tubular control arms

[THX1138]

Can you post some pictures of the front control arms you made?

- Jim

[ROB]

I made the lowers without the drop that the original has, instead they are level right across, to make up for the drop of the stock arms I fabbed a new pocket for the lower control arm to mount in. The holes in the new pocket are just under 2.5" lower than the stock holes.

Sorry I didn't catch this before, but this is the problem. The "drop" of the stock arm is not your problem, moving the pivot point is. You wound up changing the geometry in the wrong way. Keep the arm straight, put the arm back in the stock position, and lower your spring seat to simulate the drop in the original arm.

[72vega383]

I made the lowers without the drop that the original has, instead they are level right across, to make up for the drop of the stock arms I fabbed a new pocket for the lower control arm to mount in. The holes in the new pocket are just under 2.5" lower than the stock holes.

Sorry I didn't catch this before, but this is the problem. The "drop" of the stock arm is not your problem, moving the pivot point is. You wound up changing the geometry in the wrong way. Keep the arm straight, put the arm back in the stock position, and lower your spring seat to simulate the drop in the original arm.

That sucks. I just finished welding up the new pockets and hacked out the old. Don't think its gonna be easy going back to stock. What's the worst thing that can happen?

[72vega383]

Anyone know what the problem with lowering the pivot point is? Haven't had a chance to try it yet and can't find anything online. Please help!

[ROB]

The problem is your spindle will want to tilt out to positive camber during a bump up. Combine this with taking a turn and your tire will want to roll over onto itself instead of "anchoring" itself better for the turn. It needs to go negative camber.

[72vega383]

Ok that makes sense. Thanks. What can I do to combat this? I can't move back up to the original pivot point. I think I read that every vehicle was built with a positive camber curve, not sure how true it is though.

[72vega383]

ok so I let the car down yesterday to rid height. lower arm is got a slight angle down, top also has angle down of about 10-15 degrees. the lower a arms pivot points I moved about 2" lower than stock because I didn't put in the drop of the stock arms. heres the specs

caster of about 2 deg. positive.
camber at .5 to 1 degree static
wheels turned full lock to the drivers side, both wheels gain negative camber
wheels turned full lock to passenger side, the drivers wheel gains negative camber but the passenger wheel ends up with 2 degrees positive. not sure why this is?

I don't know how it will react when going over a bump, or if making a turn and hitting a bump. anyone have any input? is there any negative effects due to lowering the pivot point of the lower control arm? keep in mind my ride height is higher than stock at 27" ground to fender lip. (I know that's high for some but that's how I wanted it as it is just slightly lower than the back.

advice and suggestions are welcome.

[72vega383]

After doing some research. I found that what I have done by lowering the pivot point of the LCA I raise the instant center. At this point I have 2 ideas.

Remove the 3/4" rubber spacer I have under the coil springs which should lower the car. Bringing the upper control arm more parallel if not slight higher on the bj side. Although this will bring the lower control arm pivot point slightly lower than the ball joint as it is parallel with the spacer in.

2nd option is keep the ride height where it is and lower the upper control arm mounts by about 1 1/2". Which will put the ball joint higher than the pivot point? To do this I will have to shorten the upper a arms I fabbed up. If it's not gonna work I would like to know before I cut them.

Any suggestions? Anyone

[Monza Harry]

My suggestion is to buy a book or two (I am not trying to be a smart ass, really, I have read this 1 and a part times and there are a few nuances that are still outside my grasp ) as the task you have undertaken is pretty involved. I have and read "Chassis Engineering" by Herb Adams and this has a lot of information on the geometry you have started to change. So it would be a good choice to start with, I also have "High Performance Handling" Handbook by Don Alexander and I wouldn't buy this for what your doing as it doesn't cover any of the things you are working on it is all about improving street cars with bolt on's, (I was disappointed with this book pretty remedial for $30) I have on my wish list the "Carroll Smith ....to Win" series of books I have glanced through them years ago and these are Hard Core Racing books. Harry

Here's one (that I have read)http://www.amazon.ca/Chassis-Engineering-HP1055-Herb-Adams/dp/1557880557 and these that I want I know there is lots of information in this series http://www.carrollsmith.com/books/index.html or this one for just the chassis http://www.carrollsmith.com/books/#ngner2win-detail , it has been a long time since I looked at these but I am sure this is the right one. Nick, (NixVegaGT) Has recommended (and read) one of these to me perhaps he can chime in

[72vega383]

I know I was thinking of getting a book but i couldn't seem to find anything that covered what I needed to do. Thanks for the suggestion. I am going to look see if I can find it.

I decided to remove the 3/4" spacer under my coil and it dropped the car almost an inch and a half. I took the angle finder to the lower arms and they are now parallel. The uppers instead of pointing down toward the spindle are now also parallel right across ( the top of the spindle still is lower than the pivot point but the ball joint itself is directly parallel with the pivot points) my tie rod is at an angle of about 8 degrees down(wheel side). The ride height is now just under 26"
I am more confident with the angle of the arms now than when it was higher.