Sung@MM

HA, didn't bother reading the Ek9 thread. theres good info there!
Roll Center will change the weight being transfered during cornering and has huge effects on load transfer b/t them. you can change your vehicles YAW rate when playing with roll centers.

94eg!

iTrader: (2)

That's all well and good, but what does it mean? Numbers are just numbers. What matters is how it translates into the behavior of the car. Does it mean more grip or less grip at the front end? Does it effect corner-entry, mid-corner or corner-exit steering either on or off throttle?

Here are the answers to my own questions. If you want to reduce oversteer AND/OR increase understeer, you raise the roll center....and that effects EVERY aspect of the turn, on or off throttle:



Most people aren't trying to add understeer to their FWD's.

ra21benj

Spent some time driving my ED9 CRX with the roll center adjusters. While I installed the RCA’s, I also softened my spring rates, changed to Koni Yellow SP3, and installed front and rear ground control top hats to try and improve the ride on the street. Front spring rates went from 450 lb/in to 400 lb/in and rear spring rates went from 400 lb/in to 325 lb/in. Car height is low with the top of the tire just below the fender.

With the softer spring rates I’m now able to shift weight forward on corner-entry with the brakes. Mid-corner, the CRX corners with the same amount of lateral roll as when I had the stiffer springs. Corner exit on-throttle, the weight shifts to the back which lessens front end grip. Koni dampers set on the softest settings.

I thought the car would roll more because of the softer springs, but I was surprised it didn’t. So for my set-up, it’s great to have the improved steering and same amount of lateral roll (with softer springs). Also like how I can shift the weight around due to the softer springs. I’m fine with understeer on the street in a short wheelbase CRX because it feels safer.

94eg!

iTrader: (2)

Very interesting. I had a feeling they would need to be coupled with a softer front spring to get the most out of the setup. Thanks for the review.

Coupe-R

I'm not buying that one size fits all table posted....

How do you know how far the roll centre already is from the Centre of gravity? You can't just use the table and say, "oh yes raise the roll centre will increase understeer". Maybe put it too close to the Cog and it may

Also how do you know that they have't got "raise and lower" for the roll centre around the wrong way on that table? As many people confuse these terms.

A higher rear roll centre than front INCREASES UNDERSTEER! Raise the front further up and you will DECREASE UNDERSTEER. Generally speaking
(rear roll centre doesn't change when modding the front roll centre)

On a lowered honda with double unequal length arms the Cog moves down a little but the roll centre moves MASSIVELY down as a result of the ratio of swing angle on the LCA.

The car is now lower with lower Cog, but the roll is increased, people fit large spring rates to compensate, but also the angle the LCA goes through isn't great either!
On my track car I am getting understeer mid corner and corner exit. I have soft springs.
I want LESS roll as the tyres are wearing on the outside edge of the outer wheel, and the inside wheel is loosing grip due to outside loading from roll. I already have a BIG rear bar, and get some oversteer on corner entry.

Therefore I'm fitting some RCA's to straighten out the LCA, raising the roll centre.

The front tyres now have more grip from less roll, and the effect of stiffer springs. More tyre patch on the road.

Without measuring the tie rod angle effect I couldn't comment if it makes bump steer worse, however on the track this usually isn't a HUGE concern vs adding the RCA postive effects.

It depends on CURRENT car setup and for most of us track racers we all generally lower by a similar amount, hence the standard size RCA.
Your thoughts

P.S laptimes don't lie

Kozy.

To raise the RC increases the load transfer at that end. More load transfer means less grip. Thus raised front RC = more understeer. Care to justify your thinking on it being backwards?

My 3D model says otherwise. Yes, RC moves more than CG, but not by a massive amount.

If your tyre wear is an issue it sounds like you need more camber.

They have more grip from a more favourable camber angle at full roll, but stiffer springs generally reduce mechanical grip.

It will make bumpsteer worse, however the magnitude of the effects are directly related to the stiffness of the suspension. Soft street suspension with lots of travel will be a bit of a pig with an aggressive toe curve, however in a track car with relatively little travel it will obviously be less of an issue.

Coupe-R

Lower Roll Centre, means LARGER roll couple= bigger leaver force acting on the car= more roll. (bigger distance between Centre of Gravity and Roll Centre)

More roll means more dynamic changes to geometry of suspension, thus tyre patch.

