Rca- Roll Center Adj

[R TUNE]

Does any one know were to RCA's for a 32 gtst?

[djr81]

Moonface Racing do them. Which end do you want them for & how much adjustment are you after?

[Kaido_RR]

ikeya fourmal

http://www.ikeya-f.co.jp/en/index.html

[djr81]

ikeya fourmal

http://www.ikeya-f.co.jp/en/index.html

Please be aware you don't actually need the arms, just the spacers.

[R TUNE]

Seen the moonface racing ones. Would they do the same job as say the ikea formula ones.

my problem is the LCA angle is on a upward slope wona bring it back down.

[djr81]

Seen the moonface racing ones. Would they do the same job as say the ikea formula ones.

my problem is the LCA angle is on a upward slope wona bring it back down.

Yes they do.

All they do is lower the pivot point on the outside of the LCA. There are ones for front & rear.

The rear ones are easy enough to turn up on a lathe if you or someone you know is handy.

[R TUNE]

i take it you mean these from moonface

http://www.rhdjapan.com/moonface-super-lap...m-spacers-60215

http://www.rhdjapan.com/moonface-super-lap...k-spacers-60211

[Duncan]

either fulcrum suspension in sydney who do taller ball joints (very good idea because they are probably shot by now), or UAS who do an alloy ball joint spacer.

but what exactly are you trying to address? it is difficult to do good adjustment to r32/z32 front end because the upper arm can't move far if at all.

[RBceffy25]

either use spacers with longer threads/taller rca's or have your knuckles/spindles modified.

I know this is all doable with the S chassis however i'm not sure how much adjustment you will have because of your upper control arms.

Honestly, considering the age of most of our nissans these days, your better off coughing up for aftermarket, fully adjustable arms. They come with longer threads to correct roll center.

http://www.rhdjapan.com/nissan/r32-skyline...links-rods-arms

[RBceffy25]

AH HA! Found a great link!

Check this out for all your skyline suspension arm requirements!

http://www.driftworks.com/shop/Suspension-...9_41/index.html

[djr81]

either use spacers with longer threads/taller rca's or have your knuckles/spindles modified.

I know this is all doable with the S chassis however i'm not sure how much adjustment you will have because of your upper control arms.

Honestly, considering the age of most of our nissans these days, your better off coughing up for aftermarket, fully adjustable arms. They come with longer threads to correct roll center.

http://www.rhdjapan.com/nissan/r32-skyline...links-rods-arms

Well good luck figuring out how much of a spacer you need.

[RBceffy25]

Well good luck figuring out how much of a spacer you need.

How about you give some advice instead of a personal attack.

Why dont we stay on topic, ok?

[NZM.031]

mate, you wont get much from people on here about RCA...

the ones that know.. keep it very close to them as its alot of gobbly gook and many hours of diagrams and calcuations... and the ones that dont actually know or arent willing to find out and think outside the box, just tell you its a stupid idea to go so low..

the problem is, what you do at the bottom, you have to do at the top, and what you do at the front, you have to do at the back..

try getting a hold of a suspension plotting program or measure and plot the pivot points and draw up a diagram on a big piece of paper, then draw in up and down movement in 1cm increments and find where the lines intersect and what not.. the hardest thing with the r32 is the top arm being on an angle and being shorter than the bottom arm.. so to get in the right spot to pivot without binding and keeping the camber and bumpsteer and eveything spot on throughout the wheel travel..

though in all my readings lately, i cant seem to find where the actual RC should be.. is it under the ground.. or as close to the ground as possible?? or is it meant to be up high??

[RBceffy25]

Go to the driftworks site forum and pick their brains.

The ppl on there have a wealth of knowledge on multi-link geometry

[RBceffy25]

Check out this link!

It is a must read!

All those secrets you refer to should be right here!

http://zilvia.net/f/tech-talk/296725-roll-...ion-thread.html

And regardles of the fact they talk about S chassis the same basic theory still applies

[Risking]

Roll centers are not a black art at all. They are something very commonly talked about by suspension designers and engineers.

RCA adjusters that are available do stuff all. You need to calculate the ACTUAL angle of the arms you require and then work back to the hub from there.

There are some detailed measurements required to work out the current roll center (there is more than one type of roll center but thats far to complex for this)

Basicly you need to know the angles of the lower and upper arm, from pivot point to pivot point NOT the arm itself which may be bent or curved. The distance from road surface to the lower point inner same with the upper inner

Wheel track from center of tire to center.

From there you can model a diagram of the suspension. To work the roll center simply you draw an imaginary line along both control arms till they intersect. From that intersection another line is drawn to meet the ground at the center of the tire on the opposite side of the car. repeat for the other side and the intersection point of the two final lines to the tire centers is the basic roll center.

