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

[jaysgottaredtop]

Originally Posted by derass

has anyone broken adjustable tie rod ends when the lca is used as the steering stop? wondering if i should switch to an OE style or use a lock stop that cantacts the knuckle instead (similar to PBM modded lcas)

twice.

my 2-pc rod ends (circuit sports IIRC) were basically spherical bearings press-fit into bare rod ends.

with the car super low, the tie rods point up at a terrible angle and will bind under compression. that binding will put a massive bending load on the rod end. that bending load will physically bend the rod end, slowly opening up the circular press-fit into an oval, and slowly allowing the spherical bearing to weasel its way out. the more you bind it, the more it weasels.

the first time the spherical popped all the way out of the rod end, in the middle of a drift course too. threw on a spare a kept going.


a few months later at another drift event, the spare one started coming out. this time i noticed before it could pop out.


both of those rod ends were in fine shape when i put em in. only took a few bumpy drift events and some daily driving to bust em.

....aaand now i'm back to using OEM s14 outers

[PoorMans180SX]

Originally Posted by Axel18

Im trying to get some feedback on a problem im having, at full lock with tein rods and stock knuckles with bump stops removed im getting a strong wobble, i think im overcentering and im planning to relocate the rack forward to fix it as im happy with my current angle, but before that i wanted to get more feedback.

When the camera shakes, its the wobble but im correcting, at the end it gets to its worst, also no rubbing or scrapping on chassis nor front arches, nothing, that was throughout checked.

You have wayyy too much caster, hence caster wobble. Try running something like 7.5 degrees.

With that much caster, the tie rod end is trying to move wayyyy ahead of the rack at full lock, and probably overcentering at the same time. The rack doesn't like this.

[Def]

Originally Posted by jaysgottaredtop

twice.

my 2-pc rod ends (circuit sports IIRC) were basically spherical bearings press-fit into bare rod ends.

with the car super low, the tie rods point up at a terrible angle and will bind under compression. that binding will put a massive bending load on the rod end. that bending load will physically bend the rod end, slowly opening up the circular press-fit into an oval, and slowly allowing the spherical bearing to weasel its way out. the more you bind it, the more it weasels.

the first time the spherical popped all the way out of the rod end, in the middle of a drift course too. threw on a spare a kept going.


a few months later at another drift event, the spare one started coming out. this time i noticed before it could pop out.


both of those rod ends were in fine shape when i put em in. only took a few bumpy drift events and some daily driving to bust em.

....aaand now i'm back to using OEM s14 outers

The reason they do that is because they have no travel and you're banging the rod end housing into the shank over and over. It clearly shows how much you've been doing that on the last picture.

These rod ends don't have near enough travel for usage as a tie rod end, especially when drifting where you swing the rack from one extreme to the other constantly.

[ska]

So I just installed some PSM bent lca on stock knuckles, I honestly don't see it as a big deal without modified knuckles as stated on their website. I extended it 1 1/4 inch longer than the s14 lca so that the ballpoint can be angled in its optimal center range. I have my camber plates on top all the way pulled out and sitting at -5 camber. Went testing it yesterday, I must say it feels great compared to stock suspension. Much more solid and predictable, I also noticed faster self-steering with the same caster number I've had before. I will be planning to purchase the psm forged knuckles in the following month.

One question I've been having reading this thread. The general idea to have a good predictable range of motion is to have the arms parallel to each other and the ground?

[DC Dan MAX USA]

The scenario for the straight FLCA we offer is stock knuckle, slammed ride height, stock track width.

The wide track width you described and the fact that you are getting the forged knuckles means that you correctly chose the bent version.

Yup, thats the general idea

[jaysgottaredtop]

Originally Posted by Def

The reason they do that is because they have no travel and you're banging the rod end housing into the shank over and over. It clearly shows how much you've been doing that on the last picture.

These rod ends don't have near enough travel for usage as a tie rod end, especially when drifting where you swing the rack from one extreme to the other constantly.

exactly.


stupidfuckingmessagelengthrequirement

[huffandpuff00]

thanks for who ever found these!
B&A vs. oem


$28 shipped for the set....
http://http://www.rockauto.com/catal...h%2Bfor%2BAPWI

[az_240]

^I found them at BAP for the same price for anyone that needs them local... but yeah pretty sweet not having to worry about overstretched boots anymore.

[Johannes]

Does anyone know where I could get a tapered shank that would allow me to keep the stock pickup point taper?

Maybe 1/2 or 5/8 QA1 Heim with misalignment spacers that would let me run a shank that bolts up to stock taper? Bumpsteer adjustment is not necessary since I will be dropping the balljoint pickup and tie rod pickup point down.

My current setup now is with 5/8" Heim joint, and the pickup point drilled to 5/8"..

