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

[thefro526]

Originally Posted by Matej

This is a dumb question, but what effect do extended 'roll center adjuster' ball joints have in the rear?
The GKTech RLCA come with two different shank lengths for the ball joints, so I have been curious about it.
I suppose I know how they would change the geometry, so my question should actually rather be, would they be beneficial/not beneficial for drifting and how/why?

I know what they are good/bad for in the front, but I am unsure about the rear.

I'd imagine you'd notice some differences in your dynamic alignment change characteristics - specifically changes to your rear bump steer and camber gains. As far as bump steer (toe curve) you'd start seeing increased change during travel at a certain extent, considering that you're effectively doing the opposite of what is commonly done to reduce dynamic toe change. (making the toe arm parallel with the LCA by moving the two closer together) I'm not sure if 5mm or 10mm of RC correction would be enough to do anything that's 'actually' noticeable.

Depending on exactly what you're shooting for, it seems like the rear roll center is best corrected in the same way as the front, with that being a drop/modified knuckle. It's a lot easier to hold the desired geometric constraints at the knuckle because it's a single self contained unit and then use the various links as simple pivoting arms with adjustment for alignment.

Although, with all of the above being said, if you were to use GK Tech's Knuckles with their LCA, you could play with shank lengths all you want (within reason) and then use their adjustable toe arm mount/pivot to dial in the desired toe curve in the rear. From there, it seems that the only concern would be with your dynamic camber gains, which may be corrected in the knuckle already.

[Black R]

Originally Posted by Def

NRR all up in this thread...

^ fook ya bro!

Wtb moar angle, roll center correction, and 335's up front!

[PoorMans180SX]

I had to cut my wheel wells out today. Even after I raised it 15mm it still rubbed at full lock at the top of the left wheel well.

[jaysgottaredtop]

^ ridiculous ratio of lock angle to not-even-close-to-overcentering-ness

[Black R]

Poorman, please make your front end max tire compatible when you finalize it - so I'll know what to do in the future.

[Matej]

The coolest part is the cluter-less engine bay. Hope the finished product will stay 'tucked' in similar fashion.


How close to stock rear geometry do you gentlemen think one could get with shorter RLCA and drop knuckles (most likely GKTech RLCA and MAX knuckles) on an excessively lowered car?
My end goal is to figure out a setup where I can switch back to factory non-adjustable links while retaining reasonable camber and toe.

[Chronicle]

Originally Posted by PoorMans180SX

I had to cut my wheel wells out today. Even after I raised it 15mm it still rubbed at full lock at the top of the left wheel well.

Judging by the picture, now you've got pretty easy access to your coils

[ZacKisBacK_Fr]

Originally Posted by NismoPlsr

Spacers will work. GKtech is making them for 3x2, 5x1, 6x1 bolt patterns for any diff and hub setup.

We are also compiling a comprehensive list of axle lengths over on NRR.



OS Giken and real CV's, How to? - Page 7 - Nissan Road Racing Forums

You can see why LH Q45 with LH Z32 TT axles are the choice for 6x1 stub flange diffs in a s-chassis.

Thank you NismoPlsr for the link! Great info over there!! I'm still waiting for gktech to sell those 5 holes spacers!

[DialedLife]

Does droop effect spring rate? I'm on 9k/8k and it feels softer than my grand am.

Edit: I asked in small questions, and google is giving me formulas. I'm not a genius, really looking for a yes or no answer.

[PoorMans180SX]

Originally Posted by jaysgottaredtop

^ ridiculous ratio of lock angle to not-even-close-to-overcentering-ness

Crazy right? Blows my mind sometimes too.

Originally Posted by Black R

Poorman, please make your front end max tire compatible when you finalize it - so I'll know what to do in the future.

Do you mean like a road course setup, or just the max I can fit right now? This car is going to need a fender flare for more tire, the control arms are 40mm wider than stock, so it really eats up the "outside" space that you could normally fill with tire. If I had shorter coilovers I could dial in some positive camber at the knuckle and run a higher offset and/or wider wheel for more tire with an additional fender flare. I really want Koguchi Power front fenders!