RAISING the roll centre reduces this distance between CoG and RC, less roll couple, less roll force acting on the front.

I already have -2.4 degrees camber on the front, I need closer to -3, however even then with my current roll it’s not ideal due to less than ideal spring rates 500lb front 225lb rear. (weekend club car)

"but stiffer springs generally reduce mechanical grip" If this were true then we would all be running soft spring rates on dedicated circuit cars. However they run in the area of 1000lb front and 550-600lb rear (18kgf/mm 10 kgf/mm) in Asia Pacific (I know USA prefers it rear biased) But we don't due to the amount of dynamic suspension change soft springs cause.

By fitting these RCAs I am actually also producing the effect of stiffer springs DURING A CORNER (not in a straight line) as less roll in the front as well as overall geometry changes.

While I agree with what you are saying, too stiff in the front can cause understeer or potentially lost mechanical front grip from stupid high spring rates over bumps. So raising the RC must cause more understeer right.??....

Well you are looking at the extreme ends of these scales with your theory.
I'm not running 1500lb spring rates! Nor am I moving the RC ontop of the Cog or higher than the rear roll centre. All of these things could indeed loose front grip and cause MORE understeer.
Its about balance front to rear, RCAs will in my case NOT cause more understeer.

Currently my situation is TOO much front roll for my given spring rates. I am going to reduce this by not going overkill on my spring rates and fitting RCAs

P.S Regarding bump steer, have you seen what the length of the LCA does when its pointing upwards at a really low track race height......

Have you tested your theories at the track of NOT fitting RCA's vs fitting them to the same car?
Have you tested back to back laptimes? Have you tested how the car rides over surface changes?

Can you prove more understeer, slower laptimes, more bumpsteer from fitting RCA to a lowered weekend track car/circuit car.

Until then, this is all theory

Kozy.

Well I guess we are arguing the virtues of improved contact patch vs increased contact patch load variations.

The virtues of improved contact patch from optimum camber angles is proven. Flat contact patch will give more grip than a non flat one.

The effects of increased contact patch load variation from stiffer springs on mechanical grip are also proven. Stiffer means less more CPLV which results in reduced grip.

Finding the optimum balance between the two is black art. You'd need theory and testing to nail it perfectly. This means tyre models, hideous amounts of math and iterative simulations. You won't find anyone racing an old Honda doing that!

Another argument for 'more understeer' is that of load transfer distribution. Raised roll center = Less roll = More load transfer across that axle. Thus raising the front roll center nearly always increases understeer unless it improves the contact patch enough to overcome the forwards shift in load transfer distribution.

SHG_EasyE

As Komodo said raising a roll center closer to COG will increase load transfer, and also rate of load transfer. It is general knowledge that the end of the car with higher roll center will lose traction first, as the weight is transferred to the outside corner more abruptly than it's counterpart. It is common place in the setup of open wheel cars where all these aspects are fairly tune able.

As far as correcting the lower control arm angle, that is not affecting the roll center. Although, lower arm angle is significant in that once past horizontal, the majority of lateral load is no longer being transferred through the arm into the subframe, but depending on past-horizontal angle will be transmitted through the suspension stroke into the spring causing excess loading and roll. Preventing past horizontal travel of the arm under cornering load is how you prevent the need of overly stiff spring rates to compensate for those negative effects. That is the first point to address in your cars setup when deciding what ride height you will be running.

If you're getting uneven tire wear or temps, camber, or dynamic camber loss is a direct result. This can be fixed with either increased static camber, or increased dynamic camber by adding caster. If your static camber is reducing braking or accelerating traction then dynamic camber has to be addressed. If caster is not adjustable, or the range is too small due to class limitations, than a stiffer spring is in order. Simple as that. You're spring rate "range" is decided by the type and size of tires being used ie. available mechanical grip.

I feel that way too much emphasis is put on fine tuning roll centers when there are many other aspects of a car's setup to be focused on that will greatly affect performance before touching on those points.

There is one point of a cars behavior most affected by roll center and that is turn in and corner entry. I feel that roll center should be addressed if... You have an unexplainable snap understeer on turn in that cannot be tuned out with toe or damper settings, the front roll center may be too high causing too abrupt of a weight transfer instantly overloading the outside front wheel. OR if you're looking to loosen the rear of the car up on corner entry, but don't want to affect steady state or corner exit behavior, raising the rear roll center can let the rear of the car break away sooner under turn in but have no ill affect on rear traction through the rest of the turn as you would with a toe change or damper change.

