bolt
the lower control arm is a two piece design cast in aluminum - shims can be stacked near the crossmember bushing held by two bolts to adjust track and probably quick alignment changes.

Ah that's right, it makes sense to me again. I had forgotten how I had to think of it to make sense, haha.

By moving the inner point up, you are making the LCA angle better but the tension rod angle worse. By moving the outer point down you are making your tension rod angle and LCA angle better at the same time. The tie rod angle can be fixed with spacers and heim joints, much like the spherical bearings and spacers used for the roll center.


Here is an interesting article that somewhat explains why one type of roll center isn't ideal for everyone/every car. Unfortunately they're talking about stock cars and they have completely different suspension set ups then we do:

Accelerating Performance: Roll Center Magic

The point is, the tie rods' pick up point will differ from the FLCAs' pick up point if you move just the FLCAs. One will be higher than the other, which will cause different arcs.

When 2 arms have the same arc, you can correct for stuff much easier.

When you have 2 arms that have different arcs now, it is much harder to correct for that type of stuff....

Loving this thread, and the work that went into making it. True, this is more of a NRR-type thread (that site is awesome, btw, I just got turned on to it recently), but I love that the community is moving towards real performance modification, not just 'this looks cool', or 'check out what i did for free'.

Makes me proud :)

Luke (Blu808) and I have been talking over making some CNC aluminium LCA's since we both have access to CNC machines and I have all the heim joints. We just need to come up with a final design (which has to address roll center, bump steer if possible, big angle kits, etc) ~ maybe this thread will help.

agree, I'm interested in what you and Luke will come up with
we're in a similar situation, we can make just about anything but it's not very useful without a well thought out design
any automotive/mechanical engineers in socal that are serious about making cool shit, get at me :mepoke:

I liked this idea:
http://http://i25.photobucket.com/al...ollcenter5.jpg

It's what silk road does on their time attack car. I wish I had more data on it but have only seen one article.

wow, nice thread, you saved myself the embarrassment of making a n00b ver. of this thread. lol.


this is complicated. but it shows the importance of all the arms

In respect to rear roll center adjustment, would you guys be making a set of rear spindles with the option of using spherical inserts and a z32 for type mount for the struts? I'd like to be able to use my z32 rear e-brake assembly as well.

To add to this thread, adding additional roll center adjustment for the rear (ie lower control arm) could possible hurt the rear geometry of the other arms. The best fix would be to replace the rear spindle to ensure that the arc movements remain unaltered.

Definitely, a new spindle out all around is by far the best method to correct everything properly. An adjustable control arm on top of that would be great, then EVERYTHING could be adjusted.

Glad I found this thread. I've been trying to learn more about suspension lately. In for updates.

Has/does anyone notch the front spindle for more camber gain?

I've done this on several dirt "factory stocks" and it seems to work quite well.

Subscribed.

I have no idea what to do with the rear. I'd love to do a heim on the front with the ability to raise/adjust the rear pivot point (for squat), but I can't think of a nice way to do it.

Spindles would be do-able as well, but that's a whole 'nother headache lol. I agree that's the best way to go.

Coolest things about all of this is:
a) Aluminum is cheap
b) CNC time is reasonably cheap
c) heims/bearings are cheap
d) Lots of engineers have S-chassis cars

What you're saying about moving the inner FLCA pickup point up totally makes sense now. I've edited the thread to show it. However, The tension rods don't really have to be moved. Just look at Matt Powers car. His tension rods are pointed up.

And I'm not convinced about the rear at all. Moving the rear pickup point doesn't put it out of sync with the rest, as they all move the same way. And the Parts Shop MAX car has used this method with success.

True.

The FLCAs do have enough flex in the inner bushing for it to be tilted forward and still work to a degree, but you'd sacrifice the range of motion that the ball joint or spherical bearing will have on the outer end due to the FLCAs now having a slanted angle.

Even with Def's modified Godspeed FLCAs, his spherical bearings (that replaced the ball joints) only has 15 degrees of misalignment on it. While he will probably never use the full range of 15 degrees, if your arms are tilted down in the front due to the T/C rods not being relocated as well, then the misalignment angles decrease, and you might run into problems then.

All hypothetical of course, but still, if I were to mess with the suspension, I'd rather do it right and make sure things aren't going to go out of whack, instead of just going by the "eh... it's good enough" approach.

Yes, Matt's tension rods are pointing up, and if he raised his inner pickup point they would be even more deformed. The point is to get ALL suspension geometry correct while having the car retardedly low - at least that's the point I'm going for.