[My$800S14]

Originally Posted by huffandpuff00

thanks for who ever found these!
B&A vs. oem


$28 shipped for the set....
http://http://www.rockauto.com/catal...h%2Bfor%2BAPWI

your link didnt work if you can repost the link it would be awesome, i looked on rock auto, but i dont know what is what, i dont want to buy the wrong thing

nvm it was very easy to find on my own on the computer, the phone wasnt very friendly, here is the link to the description, and the direct link to purchase

description: http://www.rockauto.com/catalog/more...363&cc=1209046

direct link to purchase: http://www.rockauto.com/catalog/raframecatalog.php

Part#: 1032842

[huffandpuff00]

That's the wrong part number!!!
Part# 1032842

[My$800S14]

Damn really? On rock auto it showed that as the p/n for the s13

Sent from my SCH-I535 using Tapatalk 2

[DRIFT_happens]

Can I play?

This (PBM new version inners w/ spl outers and yes I know the spacers don't go that way.)


Plus these


Cut here


And extended 25mm





With PBM Eccentric Rack Bushings for good measure, equal this. (Pic below is negative camber)

[swiftmini]

bahaha PMSL. this is what happens when peeps with no idea start drawing shit on solidworks. Im with DEF, the guy hasnt a clue.

These front knuckles will have less lock than standard, unless of course he is planning on not using an upper wishbone

[Motary]

Looks like a heafy mofo aswell, I am making mine like this, except the little rib is a bit useless, more of a stress increaser in that area:

[kewilso3]

Originally Posted by Johannes

Does anyone know where I could get a tapered shank that would allow me to keep the stock pickup point taper?

Maybe 1/2 or 5/8 QA1 Heim with misalignment spacers that would let me run a shank that bolts up to stock taper? Bumpsteer adjustment is not necessary since I will be dropping the balljoint pickup and tie rod pickup point down.

My current setup now is with 5/8" Heim joint, and the pickup point drilled to 5/8"..

If you're talking about the tie rod, SPL has them, I believe the shank is 5/8...

If you're talking about the ball joint in the LCA, PSM sells their shanks which are designed for an 18mm spherical, SPL has some that are 5/8 shank (meant to be used w/misalignments in a 3/4 spherical), and N8 of s-empire or something like that on here can get you some 3/4" ones.

(SPL parts for example)

[LuckyX2]

Originally Posted by swiftmini

bahaha PMSL. this is what happens when peeps with no idea start drawing shit on solidworks. Im with DEF, the guy hasnt a clue.

These front knuckles will have less lock than standard, unless of course he is planning on not using an upper wishbone

He's not aiming for the drift market as far as I know so he's not adding any more steering angle.

[Motary]

[PoorMans180SX]

I was just going to post that. Looks very cool IMO.

[Johannes]

Just got done with my roll center and bumpsteer corrected knuckles..
52mm drop.


I have solid Heim joints (5/8") as my outer tie rods with bumpsteer correction.. (Picture of setup posted above)
Question now is.. is it worth drilling these spindles to 5/8 and running solid heim joint or just keep the taper and just run oem outers (S14) ?
I don't mind the drilling. It's just that with my current setup, (heims) the car is really twitchy considering I have solid steering bushing and solid eccentric rack bushings..

[PoorMans180SX]

Originally Posted by Johannes

Just got done with my roll center and bumpsteer corrected knuckles..
52mm drop.

I have solid Heim joints (5/8") as my outer tie rods with bumpsteer correction.. (Picture of setup posted above)
Question now is.. is it worth drilling these spindles to 5/8 and running solid heim joint or just keep the taper and just run oem outers (S14) ?
I don't mind the drilling. It's just that with my current setup, (heims) the car is really twitchy considering I have solid steering bushing and solid eccentric rack bushings..

52mm of drop, very nice. Heims, in my opinion, pose no real advantage to a stock tie rod end unless you need the bumpsteer correction that something like SPL provides.

They require more maintenance and don't really increase feel or precision over a standard ball and socket. I'd say stick with a standard end.

[Johannes]

Soo.. I installed my drop knuckles yesterday and went with S14 LCA's.
Top picture shows my other S13 with tein lowering springs (1.5" ride height decrease), and bottom picture is the one with drop knuckles. Coilover is maxed out, removed two collars and didn't flip the bracket.

You could see my homemade tension rods =p
You could make a pair of high quality with offset misalignment spacers off the shelf for around $60.



You could also kind of see the outer tie rods top left of the LCA being parallel. I'm really liking this setup.

[s13 loverr]

Does anyone know what the crescent shape washers are for in PSM's rear knuckle kit? I can't seem to figure out what I need them for. Thanks!

[az_240]

^to space the ball joint nut from the weld

[ska]

Originally Posted by DC Dan MAX USA

The scenario for the straight FLCA we offer is stock knuckle, slammed ride height, stock track width.

The wide track width you described and the fact that you are getting the forged knuckles means that you correctly chose the bent version.

Yup, thats the general idea

Also a question on your product. if i were to use your new forged knuckles, would I have to revert back to stock outter tierods? It looks like you guys already spaced down the pickup point for the tierod.I currently have pillow ball outer tierod ends with a 1 1/2" spacer to space down the pick up point. I tried to search but I cannot find wtf sort of brand it is, it was given to me. Currently with stock knuckles my LCA and tierods are perfectly parallel to each other. No bumpsteer that I can feel

Also Have you received a date on when those knuckles are coming in? I would actually like to have them before a certain date so I can use them.

[huffandpuff00]

Still use your outers just reduce the spacer amount until they are level. No spacers/small spacer should be about oem height on the outer.

[motoxris]

Cor Integration actually has 45mm of rollcenter adjustment now :-) QUOTE=PoorMans180SX;3200723]Disclaimer: Modifiying a cars 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.


Part I: The Basics.

The Front Suspension:

Tension rods: These control caster, anti-dive, and anti-lift in the front suspension. Caster helps determine camber gain over the suspension stroke, and camber change throughout steering angle. Caster also helps “auto turn” the wheel when countersteering. The angle of the tension rod (horizontal plane, front to back) also helps determine 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, track width, and camber curve. The actual arc these move in is the camber curve (as dictated by the tension rod).

Tie rods: are used to adjust toe in the front, and obviously to steer your car. Aftermarket tie rod ends can be used to adjust bumpsteer by spacing the tie rod end parallel with the FLCA pivot points.

The Rear Suspension:

Rear upper control arms: Used to adjust static camber. The actual arc these move in is the camber curve, but keep in mind that all of the rear arms help determine this. They also help determine roll center, similar to a double wishbone setup.

Toe rods:These control static toe and toe change during suspension compression. When lowered aggressively, our cars 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. As with the front, this helps determine the camber curve of the rear suspension.

Tip: On an aggressively lowered car, these should be lengthened (to about 8.5in) for a less aggressive toe curve and less bumpsteer.

Rear lower control arms: Help determine roll center, anti-squat, and can affect camber. The angle front to rear of the control arm (horizontal plane, front to back) determines anti-squat (along with the angle of the camber arm and traction arm subframe mounts). The flatter the control arm, the more squat. S13’s have a lot of anti-squat, S14 and 15’s have significantly less. The angle side to side (horizontal plane) is what helps determine roll center.

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.

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.

Roll center angles must be measured from pivot point to pivot point. Modifying merely the angle of the arm doesn't do anything at all.



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

The ways to actually adjust roll center in the front and rear are these:

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:

Sunline:



Nagisa:



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):



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 PSM made a nice diagram showing how the ackerman change happens:



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.



3. Modifying your stock arms. This is a little more complicated, but anyone who isn't afraid of some fabrication and taking his time can do this.

Here's the basics of what you need:

- (4) COM series QA1 3/4" spherical bearings
- (4) 3/4" spherical bearing weld in housings
- (4) Coleman Racing extra long ball joint studs with Chevy 7* taper
- (1) 7* taper drill bit from Speedway*Motorsports
- (4) pairs of 3/4 to 5/8 high misalignment spacers

And 95KA-turbos' old setup:



4. Modify the subframe pickup points (moving them farther up), thus changing the angle of the arm.

NOTE: If you plan on raising the front control arms' inner pivot point, it’s a good idea to move the steering rack up an equal amount or you will run into some big bumpsteer issues.

JIC Magic S15 front setup:



5. Modifying the pickup points on the knuckle (usually by creating a whole new knuckle), dropping them lower.

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



Stock knuckle:



Driftoworks knuckle:



Here they are installed, you can see the control arms are nearly flat.





Parts Shop MAX Pro knuckles with 45mm correction:





And their new forged pro knuckle:





Parts Shop MAX rear 25mm drop knuckle with spherical bushings:





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



Cor Integration's knuckle with 32mm correction:



Wisefabs front suspension kit, with a 56mm drop knuckle:



GKTech's new billet aluminum knuckles have 40mm correction:







And their soon to be a reality rear 40mm forged aluminum drop knuckle:



And GKtechs bolt on knuckle adapter with 40mm of correction:



Track Day Performance has a billet aluminum front suspension kit with 90mm of correction; a 30mm drop knuckle and 60mm control arm drop:









You can also modify your knuckles yourself if you have some fabrication experience.









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

You can do this with Parts Shop MAX’s subframe risers:



Installed:



Or 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:



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

Some guys have taken this to the extreme:



You Z and R-chassis guys are left to either convert to McPherson strut front suspension, or modify S-chassis parts to work. Luckily your dual control arm setup isn't nearly as suseptible to roll center drop as ours:





Another geometry trick is to adjust the toe arm mount on the knuckle, helping correct the toe curve, which helps traction. (Modify the toe arm on the knuckle so that your toe rod is parallel with your LCA): You can do this with your regular cast iron uprights if you don't plan on buying drop uprights as well. GKtechs rear knuckle will have an adjustable toe arm mount for this reason.



Here's a cool Drift Tengoku article about chopping the re-welding the lower part of the knuckle, including the LCA pickup:



JIC rear setup:



[/QUOTE]

[PoorMans180SX]

Originally Posted by motoxris

Cor Integration actually has 45mm of rollcenter adjustment now :-)

Haha that's good to know, you didn't have to quote my whole post to say that . I'll ask them for some updated pics.

They also came out with these new tension rods that have even more clearance than their old version.

[LuckyX2]

Way to quote the entire first page lol. Could you edit that please? It slows down my shitty work computer.

[motoxris]

Hahaha. Sorry guys, I was using my phone and not paying attention.