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

[mr.nismo.]

Originally Posted by Sarjh

Anybody ever gotten stock s13 rear knuckles modified? It would seem like a lot of work to do, but I am curious.

You probably could. For the price probably better off going A/M like GK or PBM.

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[tb13]

I installed GKTech's RCC kit on my S13 recently, went with this kit because of its cost and since I am new to drifting I wasn't trying to go crazy. Full front setup consists of S14 knuckle, S14 LCA, GK RCC, GK Outer tie rods, GK tension rods.



I didn't think much of the extra LCA length and +25mm track width added by the kit, I am running a 17x8 +35 wrapped in a 235/45r17. These pictures are with camber plates maxed out. For anyone considering this kit, high offset, narrow wheels and small tires will be the only way you fit under a stock metal fender. If you are running low offset wheels you will need a wider fender.

[tuzzio]

So, my car feels awfully darty sometimes while corning (100% street car) For the first little bit of turning the wheel, it seems to not be very responsive, but when I reach a certain point lets say maybe 25* of the wheel turned (out of 360) then it becomes extremely responsive. It almost seems like slight understeer to a point.

For what its worth: BC coils 8/6K springs, GKtech grip front knuckles (stock rear) Subframe risers, Suspension techniques front sway bar (stock rear) and a kaaz 2 way.

Obviously anyone whos driven a kaaz notices that if you let off throttle in a corner the car responds to it for sure, but even on throttle I notice this. I wasnt sure if its because the diff its basically trying to push the car straight to a certain point, or if the stock rear sway bar is effecting this.

[sr vegas 240]

Originally Posted by tuzzio

So, my car feels awfully darty sometimes while corning (100% street car) For the first little bit of turning the wheel, it seems to not be very responsive, but when I reach a certain point lets say maybe 25* of the wheel turned (out of 360) then it becomes extremely responsive. It almost seems like slight understeer to a point.

For what its worth: BC coils 8/6K springs, GKtech grip front knuckles (stock rear) Subframe risers, Suspension techniques front sway bar (stock rear) and a kaaz 2 way.

Obviously anyone whos driven a kaaz notices that if you let off throttle in a corner the car responds to it for sure, but even on throttle I notice this. I wasnt sure if its because the diff its basically trying to push the car straight to a certain point, or if the stock rear sway bar is effecting this.

Possibly worn/loose rack and pinion bushings. I'd check those first. If not already replaced i'd get some energy suspension polyurethane bushings.

[tuzzio]

Originally Posted by sr vegas 240

Possibly worn/loose rack and pinion bushings.

Replaced with ES bushings less than 2 years ago.

[mr.nismo.]

Originally Posted by tuzzio

Replaced with ES bushings less than 2 years ago.

What are your alignment settings?

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[tuzzio]

Originally Posted by mr.nismo.

What are your alignment settings?

Off memory..

2.5* Front camber
2.0 Rear
8* Caster up front.

[mr.nismo.]

Originally Posted by tuzzio

Off memory..



2.5* Front camber

2.0 Rear

8* Caster up front.

Are you running a staggered setup?

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[tuzzio]

Originally Posted by mr.nismo.

Are you running a staggered setup?

Wheels are 18x9.5 +22 all around,

Front tires are 215/40 and 235/40 rear

[!Zar!]

When was your last alignment?

[tuzzio]

Originally Posted by !Zar!

When was your last alignment?

Last alignment was in the spring. Car has acted like this for a bit. More so wondering if a properly sized rear sway bar would help this issue. or if the 2-way is basically just pushing the car straight

[battery1882]

Originally Posted by tuzzio

Last alignment was in the spring. Car has acted like this for a bit. More so wondering if a properly sized rear sway bar would help this issue. or if the 2-way is basically just pushing the car straight

It could be million things but easiest would be to adjust your rebound on coilover, next is front toe. try slight toe out.

[PoorMans180SX]

Originally Posted by battery1882

It could be million things but easiest would be to adjust your rebound on coilover, next is front toe. try slight toe out.