Its counter productive to do something that requires extra steps for no reason. Moving the inner point up 1" like Formula-D allows will not correct the roll center enough, so you'll still need to change the spindle or LCA.

this thread is fucking legit

A set of knuckles wont be any help if you cannot correct the angle of the LCA at a given ride height. This means that the only solution to this would be a set of 2 piece spindles that can be taken apart to install a roll center spacer. One of the J-land companies has these.

^^Or raising the pivot points on the crossmember, wont happen with stock control arms but if you are running heims there is room for moving the mounting hole up 15mm.

Edit: but now that I think about it the swing arc on the tension arms is still going to be messed up. I guess you could achive the same thing with adjustable ball joint studs but youre still left with the steering arms. Do the J-land spindles raise the roll without messing with the steering arms?

The J-Land one is the GP Sports knuckles.

There are two versions.

One version has a fixed 20mm or something adjustment plus added angle at full lock.

The adjustable one can be spaced with spaces that will space both the tie rod end mounts and ball joint mounts together as one unit.

Ideally you would have an adjustable LCA with a spindle that corrects geometry, so you can fine tune it with the LCA and the knuckles could adjust like 30mms or so.

A way to bypass the whole tension rod issue is to get rid of the 2 prong bolt on method and make a LCA with a bracket to allow a double heim joint tension rod. So you can weld it on however higher or lower depending on what you do with the inner LCA pick up point.

Something similar to this:

http://www.e30m3project.com/e30m3per...arms/pic-2.jpg



A company called SP-Tec in Japan makes these:

http://sp-tec.com/shop/goods_image/A28_Z1.jpg

http://sp-tec.com/shop/goods_image/A29_Z1.jpg

Nice thread.

What do you guys think about the new driftworks spindles?

Stock front balljoints have about the same amount of articulation. Can't remember if I said it was about 15 degrees each way, but it's probably a bit more that that. Maybe 20 degrees each way. Regardless of the amount, it is not far off a stock balljoint.

Correcting the front roll center brings the front tension rods to about the stock angle. Not sure why you guys are stressing out about the front tension rod, as any higher you make the front roll center.

Are any of you guys that are running a lot of caster having any issues with the tie rods binding?

95KA-turbo, that tension rod setup makes sense! Thanks! It looks like the Ikeya Formula arms, just more basic. But you could definitely adjust tension rod position if you made them yourself.

Also those knuckles look crazy similar to the Driftworks ones. Right down to the bushings, haha.

So here's a thought;

Say you have PSM knuckles, which already correct for bump steer. Then you get SPL tie rod ends, which have spacers to correct for bumpsteer. Third, you move the inner pivot point of the control arm up and install SPL's spacers to space the tie rod down even farther. Wouldn't this make the tie rods parallel to the new control arm location?

I know it's kind of a drastic amount of adjustment, but it should work.

I wanted to draw this in paint, but I can't find a good picture to do it with.

You can move the tension rods up a little bit, seeing as with decently high spring rates they don't move up and down a whole lot. Also, what about mounting the tension rod to the bottom of the control arm instead of the top?

And no one has any idea of where you actually want your roll center? To me, stock makes sense. All of my ideas won't really matter if it's ideal to have your roll center farther down than stock, as you won't need such drastic adjustment, hahaha.

BTW, thanks for all the input and compliments guys, I'm really enjoying this thread!

You can get the roll center up close to your CG without moving the inner pivot of the FLCA, so no idea why you'd consider that.

You don't really want your roll center right at your CG height either, as it can create weird handling as it moves from very close to your CG to far away upon corner entry.

AH! This makes sense. I'm guessing the center of gravity in the 240SX is farily low? Say, just about seat (butt) level?

I knew there must be some reason no one was doing those kind of crazy modifications.

Keep this thread going, shit is great.

I have the SPL tie rod ends and it lowers the tie rods a BUNCH. but i feel like the control arms need to be moved still..

This is kind of irrelevant but, when i reverse out of say a parking spot and i hit full lock, i cant turn the wheel the opposite way right away, its ilke completely locked until it moves forward a bit.

I dont have this problem while drifting or any other type of driving, only when reversing.

I know this shouldnt be happening...

Front CG in ours cars is probably just above the crank centerline, give or take a couple of inches. It doesn't take too much outside pivot lowering to at least get close to there.

Wow, yeah, that's not high at all. Thanks so much for the info, I'll edit the original post to reflect this.

It was GP Sports. They no longer make them for the S-chassis.

awesome thread. learned something new!

