Tubular Front control arms - Discussion

[jman093]

Mach 5, I don't have bump steer issues. W-body's seem to have very forgiving suspension. Do you have stock control arm bushings and strut mounts? That may contribute to your bump steer. There's also a ton of heim joint bump steer "fix" kits out there to solve this problem.

 

x2. Even when mine was dropped 4 or 5 inches, it never had noticeable bumpsteer. It all depends on the vehicle. Every one is different. You can't use an AE86 or even another vehicle with a similar MacPherson strut suspension as a comparison.

[Mach 5]

yes I have poly bushings.. It might be just in relation to the shitty NY roads here. grooves all over makes the car track funny. I know that on the ae86 it did fix when I added rca's.

[gtp237]

yes I have poly bushings.. It might be just in relation to the shitty NY roads here. grooves all over makes the car track funny. I know that on the ae86 it did fix when I added rca's.

RCAs shouldn't make a difference because the wheel center(and tie rod end mount) would be in the same place. The control arm would just be lower, which will give you camber issues probably causing uneven tire wear and traction issues.

 

Let me try to explain.. Forgive me if this doesn't come out right or make sense. As the control arm raises(lowering or hitting a bump) it will cause positive camber. But because our upper link is also the strut, as it compresses (lowering or hitting a bump) the length of the upper link(strut) shortens causing negative camber. Thus canceling the positive camber out, keeping the tire flat to the ground. If you add RCAs or balljoint spacers you lengthen the upperlink(strut assembly), adding negative camber.

 

Same goes for flat, dip less control arms. If you make it so the control arm doesn't point up and provide positive camber you will be left with the negative camber all the time.

 

 

Please note that everything in this post only applies to lowered cars.

[skitchin]

After reading over all the discussions, I'm totally confused about what benefit tubular control arms can actually give you.

[AWeb80]

should be stronger and lighter weight.

[CSI_MuNkY]

RCAs shouldn't make a difference because the wheel center(and tie rod end mount) would be in the same place. The control arm would just be lower, which will give you camber issues probably causing uneven tire wear and traction issues.

 

Let me try to explain.. Forgive me if this doesn't come out right or make sense. As the control arm raises(lowering or hitting a bump) it will cause positive camber. But because our upper link is also the strut, as it compresses (lowering or hitting a bump) the length of the upper link(strut) shortens causing negative camber. Thus canceling the positive camber out, keeping the tire flat to the ground. If you add RCAs or balljoint spacers you lengthen the upperlink(strut assembly), adding negative camber.

 

Same goes for flat, dip less control arms. If you make it so the control arm doesn't point up and provide positive camber you will be left with the negative camber all the time.

T

 

Please note that everything in this post only applies to lowered cars.

 

That doesn't make a whole lot of sense to me... The strut compressing and getting shorter will pivot on the mount and the control arm raising when you hit a bump will push the bottom of the strut outwards. Thus creating negative camber (bottom of the wheel sticking out farther than the tops)

 

It is my understanding, that by putting a ball joint spacer in there you will effectively lower the location of the control arm back down closer to a stock orientation

 

I think when I get my car running, I may have to mount my go pro camera under the car so we can all see what the control arm does.

[jman093]

That doesn't make a whole lot of sense to me... The strut compressing and getting shorter will pivot on the mount and the control arm raising when you hit a bump will push the bottom of the strut outwards. Thus creating negative camber (bottom of the wheel sticking out farther than the tops)

 

A McPherson strut suspension will gain negative camber up until the angle between from the lower ball joint to the center of the strut mount and the lower control arm mounting point is 90 degrees. If the suspension has compressed so that the angle is past 90 degrees (obtuse) it is now starting to gain positive camber. The more acute the angle is, the more dynamic negative camber gain there is, which is why lowering the car hurts the camber curve. However, lowering also helps gain a little negative static camber since it is essentially the same as compressing the suspension. All-in-all it isn't going to make that much of a difference. I bet it's going to be pretty close to what it was before. Hell, if the angle still isn't over 90 degrees under full compression, lowering will actually help. Overall, it isn't really anything to worry about and even if was, McPherson strut suspensions do not have a large camber curve to begin with. Even on a car at stock ride height where the angle is most acute, dynamic camber is not changing a whole lot. It's nothing like the negative camber gain vehicles can get on a properly-engineered SLA suspension or a multilink suspension. McPherson struts aren't a bad performance suspension (it's way, way better than the short knuckle SLA on my 87 Monte Carlo for example), but it isn't particularly great either.

 

It is my understanding, that by putting a ball joint spacer in there you will effectively lower the location of the control arm back down closer to a stock orientation

 

As I mentioned in an earlier post, any spacer will have to be between the ball joint and the knuckle. If it's between the ball joint and control arm absolutely nothing will have changed. If you want to get as much negative camber gain as possible make as thick of a shim as possible to go between the knuckle and control arm without making the ball joint hit the wheel. You'll obviously have to drill the holes for some larger bolts. The factory ones are inadequate long before spacing things like out. Even without a spacer there they are still inadequate. My car with all its upgraded suspension, bent those little bolts that come in the ball joint kits a couple of times. Looking back now, it was really pretty stupid of me to keep autocrossing without drilling and putting larger ones in there. I'm probably damn lucky I didn't shear those right off and have the control arm and knuckle separate.

