Optimal lower control arms angle?

[Tom86]

Hi everyone,

For good handling what is the optimal angle of the front lower control arms? on my car with no RCA it currently sits horizontal/parallel to the ground would I see any improvement by installing an RCA to lower the arms slightly?

Tom

[AJPS]

how low is your car?

[Skylar]

Lower control arm angle controls two vital suspension factors among other things. They are front roll centre and camber gain through body roll.

You want the roll axis to be parallel to mass centroid; and I'm guessing since we aren't going to be moving rear roll centre down to suit the front, you're going to have to bring the front up. I done the maths before in an excel sheet to figure out the roll centre locations on lowered corollas, I'll dig it up if you're really interested. The engineer said something around 3-5 F and 7-9 is ideal.

When the arms are parallel to the ground, the wheel will lose (go towards + camber) when the wheel moves up into the well. So along with the body roll causing pos camber, the outside wheel will move up into the arch making the wheel lose more camber and decreasing your contact patch. The band-aid to this is to run more static camber than necessary.

[meadan]

Aim to get them pretty much parallel to the ground, or slightly angled down if your springs arent very stiff.

Obviously it depends on what you want to achieve and how far you want to get into it, but Id say thats a pretty good place to start as a rough guide.

[Stain]

Would be interested to have a look at that info Skylar.

[Tom86]

The car is not really low there is a 1.5-2cm gap between the tire and the lowest part of the wheel arch.

I'm running a Greddy coilover suspensions with 8kg front and 6kg rear with -2.5 camber. The arms at the moment are parallel to the to the ground.

I think Skylar might be on to something here about getting positive camber when the arms are parallel to the ground as I often get the feeling as if the inside wheel is folding inward when I hit a bump mid corner.
So I'm thinking if I install an RCA and push the arms further downward this would give the arms extra room to move so the wheel won't go up into the well when the suspension is compressed and therefore no positive camber?

Am I on the right track?

[Skylar]

Stain, Ima have to get back to you on that. You want a ride height vs roll centre chart? + another with say 40mm rca installed?

Tom, yeah, ideally you want to take the spring out and plot wheel travel vs camber to figure out how much static camber you should have for how much body roll you get/how much camber you gain through body roll but just throwing RCA's in would be a good start. and by putting RCA's in, the front will roll less and your camber change will be less than before. Like if you lost 2deg at 1g cornering, you'll only gain 1deg after installing the RCA and making the front 'harder' in roll.