Coupe-R

The lower arm angle is DIRECTLY related to roll centre in a unequal length double Arm honda setup.



My LCA IS going past horizontal under cornering, thats why I am wanting to fit RCA's. If I wanted to stop this through ride height, the car would be stock height....
The car drives to the track, hence me wanting to fit RCA's as opposed to overly stiff spring rates.

Agreed, the plan is to add as much dynamic camber as I can (it won't be much 3-4 degrees max I'd say) and add up to -2.8-3.0 degree negative camber.



What is the LCA is doing to the suspension geometry when its past horizontal also, what is the length of the arm doing to camber.... Any thoughts?

Ok but what about the relation to rear roll center vs front? Higher rear than front maybe? or bringing the front roll center closer to the rear.Currently I can get snap oversteer on corner entry.

Since I have already purchased these I am keen to try them out. Believe me, I will remove them up the laptimes don't drop.
However much of this thread says "Don't fit these, they will increase understeer and increase bump steer on your lowered honda"

So to those claiming this, can they prove it through real world back to back testing?

Agreed, but for the price of these and the aspects you can change of the car for a small price, they are worth testing IMO.

SHG_EasyE

Its not the angle of the arm, its the relationship between inner and outer pivots, which would be the inner control arm bolt, and the center of the lower ball joint. Lower arm angle can be corrected without correcting roll center.

This is an example of how different ball joints can have different effects on roll center and arm angle. This is a Hardrace RCA on the left vs a Buddy Club RCA on the right (Hardrace was replaced by the BC part on my EP3 after 2 years of use since one developed some play)

Buddy Club's unit moves the joint 10mm down (roll center) vs the Hardrace's 15mm. Overall length of the P1 is 7mm longer giving more LCA correction. So the Buddy Club provides more arm correction while giving less roll center correction than the Hardrace.






As the arm travels up past horizontal, its tucking in the lower pivot, but the same this is happening with the upper. Due to the shorter length of the upper arm it has a more aggressive arc hence the reason the Honda double wishbone gains camber under compression all they way until the upper arm hits the chassis.


On FWD you usually want the rear to be higher, but it really all depends on your setup and driving style. Someone that does alot of trail braking may not need the effects of a higher rear RC.

I think it's a good investment in any car that's significantly lowered. RC aside, the control arm angle needs to be corrected. Then the rear roll center adjusted accordingly if need be. To negate bump steer effects (although minimal on the double wishbone cars) the outer tie rod pickup would need to be dropped the same amount as the LCA.

bks84

iTrader: (9)

I wish I understood all this technical talk going on in here, I'm just not sure if having both the hard race super TRE's and buddy club RCA's is good or bad.

I hate being stupid.

Coupe-R

Thanks for the pictures and informative reply EasyE

I was going to go with Buddy Club RCA my self but ended up getting sent a set of hardrace units with a few other arms I purchased at the time, mine actually look like a different batch (mine are silver yours are black)

Yes but with the corrected LCA angle would the camber curve be MORE agressive, or the same...

Ahh indeed you are correct, however for a basic comparison with stock honda suspension you can generally say the LCA angle relates to roll centre.

UNLESS this is modified from factory.
I have never seen a honda with extended joints to change LCA angle but leave the pivot in the same place. Hence leaving roll centre but only changing Angle.??

Therefore all these RCA kits are indeed changing the RCA AND the LCA angle. However as you have pointed out, the different brand kits are ever so slightly different.

When you are talking 5mm in length over an angle of pivot I wonder what the real Roll centre change between the two are. I'm guessing you probably wouldn't notice the difference between these two? Correct?

I noticed earlier in this thread the feeling was not to fit RCA's due to increased understeer, increased bumpsteer.

Now is the feeling different?

I feel that on dropped race car, the RCA ARE beneficial for the end user. IF we didn't want to change RCA we would have to fabricate our own items that shifted the LCA without changing the pivot point.

I really don't feel the change in pivot point (Roll center) is going to negatively affect my car,

But do you both feel I would have been better off changing the LCA angle and leaving the roll center well alone?

Wouldn't the effect of bringing the front RC closer to the rear actually DECREASE understeer. Yes the front is stiffer now but I have soft front springs anyway, higher rear than front tends to promote more understeer right.

I bet when lowering a honda the rear RC doesn't move down as much as the front. Im sure you could calculate this

Runnerdown

I have had the spoon RCA on my dc2 for quite some time now. I noticed upon installing them that it felt like my front sway bar had increased in size a touch. A little more steering response, and no more push at the limit than previously. Set to the same ride height and corner balance

Coupe-R

So were they worth it? Or no measurable gains?

I talked to a shop yesterday and they felt that you wouldn't notice the difference if you set the car up with the correct sway bars and shock/spring combo.

However I have paid for these so they just just put them in and try. I have a 21mm front bar and a 22mm rear bar so could probably do with some front end roll stiffness (spring stiffness) to be honest

However for an all out race car, are these really worth it? Measureable gains at all?
hmmmm maybe not

Runnerdown

I feel like they were worth it for my use which is 95% street. On a properly setup race car I'm not sure about these making a worthy difference, but I would try for the sake of knowing.

Coupe-R

I'm feeling that too, my car is 50% street %50 track.

Also what about hillclimb hondas, targa cars. You may not want the stiffest spring setups, its funny that when people have worked out the geometry they say you MUST change the toe arm angle to reduce bump steer. Except others claim they have LESS bump steer when fitting RCA's.

Maybe thats on Mcferson, not double wishbone?

94eg!

iTrader: (2)

With un-equal length double wish-bone suspension, there is no such thing as perfect bump-steer. The real question is, is it that important?

BTW: The length of the stud on the RCA as well as the angle of the metal within the LCA isn't that important. What is important is the angle between the inner LCA bushing and the pivot point of the lower ball joint. The arm itself could be any shape or angle and still not effect camber curve whatsoever. That is as long as the distance between those two pivots, as well as the angle between those two pivots remain the same. The arm itself is inconsequential as well as misleading. The truth is, a few millimeters of extra length on the ball-joint stud is not going to effect either of those variables in any measurable way (IMO).

Kozy.

I personally believe that these were developed primarily for MacPhearson strut setups, and that someone then thought, "Hey, I could flog that to those kids in old Honda's that have no clue how well set up their cars are from the factory!"

Also, you cannot compare bumpsteer between different cars. One might be at the right ride height that it makes a difference, one might have different static toe settings that negate the dynamic changes, another might have no clue what he's talking about.

If you fitted them, and you liked them, then that's great. The theory says they're still pointless, and since I have no idea who you are, how much experience you have or how much you really know, I'm going to believe my research over your opinion. For all I know, you could be posting somewhere else on the net that you're really impressed with the ride and handling of your Raceland coilovers! No offence or anything.

Coupe-R

Agreed,

However it was discussed that shifting the LCA without changing roll centre

Totally agree

Likewise, I don't know if you have applied your research or you are an e-racer. However I value your comments. I have not fitted the kit yet. I am beginning to think that they are pointless IF you set the car up for track racing via sway bars and springs/ vehicle height, camber/caster etc.

I wonder if they are beneficial to a street/track car that doesn't want agressive spring rates. It's all a balance. Now that I have these I may fit them and try them out.

I live and race in New Zealand. Many have fitted them and said "oh bump steer is less, turn in is better" However this all maybe a placebo....

I don't know what Raceland coilovers are, I don't really keep in touch with honda-tech.com. My area is EFI tuning, electronics etc.

Nice to get some opinions from you all, and would be nice to see some REAL world testing also

Somalie187

iTrader: (1)

Thx everyone for your great contributions to this thread. I hope to see a lot more in regards to practical applications and theory.

JDMCRX

iTrader: (2)

Would love to see more on this subject

itr1244

so .. i have a roll center adjuster ball joint thingy..
rubber boot is ripped.. i was thinking of getting another but i have heard its not good..
so long story short.. should i get oem?

00IntegrAllmotoR

iTrader: (1)

Short answer: YES

Long answer: YEEESSSS

JamesSmith

Just a quick Thanks. I like the drawing. I have a frame I am building and am looking for the solution. An active pivot point and the steering rod is the solution. See how easy it is to say it lol. I'm dreaming but that's where solutions come from.