Riviera

I have a question, when you're lowering the car by a set of coilovers, is it necessary for roll centre to be adjusted as well?

I will install Bilstein PSS9 soon paired up with a set of 17inch wheels. I will get my S re-aligned afterward, but I stumbled across this roll centre adjuster and can't help but wonder if this is necessary. The last thing I would want is upsetting the balance and subsequently the handling making it worse.

I don't understand Japanese so maybe someone can summarise below page?
http://www.jsracing.co.jp/js3/index.asp?xM...TENT=ROLLCENTER

Or perhaps it's just as easy as install coilovers, adjust, re-align, and off you go??

Cheers!

User 121020

Bingo. You'll be fine without them. The change in roll center height won't cause a very noticeable change.

s2kslav

^Is that necessarily true? I know that many other cars like evos once lowered almost require an RCA kit. I've heard and read so many different arguments for and against this. At this point the only thing I know is that I did lower my car with in factory lowest settings, however my car is lower than most(no gap between tire and fender) I know that I certainly feel a good amount of unwanted body roll despite a stiff setting on my KW V3s and a CR sway I have on my MY05. This is clearly cause due to the suspension geometry being quite different from what it is meant to be stock. From what Ive learnedthe RCA kit allows you to basically lower the car but keep your suspension travel optimized and bring the suspension arms backto close to stock angles and specs. I'm in no way an expert just reiterating what little info I could gather on this.

Since I've never found any solid info, I've been meaning to try the Js RCA but unfortunately between the cost of the kit, approx 1k, and installation and alignment costs it makes it financially hard to experiment with. Recently someone on this board has brought a Megan racing RCA kit for half the price ofthe Js. Hopefully I'll be able to purchase and try it out despite the fact that Megan racing hasn't exactly been known for the best quality. Anyone who can shed light on the Megan kit or RCAs in general please chime in.

robinson

The only way you will know if you need a RCA kit is to measure your suspension and model it in a kinematic software package like WinGeo.

This is the only definitive answer, anyone else who says otherwise is guessing.

spook

This.

User 121020

I think we can do a bit better than guess...how about an educated guess, based on experience? Robinson, you lowered your car. Were RCAs necessary? It's all in how you define "necessary".

The real question should be, "At what point does an RCA become necessary?"

Let's think about how the J's Racing RCAs work, for a minute. They do increase the height of the roll center but they do so by increasing the distance between the outer ends of the upper and lower control arms. This brings the intersection point of the upper and lower control arms closer to the center line of the chassis (laterally) and causes roll center height to change more for a given suspension travel, which could be disadvantageous. In turn, the roll lever length would vary more through a given suspension travel then it would with the stock setup. This will cause the roll stiffness to vary more.

SvkBBS2k, you mention RCA with respect to EVOs. McPherson suspension is more sensitive to lowering the chassis to the point where the inner ends of the LCA are lower than the outer ends. As you lower them, their camber curve deteriorates quickly and they will actually lose negative camber (gain positive camber, if you want to look at it that way) as the suspension compresses. So, RCAs help avoid the camber loss associated with lowering a McPherson chassis.

s2kslav

Hmmm, I'm still unclear as to wether purchasing the RCA kit for MY car will help, I think there really is only one way to find out.

R00567

if you dont know why you need them or cannot find justification for getting them, dont get them?

EternalLx

Most of the faster S2000s dont run RCAs.. why should you?