Yes, what he said ^

[PoorMans180SX]

Originally Posted by Sarjh

Anybody ever gotten stock s13 rear knuckles modified? It would seem like a lot of work to do, but I am curious.

This was done well before anyone had released drop knuckles on the market.

[Speed Junkie]

Originally Posted by tuzzio

Off memory..

2.5* Front camber
2.0 Rear
8* Caster up front.

You left out toe which is the biggest driver of "darty" steering. The front suspension toes out under compression. OEM spec alignment calls out for a bit of toe in for that reason.

I had set my front toe to zero before knowing it and the bump steer was horrible. The car would dart around and yaw into every unevenness in the road. I took it back and set the front toe to factory spec and that drastically reduced the effects of bump steer.

As a side note, the rear also toes out under compression and running 0 toe will result in the rear yawing out under compression. I think factory rear toe setting is slight toe in.

[tuzzio]

Originally Posted by Speed Junkie

You left out toe which is the biggest driver of "darty" steering. The front suspension toes out under compression. OEM spec alignment calls out for a bit of toe in for that reason.

I had set my front toe to zero before knowing it and the bump steer was horrible. The car would dart around and yaw into every unevenness in the road. I took it back and set the front toe to factory spec and that drastically reduced the effects of bump steer.

As a side note, the rear also toes out under compression and running 0 toe will result in the rear yawing out under compression. I think factory rear toe setting is slight toe in.

This is good info. Thanks.

[91stockcoupe]

I recently installed a angle kit in my s13 and I am having a problem with a popping noise that happens at low speeds on dips or bumps with the wheel turned. I have heard it once while spinning out but mostly happens with normal driving, hard to explain but almost feels like something binding and a really really loud pop. I am running b knuckle, gktech +25 stock style lcas, gktech tension rods, gktech inner tie rods, outer misalignment tie rods and offset rack spacers, also have gktech solid steering rack bushings. To install the offset rack spacers I had to notch the rack on the passenger side and it is not 100% even with the drivers side, as the angle is a little bit different on the way the tie rod sits, not by much though. I am leaning towards that being the problem, another thing would be the solid steering rack bushings are supposed to move the rack forward a bit and maybe something there is not sitting right. Alignment isn’t the best as caster is pretty low at 5 degrees but I don’t think that would cause it. Any help and insight is appreciated, thanks.

[TheRealSy90]

Originally Posted by 91stockcoupe

I recently installed a angle kit in my s13 and I am having a problem with a popping noise that happens at low speeds on dips or bumps with the wheel turned. I have heard it once while spinning out but mostly happens with normal driving, hard to explain but almost feels like something binding and a really really loud pop..

Sounds exactly like spring bind on the front coilover when turning. Very common on most coilovers that don't have a radial bearing.

[91stockcoupe]

Originally Posted by TheRealSy90

Sounds exactly like spring bind on the front coilover when turning. Very common on most coilovers that don't have a radial bearing.

Don’t think it’s the coilover because the car drove perfect before putting the angle kit on, sound came only after the kit. But I will check that just to be sure

[Bleakley]

S13 subframe or S14 subframe?
Not sure if I wanted to pull the trigger and devote a LOT of time reading on suspension at this point in time.
Figured I’d try and have my question answered here.

Kinda thinking S14 subframe.
Project vehicle is a mild s13, looking to go wild. Most of its time will be spent on street, with the occasional grip event, and maybe/probably a couple drift events if I can afford it.

[PoorMans180SX]

Originally Posted by Bleakley

S13 subframe or S14 subframe?
Not sure if I wanted to pull the trigger and devote a LOT of time reading on suspension at this point in time.
Figured I’d try and have my question answered here.

Kinda thinking S14 subframe.
Project vehicle is a mild s13, looking to go wild. Most of its time will be spent on street, with the occasional grip event, and maybe/probably a couple drift events if I can afford it.

First, I would tell you to go do the reading.

But basically it comes down to ride height. Is the car going to be low, tucking tire and such? Run an S13 subframe. If you're into a more oem-spec height, S14 subframe.

