rallyeman

Anyone using J'S roll center adjusters on their autocross EG?
Is it worth it anyway?
Thanks.

luckymachine7

can anyone else comfirm that this work? I might pick up a set if it people give it good feedback on street and track.

TunerN00b

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rallyeman &raquo;</TD></TR><TR><TD CLASS="quote">Anyone using J'S roll center adjusters on their autocross EG?
Is it worth it anyway?
Thanks.</TD></TR></TABLE>

Aren't these only legal in SM and mod classes?

Higher roll center and increased camber curve, sounds like a win win situation if your current roll center is below the pavement (and you don't want it that low).

rallyeman

Exactly. Changing the arm angle, it supposes to bring the RC where it should be.
I ordered it from my EG!





(http://www.jsracing.co.jp/)

ra21benj

I have a set for my EF CRX, but I've not yet installed them. I'm still waiting to get the rest of my suspension.

I have roll center adjusters on my '87 Corolla GTS (AE86) that's for street use and I notice an improvment in the handling (when used with the proper suspension).
There was less bumpsteer with my lowered suspension. I guess this is why the Datsun 510 guys call RCA's "bumpsteer spacers".

vincent001

can some one explain the diagram please =/ haha

Wai

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vincent001 &raquo;</TD></TR><TR><TD CLASS="quote">can some one explain the diagram please =/ haha</TD></TR></TABLE>

Amount of body roll is proportional to the distance between the CG and the RC. The larger the distance, the more body roll you have. Lowering the car would not change that distance much because the CG and RC both move at approximately the same rate.

But by installing this kit, you are raising the RC and make it closer to the CG, hence less body roll.

It's a very smart piece, I would say it works from the engineering point of view. Unfortunately, for most sanctioned club racing, it would be illegal because it is changing the geometry of the suspension.

For J's stuff, check out GT Motoring as they are the main USA distributor.

ra21benj

R you serious:

I agree with you about turn in being very smooth.
With less bumpsteer, you can just concentrate steering the car to hit the apex of the turn. Without the RCA's I would have to steer the car to hit the apex and also correct everytime the car darted after going over road imperfections.




Modified by ra21benj at 4:09 PM 5/24/2007

MAFDARK

Whats the price on these? The Gt site isnt working.

luckymachine7

do they still sell it overhere?

Edit: nevermind I found it at http://www.aj-racing.com/catal...age=1

vincent001

thought someone posted diagrams... i just left for work and i think someone edited their post or something, anyways are the EF and DA center adjusters interchangeable? i have a DA and might want to get these.

ED9man

who sells an EF set?

pos_cd5

so do the J's RCA come pre-adjusted or do you have to adjust and tune yourself. whats the process in tuning your RC?

Wai

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MAFDARK &raquo;</TD></TR><TR><TD CLASS="quote">Whats the price on these? The Gt site isnt working.</TD></TR></TABLE>

Looks like it's working now:
http://www.gtmotoring.com/js-racing-suspension.htm

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vincent001 &raquo;</TD></TR><TR><TD CLASS="quote">anyways are the EF and DA center adjusters interchangeable? i have a DA and might want to get these. </TD></TR></TABLE>
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ED9man &raquo;</TD></TR><TR><TD CLASS="quote">who sells an EF set?</TD></TR></TABLE>

From the GT Motoring link above, towards the bottom:

FCJ-T1 INTEGRA DA6 FF role center adjuster
FCJ-T2 INTEGRA DC2 FF role center adjuster
FCJ-H2 CIVIC EF9 FF role center adjuster
FCJ-H3 CIVIC EG6 FF role center adjuster
FCJ-H3F CVIC EG9 FF role center adjuster
FCJ-H4 CIVIC EK4 FF role center adjuster
FCJ-H5 CIVIC EK9 FF role center adjuster
FCJ-T5 INTEGRA DC5 FF role center adjuster
FCJ-P3 CIVIC EK9 FF role center adjuster

ra21benj

vincent001:

I posted an english explanation and pictures on how the J's Racing Roll Center Adjusters work, but the Mods removed it (I'm guessing) because it came from an JDM Option 2 magazine.

It's a really good explanation as to why Roll Center Adjusters improve the handling of a lowered vehicle.

Who ever wants to read it, I can email it to you. Just send me an email at ra21benj@yahoo.com


Modified by ra21benj at 8:02 AM 5/25/2007

TunerN00b

Earlier I posted:
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TunerN00b &raquo;</TD></TR><TR><TD CLASS="quote">Higher roll center and increased camber curve, sounds like a win win situation if your current roll center is below the pavement (and you don't want it that low).</TD></TR></TABLE>

However, is your roll center too low now? What makes its current location "too low"?

Personally, I wish I could run my chassis low enough to get the front roll center below the ground. You guys are trying to bring it back up. Something doesn't add up...

rallyeman

Firstly thanks for replying my email!
Here you go in English...

Wai

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TunerN00b &raquo;</TD></TR><TR><TD CLASS="quote">However, is your roll center too low now? What makes its current location "too low"?

Personally, I wish I could run my chassis low enough to get the front roll center below the ground. You guys are trying to bring it back up. Something doesn't add up...</TD></TR></TABLE>

The location of the RC relative to the ground is irrelevant.
Again, it's the distance between the RC and CG that this part is trying to change/shorten.

At cornering, lateral force at CG creates a moment about the RC, causing the chassis to roll. The longer the distance between the RC and CG means a longer moment arm, thus larger moment about the longitudinal axis and more body roll.

