Lower front control arm is not an A-Arm

[HellTriX]

Ok I guess this is a new forum for you guys and I couldn't quite find what I was looking for so I will make this my first question post

Front of car, my B-Body has upper A-arms but the lower control arm is not an a-arm. Its just a connection to the frame from the spindal then it has a bar that connects from the spindal side to the front of the car frame at about a 40 degree angle (not sure of what its called as I am still new to suspension).



Can someone tell me the pro's & cons of this type of suspension?
I am trying to determine if I can still use a modified geometry upper arm without the lower link changing geometry too much?

Depending on the answers I been considering modifying the frame myself to accept more common upper and lower control A-arms. I also noticed while reading one of my 3 magazines (hot rod, car craft, chevy high performace) that a mustang in one of these mags was turning into a pro touring and it used the same lower control arm with support bar setup I am discribing so I assume from that it may not be all that bad?

Thanks
-TriX-

[MrQuick]

what year and what type? B body GM or B body Mopar? Cant seem to remember what the GM caled it...similar to Fords.

[ZZ430]

Strut rods.

They have been used on everything from early Chevy II's to Mustangs as you mentioned.

They are how you adjust caster.

Not the best setup, but there were millions made.

I'd say cut the frame off at the firewall and graft on a later clip.

[David Pozzi]

I think tha'ts called a torsion rod or maybe strut rod type suspension. The threaded rod adjusts caster if I remember right.
The front frame mount for the rod needs a spherical bearing on it to control movement, also the inner pivot needs a spherical bearing.

This system is used a LOT in circle track racing, nothing wrong with this design in general, check with Coleman, AFCO, Port City Racing, Stock Car Products.
See if Global West has a kit for it.
David

[Norm Peterson]

There's nothing inherently wrong with the strut and lateral link, as it is nothing more than a multi-piece lower A-arm. My '72 Pinto had a very similar arrangement (with the strut going back toward the firewall rather than forward to a crossmember) and it was more than a match for the sports cars of the day on an autocross course.

The issues begin to develop when you consider how the pieces attach to the chassis. Rod ending the strut (and the lateral link) will give you the accurate kinematics, along with ride quality and inspection/maintenance penalties. For good isolation, though, the strut is normally mounted through a bracket using a split bushing, much like endlinks on a sta-bar. But the same bushing compliance that takes the sting out of the bumps gives away some accuracy in caster control (ultimately affecting bumpsteer a little). And the stiffness that remains adds some nonlinear amount of wheel rate. You can take that to mean that this is another bad place for poly unless the split halves, the holes through them, and the washers, closely approximate spherical joint behavior.

Norm

[HellTriX]

Thanks guys that helps alot.
I just may consider sticking with it after all. I didn't relize I could control caster with the lower link, though I should have. It makes lots of since that the strut link was threaded for adjustments yet I was to limited into thinking I should set back the top of my spindal with a new upper control arm.

In this case I will likely replace with some high quality bushings and rebuild the front end. There are also a few parts for steering components that I can use for added strength. I will also weld some tangs onto the lower control arm or make a tubular replacement for coilovers to get the lower spring closer to the lower ball joint. I will also replace the sway bar with something a bit higher rate and stiffness. I would like to connect it with heim joints on the control arms and a good quality bushing for the frame mounts (about my level of balance stiffness vs ride quality).

My main concern was getting enough negative roll camber. But I guess if I can stablize the roll enough and with a lower CG It should come pretty close to my goal. My goal being a cornering load of around 0.9-1.0 Gs with a good quality road race tire and 0.98-1.0+ G with slicks of some sort. Are these realistic goals? Either way I tend to meet and exceed my goals so hopefully it will workout again.

Car: 1966 Impala, 387 cid 550hp, Th400 w/Gear vendors.
Twin turbo is in the future after some suspension work.
When I first started my project it was hard to describe what I was building. Then I a perfect exsample of what I was trying to accomplish, here is a like that best discribes it: http://www.chicayne.com