I never quite understood adjusting squat/anti-squat. I know you can angle the rear subframe and/or lower control arm, but which way to reduce anti-squat?

And i've heard good things about doing that in S13 drifting applications, is it really that noticeable/wanted of a change? People aren't very specific when it comes to talking about the after-effects.

Basically you want to "flatten" the lower control arm. Usually by moving the back pickup point up.

Basically it gives you more weight transfer to the rear, more "squat", and better traction when accelerating hard. This really helps for higher-powered cars that have problems putting the power down.

This thread assumes that people actually have suspension travel. That's a pretty big assumption on Zilvia.

Nice thread... i have also zero suspension travel.. i just hop down the road.

what would be a good daily and track suspension set up...im currently running apexi n1 coilovers but i may sale and buy dmax coils lmk

This is not really the thread for that...there were like 6 threads made in the past month about coilover choices in general discussion. I personally love the Fortune Auto coilovers on my car though.

Yeah, let's try to keep it on topic people.

No coilover talk please.

Just to add some FYI stuff, I'm running the GP Sports Hyper Knuckle (Adjustable). I originally had a 20mm spacer in there in additional to the 15mm? that the knuckle added and it was a bit TOO much roll center adjustment causing major understeering issues. This is due to the front vs rear roll center, or in other words the front roll center was far too high compared to the rear, which doesn't allow the car to rotate. So without much, or any rear roll center adjustment, adding a crap load of front roll center adjustment will hurt performance. So if you're interested the GP Sports knuckle, or any sort of front roll center adjustment is fine. Ultimately, there needs to be an effective rear roll center adjustment to balance the car. The Driftworks option posted on page one looks like the best option, though I'd like to know if it can be used with a z32 brake setup.

http://i7.photobucket.com/albums/y25...c/IMG_0663.jpg

My next question......

Could we technically split in half a set of knuckles and build the bottom half out of 6160 aluminum? I have been wanting to do this for a while now. I threw this idea around the shop and Im gonna talk to my machine shop to see what he can come up with.

I have some concerns about adjusting the rear roll center by simply spacing the joint down. The balljoints are mounted at an angle. That means that if you simply space the joint down you end up with a longer lower control arm to put the upright in the same position. Since the rear is a multilink that could affect the camber and toe curves. The affect could, of course potentially be positive or negative, but negative is much more likely. IMO in the rear the way to go is to re-locate the subframe and modify the spindles.

Man, it's too bad GP Sports stopped making those for the S-chassis.

Supposedly you can use the Driftworks knuckles with the Z32 rear brakes, but they require "modifications" to fit.



Are you talking about using a longer ball joint/shank in the lower control arm? This would affect the suspension curves, but really the affect would not be large.

Most roll center adjusting control arms/ball joints only move the pivot point down by 15mm or so and that 15mm only increases control arm length probably 5mm effectively, which should be able to be offset by the adjustment of the inner heim joints if you have an adjustable arm. And if not, just adjust all your other arms 5mm longer.

He's talking about the actual arcs that the arms go through being effected in a negative way. Which is why a modification to the rear toe arm mount on the knuckle is likely necessary to achieve proper suspension geometry out back (like the picture I posted of the S15 with Z32 uprights).



Danny, I do not believe there is enough material on the front spindle to just cut the bottom off and bolt something else on. You can see the GP Sports knuckles have a good 1/2 inch more material then the stock knuckles where the bottom part bolts on.



It IS a shame that GP Sports stopped making them....but at the same time it was an unmarketable product. Very few S-chassis owners can afford/are willing to throw a good 1000-1200 bucks for a set of knuckles here in the US. Especially when it can be corrected by just raising the car up (which is what people who care about performance usually do).

Can we sticky this? This is very good.

Using a longer shank doesn't affect the arc of the control arm at all. It merely moves it down in it's arc. It moves exactly the same way, think about it. The other control arms stay the same as well.

EDIT: The relationship between the arms does change slightly, but as stated below, the change is not really a performance-hurting one.

wrong. For the front, being a macphearson strut design, has a 1:1 ratio in relation for the lca moving 1" and the shock compressing 1", so you could almost assume it does not affect other suspension components. The problem is more apparent in a multilink suspension such as the rear links on our car. It's difficult to conceptually visualize, but a few hardcore racing companies have developed new spindles in contrast to addig spacers under the lca to combat the negative affects of lowering a production based vehicle while preserving the initial suspension dynamics from the factory. In other words there more to adding spacers between the knuckle and lca.

Not really sure what you're getting at, but all you would change(besides the roll center) would be the camber and possibly toe curves(I'm imagining this might stay the same). If anything, you'll probably increase your camber gain in the rear, even though that's not really a problem when lowered.

As for the GP Sports knuckles - if you're fine with two bolts in bending, why not just drill out the stock spindle and use a 3/4" bolt in bending in place of the balljoint?

Just making the point that it requires more attention to correctly raise the roll center given a multi-link suspension. Unless I misread.

Do you realize I started this thread? Hahaha, I know more than you think, though I think Def knows more than all of us.

Did you read through the first post? There are a couple that I posted up.

Anyway, I was responding to racepar1's post.

You have a point, but as I stated in my post, the only real difference is LCA length. Which is really quite slight, as the angle of the ball joints makes the additional length of the ball joint/shank not the length the control arm is extended. Here's my crude Paint example:

http://i24.photobucket.com/albums/c25/Turbo711/LCA2.jpg

And as Def stated, the camber and toe curves change very little with this.

I think you guys are making it out to be a bigger deal than it actually is.

Geder done andy!!!!!

This is the reason we went ahead with making our set up. Alot of assumptions, I think's, and what if's. Until we get this 95katurbo's car on an alingment rack and take it to the track we will not know the results. Kinda ol'skool engineering I call it. Build it and take it to the track and beat the piss out of it. If it works everyone will want to have his set up. If it breaks into a billion pieces then we will get "the i told you so". As I look at the set up on the ground with the new GM ball joint set up we will be spacing the LCA about 20mm down. The spherical bearing that I intalled works with the up and down movement of the LCA. Essentially affecting nothing at this point. Under lateral G's we will have to wait and see. As far as I can tell I see nothing but positives from our set up. It beats the crap out of an old worn out rubber set up.

Where did you find the pic of Powered Max fabbing some new hubs?

BTW, it's Parts Shop MAX. Powered By MAX is the website name.

POWERED BY MAX: Forums　フォーラム/ 作ã�£ã�¦ã‚‚らã�„ã�Ÿã �„パーツ Wish List / Rear knuckle

good info subscribed

Found these on Driftworks' website here.

http://media.driftworks.com/assorted/NewUprights1.jpg

http://media.driftworks.com/assorted/NewUprights2.jpg

Solid! I've just found out they also make tie rod offset spacers (found them in that link). These space the tie rods farther forward to correct for "over centering" of the steering rack with all that increased angle. Sick!

Check them out:

http://i24.photobucket.com/albums/c2...RackSpacer.jpg

http://i24.photobucket.com/albums/c2...ckSpacers3.jpg

http://i24.photobucket.com/albums/c2...ckSpacers7.jpg

Original post edited!

^^^ Driftwerks = killer stuff. I'm happy to see innovation still being done in the S-chassis community!

I might have to get some measurements and CNC a spindle... I wonder how long it would take and how many pieces I'd screw up before I got it right lol...

i love learning things about my car. this is the most ive learned in probably the 3 weeks ive been on break. awsome.

i believe nigel from AUS also has these CNC'd :fruit:

I'd like to try out those offset tierod spacers. Are they up for sale yet?

Negative. Not on their website at least.

It would be kinda nice if some people in the US made some of this stuff. Not that I don't want to support Drift Works, but I can't imagine it being very affordable to ship stuff from England.

Oh well.

I'm oblivious, are those only for drifter knuckles with stupid crazy steering angle?
looks kinda sketchy to me.

Yeah, they keep the tie rods from moving ahead of the knuckle at extreme steering angles.

That's a Chromoly bolt, CNC'd billet aluminum, and a tie rod. How is that sketchy?

wow... driftwerks if amazing... so genius.

when i end up getting knucles and fun, im buying those.

those have been around for about 2 years now. The first time I saw them was on the C's garage yellow coupe.

just wondering how a car would drive under normal conditions, daily for example, with those
or are they a drift only, trailered back and forth to track car deal?

I dont see how it could effect anything. All you are doing is correcting geometry when the car is lowered or has extreme angle. I daily drove my car with modded knuckles and super low ride height. Did it suck? Yes, but I knew that was going to happen. Now did it perform on track. Hells yeah!!!! I dont drive my track car on the street anymore. The coilovers will rattle your teeth lose and the road noise is loud. hahaha.....I just realized I sounded OLD.

I read a post on driftworks concerning those offset spacers. They were originally developed and used in japan, but during usage they either broke or caused heavy wear on the steering rack causing it to deform. I'll try to find the post.

They were talking about the URAS ones, which are a different design and less quality.

Driftworks designed theirs to be better.

I'll quote: