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I figured this is the best place to put this, since the 6th genners are fortunate enough to have double wishbone.

Anywho, been doing a lot of research on whether these are worth it or not. They're expensive, no doubt. My initial suspicion of the good reviews that they've been getting are probably from people who had shoddy ball joints to begin with. The purpose of this thread is to bring forth the research and data I have done to better educate.

Do not take this information as gospel. Feel free to critique, as I am not an engineering major. I just scored really high on my SAT's

I would like to thank Malhoun from team-integra, as I used one of his diagrams (which I fiddled with a bit) for the basis of my research.



Here is the suspension geometry of a double wishbone suspension setup, at rest, on entirely stock settings. We cool? Cool.



Here is the suspension geometry of a double wishbone suspension setup, at rest, when lowered without the extended ball joints. Notice how at rest the LCA's are at an angle. This is bad. Notice how the RC (roll center) is increased. By moving the roll center closer to the center of gravity (COG), the car will have less roll under cornering. This is good (with a caveat, see below).



Here is the suspension geometry of a double wishbone suspension setup, at rest, lowered, with the extended ball joints. Yes, the LCA's are now once again parallel to the ground, thus restoring the original geometry of the vehicle. Fantastic. However, the roll center was also moved to it's original position. By doing so, you've increased the amount of roll that the car will have under cornering. In a way, having increased roll under cornering is a good thing on double wishbone suspension, because the more you roll, the more it compresses and gains negative camber, thus retaining more grip (thanks Sdaidoji )

My conclusion is: yes, even though the roll center is put back to its stock setting, this issue is almost entirely negated through installing stiffer springs, roll bars, etc. By having increased camber adjustability, and by correcting the suspension geometry of the vehicle, the pros far outweigh the cons. Though it's expensive, given the extensive quality of the product, I can't see you ever having to replace a ball joint again. And on a track car, that's peace of mind.

I have heard unconfirmed rumors that the wilwood BBK for EK's will cause these to rub against the rotor.


I am sure some of the suspension gurus on this forum will have their own opinion on this and I very much welcome it. Most of you guys have a lot more experience and knowledge about this stuff, so if I have this totally wrong please correct me.

~Zef
p.s. it's good to be back

 
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Great thread!

 
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Nice write up. Had to do some research too before installing RCAs on my car.

 
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Thanks guys. Max, do those rub on your BBK at all?

 
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No probems on my end, it's a 7th Gen. I believe the 6th gens have 2 ball joints, an upper and lower. I'm not sure if the rubbing you were talking about, is from the upper ball joint contacting the larger diameter rotors. I really can't see how the lowers would interfere. I'd have to look at the suspension to confirm.

 
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Nope, just lower ball joints. The issue of the lower ball joint rubbing on the rotor was hearsay, so I have not 110% confirmed this. Perhaps it's only for people who have serious body roll issues? ..I'll have to look into this.

 
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I've heard of issues with RCAs rubbing against brakes on 7th gens with BBKs, it depends on the specific set-up I believe.

 
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I don't think it's a problem with the diameter, but the rotor thickness. I'm running 12.19" / 0.81" rotors (with plenty of room to spare). Anything wider than that (1 to 1.25" wide) however, may cause problems. That I can see.

 
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great writeup
i would say that having inceased roll for a doublewishbone is not bad, rather desired per se. PS: your rear is not double wishbone :P
the more it roll, the more it compresses and gains neg camber, so will reatin more grip. Not desirable in 7th gen and above, since struts will not increase neg camber gains when compressed, opposed to double wishbone in 6th gen

 
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this is why you're awesome, haha

 
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^ that's because i have a miata
hey! yoda smiley... that brings memories...

 
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Hahaha, oh if only I could fit in a miata, I'd be doing an LS1 swap right now