This piece raises the RC while keeping the CG at the original location, so the moment arm is shortened.

kb58

What's not explained is why you need these. You need them only if you've lowered your car. By lowering the car in the first place, it puts the RC much lower than it was originally designed for. This product simply "repoints" the lower arms, raising the RC back up to near where it was orginally. You would NOT want to add these to a stock ride-height car.

About why raising the RC is good, it's a relative thing. You aren't raising the RC per se, you just putting it back where it belongs. If you raise you RC above the stock value thinking it'll automatically make the car handle better, that's wrong. If you raise the RC high up, around the CG, say, then the car won't roll at all. Seems like a good thing, right? The trouble is, since the car doesn't roll, how can shocks, springs, and anti-roll bars tune the handling? They can't. Plus, it's going to cause a lot of scrub.

All this spew aside, add them only if you've lowered your car. And BTW, I hope those things are mega strong, because there's literally a ton of force trying to push those lower mounts sideways.

rallyeman

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kb58 &raquo;</TD></TR><TR><TD CLASS="quote">What's not explained is why you need these. You need them only if you've lowered your car. By lowering the car in the first place, it puts the RC much lower than it was originally designed for. This product simply "repoints" the lower arms, raising the RC back up to near where it was orginally. You would NOT want to add these to a stock ride-height car.

About why raising the RC is good, it's a relative thing. You aren't raising the RC per se, you just putting it back where it belongs. If you raise you RC above the stock value thinking it'll automatically make the car handle better, that's wrong. If you raise the RC high up, around the CG, say, then the car won't roll at all. Seems like a good thing, right? The trouble is, since the car doesn't roll, how can shocks, springs, and anti-roll bars tune the handling? They can't. Plus, it's going to cause a lot of scrub.

All this spew aside, add them only if you've lowered your car. And BTW, I hope those things are mega strong, because there's literally a ton of force trying to push those lower mounts sideways.</TD></TR></TABLE>

Well, we are talking about autocross and track use here, so we are talking about a lowered car anyway! Right?
Like you said, we want the Roll Center where it was in the first place (before lowering) or ever closer to the CG!

And something that i read in that option magazine our friend mailed me:
"In the aftermarket parts industry today, a plethora os suspension components are out there, but the element that we still lack today is the roll center adjuster.The primary area that is affected when a vehicle is lowered, is the roll center. The roll center is typically placed closest to the center mass of the car, and is set by the factory to the appropriate specs. A true race car for exemple, an F1 car, has their two key points: Roll center and vehicle center of mass (CG) dead on one another. But if the street cars were to have these two key points atop one another, they will end up taking shape of a F1 car.The only thing the vehicle manufacturer can do is to get these key points as close to each other as possible for the best handling characteristics. When a car is simply lowered, the distance between the center of mass of the vehicle (CG) and the roll center is increased. Thus, the increased distance between those key points results in heavy body roll. The amount of roll can be counter attacked with a stiffer spring and shock combination, but ride quality and handling suffers as an outcome."

rice r0cket

It reduces bumpsteer, yes, but by raising your roll centers, you experience increased jacking effects, and reduce your camber gain on compression.

pos_cd5

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rice r0cket &raquo;</TD></TR><TR><TD CLASS="quote">It reduces bumpsteer, yes, but by raising your roll centers, you experience increased jacking effects, and reduce your camber gain on compression.</TD></TR></TABLE>

with less body roll you dont need as much camber, which will benefit straightline aceleration and braking.

kb58

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rallyeman &raquo;</TD></TR><TR><TD CLASS="quote">
And something that i read in that option magazine our friend mailed me:
"...But if the street cars were to have these two key points atop one another, they will end up taking shape of a F1 car.The only thing the vehicle manufacturer can do is to get these key points as close to each other as possible for the best handling characteristics. "</TD></TR></TABLE>

Ugh! No, no, no. It's stuff like this sentence in magazines that messes with people's heads, leading them off on the wrong path. You do NOT want your RC and CG "as close as possible". The way it's worded, they're implying that it's really hard to do, which it isn't. However, if you do make them really close to each other, the car will handle like crap and you won't be able to tune it with the shocks, springs, or bars. Bonehead writers.

ra21benj

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rice r0cket &raquo;</TD></TR><TR><TD CLASS="quote">It reduces bumpsteer, yes, but by raising your roll centers, you experience increased jacking effects, and reduce your camber gain on compression.</TD></TR></TABLE>

When you use roll center adjusters on an AE86, you use it with the correct suspension modifications which include short stroke dampers, shortened front structs with ride height adjustable spring perches, adjustable camber plates, and a balanced set for front and rear lowering springs.

Adding RCA does raise your front ride height a little because they are spacers, but you just lower your front ride height. To adjust camber you would use the camber plates(usually around neg. 3 degrees). You do have to have your car realigned to your prefered set-up because of the geometry change.

For my EF CRX I do plan on adding RCA's with grond controls, koni dampers and adjustable camber upper arms from cusco so I can realign the suspension.

When you say "increased jacking effects" do you mean the RCA' caused increased pitching of the front, because I haven't experienced this?


Modified by ra21benj at 12:35 PM 5/29/2007

rallyeman

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kb58 &raquo;</TD></TR><TR><TD CLASS="quote">
Ugh! No, no, no. It's stuff like this sentence in magazines that messes with people's heads, leading them off on the wrong path. You do NOT want your RC and CG "as close as possible". The way it's worded, they're implying that it's really hard to do, which it isn't. However, if you do make them really close to each other, the car will handle like crap and you won't be able to tune it with the shocks, springs, or bars. Bonehead writers.</TD></TR></TABLE>

I very happy you are posting here ,
i've seen your "work" and i really admire what you do..!

Anyway,
what you say in other words is that we need some body roll, and that sounds right to me too.