Optimal front ball joint length for RC correction on S chassis

[Umai Kakudo]

I need to finally fix my RC on the front S13.

I stumbled across these beauties thanks to Jason M.



http://www.colemanracing.com/Integra...rms-P6201.aspx

They are the same parts as the nice Billet aluminum units Jason has but with a steel housing meant to be directly welded to the control arm saving 0.5 lb over stock steel ball joints and lowering parts count / cost for LCA fabrication.

Anyway, the max length these joints have is +0.75" over stock.

Howe and Titan have domestic sized ball joints with +1.0" studs. That looks to be the limit of circletrack extended balljoint options.

I've seen people running anywhere from 20mm (0.787") to 3" (76.2mm) drop (or more) on various spaced ball joint FLCA setups.

What is the consensus on the correct amount of drop? Has anyone done roll center and moment center calcs that would care to share.

Bonus points if you have matched the front to the back!

[Def]

I did a little analysis up front and I think you're looking at 1.25-1.5" for the average ride height (~.5-1" tire to fender gap) to get the RC slightly above ground level, which is probably a good level based on where you can easily get the rear to.

Which brings me to the rear - just raising up the subframe to the body puts the RC very roughly just below the rear diff at a reasonable ride height.

This gives a reasonable roll axis inclination, sloping downwards slightly towards the front, and the roll couple isn't huge. You eliminate some jacking that you get with a really high roll center, and the roll center migration isn't horrible from my analysis.

[Jason M]

I have some super low friction, and extended travel lightweight billet aluminum
ball joints, (screw in style) from Speedway motors, that I'am going to start using. I also bought the screw in style QA-1 adjustable ball joint's but, I don't like them much, they are heavy, & the threads are not a good match (loose fit) for my weld on ball joint adapters.

For overall lightness the monoball/spherical is still the best, but the billet setup has a ton more articulation, & a dust boot, like a proper ball joint. It would be optimum for street use. It has many different studs available, & adjustable preload.

[Def]

Can you get shanks with enough length for our usage though?

[Jason M]

Just got a computer where I could actually see that link, & the pic. Those are new to me, and very nice. The billet models that I have require a weld on bung/adapter. Those are perfect for fabricating RLCA's. They are .75" over standard oem lenghts, but potentially a little more or less, on our setup (Nissan spindles) after reaming.

[Jason M]

These are what's sitting on my shelf at home right now... http://www.colemanracing.com/%2fBall...125-P4842.aspx

I'll try to take measurements sometime soon, to see what kind of adjustement we could see after reaming.

If we went with the larger 727 tapered stud (vs, the 772) It would increase the RC correction a bit, but also the weight.

[spent]

Great post on, *gasp*, zilvia...

http://zilvia.net/f/tech-talk/296725...ml#post4400318

The only reference he has to his ride height though is that picture which is unfortunate. It appears mine rides a tad higher than his and I did 1 7/8" spacing and my flca are perfectly parallel with the ground. I think my fender lips measure ~ 24 3/4-7/8 " on all 4 corners.

[logr]

Not sure how many people worry about it but stock rake is 1" higher in front measured at the fender lip.

[Def]

Not sure how many people worry about it but stock rake is 1" higher in front measured at the fender lip.

The "cool" stance I see on most cars is about 1" less front fender height than rear. So 2" more rake than stock.

[Umai Kakudo]

As an aside, why does everyone measure ride height at the fender? Sure the FSM does it but fenders very a bit based on steel vs fiberglass vs beat and bent vs rolled vs show car straight.

I've had good luck with measuring from the main frame rail perpendicular to the A pillar. 80mm is a good height for being low, still having enough compression travel, and being able to drive over speed bumps and angles.

Jason M - I'd appreciate it if you could post the actual length measurements for your Coleman balljoints.

I see that Howe and Titan have domestic sized ball joints with +1.0" studs. That looks to be the limit of circletrack extended balljoint options.

[Beejis60]

What would be the benefit to run some of these aftermarket type of BJs instead of the bearing + bolt method? Greater articulation?

[Matt93SE]

The big one is strength and reliability. With the longass bolt, I've had mine come loose on track twice now in 6 months, and im torquing it to at least 250ftlb (tight as I can get it w 30" breaker bar.)

A tapered balljoint will lock into place and not work loose like that, while still allowing the adjustment on the bottom.

[Beejis60]

Wow I never would have thought that shyt could come loose like that... scary.

[Matt93SE]

It didn't come OFF, but it became loose enough that I was having front end wandering issues. I jacked the car up and they were loose on both sides. If you choose to go that method, i highly recommend red loctite on all bolts.

[Def]

The big one is strength and reliability. With the longass bolt, I've had mine come loose on track twice now in 6 months, and im torquing it to at least 250ftlb (tight as I can get it w 30" breaker bar.)

A tapered balljoint will lock into place and not work loose like that, while still allowing the adjustment on the bottom.

Never had mine come loose. You using a distorted thread locking nut? Might be worth it to pony up the $$$ and put some wedge washers under those.