[Bleakley]

A little lower than OEM. Whatever the PBM/PSM kit(s) drop the car by switching over, that’s probably how it’ll sit.
You’re from Michigan, so your roads might be similar... In PA, there are definitely potholes. Between those and speed bumps, etc. I favor a more practical / functional ride height.

Thanks for the basic answer. I was already leaning towards S14 subframe w/ risers based on GKTech’s article / paper and recommendations.
I’ll probably take the advice and follow it up with some more reading. Thanks again.

[super.trick]

Random thought/question:

The way I see it, a steering rack spacer (between the inner tie rod and rack) is pushing the inner pivot point of a 'suspension arm' (in this case, the tie rod) outwards, which would shorten the arm (assuming you want to maintain toe), as well as change the travel arc.
Is this a correct analysis? Would those a changes make any noticeable difference to the way the car behaves?

The reason I care is because I have HICAS and I don't want to delete it, so that means my toe rods are tie rods. I'm looking at the beefy PBM inner tie rods because the stock HICAS ones are a known weak point. The problem is that PBM decided to add a 'built in' rack spacer on the end.

Any similar options out there instead?

EDIT: Just read the discussion up the page about toe-out under compression stock... wouldn't this effect be multiplied with a shorter tie rod?

[TheRealSy90]

Originally Posted by super.trick

EDIT: Just read the discussion up the page about toe-out under compression stock... wouldn't this effect be multiplied with a shorter tie rod?

When you add a tie rod spacer you have to then adjust the tie rod length via the outer tie rod to compensate the toe change. After that it is the same aside from more rack travel.

[super.trick]

Originally Posted by TheRealSy90

When you add a tie rod spacer you have to then adjust the tie rod length via the outer tie rod to compensate the toe change. After that it is the same aside from more rack travel.

Originally Posted by super.trick

... a steering rack spacer (between the inner tie rod and rack) ... would shorten the arm (assuming you want to maintain toe) ...

A shorter arm means a smaller travel arc. That is what I'm asking about.

EDIT: If that would cause any perceptible change, that is. Obviously it is different.

[ka-titties]

Originally Posted by super.trick

A shorter arm means a smaller travel arc. That is what I'm asking about.

EDIT: If that would cause any perceptible change, that is. Obviously it is different.

Yes.

If you look at the first page in this thread, it has a list of compatible inner tie rods. See which ones are the thickest and go from there.

[mechanicalmoron]

Originally Posted by tuzzio

So, my car feels awfully darty sometimes while corning (100% street car) For the first little bit of turning the wheel, it seems to not be very responsive, but when I reach a certain point lets say maybe 25* of the wheel turned (out of 360) then it becomes extremely responsive. It almost seems like slight understeer to a point.

For what its worth: BC coils 8/6K springs, GKtech grip front knuckles (stock rear) Subframe risers, Suspension techniques front sway bar (stock rear) and a kaaz 2 way.

Obviously anyone whos driven a kaaz notices that if you let off throttle in a corner the car responds to it for sure, but even on throttle I notice this. I wasnt sure if its because the diff its basically trying to push the car straight to a certain point, or if the stock rear sway bar is effecting this.

Depending on your camber, that can be the tire laying meat down, and not riding on it's tippy toes. Especially with McPherson.

[TheRealSy90]

Man this thread used to be thriving with regular content. I wonder what happened. Everyone stopped drifting?

[e30gangsta]

Nah they're still out there. Social media took over and the forums died imo.

[PoorMans180SX]

Originally Posted by TheRealSy90

Man this thread used to be thriving with regular content. I wonder what happened. Everyone stopped drifting?

Everyone started running B knuckle and reverse rake

But in all seriousness youtube and social media have taken over. The information is readily accessible on those platforms by messaging your favorite drift dude and buying what he runs. This thread made it's mark, and I hoped it help customers push companies to make awesome roll center correction parts for the s-chassis.

It's with great fondness that I remember when Dousan imported some cut n' shut knuckles and it sparked my interest in steering and suspension geometry. Those days people were running tie rod spacers and nothing else, and look where we are now! Tons of companies making varying levels of awesome products. We have anything from 25-90mm of roll center correction available.