With the GTR the best place to start is with a 150-160mm front and a 240-250mm rear roll center height.

There is many arguments about the idea roll center height, be it plus or minus road height. Ive never used a minus roll center and never would. Its to complicated to breifly explain but in theory the RC should be a plus.

Ive spent years stuffing around with GTR's are all types of nissan chassis but you will never get anything that is compromisless. Which is why I binned all the factory stuff and engineered my own chassis from scratch which has none of the flaws an OEM chassis has nor the restrictions they impose.

the problem is, what you do at the bottom, you have to do at the top, and what you do at the front, you have to do at the back..

Far far from the truth. You can do one arm at a time and make massive and correct alterations. Same goes for the front to rear. Go and make some mock up drawings and change the angle of the upper arm by 3 degrees up and down then work out the roll center on your theoretical car. You'll find big differences. Do the same for both arms and see what the results are.......

I have never had an issue helping people with geometry changes and advise. Ive desgined and built an entire chassis from scratch with good theoretical results. The input has come from far including overseas. Its all about understanding what the geometry needs to revolve around and how to achieve the results.

If people are interested in a good read and diagrams Im willing to scan and post up alot of the diagrams I have done for the design and development of my chassis.

[NZM.031]

huzzzahhh... a half decent post about roll centre!!! yaaaay... thanks risking..

but what i dont get.. is you say that its not a dark art.. but then you say its far too complicated for here... and there are different roll centres but its far to complex... which is what i meant by what i said about front to back.. if your going to stuff around with one arm... then you will need to change others to keep it in suit..

its also one thing to get it right on paper... but you also need to know centre of gravity, sideways forces, tyre movement, tyre friction, etc.. which are the things that you need a uni degree to understand.. and even then it may not apply in the real world

im drawing mine up and keeping the front LCA as it is.. and will make a new hub and top arm to suit.. which i will then have to work out what to do at the back, to keep it in sync with the front.. and 5cm of suspension travel makes a massive difference to the angle of the arms.. so getting the right length and the inner pivot point in the right spot is going to be a big thing... it will either work well, or go completly pear shaped.

nothing is impossible.. and nothing is unlearnable.. and its only metal... designed and made by men with knowledge and machines.

[djr81]

huzzzahhh... a half decent post about roll centre!!! yaaaay... thanks risking..

but what i dont get.. is you say that its not a dark art.. but then you say its far too complicated for here... and there are different roll centres but its far to complex... which is what i meant by what i said about front to back.. if your going to stuff around with one arm... then you will need to change others to keep it in suit..

its also one thing to get it right on paper... but you also need to know centre of gravity, sideways forces, tyre movement, tyre friction, etc.. which are the things that you need a uni degree to understand.. and even then it may not apply in the real world

im drawing mine up and keeping the front LCA as it is.. and will make a new hub and top arm to suit.. which i will then have to work out what to do at the back, to keep it in sync with the front.. and 5cm of suspension travel makes a massive difference to the angle of the arms.. so getting the right length and the inner pivot point in the right spot is going to be a big thing... it will either work well, or go completly pear shaped.

nothing is impossible.. and nothing is unlearnable.. and its only metal... designed and made by men with knowledge and machines.

There are many issues when you start playing about with this stuff. For example:

Roll centres move (migrate) when the car rolls. This is one of the reasons you need to draw the suspension up.

You may well want to move the front and rear roll centres by differing amounts.

The centre of gravity (which with the roll centre is what defines the roll couple) is next to impossible to work out. What this means that even with a plotted roll centre you are going to struggle to determine the couple - which is what you actually want to know.

Roll couples & suspension roll resitance are different front & rear. But for the purpose of the exercise the chassis is stiff. You need to understand and reconcile these two concepts ie car is wanting to roll different amounts front & rear but cannot. This is very important as it is a powerful tuning tool.

There is no point getting the roll centre spot on at the price of making a nonsense of the suspension geometry.

Moving the pivot point on the LCA is the easiest way of moving the roll centre - both front and rear.

Having tried this (& failed to get a result) I would suggest the best way forward is to get yourself a set of spacers (Front & rear) and then do a bit of testing. The downside of this is it takes alot of time & effort. From which you may not get a result. This is why most people recommend a sensible ride height that stops too much roll centre movement relative to the cog.

Theory always matches reality - except when it doesn't. In which case it usually works in the opposite way to what you think.

Hell I would be happy if someone could acccurately measure the pickup points for the suspension arms front and rear....sounds easy. Isn't.

[Risking]

Pretty much every reason for me saying its to complex to go into detail is outlined in the above post, and then some.

If you want to learn how its done im more than happy to show you around a purpose built chassis and explain how we come to the decissions we come to regarding geometry.