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-   -   This is the roll center, suspension pickup, and steering angle modification thread. (#/f/showthread.php?t=296725)

PerilousActs 12-24-2009 12:59 PM

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

RHD95S14 12-24-2009 01:00 PM

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.

GSXRJJordan 12-24-2009 01:56 PM

Quote:

Originally Posted by mmdb (Post 3201553)
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.

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.

Quote:

Originally Posted by 95KA-Turbo (Post 3201577)
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.

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

PoorMans180SX 12-24-2009 02:04 PM

Quote:

Originally Posted by SoSideways (Post 3201330)
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.

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.

SoSideways 12-24-2009 02:23 PM

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.

95KA-Turbo 12-24-2009 02:57 PM

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.

KoukiMonsta 12-24-2009 03:10 PM

this thread is fucking legit

ballinnmiami240sx 12-24-2009 03:18 PM

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.

Otto347 12-24-2009 03:52 PM

^^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?

SoSideways 12-24-2009 05:17 PM

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.

95KA-Turbo 12-24-2009 06:04 PM

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

mothon 12-24-2009 08:41 PM

Nice thread.

What do you guys think about the new driftworks spindles?

Def 12-24-2009 09:16 PM

Quote:

Originally Posted by SoSideways (Post 3201720)
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.

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.

mothon 12-24-2009 09:46 PM

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

PoorMans180SX 12-24-2009 10:18 PM

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!

Def 12-24-2009 11:03 PM

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.

PoorMans180SX 12-25-2009 12:51 AM

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.

nieko 12-25-2009 12:59 PM

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...

Def 12-25-2009 07:28 PM

Quote:

Originally Posted by PoorMans180SX (Post 3202506)
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.

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.

PoorMans180SX 12-25-2009 08:26 PM

Quote:

Originally Posted by Def (Post 3203290)
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.

Quote:

Originally Posted by ballinnmiami240sx (Post 3201789)
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.

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

nathanong87 12-26-2009 03:58 PM

awesome thread. learned something new!

240sxaddict 12-27-2009 11:45 AM

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.

PoorMans180SX 12-27-2009 01:16 PM

Quote:

Originally Posted by 240sxaddict (Post 3205009)
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.

Omarius Maximus 12-28-2009 07:06 AM

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

BlitzRPS13 12-28-2009 08:26 AM

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

rb26man 12-28-2009 08:37 AM

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

95KA-Turbo 12-28-2009 08:51 AM

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.

PoorMans180SX 12-28-2009 01:44 PM

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

No coilover talk please.

mmdb 12-28-2009 02:16 PM

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

ballinnmiami240sx 12-28-2009 02:31 PM

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.


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