Edited April 22, 2012 by jman093

[gtp237]

That doesn't make a whole lot of sense to me... The strut compressing and getting shorter will pivot on the mount and the control arm raising when you hit a bump will push the bottom of the strut outwards. Thus creating negative camber (bottom of the wheel sticking out farther than the tops)

 

It is my understanding, that by putting a ball joint spacer in there you will effectively lower the location of the control arm back down closer to a stock orientation

 

I think when I get my car running, I may have to mount my go pro camera under the car so we can all see what the control arm does.

 

What is it that you don't understand? I'll try to explain it a little better. At stock ride height the control arm is level, this makes the ball joint point out as far as it possibly can. Any further up or down will cause the ball joint to pull inward(very slightly) causing the lower portion of the wheel to be pulled in (POSitive camber). A few things contribute to the NEGative camber that cancels that out. The strut is angled so as it compresses, it pulls inward. Plus any time the angle between the control arm and strut assembly changes the wheel's angle will be affected. In this case every thing works out but if you used flat control arms, yes you will keep the control arm level but you will change two things, the ball joint will be further outward (promoting negative camber) and the angle between the control arm and strut assembly will change.

Edited April 22, 2012 by gtp237

[jman093]

At stock ride height the control arm is level, this makes the ball joint point out as far as it possibly can. Any further up or down will cause the ball joint to pull inward(very slightly) causing the lower portion of the wheel to be pulled in (POSitive camber)

 

This is incorrect. As I said in the post above. Dynamic camber won't go positive until after the angle from the ball joint to the center of the strut mount and the control arm mounting points is less than 90 degrees. If the center of the strut mount is directly above the lower ball joint when the arm is parallel with the ground, then yes, dynamic camber becomes positive as soon as the arm is angling upward. It's hard to understand your post, but I think you're also to be under the false impression that the shape/angle/ball joint spacing of the control arm itself has anything to do with camber. The only way to change camber with the control arm, dynamic or static, is to change the ball joint mounting location. From stock location, moving it outwards (making the arm longer) will provide more static negative camber and help the camber curve. Moving it inwards (making the arm shorter) will provide more positive camber and hurt the camber curve. The same can be applied to caster. Moving the ball joint forward on the control arm will provide more caster. Moving it rearward will provide less.

 

Everything (caster, static camber, dynamic camber) is all determined by the suspension's pickup points. This is why the only way to get a better angle on the control arm is to change the ball joint mounting location and/or space the ball joint further from the knuckle. You can reshape the control arm or space the distance from the ball joint to the control arm all you want. The control arm angle may visually look different, but it actaully isn't if the center of the ball on the ball joint has not moved in relation to the control arm mounting point and the upper strut mounting point.

[gtp237]

I drew a picture to help explain heh. Here it shows the ball joint center is getting pushed in due to angle of the control arm alone.

 

 

Hope that helps explain it a little better. When you lower your car the control arm points up, pulling the ball joint in, causing positive camber. If you make the control arm flat or mess with how far it is from the knuckle, you change the control arms angle, which does affect the wheels angle.

[jman093]

I drew a picture to help explain heh. Here it shows the ball joint center is getting pushed in due to angle of the control arm alone.

 

 

Hope that helps explain it a little better. When you lower your car the control arm points up, pulling the ball joint in, causing positive camber. If you make the control arm flat or mess with how far it is from the knuckle, you change the control arms angle, which does affect the wheels angle.

 

If all three of those control arms represented are the same length, they are all following the same arc since the pickup points still haven't changed. Once again, if you want the control angle restored for better camber curve, you cannot do it with the control arm itself without unless you the ball joint outward from the car with a longer arm. You cannot space the ball joints on the arm or reshape the arm to any effect. Pickup points in same spot = no changes in anything.

 

The other problem with your picture is it only shows the control arm in relationship with the ground. That means nothing. You need to take the entire suspension into the picture. The defining angle is the angle made by the ball joint to the control arm mounting point and the upper strut mounting point.

Edited April 22, 2012 by jman093

[CSI_MuNkY]

I get what he is trying to say though... I see what you mean with it creating negative camber above the center of the arc.

 

 

So best I can get out of this is OEM mounting locations and if you want to correct BJ angles, then you do it with a spacer between the knuckle and the BJ, so nothing to do with the arm itself.

 

When I can free up the funds I will likely take my spare set of arms to the guy and see what he can do, but at $500 a set, I'm not sure how soon that will be

 

Thanks for the input guys

[topless94style2]

I'm in if there is performance value to it than simply a stock replacement.