Originally Posted by Matej

The coolest part is the cluter-less engine bay. Hope the finished product will stay 'tucked' in similar fashion.

How close to stock rear geometry do you gentlemen think one could get with shorter RLCA and drop knuckles (most likely GKTech RLCA and MAX knuckles) on an excessively lowered car?
My end goal is to figure out a setup where I can switch back to factory non-adjustable links while retaining reasonable camber and toe.

Thank you sir, and indeed it will. The brake lines are getting replaced with braided ones that go under the engine, and the VQ's wiring harness is small and I shortened it to go behind the intake. My fuse blocks are now underneath my glove box.

As far as your question goes, you're going to need more knuckle drop if you want to use stock arms. Driftworks would probably work.

Originally Posted by Chronicle

Judging by the picture, now you've got pretty easy access to your coils

Haha, indeed. I could even adjust toe without jacking the car up, haha.

Originally Posted by DialedLife

Does droop effect spring rate? I'm on 9k/8k and it feels softer than my grand am.

Nope, but it does change how the damping and spring react to each other if there is no preload on the spring. If your car rides nice with stiff springs, it basically means you have properly valved coils.

[PoorMans180SX]

The Brill Steel Motorsports S14.5 rocks this tubular rear subframe, I thought it was interesting because you don't see a lot of these due to rules. Looks like driftworks knuckles out back, and TDP stuff up front.

[thefro526]

Originally Posted by DialedLife

Does droop effect spring rate? I'm on 9k/8k and it feels softer than my grand am.

Edit: I asked in small questions, and google is giving me formulas. I'm not a genius, really looking for a yes or no answer.

Spring rate is a constant. Basically it's expressed in force over distance, i.e. 6kg/mm or 350lbs/in. (They're approximately the same rate, FWIW.) Basically what that means is that for each unit of force, a spring will compress that distance. Apply a 6kg load to a 6kg/mm spring, and the spring will compress 1mm - 60kg load, spring compresses 10mm. (This assumes the spring has a linear rate)

Now imagine the spring rate as a line on a graph, with the slope corresponding to the spring rate. Pre-load and/or droop will effect where you start on that line, but not the rate at which the line changes (assuming linear spring). So basically, when you preload the spring, you're applying more force to it, causing it to compress more. This means that it won't move until that force is overcome.

So basically, preload does not effect spring rate, as a spring rate is a set constant according to the spring. (Technically, a progressive spring rate is also 'constant' although it varies, but the variation will happen at a specific rate in a repeatable fashion)

Now to answer your question, removing preload from the spring will make it feel softer (easier to compress), but spring rate hasn't changed. Basically what you're noticing is that spring is more likely to compress at lower force since less is applied via preload. Just playing with numbers, but if you compressed an 8kg/mm spring about 10mm via the adjusting collars, it'd be preloaded with about 180ish lbs of force, give or take. You'd have to over come that 180lbs of preload to get the spring to even move at all. Remove 50% of the compression (5mm) and now the spring only requires half as much force (90lbs) to move as before.

As Poorman said in the post above, damping as a big effect on how a spring feels too, so your issue could have something to do with how the entire system is working together.

[Black R]

Originally Posted by PoorMans180SX

The Brill Steel Motorsports S14.5 rocks this tubular rear subframe, I thought it was interesting because you don't see a lot of these due to rules. Looks like driftworks knuckles out back, and TDP stuff up front.

I'm surprised there isn't an off the shelf "kit" that has a tubular front subframe for s-chassis.

[tauntdevil]

Originally Posted by Black R

I'm surprised there isn't an off the shelf "kit" that has a tubular front subframe for s-chassis.

Maybe I am not understanding correctly but are you talking about the rear subframe of the car? the front crossmember is really all there is in the front, nothing to really tube on there and for the rear, the price it would cost to make it vs how much would really sell and what for wouldn't be worth it as people dont really spend much for a rear subframe unless they are doing a major build like that one.

