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

[PoorMans180SX]

Originally Posted by Tulok

You were right on both points. I actually had 1.5* of caster On one side I couldn?t believe my eyes. I did not notice that the tension rod had unscrewed itself most of the way within minutes of doing some practice drifts due to the wheel rubbing on it. The other side was not great either.

I dialed it back as far as I could to 6*, and added a larger spacer so I?m at -32 effective. And adjusted the coilover lower mount to reduce camber. And installed s13 lower control arms which are about 7mm shorter. So I?m sitting at about -4 front camber.

I have the Gktech v2 lower adapter on the low Ackerman setting.

It feels very good now, it?s easy to control the line and the front end has a lot of bite when I?m aggressive and it?s easy to widen the line and float out.

It feels a lot more like when it was stock just with a ton of angle, and more bite Which is great.

Good to hear!


Okay so these RLCA brackets were interesting. I think it's partly because I have wisefab, and partly just the way this goes, but be prepared to do a lot of fitting and triple checking. Also don't be like me and weld the inside seems without checking clearance first, I had to do quite a bit of grinding to get the heim joint spacers to fit back in .



In order to get the rod end to not be maxed out, I twisted the bracket quite a bit. This helped a ton, and allowed me to not have to hammer the LCA or bolts into place, hah. I did also have to grind down the "seam" on the subframe pretty heavily to allow me to slide the bolt in easily.





Click for articulation video:
https://imgur.com/ICrxKoe

Wisefab with dropped front pickup:



Fitment should be pretty nice, even with these second hand G35 wheels and maybe a few mm spacer.

[TheRealSy90]

Aren't the wisefab knuckles designed with different geometry? Isn't lowering that pickup point going to ruin the built in geometry of the knuckle?

[PoorMans180SX]

Originally Posted by TheRealSy90

Aren't the wisefab knuckles designed with different geometry? Isn't lowering that pickup point going to ruin the built in geometry of the knuckle?

Wisefab was built around the S14/15 subframe and adapted to the S13. The S13 has too much anti-squat with wisefab. Watch Matt Coffman?s car move backwards on the e-brake and you can tell.

[PoorMans180SX]

Got the subframe and Wisefab in the car. Really looking forward to testing this out. I modified this subframe by welding in my own steel 'bushings' aka two giant washers and a short length of pipe. It doesn't give the most absolute amount of roll center correction possible but I wasn't too concerned with that. Wisefab is still a PITA to install compared to individual arms, but a little less so now that I made sure everything fit before welding up the reinforcement brackets, haha. Eccentrics have also been deleted.

[PoorMans180SX]

This is factory S13 control arms with the factory lock stop and Geomaster V3s on a 17x7 G35 wheel with a 15mm spacer. Unfortunately the trailing wheel still hits the front of the LCA, but I think with tires the tire will hit the tension rod before this happens. An aftermarket tubular control arm would fix this. I'll have to make a small lock stop to try and limit the arm for now, as I imagine the 17x8s I'll be running will make this worse.

[Marphie21]

Just installed a full Gktech knuckle and suspension arm package, with the anti squat kit, on my s13. I also got new fortune 510s customized for longer stroke.

The first test drive was pretty darn good. The car feels different from every other S/A31- chassis I've driven so far.

Hoping to get more test drives in by next week, and I'll also try checking the bump & toe curves front and rear.




Seems like my 510s are most live-able at 1 click on the dampers.

As for the toe/ camber curves, it seems like the fronts gain negative camber and toe in as the suspension compresses. The rear seems to have toe in and a positive camber gain (??) under compression. I was just using a level app on my phone to measure the rear camber; unsure if it was just inaccurate if my car actually gains positive camber when it squats

[Marphie21]

I was able to do a track day with the initial setup. Based on the tire wear (in the rear), I have a bit of negative camber gain. Im wondering if i should play around with the traction rod to keep the rear more consistent at ~0 camber through the compression stroke.

