Mechanics

LOWER CONTROL ARM

1998 Ford Ranger • 4 cylinder 2WD Manual • 130,000 miles

I have replaced all my control arms. I now notice that the RH lower control arm rear pivot bolt has a cam on the bolt-head and a cam on the nut end. The bolt holes in the chassis are actually horizontal slots. I didn't pay any attention to the cam positions during removal because the Haynes manual simply said to remove the bolts. How do I set these cams (and the bolt) up?
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Marty1947
March 12, 2011.




It is impossible to set them correctly without an alignment. Even if you put them back in the same orientation, there are differences in control arms, hence the need for adjustments. That is one of the alignment adjustments. Also, if you had the truck jacked up when you tightened the pivot bolts, mention that to the alignment mechanic. He will loosen them all up and retighten them while the truck is sitting on the hoist at normal ride height. If those bolts are tightened when the suspension is hanging down, the rubber bushings will be in a permanent twist which will shorten their life quite a bit.

Caradiodoc
Mar 12, 2011.
Thank you, caradiodoc, that is very helpful. I didn't tighten the pivot bolts (upper or lower) until I had the truck on the ground. It just seems a little weird to me that only the RH lower arm can be adjusted. Thanks again.
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Tiny
Marty1947
Mar 12, 2011.
I'm surprised to hear the adjustment is on the lower arm. Some models had a two-piece right upper arm. The idea was to set camber on the left and get the caster just close to specs. Camber was set next on the right side, then the outer half of the upper arm could be adjusted independently to change only caster to match the left side. The actual caster value is not critical but it is important that both sides be nearly the same. Funny thing was though, that entire upper arm had to be replaced to replace the ball joint and the outer half was not available from Ford. You were to replace it with a one-piece arm just like on the left side so you lost that ability to easily adjust caster. Turns out you CAN get that half arm from NAPA.

Caradiodoc
Mar 12, 2011.
I'm afraid that I am an ignoramus regarding caster and camber. There are adjustable cams on both upper arm pivot bolts (front and back) which I marked and put back in the same place. From what you said about different arms not being exactly the same size, maybe I need to ensure that they are checked during the alignment procedure. The adjustment on the RH lower arm, rear pivot bolt makes me wonder if it is used to roughly adjust the toe-in. As I was initially tightening the bolt, the cam turned. This resulted in the bolt (and the back of the arm) moving towards the centre of the truck. This caused the wheel to turn right slightly. I guess the alignment people will know exactly what to do if I tell them what I have done. Thanks again for your interest and assistance. I appreciate it.

Tiny
Marty1947
Mar 12, 2011.
Having given more thought to what I just wrote previously - of course the wheel turned as the bolt on the RH lower arm moved inwards. I expect both front wheels might have moved slightly. But also the bottom of the wheel would have been pulled inwards (camber?) And backwards (caster?). Thank heavens there are experts out there! Lol

Tiny
Marty1947
Mar 12, 2011.
You got it right. Camber is the tilt in or out on top as viewed from the front. Each tire must be set to specs to prevent excessive wear on the inner or outer edge, and, a tire wants to roll in the direction it's leaning. For that reason both tires must be set the same but with the left one leaning out just a little more to make up for "road crown". That is the road leaning to the right so rain runs off.

When you look at the ball joints from the side of the truck, caster is the upper ball joint is further back than the lower one. That makes the spindle sit at an angle much the same as a bicycle fork goes forward as it goes down. 0 degrees caster means the upper ball joint is directly over the lower one. If you could imagine the upper joint straight behind the lower one, that would be 90 degrees caster. In reality, 3 to 4 degrees caster is typical. The exact value isn't critical because it isn't much of a tire wear angle but it's more important that both sides are the same. When you put weight on the bicycle wheel that angle is what makes the tire go straight and you can ride no-handed. On a car, since the weight is on the side of the wheel, when putting the weight on the right tire, caster makes it want to flop to the left. 3 degrees caster will make it flop in so hard you won't be able to pull it back straight by hand because doing so also raises the corner of the vehicle a little. That can be over 1000 pounds you're lifting. The idea is the other wheel is doing the same thing. When you connect a steering linkage between the two wheels they counteract each other much like a balanced teeter totter. Caster can also be increased slightly on the right to make it flop in harder than the left side to offset road crown.

Camber is pretty easy to set because it takes a big adjustment to make a small change. It's easy to sneak up on the desired setting. Caster is harder to set accurately because the slightest adjustment makes a big change in the numbers. That's why having a dedicated adjustment for just caster makes it easy to match one side to the other.

Caradiodoc
Mar 12, 2011.
Forgot to mention too that your observation of the wheel turning left or right is correct, but you aren't adjusting toe. It IS changing toe as a byproduct of adjusting caster and camber, but actually adjusting toe is done last. Depending on the car model and suspension system used, adjusting camber moves one of the ball joints left or right. Suppose you move the upper ball joint out 1". (That's a real lot; 1/4" is a bunch). That means the middle of the spindle between the two ball joints would move out 1/2". If that's the height where the steering linkage is attached, that linkage will have to be lengthened 1/2" also to keep the wheel straight ahead. If you don't make that adjustment the wheel will turn one way or the other depending on whether it's connected in front of the spindle or behind it. Once caster and camber are set, toe is adjusted last because changing toe has very little effect on those first two angles. Oh, by the way, toe is the direction the wheels are steering. The tires are normally adjusted so the fronts are about 1/16" to 1/8" closer together than the rear so road forces pull them back perfectly parallel on the highway. Those two adjustments, one on each side, are also what sets the steering wheel straight ahead. Some trucks, such as Dodges, use a single "total toe" adjuster for the alignment, then a different adjuster that only sets the position of the steering wheel. Ford used that design at one time too. Gm also had their version of that system on some trucks.

Caradiodoc
Mar 12, 2011.

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