GP Hyper Knuckle - Roll center adjusters

[mmdb]

To start off I wanted to increase the handling performance of my car. I did everything from adjustable arms, roll center adjusters in the rear (moonface), custom coilover settings, etc. I still was getting a bit of roll in the front accompanied by a feel of uneasy handling near the limit. Speaking with my bro who a mechanical engineer major, suggested I look into roll center adjusters. Doing a bit of reading, roll resistance could be tuned in by: increasing spring rate, increasing sway bar diameter, or heightening roll center. For the s14 chassis, everything but the latter is much more obtainable; but at a cost.

Increasing front spring rate increases road harshness. Also, If the spring rate is TOO high this could lead to loss of road traction during bumpy road encounters. A front sway bar on the other hand only works during lateral load transfer, which is good, but if you excessively lower the car and ultimately lower the roll center a thicker sway bar might not be enough.

So that leaves us with roll center adjusts. Increasing the roll center on the 240sx chassis has a few options. One of the ways is to change the inner height of the pickup point of the front lower control arm. D-Sport magazine (April issue I believe), illustrated an s15 with roll center adjustment, although they defined it as being more of a bump steer concern. The main drawback is that the tension rod now moves in a different arc and will cause binding. The s15 in the D-sport magazine alleviated that problem by mounting the tension rod below the LCA in conjunction with a set of custom FLCA (can't remember the name). I wouldn't recommend this method though as it is very easy to damage the suspension geometry of the car.

The 2nd option is to space the distance from the spindle to the lower control arm pick up points. This is where GP Sports Hyper knuckle comes in. The unit is a fully casted for strength and the dimensions of the unit are a bit bigger than the OEM stock. The GP Sports knuckle allows drivers to increase, or decrease the heights of roll center and bumpsteer respectively. Without spacers (+10mm or +20mm), the Hyper knuckle adds 20mm of height adjustment. The unit also allows for more steering angle which is a plus for drifters (my car is built for grip). Depending on how much you lower the vehicle, having the ability to adjust roll center is a big plus when fine tuning the balance of the car.

As for driving impressions I could not be happier. There is less body roll, more cornering power (seat of the pants feel), and much more stability during low/high speed transitions. I'd rate installing a 4/10 assuming you have the right tools (wrench, mallet... i think that's it). You will also need to realign the car as well.

Now the unit is not cheap. I purchased the unit with spacers which came out to be approx $1400 through JDM Option (Thanks Inada for delivering the unit yourself!!!). But there's an upside. There is an equivalent unit GP Sports provides called the Super Knuckle which adds 20mm of adjustment at the fraction of the price (approx $800ish). Both units are fully cast and VERY strong. There isn't welds to break or snap. The unit not only adjusts roll center and also allows for more steering angle and bump steer correction. These adjustments alone could run over $500 dollars ($200 for roll center adjustment and $300+ for spindle modification.

And for pictures...

Picture of actual unit...





Notice inner pickup point to the center of pillowball are parallel to the ground.



The topic of suspension geometry is very complex, and this thread only scratches the surface. For more reading do a search on "roll center + center of gravity" to get an understanding of it.

[J_Konnexion]

Great info !
Those knuckles are definitely next on my list.


Edit-
Got any pics of the increased angle ?

[mmdb]

Originally Posted by J_Konnexion

Great info !
Those knuckles are definitely next on my list.


Edit-
Got any pics of the increased angle ?

I didn't, but you can find pictures HERE

[undesiredshoe]

Just drill a hole on the crossmember 20mm's up, bolt your control arm onto that hole and you have the same thing for free.

[cdlong]

Originally Posted by undesiredshoe

Just drill a hole on the crossmember 20mm's up, bolt your control arm onto that hole and you have the same thing for free.

you're right. it is the same. i don't know why all those engineers waste their time actually designing stuff.

[S14DB]

Originally Posted by undesiredshoe

Just drill a hole on the crossmember 20mm's up, bolt your control arm onto that hole and you have the same thing for free.

What SilkRoad does on their time attack S15. Slots it vertically so it is adjustable.

[Def]

Originally Posted by undesiredshoe

Just drill a hole on the crossmember 20mm's up, bolt your control arm onto that hole and you have the same thing for free.

Not really, it changes a bunch of other geometry in the suspension in addition to changing the roll center.

[Maximamike]

Originally Posted by mmdb

Now the unit is not cheap. I purchased the unit with spacers which came out to be approx $1400 through JDM Option (Thanks Inada for delivering the unit yourself!!!). But there's an upside. There is an equivalent unit GP Sports provides called the Super Knuckle which adds 20mm of adjustment at the fraction of the price (approx $800ish). Both units are fully cast and VERY strong. There isn't welds to break or snap. The unit not only adjusts roll center and also allows for more steering angle and bump steer correction. These adjustments alone could run over $500 dollars ($200 for roll center adjustment and $300+ for spindle modification.

