There's some other things to consider. First of all, GM had almost no trouble with their steering gears getting out of adjustment. If you tightened the sector shaft it is going to make the shaft bind when it comes back to center. Rather than stay there, the steering shaft is going to keep bouncing off to one side and you're going to have to hold it centered. That can be very tiring and miserable to drive. If you counted the fractions of a turn you tightened it, put it back and continue with the diagnosis.
The next thing to look at is the new wheels. When a wider wheel was available as a factory option, they will usually give different alignment specifications. The Camaros and Firebirds came with wide wheels and tires that caused you to feel every tiny pebble and bump in the road. Strike one. "Camber" on most cars is supposed to be about 1/2 degree positive which means the top of the wheel is tipped out a little on top. That would cause excessive outer edge wear on wider tires so for those, camber is lowered closer to 0.0 degrees meaning perfectly straight up and down. That puts more of the tread in contact with the road, so again, you'll feel every bump. Strike two.
You also need to understand a non-adjustable alignment angle called "scrub radius". If you stand in front of the car and look back at the wheel, draw an imaginary line through the two ball joints. That line was designed to intersect the road surface at the center of tire tread. That splits the tread surface in half. The left half of each tire will want to pull the steering system to the left. The right half of each tire will want to pull the steering system to the right. Those two forces balance each other out so both tires want to go straight.
Taller tires, wider tires, and deep offset wheels will change scrub radius. Now you have both tires tending to pull to the outside of the car. They still balance each other out but the two halves of each tire don't balance out. If one tire hits a very small bump in the road, it is going to tug the car that way momentarily. In addition to that, camber affects tire pull. Each tire wants to roll in the direction it's leaning. The left tire is always set a little higher, (about 1/4 degree), to offset road crown. All roads lean to the right so rain will run off. That's road crown, and all cars will drift that way if that extra 1/4 degree camber isn't there to offset it. That 1/4 degree has very little affect on tread wear on normal tires, but with wider tires there's going to be more outer edge wear unless camber is lowered. Now, to get the needed camber offset for road crown, you may need to tip the right wheel in on top a little. With both wheels tipped to the left, that sets up an unstable condition. Strike three.
The last thing to consider is that GM had a really huge and common problem with their idler arms in the '70s and early '80s. They didn't fail in a way that presented a safety problem, but they develop looseness that allows the right wheel to turn left and right. You can see that pretty easily if you crawl underneath, grab the center link right by the idler arm, and push it up and down. That arm shouldn't move more than about 1/8" with hand pressure. If it moves more than that, you'll see the right wheel move left and right too. THAT is what contributes to steering wander. Strike four.
I assume you had the car aligned after the parts were replaced. Did you get a printout? If so, what are the camber, caster, and toe readings? "Caster" has very little affect on tire wear but it has a big affect on pull. All that's important is the two wheels must be the same. Beyond that, as caster is adjusted higher, high-speed steering stability increases, steering wander decreases, the steering wheel will be harder to turn, (that's why power steering was added), and the steering wheel will return to center on its own faster after you turn a corner. There is a point where too much caster can cause problems, but cars like yours don't have enough adjustment range to set it too high. Normal caster for your car is around 3.0 degrees. If you have the rear of the car raised up, that will decrease caster, leading to steering wander, and it will shift more weight onto the front which will aggravate all the things working against you already.
Finally, you must look at the weight of the engine and transmission. If what is in there now is heavier than what came from the factory, you need to install front coil springs with higher capacity. Weaker springs will contribute to excessive weight transfer when braking, reduced steering control, and excessive bouncing. Lawyers and insurance investigators love to find things like that when they're trying to shift the blame for the crash from the guy who ran the red light onto you. They'll argue you were less able to avoid the crash, and they will be right. The more of those modifications you can eliminate, the better. You don't need to give them ammunition to shift the blame.
As for going to a rack and pinion steering system, people do that on heavily-modified cars like race cars because it's easy to install. The biggest drawback is the feel. Look at the path the forces have to take to shake the steering wheel when a tire hits a bump. The tire, wheel, and spindle move up. If the force is trying to turn the tire too, the spindle has to push on the inner and outer tie rod ends. Those are not exactly on the same plane as the center link, so some force is lost there. The center link has to push on the pitman arm which has to push on the input shaft. With each change in direction, some of the force is dissipated. With a rack and pinion assembly, the forces have a more direct path to the steering wheel. Control arm bushings are just one thing that has been modified to add comfort to cars with rack and pinion systems.
If you look at your current "parallelogram" steering system, you'll see the steering linkage consisting of the inner and outer tie rods and the adjusting link between them is nearly parallel to the lower control arm, and the pivot points are close to the same place. That eliminates any turning of the wheels as the suspension goes up and down. To switch to a rack system you would have to mount the assembly at the exact height to maintain that geometry. You can't do that with the transmission in the way on most cars. You DO not want to drive a car with that geometry messed up. If you think the car wanders a little now, "you ain't seen nuthin' yet". Your car is a "front steer" meaning it has the steering linkages in front of the wheels. There are no provisions there to mount a rack, and the steering shaft wouldn't reach or connect to it. You'd also have to modify the fan shroud, transmission cooler lines, anti-sway bar, etc. Stick with what you have. It's much heavier and more complex than a rack system but it was designed to work as part of the suspension system. If there's a handling problem, it needs to be diagnosed and corrected. We don't fix a problem by doing things like changing the steering system.
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Monday, October 7th, 2013 AT 11:41 PM