With a completely stock SR20DET, blow-by, and 0.7-0.9 Bar, the car was one of the faster cars I've ever driven sideways. I could only compare it to my 230whp 1uz corolla running the same gktech antisquat kit (albeit with driftworks knuckles vs the S13's Gktech)

[PoorMans180SX]

Originally Posted by Marphie21

I was able to do a track day with the initial setup. Based on the tire wear (in the rear), I have a bit of negative camber gain. Im wondering if i should play around with the traction rod to keep the rear more consistent at ~0 camber through the compression stroke.

With a completely stock SR20DET, blow-by, and 0.7-0.9 Bar, the car was one of the faster cars I've ever driven sideways. I could only compare it to my 230whp 1uz corolla running the same gktech antisquat kit (albeit with driftworks knuckles vs the S13's Gktech)

Some negative camber gain is good for side bite. Interesting news though. What are your current alignment specs?

[Marphie21]

Since this was the baseline test, i had the rear at 0 camber and 0 toe.

Unfortunately i think the next time ill be able to drive the car will be next year, as Ill send out the chassis to be fully restored.

I didnt plan on going straight to this stage of the build this early, but since the SR that came with the car is now spitting oil everywhere, i might as well finish the chassis work and put in my built SR20. From there I can do more tests.

It was also obvious that the chassis flex wasn't letting me feel all of the performance from the suspension, so further testing after restoration might lead to more accurate results/feedback.

[TheRealSy90]

Front toe-in under braking is intentional so the car doesn't dart off the track/road when you slam the brakes.

[Marphie21]

Originally Posted by TheRealSy90

Front toe-in under braking is intentional so the car doesn't dart off the track/road when you slam the brakes.

Yes, the fronts are normal. My initial measurements in the rear were what worried me. Although after jacking up the front left of the car, i noticed the rear right maintain 0 camber as it was loaded up. That meant the rear was gaining negative camber. Because as you jack up one corner, in this case the front left, it causes the car to roll or tip over, while loading up the opposite corner. The fact that the rear right maintained 0 camber while the chassis was rolled over meant that i was actually seeing a negative camber gain.

This was confirmed after the first test, my rear tire wear was showing me just a little bit of too much negative camber.

[PoorMans180SX]

Originally Posted by Marphie21

Yes, the fronts are normal. My initial measurements in the rear were what worried me. Although after jacking up the front left of the car, i noticed the rear right maintain 0 camber as it was loaded up. That meant the rear was gaining negative camber. Because as you jack up one corner, in this case the front left, it causes the car to roll or tip over, while loading up the opposite corner. The fact that the rear right maintained 0 camber while the chassis was rolled over meant that i was actually seeing a negative camber gain.

This was confirmed after the first test, my rear tire wear was showing me just a little bit of too much negative camber.

You do still want negative camber gain on the rear. This helps with side bite in drift and grip in normal cornering as well. You just want less of it than what a normal low s-chassis has, as it becomes a very steep curve. Zero rear toe means you weren't taking advantage of anywhere near the grip you could have with some static toe in.

[TheRealSy90]

On my stock rear knuckle s13 that was drift only and not street driven I ran 3/4inch toe in on the rear lol. Thing was hooked up on throttle.


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[Marphie21]

Originally Posted by PoorMans180SX

You do still want negative camber gain on the rear. This helps with side bite in drift and grip in normal cornering as well. You just want less of it than what a normal low s-chassis has, as it becomes a very steep curve. Zero rear toe means you weren't taking advantage of anywhere near the grip you could have with some static toe in.

Yes, i understand that. I tend to adjust the camber depending on what tire or tire pressure I use. But right now im still seeing the majority of the tread disappear a little towards the inside of the tire. Id rather have a camber setting that maintains an even tire wear through the whole face of the tread. Maybe if i lowered the tire pressure a bit more during this test, it wouldve been perfect, but the car still being tested with a stock SR20 (condition unknown) so I kept the pressures at a modest 24PSI.