So there are 2 sets of knuckles available? Is the other just cast with no bolt in spacer?

[UNITEDMASTER]

Originally Posted by Maximamike

So there are 2 sets of knuckles available? Is the other just cast with no bolt in spacer?

That is correct

[UNITEDMASTER]

Hello all, I saw this new peice from GP in the latest edition of Doriten. I was interested to see some close up pics of the peice. This is an awsome product I think,it solves alot of issues in one shot. Question, is the pick up point for the tie rod actually modified VS OEM location.

[mmdb]

Just drill a hole on the crossmember 20mm's up, bolt your control arm onto that hole and you have the same thing for free.

For obvious reasons, I'm going to ignore this comment.

Originally Posted by UNITEDMASTER

Hello all, I saw this new peice from GP in the latest edition of Doriten. I was interested to see some close up pics of the peice. This is an awsome product I think,it solves alot of issues in one shot. Question, is the pick up point for the tie rod actually modified VS OEM location.

I think you can think of the pickup point of the tie rod being static, while the distance of the axle moves up or down according to the spacer used.

[Otto347]

I just cant justify the price on those things. I would much rather ream my stock spindle to accept a GM style lower ball joint and build a set of lowers that us the GM ball joint. (far more options on correcting suspension geometry with the GM pieces)

One good thing about them is the built in drop, that would be nice to have.

[brokeAs240sx]

that's really neat.

From what I gather (and please correct me if I'm wrong), you can achieve the same effect via:

- moonface roll center adjuster ball joints for the flca
- kazama outer tie rod which has spacers so you can stack depending on how low you are.

Seems like a more affordable/readily available solution to me. The advantage of the unit you posted is that you don't need to use spacers on the tie rod ends & you have more customization w/ the spacers for the knuckle vs. the default spacing on the ball joint adjuster.

On a side note: how did you like the rear roll center adjusters? I was contemplating about getting these, but I didn't really see them as help all that much - from what I saw, it will only lower the rear lower control arm & sway bar while all other arms are still angled.

[mmdb]

Originally Posted by brokeAs240sx

that's really neat.

From what I gather (and please correct me if I'm wrong), you can achieve the same effect via:

- moonface roll center adjuster ball joints for the flca
- kazama outer tie rod which has spacers so you can stack depending on how low you are.

Seems like a more affordable/readily available solution to me. The advantage of the unit you posted is that you don't need to use spacers on the tie rod ends & you have more customization w/ the spacers for the knuckle vs. the default spacing on the ball joint adjuster.

On a side note: how did you like the rear roll center adjusters? I was contemplating about getting these, but I didn't really see them as help all that much - from what I saw, it will only lower the rear lower control arm & sway bar while all other arms are still angled.

Your assumptions are correct. The Moonface roll center adjusters add ~15mm of height adjustment and cost ~$300 (a rip i know). The bump steer adjustments from Kazama will do the same. But just to note, I was running bump steer adjusters prior to this mod and ended up snapping the shank while pulling out of a parking lot. Luckily I wasn't on the freeway or street. So the added benefit of running this knuckle is added safety as well.

At first I hesitated purchasing the roll center adjusters as they were VERY expensive for what they were. I took the dive and added them to the rear of my car and I noticed a difference in cornering power. There was noticibly less roll. I can attribute this to the roll center height increase which decreased roll, resisted roll and kept camber settings in a happier place.

You're right about changing the rear LCA in respect to the other arms. There could be possible binding, or unwanted alignment changes during movement. For the most part though I'm happy with it.

[INeedNewTires]

so wouldnt the Battle Version FLCA's (and RLCA's for that matter) achieve the same effect with their adjustable ball joint? and for $450 you get the entire tubular arm, with a heim joint on one of the biggest suspension bushings, adjustable roll center, and adjustable steering stop.

[mmdb]

Both can achieve the same thing. It just depends on how much you lowered the car. You might need more or less adjustment. I'm not sure how much the arms posted above will add, but it should be effective nonetheless.

[xs240]

Very awesome thread and definitely on my to do list

[kognition]

Some great info!

[GSXRJJordan]

MMDB I remember us talking about this via PM a while ago - I didn't know it was a fully cast piece that does extra angle also!! That's awesome! I definitely dig the spacer's adjustability, rather than just replacing the ball joint with a taller ball joint (GM-way, Megan/Moonface/etc way), and of course the extra angle is a plus.

I agree that FLCAs like the Battle Version, Ikeya Formula or Driftwerks ones would also accomplish the same thing, but without the extra angle (so you'd still have to pay for the knuckle mod) - I'm currently designing a set with Luke (Blu808) using my heims and his fab skills, hopefully we'll have a working prototype for us to try out soon - and the target price point is as close to $300 as we can get.

