Part Request: FC front roll correction

[josh18_2k]

yep- we need this.  the community needs this.

S4 ball joints bolt onto the control arm, so it should be a relatively easy part to design/produce.  this coupled with a "bumpsteer kit" should help a ton with the mac strut shittiness.  i'm thinking lower the ball joint at least an inch.  either make them clear 16's for road race guys, or just 17's for everyone else.  or maybe both setups
240s have had F/R roll correction available for a while now.  It would be a huge benefit for both drift and grip guys.

[theantirotor]

ok i''m dumb on this.  explain further please.

[josh18_2k]

i'm no good at explaining stuff, so i'm hoping someone else chimes in lol

but basically its a part that relocates the ball joint further down, raising the roll center of the car.  smaller roll couple would allow you to run softer springs/bars for a given roll angle.
also with the control arms angled down, you would actually have some camber gain in roll.  (most lowered mac cars lose camber)

since mac struts are a gay design, you generally want as little roll as possible to avoid making the geometry any worse than it is.   stupid high spring rates accomplish this, but obviously compromise the car over bumps.

some SCC article about it-
http://www.modified.com/tech/0508_sccp_making_it_stick_part_3/index.html

[largeorangefont]

We would first need bump steer adjustable tie rod ends before we do anything (I was researching this before I began my swap). This is actually one of the things on my long term to-do list.



The camber curve change could be made by moving the ball joint on top of the arm instead of below it, and adjusting its position with spacers. Just flipping it to the top of the control arm may be enough however.   This is not a complete fix, but it will  keep the tires in the "sweet spot" of the camber curve which is what we are looking to do.

I have ran extended ball joints in Mustangs before, and in my experience it didn't allow me to run a softer spring and/or bar. It will keep the tire planted better as the car travels, making the car a bit more consistent and planted.

[gadzooks]

LOF, josh18_2k, is right on with his line of thought, it's accomplished by using an adapter for the tapered hole in the spindle, a custom ball joint; typically with a heim joint and bolt,  and spacers that move the ball joint lower. This type of set up makes the control arms point downward toward the wheels, raising the roll center and improving the camber curve so that when the car does lean the control arm will become closer to parallel and pushing the bottom of the tire out so it gains negative camber.
Moving the ball joint on top the control arm will not change the geometry since it is dictated by the positions of the inboard mount point of the control arm and the ball joint relative to the spindle. The only way moving the ball joint above the control arm will have any effect is if the arm is binding during suspension travel where it mounts to the chassis; or if you move the ball joint farther out on the control arm, which basically works the same as having a longer control arm.

[largeorangefont]

You are right, with a "spacer" on the hub side this will work as intended, without flipping the ball joint. It does put more stress on the hub, and there have been failures on other types of car that were in a in race configuration.

[frijolee]

I did a quick CAD study on camber changes...  Dimensions are estimates based on memory so treat this as ballpark.
 
Control arm length (pivot to ball joint) = 12"
Mac strut length (pivot to ball joint) = 18"
Strut inboard lean angle = -10 deg
Cornering wheel travel = 1"
 
At my ride height my FC sits with it's control arms just about level.
 
Note that because the strut leans inboard I still see greater negative camber under wheel compression so I think the argument about "losing camber" is not correct.  With the assumptions above I should be seeing 0.45 deg neg camber gain cornering as my car sits now.  If I were to move my balljoint down by 1" it would increase 0.2 deg to a 0.65 deg change.   

Anyone want to do the roll center study using the SCC article as a guide?   I'm curious what the upside is there because in terms of pure camber benefits I'm doubful I get my car's camber tuned to with 0.2 degree on a given day.

[V8Mongrel]

I am going to need more data to do this.  To be honest, I am not sure that the program I have even does struts, but I might be able to get things working.  No promises.



If you can give me A thru L as best they transfer to a strut design, I am willing to give it a shot.  Once I have the dimensions input, we can play with the variables.

For a strut system, this is all about instant center location.  Camber gain is a lost cause.

[largeorangefont]

Good observations Joel.

There will be little upside to this if your control arms are already level, and that is good news. That is not to say the factory geometry is perfect, but the geometry we have is opperating in an acceptable range and we may not be working with a subterrainian roll center at our lowered ride heights.

It would be interesting to check the roll center of the car and see where it sits now.

I have not checked the bumpsteer on my car as it sits currently, but I want to check that as well.

[Bowtie7]

I don't know that we can get our cars low enough to need this anyway running the size of wheel/tire combo's that we run. The ITS and eProd cars run on 15inch wheels and run ride height of 4-5" measured at rocker panel. Not gonna happen that I can see. I do think that AWR sells the spacers that the o/p mentioned.

[largeorangefont]

I don't know that we can get our cars low enough to need this anyway running the size of wheel/tire combo's that we run. The ITS and eProd cars run on 15inch wheels and run ride height of 4-5" measured at rocker panel. Not gonna happen that I can see. I do think that AWR sells the spacers that the o/p mentioned.

After sticking my head under my car this evening, I agree.

[V8Mongrel]

It would be interesting to check the roll center of the car and see where it sits now.

I am willing to help.  Here is a visual for those having difficulty following along.