As for toe settings, i would run up to 1/2" toe in on my driftworks geomaster 2 car (used to be used for competition). I wanted to keep things "zero'd" for this test so i would have a better idea of what the gktech kinematics were doing. Also with just about 200whp, i find that too much toe in creates a bit of an awkward flow when driving longer corners. Although i feel anything north of 250whp would greatly benefit from a good amount of toe in, without needing to reduce mechanical grip to keep the car more
predictable/forgiving.

[DRIFTER-M]

Just picked up B-Knuckles. As I have always been the old school dude who never did knuckle mods (this being my first), anybody have suggestions on the inner / outer tie rod combo? Not sure what to go with. Stock s13 LCA or no?

I am worried about that speed boat look, hoping to keep my car a little more even on lowering (similar to how Julian runs his), but overall pretty pumped to get these going.

Thanks you!

[TheRealSy90]

just get whatever oem tie rod combo works for your track width.

[240sx_sr20det]

Originally Posted by DRIFTER-M

Just picked up B-Knuckles. As I have always been the old school dude who never did knuckle mods (this being my first), anybody have suggestions on the inner / outer tie rod combo? Not sure what to go with. Stock s13 LCA or no?

I am worried about that speed boat look, hoping to keep my car a little more even on lowering (similar to how Julian runs his), but overall pretty pumped to get these going.

Thanks you!

OEM Outer, Maxima Inner.

S13 or S14 LCA (7-11mm difference, can't remember). Use whatever BJ will work with knuckles. (ie: S13 knuckles = S13 Ball Joint in S13 or S14 LCA).

[808drft]

PS sorry for the huge pics. It how it uploaded to imgur

Originally Posted by PoorMans180SX

Good to hear!


Okay so these RLCA brackets were interesting. I think it's partly because I have wisefab, and partly just the way this goes, but be prepared to do a lot of fitting and triple checking. Also don't be like me and weld the inside seems without checking clearance first, I had to do quite a bit of grinding to get the heim joint spacers to fit back in .


In order to get the rod end to not be maxed out, I twisted the bracket quite a bit. This helped a ton, and allowed me to not have to hammer the LCA or bolts into place, hah. I did also have to grind down the "seam" on the subframe pretty heavily to allow me to slide the bolt in easily.

Im running gktech RLCA brackets with their full rear catalog. With a 1jz making 345whp running cheap 245 ironmans car has solid grip. Even more with falken rt615k and kenda kr20a I ran at last drift event. Car is smooth, predictable and easy to drive.

[PoorMans180SX]

Check out the anti-squat in Keoni Rodrigues car. It lifts the rear doing a burnout! The car is a rocketship. (Video starts just before burnout)

EDIT: The time stamp thing doesn't work anymore. Skip to 1:18:20 for the burnout.

[steveff]

Originally Posted by PoorMans180SX

Check out the anti-squat in Keoni Rodrigues car. It lifts the rear doing a burnout! The car is a rocketship. (Video starts just before burnout)

Anti squat seems to make the cars faster but significantly harder to drive. I?ve heard the RTR cars were using up to 125% anti squat when they were really picking up front wheels off the ground. But they?ve since dialed it back a little to make the cars easier to drive.

Anti squat isn?t the enemy and personally, my car felt faster with standard S13 LCA mounts compared to the 0% anti squat adjustment I made recently.

Car is easier to drive now with 0% anti squat but it?s not as fast as OEM S13 45% anti squat.


Sent from my iPhone using Tapatalk

[PoorMans180SX]

Originally Posted by 808drft

PS sorry for the huge pics. It how it uploaded to imgur

Im running gktech RLCA brackets with their full rear catalog. With a 1jz making 345whp running cheap 245 ironmans car has solid grip. Even more with falken rt615k and kenda kr20a I ran at last drift event. Car is smooth, predictable and easy to drive.

Looks good man!

Originally Posted by steveff

Anti squat seems to make the cars faster but significantly harder to drive. I?ve heard the RTR cars were using up to 125% anti squat when they were really picking up front wheels off the ground. But they?ve since dialed it back a little to make the cars easier to drive.