[xs240]

What else does it change? Kingpin angle?

[Propaganda]

I thought about slotting the crossmember, but when I looked under there, doing so makes me think that it would make an even crazier angle for the tension rod

[GSXRJJordan]

Originally Posted by xs240

What else does it change? Kingpin angle?

Originally Posted by Propaganda

I thought about slotting the crossmember, but when I looked under there, doing so makes me think that it would make an even crazier angle for the tension rod

Yes, the kingpin angle changes, but not very much - if you've got a decent ball joint in there, it'll be ok.

The tension rod is the larger problem - even with a good heim in there, it looks like it will bind, and that's not a nice place to have that happen.

[Streeter]

They are really about the extra lock and not so much the Roll centre correction.

very pricey and Ive seen them break, dont think Ill be replacing my cut and shut knuckles any time soon.

[zaquanh]

Originally Posted by Streeter

They are really about the extra lock and not so much the Roll centre correction.

very pricey and Ive seen them break, dont think Ill be replacing my cut and shut knuckles any time soon.

ur saying you have witnessed a full cast iron knuckle break and your cut and welded knuckles are stronger?

[Streeter]

Ive seen a GP sports knuckle break yes. I have given my crappy cut and shuts hell and they are yet to give up. Last crash bent my steering rack as I got side swiped that hard and the kuroi knuckles are still rocking.

I can post pics of busted GP sports knuckles if you want? just looks like a busted piece of cast iron/steel though.

I think casting is only as good as the material and process used and maybe the GP knuckles arent that great?

[mmdb]

Originally Posted by kognition

Some great info!

I like your sig btw

Originally Posted by Streeter

Ive seen a GP sports knuckle break yes. I have given my crappy cut and shuts hell and they are yet to give up. Last crash bent my steering rack as I got side swiped that hard and the kuroi knuckles are still rocking.

I can post pics of busted GP sports knuckles if you want? just looks like a busted piece of cast iron/steel though.

I think casting is only as good as the material and process used and maybe the GP knuckles arent that great?

What sort of conditions did they break? Was it involved in a heavy impact? Please explain.

[GSXRJJordan]

Originally Posted by mmdb

What sort of conditions did they break? Was it involved in a heavy impact? Please explain.

Yeah, definitely sounds suspect - it's not a piece that has much leverage put on it, I can't see something that's cast that thick breaking... just like to know more, as I'm sure you would mmdb.

I mean... uh... damn mmdb, up need to get rid of those 'death trap' knuckles you put on! Let me know when you want to slide up to my house to swap with my safe stock knuckles.

[mmdb]

^

hahaha...

Originally Posted by Streeter

They are really about the extra lock and not so much the Roll centre correction.

very pricey and Ive seen them break, dont think Ill be replacing my cut and shut knuckles any time soon.

Your statement makes no sense. So what's the spacers used for? Added angle adjustment? *scratches head* Take a look at the picture. If you understood what roll center is I doubt you would've made that comment.

[Streeter]

Originally Posted by mmdb

^

hahaha... another comment that bugs me...

It was in a 'light' accident, although I didnt see the crash. I figured any crash you cant expect the parts to hold up in those kind of circumstances so didnt see any problem.

*bit of back ground info*

I supply alot of items from Japan and my customer wanted another lower left side to replace the broken piece. When I first phoned GP sports they werent keen on supplying just one side and said it was from an accident bla bla bla.


I called again about 2 weeks later and explained that it was broken and didnt say it was from a crash (just trying to source a single side as these things are bloody expensive!)

The first question they asked was what lower arms I was using. I said ikeya formula and it was almost as if it was a rehearsed line the way they said "oh, the knuckles arent designed for anything else but stock lower arms" please dont use the knuckles with anything but stock lower arms or you might experience trouble.

***********************

now I havent fit any of these gp sports knuckles to a car before but thought it was pretty odd that by using an aftermarket lower arm it can put so much leverage/force that it will break knuckles with out being involved in an accident.


Im not bagging these things out, Ive sold a fair few sets myself. Just thought I would share the info and mention that assuming these things are super strong (more so than cut and shut knuckles) might be a dangerous assumption.

[Streeter]

Originally Posted by mmdb

^

hahaha...



Your statement makes no sense. So what's the spacers used for? Added angle adjustment? *scratches head* Take a look at the picture. If you understood what roll center is I doubt you would've made that comment.

*sigh* do we need to have an E fight?

what I meant was that there are much cheaper ways of achieving roll center correction. the spacer on the bottom of the knuckle is a neat adjustable way of doing it but that isnt what the knuckles were marketed for. Atleast not here in Japan anyway.