Hey guys,

I was hoping that someone may be able to help me (& others I'm sure) with some basic concepts regarding suspension & tires for our chevelles. Oversimply I understand that stiffer bushings, boxed or tubular control arms, and big fat (tall & wide) tires help with overall handling & driveability, front to rear weight transfer for traction or all of the above. Can anybody expand on the above? It would be great to translate the science into what the car will feel like with these different upgrades. I had a '67 GTO a few years ago that rode like an ambulance and the rear end almost bounced around every corner. All that was done to that car were the bushings but it was a pretty hard ride. What does dropping the car an inch or 2 and slapping 17 x 10's on really do for the ride? I am building a fuel injected big block '66 Malibu to drive everyday and I want to make my suspension choices smartly. Also is the reason for adjustable upper rear control arms soley to change the pinion angle? I plan on putting a 700R4 in the '66 and I have read that the pinion angle will need to be adjusted. I appreciate any thoughts & info you guys can offer. I like a lot of people here are self taught regarding this restoration thing & really rely on you guys for the know-how you just can't read about in a book.

Thanks as always!

George
george@spattaweb.com
TC #1921
ACES #5880

Adjustable rear arms adjust the pinion angle. That's it.

A taller, wider tire, increase the size of the contact patch. More rubber on the road = better traction in corners and in the straights. A larger wheel with low profile tires increases cornering stability, also because the short sidewall of the tire is very stiff.

Stiffer bushings prevent the suspension from deflecting. A control arm is bolted to rubber (stock bushing), and can therefore move when forced to. The idea was to absorb road vibration and impact with pot-holes and bumps. The bad side is, it can sort of steer the car.

Same thing with tubular arms. Unboxed arms can flex and point the suspension in a direction you don't want it to go. It is a notorious cause for wheel hop in Chevelles.

Stiffer springs keep the car flatter in corners. Think of the extreme, a spring so stiff it doesn't move at all, like solid metal. Think the car will roll much in the corner?

That's all for now...time to go home.

Tim.

Home now :D

Springs and shocks change weight transfer. Stiffer shocks add more resistance to the spring's movement. A 90/10 shock, used in drag racing, will be very loose on expansion, allowing the front end to be lifted up by the springs easily. They are stiffer on the way down so the car doesn't go up and then slam back down taking the traction off the rear. Drag racers also prefer a taller lighter front spring. The more the spring is compressed, the more energy it has stored. On launch, it uses that energy to pick up the heavy front end of a BB Chevelle. The opposite is the case for a road racer who doesn't want the car to move around at all.

hmmm...anything else?

Tim.

Here are a few observations...
1) Stiffer bushings are good for solid predictable suspension geometry. There is nothing wrong with rubber bushings, except that they wear more rapidly and when they do, they can cause the geometry of the suspension to contribute to more unpredictable behavior in cornering. You want stiff bushings, but you also want the suspension to move freely up and down. Polyurethane bushings DO contribute to binding in the suspension. Bushings like the Del-A-Lum bushings are much better. Anything stiffer than rubber bushings will contribute more to vibration in the frame and body. Which by the way is that nasty thing that helps to loosen all of the bolts in your frame and body.
2) Boxing the Rear Trailing arms does one thing and one thing only...it causes the rear suspension to be more stiff in roll. The upper trailing arms are responsible for locating the axle side to side in a 4-link style suspension (where the upper arms are angled inwards). Because the lower arms must twist to allow the body to roll side to side over the axle, boxing them adds to the resistance of this motion. This is why some very intelligent aftermarket companies have come up with boxed (or tubular) control arms that have a ball joint on one end.
3) On the issue of big fat (tall & wide) tires, there are some things to say...wide tires add to the contact patch area. Tall tires also increase the contact patch area, but to a lesser degree (they also effectively lower numerically your gear ratio). The part that affects ride quality of the tire is the air volume contained inside. Low profile tires have stiffer sidewalls for cornering, but with increasing rim size they also remove air volume. This causes the harsh ride. Look at the innovative old Porsche rims that had hollow spokes. This increased the air volume of the wheel.
4) Stiffer springs cause more weight transfer to that portion of the vehicle. Stiffer springs in the rear...more weight transfer to the rear. Stiffer springs in the front...more weight transfer to the front. You can't severely unbalance the vehicle however if you want to drive it on the street because it will be unstable.

I hope that helps to clarify a few things!

Thanks a lot for the replies. This is exactly the kind of info I was looking for!

George
george@spattaweb.com
TC #1921
ACES #5880