Anti squat isn?t the enemy and personally, my car felt faster with standard S13 LCA mounts compared to the 0% anti squat adjustment I made recently.

Car is easier to drive now with 0% anti squat but it?s not as fast as OEM S13 45% anti squat.

How did you calculate your anti-squat at 0%? Factory S13 is like 180%. 120% is about ideal for a really aggressive sportscar, but it varies depending on suspension design.

On the anti-squat note, it seems like Keoni's car is faster once it's really churning out the smoke. This kind of makes sense given the nature of anti-squat, increasing weight transfer to the rear and really hitting the tires hard isn't really good for traction (when it's limited by the tire) during the initial launch or when you're trying to keep the tires from spinning, but once you've transitioned to spinning, it makes sense to have maximum weight transfer in the rear. Maybe you don't have to run so much static toe-in this way?

Clearly it's not the be-all, end-all, as Alec Hohnadell's car is ridiculously fast, and it's got quite a bit of squat. I wouldn't be surprised if it was modified similarly to Odi's with the way it moves, or just has very soft springs. It very clearly works, as he's now the champion of that series.

These are just my observations and things I find interesting about driving style/setups.

[kcswiz]

(Deleted)Posting error

[kcswiz]

Please help!
I drove a friends 350z that had a wisefab kit installed on it. I have a g35 that happens to share a lot with the Z platform. I was wanting to purchase the wisefab kit myself but I noticed his kit caused his wheels to significantly push out more than stock. But he has a wide body on his car and I do not plan to cut my fenders at all. And the only wide fenders the g35 offers is 10mm wider ones that don’t require cutting.
My question is what are my opinion if I were to install a wisefab kit as far as fitment and not destroying my tires and fenders. Would it be possible to roll and pull my fenders up enough to then install some 50mm fenders, so I wouldn’t have to cut anything?
Also, I was told the majority of other angle kits keep your car looking stock as far as original fitment.
Which kits have you used that you can confirm this? Would love to hear some brand names.

[Speed Junkie]

Hi guys. I've been lurking this thread for while and have finally decided to post. I've done a lot of research into 240sx suspension design and put together a decent package for what is primarily a street car that I occasionally drive on the mountains and even fewer times at drift events. After all of this I've come to realize just how compromised the 240sx design is from the factory.

I have an S13 coupe, not very low. Front height is about a finger gap between the top of the tire and fender. Rear is about a finger of tire tuck.

Here are the suspension mods:
Front: GKtech grip/drift knuckles, FA500 coilovers with hyperco springs, GKtech tension rod, Energy Suspenion rack, sway bar, and LCA bushings.
Rear: S14 subframe with risers, FA500 coilovers with hyperco springs, aftermarket sway bar with poly bushings, ISR adjustable and heim joint links.
I also have GKtech rear knuckles and frame reinforcements that I plan on installing this winter.

Wheels are 17x9 +25 and 215 all season tires.
My front alignment is -3* of camber, OEM toe-in, and 6* of caster.
My rear alignment is -2* of camber and OEM toe-in. Trac rod is OEM length but I plan on adjusting it to reduce excessive toe out during compression.

Quick notes:
All of my suspension components are tightened and in good working condition.
All of this is under the context of grip driving. Drifting is super easy in this car and these issues aren't really a problem when sliding the car.


1st and biggest issue: Bump steer. I was hoping that the knuckles would eliminate this but they didn't. They did help A LOT which was great. But far from really any other car. It's really been the one factor that keeps me from truly enjoying the car. Through my research I've learned that this is primarily an issue with rear-mounted racks that naturally produce toe-out under compression. Front-mounted racks (like on Miatas) produce toe in. This is why the OEM alignment specs call out for slight toe in. Despite this, the bump steer is still there. It's not wheel-kickback from an increased scrub radius caused by lower offset wheels. It's the car moving left and right as the front suspension corners flex independently.

2nd issue: the rate at which the car turns in varies as you turn the wheel. Steering between around 10 and 2 o-clock produces less response from the car than steering further. In other words, as you turn in, the initial response from the car is slower than as turn turn the wheel further and past 10 o-clock. The opposite is true of course. As you straighten out the wheel, small changes of steering angle produce a large response from the car. And as you approach straight, the car response is less. I want to make it clear that this is not free play in the steering system or movement in the rack. I think this is due to a combination of Ackerman and the OEM toe in. Since the initial input in steering would first have to get past the wheels pointing in. And as the steering angle increases, you get the inside wheel pointing further and further in due to ackerman (which also adds a moment arm to the car, further helping turn in). Thus, the car turns in more once the wheel is turned past a certain point. It's non-linear and it sucks to drive.


Solutions that I want to run by you guys:
I know that relocating the rack forward will reduce ackerman and if my hypothesis is correct then it will help with the 2nd issue. My only worry is how this will affect every day driving and I don't want to create yet another compromise. Any input?

In regards to bump steer. I can add a spacer/washer to the inner tie rod. Not for more angle, but to get the inner tie rod pivot in line with the LCA inner pivot. I think this should help with bump steer(?)

And at the outer tie rod, do you guys think I should try adding spacers to lower the outer tie rod end further? Again, I thought the knuckles would've fixed this but I can always lower the rod end joint further.

In regards to the rear bump steer. This is less critical than the front but the fact is that it does toe out under compression which is the opposite of what you want. I've ran the car with 0 rear toe before and was surprised at how easily the rear end slides out when I turned in. OEM toe in fixed this but I think I can make it better by adjusting my trac rod.

I'm sure you've all see this from the motoiq article on trac rod adjustment.

EDIT: Last I posted here was 2019.

[e1_griego]

Autocross snob in me is looking at all your geometry concerns and then seeing 215 all seasons :-|

[Speed Junkie]

Originally Posted by e1_griego

Autocross snob in me is looking at all your geometry concerns and then seeing 215 all seasons :-|

Originally Posted by Speed Junkie

...for what is primarily a street car that I occasionally drive on the mountains and even fewer times at drift events.

Tell me how you don't know what you're talking about without telling me that you don't know what you're talking about.

[e1_griego]

Yeah but a mushy tire is still gonna do mushy tire things on a back road. Before you change a bunch of stuff a better tire might feel a lot better, something with sidewall rigidity.

And most of the cheaper shocks will make the car unsettle on top of that.

But I don't know anything so don't worry about it.

[Speed Junkie]

If the issue was having all season tires then every car out there with all season tires would have this issue. I've also driven plenty of other 240s with the typical 595R/NS-2x and they have the same issue. In fact my previous S14 had NT05s and it had the same issue.

So yeah, saying that 240s have a bump steer/suspension design issue isn't surprising to anyone. And when I post a comprehensive, informed, descriptive post on a suspension geometry thread that also covered your snarky reply, it raises an eyebrow on your intent and knowledge on the subject.

[e1_griego]

Fair enough. You've added considerably since the first post, it's just odd to me to focus on perfect geometry for a street driven car on all seasons, but to each their own.

There has been pretty reasonable bumpsteer discussions on NRR over the years, though most of the graphs are missing. In competitive classes you can't usually touch that stuff, though, so prob not as much info as you want.

https://www.nissanroadracing.com/for...mann-questions

https://www.nissanroadracing.com/for...teering-angles

https://www.nissanroadracing.com/for...stment-article

Jason's pcitures are gone but I'll see if he still has them squirreled away somewhere.

[PoorMans180SX]

Speedjunkie:
Get rid of toe in up front. That’s killing your front end. Secondly those mushy tires are something I would address after that. If you’re after response you’re going to want something with a stiff sidewall.

Your traction rod should be extended the same amount your camber arm is.

You may want to consider extending your lower control arms, this helps with understeer quite a lot.

I think those changes alone will make the car wildly better to drive, but if you’re still having issues with bumpsteer then you need to take the time to measure it. You’ll have to test different tie rod heights yourself, I don’t think anyone has done that with the gktech grip knuckle.