Looks sexy though and TDP knuckles look sexy, I will definitely have to save for those instead of wisefab replicas.

[xoxide]

I did an internal thread search but didnt turn up what im looking for...

Im about to have my LCA's extended... I was thinking 2 inches, but someone told me that is too much, what is the "optimal" amount of extension for S14 LCA's on a s14? I dont want -24858 degrees of camber... somewhere between 4-6 degrees, which i would assume would be achievable with 2 inch extension still?


If it helps my setup will be:
tien tierods
Abercrombie Motorsports outer tierods
2 inch (or less?) extended LCA's with new bumpstops welded on most likely
Modified knuckles with ackerman correct
new balljoints

[tauntdevil]

I have -5 degrees of camber with my stock arms and Ksport coilovers. Rest was stock.
Normally everyone goes by mm instead of inches. 1.5 inches would probably be enough for what you are asking to do.

[xoxide]

Yeah I mean I can get plenty of camber on my stock arms as well haha, what I meant by that is with a 2 inch extension, would I be able pull enough camber out of the front end (coilover notches and camber plates) to reach 4-6 deg camber, if that makes any sense at all?

[az_240]

Originally Posted by PoorMans180SX

As far as your question goes, you're going to need more knuckle drop if you want to use stock arms. Driftworks would probably work.

I'm not sure how well the stock arms will work with the Driftworks knuckles but when I had them I couldn't get them to go very low because the Cusco RUCAs I had would go right into the axle boots. A friend had some Isis RUCA laying around, which have a straight design and smaller diameter and s13 axles, which have smaller boots so I tried those out and was able to go lower but the lower I went the more the axles wanted to bind because they're so high up on the knuckle. I'm afraid the Driftworks knuckles just aren't made for going really low without extensive work (cutting/raising the shit out of the subframe/diff)

Haven't had these issues with my PBM rear knuckles...

Originally Posted by Matej

My end goal is to figure out a setup where I can switch back to factory non-adjustable links while retaining reasonable camber and toe.

I imagine you'd need to shorten the RLCA a lot to get the stock arms to work on a slammed car. Are you wanting to keep stock arms for comfort?

Originally Posted by xoxide

Yeah I mean I can get plenty of camber on my stock arms as well haha, what I meant by that is with a 2 inch extension, would I be able pull enough camber out of the front end (coilover notches and camber plates) to reach 4-6 deg camber, if that makes any sense at all?

Someone correct me if I'm wrong but 2" is probably too much. I'd shoot for 1" to 1.5" with S14 FLCAs if you don't want to modify your camber plates/strut towers.

[PoorMans180SX]

20mm gives roughly 2.5* more camber.

[PoorMans180SX]

Originally Posted by Black R

I'm surprised there isn't an off the shelf "kit" that has a tubular front subframe for s-chassis.

Originally Posted by tauntdevil

Maybe I am not understanding correctly but are you talking about the rear subframe of the car? the front crossmember is really all there is in the front, nothing to really tube on there and for the rear, the price it would cost to make it vs how much would really sell and what for wouldn't be worth it as people dont really spend much for a rear subframe unless they are doing a major build like that one.

Looks sexy though and TDP knuckles look sexy, I will definitely have to save for those instead of wisefab replicas.

I think he means with the rack moved forward, an easy bolt-in solution.

Unfortunately turbular subframes are illegal in basically every racing series besides unlimited time attack and drag racing.

Brill's version looks like it's mostly for weight reasons, as the factory geometry looks mostly intact.

[Nissansota240]

Originally Posted by PoorMans180SX

Brill's version looks like it's mostly for weight reasons, as the factory geometry looks mostly intact.

Also probably because it was smarter/more beneficial to remake the whole sub frame instead of only modifying the stock one to mount that dif to.

[PoorMans180SX]

Anyone have input on what spring rates I should run? I'm kind of stuck on deciding.

