JETPILOT

iTrader: (51)

Good lord... I know how roll center adjusters work and the dynamics of roll center and CG. I simply want to see how these install before I spend $500.

Colin_S

iTrader: (2)

I think people are looking for something special here when actually it is so simple. You change the ball joint, you put a cone shaped spacer (see pic in first post) on the ball joint, you then slide the ball joint bolt up and bolt it down. The arm is now lower than before. Another arm also bolts on and as this arm is now lower a spacer is require to keep this arm flat.

These are NOT adjustable, the arm will be lowered the same on EVERY application. It is a very simple idea with great effects. The 'special' bit is how the new ball joints pivot point is different to allow for the spacer.

Z1 Performance

iTrader: (564)

Thanks for that Colin

These were designed for correcting cars that have been lowered more than 30mm according to our discussions with Moonface. The shank of the bolt is different than stock and that is why the pivot point differs and thus why these work as advertised

I can post a picture of them installed but again, there really is nothing much to see as Colin mentioned a few posts back

guitman32

iTrader: (15)

Thanks Adam, great article with diagrams to really drive it home.

So if I am understanding correctly, when you lower the car, you increase the vertical distance between the CG and the roll center, creating a larger "moment arm." As a result, when a car experiences a lateral load the larger moment arm acts kind of like a longer lever, allowing the cornering force to be "more effective" in rolling the car. This results in more body roll as compared to the same car with a smaller moment arm.

Apologies for sounding harsh...no bad blood intended!! I just get frustrated seeing new parts that I want for my car (I am a man, after all ) but cant justify buying because of inadequate conceptual and real world justification.

Z1 Performance

iTrader: (564)

no worries Yes, you're spot on. Pre lowering if you were to look at the lower control arm, you would see both the pivot points (on the subframe side and the hub side) in a parallel plane to one another. Now, when you lower the car, whether it's with springs, or coilovers, those 2 points are now no longer on that same horizontal plane. The lower you make the car, the more pronounced it becomes. To rectify this, the MFR kit gives you new ball joints with a longer shank to the bolt, which changes the pivot points and puts them back in the same plane with one another

kuah@splparts.com

iTrader: (10)

The longer (or shorter) shank does not matter in this case because it will not alter the roll center. To change the roll center, the pivot point has to be moved relative to the upright/wheel hub. In other applications where the ball joint is on the control arm, having a longer or shorter shank will change the roll center because you are shifting the pivot relative to the upright. However in this application, the ball joint itself is pressed into the upright. Therefore to modify roll center, the pivot (ie. center of the spherical bearing) has to be pressed into a different spot within the upright. Based on the stock upright, to improve the roll center on a lowered car the ball joint would have to be sticking out under the bottom of the upright.

We have seen many "roll center" adjuster ball joints on the market for the 240SX that alter the physical angle of the lower arm, but do not actually modify roll center because the pivot point is not actually moved. MFR themselves sell some roll center adjuster ball joints for the 240SX that are that way, though their "race" version does in fact change the roll center. It is not clear, based on the product picture, whether these do alter the roll center on the 350Z/G35; I admit I am skeptical but I am open to the possibility that these do move the roll center a little. To demonstrate that these ball joints do change the roll center, you just need to press them into the upright, take a picture, compare that to a picture of the stock upright and show that the MFR pivot/ball is moved relative to the stock ball joint.

Z1 Performance

iTrader: (564)

Kuah - yes I know what you mean. However the position of the shank does matter relative to the rotating part of the ball, and that is what I was trying to convey. Unfortunately I didn't do the install here, they were done at a friends shop, so I don't have side by side pics

Z1 Performance

iTrader: (564)

here is a quick picture I just took of them installed on my car. On the other side of the lower control arm is where the second spacer goes, so that everything is kept on the same plane with one another.

Colin_S

iTrader: (2)

Adam, had a chance to drive it yet? What's your thoughts. I noticed an immediate dramatic improvement.

Z1 Performance

iTrader: (564)

Colin -I drove it from my friends shop back to mine but it had been raining so really didn't get a chance to put it through the paces yet. But, the weather finally broke here so I plan on taking the long way home

JETPILOT

iTrader: (51)

The only thing you should be noticing is less body roll. Am I correct?

Z1 Performance

iTrader: (564)

I didn't take the car home last night afterall guys - I'll make sure I drive it tonight at some point

Colin_S

iTrader: (2)

I had a huge amount of bump steer after I lowered my car and installed the sways and after fitting these that basically disappeared. They are meant to give you a linear camber curve which I think may be what solved this.

rrmedicx

iTrader: (54)

Subscribing for results.

Z1 Performance

iTrader: (564)

ok, so I took the long way home tonight. Basically a one lane, windy road with some mixes of rough pavement, smooth pavement, and alot of switchbacks (right/lefts in succession). A really nice road in the day time without traffic. Anyway, here is what I noticed:

1. Much quicker turn in response - I never had any complaints in this department at all, as my car was always quick to respond and never had that sloppy turn in I've experienced on some other Z's. This really was a major improvement now - it is now razor sharp - a very pronounced difference from where it was before. It's still not Evo-esque, but it's awfully close.

2. The body roll up front is now very minimal. Again, I never took major issue with this in the past as I just though "that's the way it is". Previously if you entered a sharp turn on the hot side, you would feel the inside wheel go light. That is no more. The nose rolls much less now and I guess the only way I can describe it is that you feel the weight still over both front wheels equally.

3. bump steer - lowered Z's do it to some degree, but admittedly alot of it is in the camber/toe settings. I had the alignment redone when these were fitted, and my camber up front is now down to -1.25....it's just where it ended up with the a arms at max positive. I previously was around -1.5. Toe is also set to zero. I don't know if it's the alignment, or the RCA kit, or a combo of both, but through the turns over the rougher sections of pavement, the steering wheel wasn't quick to go loose on me.

so that's it so-far - I'll post some more when I spend some more time with the car over the weekend

JETPILOT

iTrader: (51)

I will have mine installed for my next track day @ Sebring on Dec 14th. So I'll give an on track opinion after.

Adam... how much was your car lowered? You didn't need to legnthen the front shocks after the install?

Z1 Performance

iTrader: (564)

I can measure the height of the fender centerline to ground tomorrow for you Larry. I had the car cornerbalanced too, so heights were definitely adjusted from before anyway.

here is a pic though that kwame snapped when it was done

http://cornerbalance.wordpress.com/2...rner-balanced/

Edit - my car is now at 25 inches front, 25.2 inches rear from the centerline of the wheel wells to the ground

JETPILOT

iTrader: (51)

I got my roll center adjusters today. Thanks Adam!

Z1 Performance

iTrader: (564)

good stuff - use 'em well

kuah@splparts.com

iTrader: (10)

The position of the shank does not matter, only the location of the (pivot) ball. Take the front compression rod for example, its a big curved arm, but the only thing relevant is the pivot points. I could replace that arm with a straight arm joining the 2 pivot points, and everything works the same; only reason why that arm is not straight is because it won't clear the wheels.

I took this picture of a stock lower arm/ball joint yesterday, and roughly marked the relevant pivot points (red crosses) and the effective angle (yellow line) for the lower arm. To change roll center, the pivot points have to change, nothing else matters (shank length, the angle of the physical arm). The moonface ball joints appear to have a shorter shank, but that is irrelevant because it does not define the pivot point. The pivot ball appears to be roughly in the same spot, though it could have been moved 1/8"-1/4", hard to tell without taking exact measurements of the ball joints.



The scenario for, say, the outer tie rod ends (as seen in my pic) is different. Using a longer shank there moves the pivot point relative to the wheel hub, that is because the ball joint is on the arm/tie rod itself, not on the hub as with the lower arm.