I'm know with the roll center correction in the front I won't have to run anything too crazy, but I also don't have a swaybar at the moment. I do plan on grabbing a Cor Integration one eventually, as I'd like to use one on a few road course days, and possibly drifting.

The car is 50% drifting, 40% street, and 10% road course use, and is pretty dang low.

I'm thinking something like 9/8? I want the car to be balanced well on the street.

I know it'll change once I get a rear suspension setup that has roll center and camber curve correction, but that'll be a little bit too.

[xoxide]

9k/7k... What motor are you running?

[PoorMans180SX]

Originally Posted by xoxide

9k/7k... What motor are you running?

VQ35DE good sir.

[Guilty1s]

I wanted to move to a 9/7 setup from my 8/6 but When I did my roll center correction, the car was transformed and haven't really put any other thought into it. In all honesty the car performs so nicely I haven't seen any limits I haven't really had any reason to adjust my dampening or anything else. So I'm happy with my 8/6... But I want swift springs now.


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[PoorMans180SX]

Originally Posted by Guilty1s

I wanted to move to a 9/7 setup from my 8/6 but When I did my roll center correction, the car was transformed and haven't really put any other thought into it. In all honesty the car performs so nicely I haven't seen any limits I haven't really had any reason to adjust my dampening or anything else. So I'm happy with my 8/6... But I want swift springs now.


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Do you run a front anti-roll bar? I think that's what I'm most concerned about, the balance of the car without a front bar. I also really don't like body roll.

I've driven several S-chassis with different rates, but I only have a lot of time in my old personal cars with 12/10 and 10/8, neither of which had any roll center correction and had front bars. No body roll was great, but the 12/10 Megan tracks were just far too stiff for the chassis, and the Tein Super Drifts just rode terrible. I had Fortune Auto Version 1's with 9/8 springs but I drove the car once before I sold it .

That's why I ask, I don't have much experience with the new, much better valved coilovers that are available now.

[Guilty1s]

Yeah I do have a factory sways. I also don't have the huge desire to upgrade them anymore since RC correction.

I really love my Fortune Autos.. granted the low speed dampening is ishy, they really shine where they where designed to at high speed dampening. Is that the digressive valving?

I know they aren't high quality coil overs but I think they are the best of its price range. (Anything below 1500 dollars)


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[maverickmotorsports]

start with 8/6. you already have roll center correction up front so it's going to help keep the car from rolling as much. i'd get some swifts and call it a day. if you want anything crazier you could go to like a 5k in the rear for more grip but anything softer than that will suck.

[Black R]

Originally Posted by PoorMans180SX

Do you mean like a road course setup, or just the max I can fit right now? This car is going to need a fender flare for more tire, the control arms are 40mm wider than stock, so it really eats up the "outside" space that you could normally fill with tire. If I had shorter coilovers I could dial in some positive camber at the knuckle and run a higher offset and/or wider wheel for more tire with an additional fender flare. I really want Koguchi Power front fenders!

I mean 65 degrees of lock and 315/30/18's up in those wheelwells!

Originally Posted by PoorMans180SX

I think he means with the rack moved forward, an easy bolt-in solution.

Unfortunately turbular subframes are illegal in basically every racing series besides unlimited time attack and drag racing.

Brill's version looks like it's mostly for weight reasons, as the factory geometry looks mostly intact.

You hit the nail on the head.

I forget sometimes about regulations, etc.


Anybody got any input for me on the gktech knuckles?

They have opened the preorders and I can't decide what options to get: s13 or s14 spindle, which brake caliper mounts, which steering arms, which balljoint inserts etc.

http://www.gktech.com/index.php/s-ch...nuckles-1.html
I have an s13 (5lug) currently, but my coilovers can accommodate s14 mounting holes also.

[PoorMans180SX]

Originally Posted by Black R

I mean 65 degrees of lock and 315/30/18's up in those wheelwells!

I forget sometimes about regulations, etc.


Anybody got any input for me on the gktech knuckles?

.

GKtech knuckles are already on the market and people are raving about them.

You'll just need arches bigger than these: