Caster In Layman Terms.

[Cthehentz]

There are ten million threads regarding caster and bad steering that all seems to wander off track without getting to the point. Can some help this simpleton out so I can understand it. I am running a 2.5" lift with 35" tires and I do have adjustable LCA's. My current caster is at 3.1 even on both sides top of the knuckle and 92.1* on the dif. With my current setup what are you guys running with this type of setup?

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[plex]

Have you ever used a shopping cart at Walmart, wonder why sometimes it is so hard to steer that thing or to go a straight line? It is because that thing has a caster of zero.

Caster is the angle between 90 degree perpendicular line to the ground and your axle/ball joints plane, so positive caster means your steering plane is leaning backwards, kind of laid back, makes steering easier, stable, and tend to return center.

 

[blnewt]

Your current caster is way too low, try to get it in the 6 degree range, probably an additional 3/8" to 1/2" in length to get you there.

 

[rustyshakelford]

Look up rock krawlers instructions and take the measurements that have for their lift that replaces the LCA.

To put it easy, the closer your front pinion is to the ground the higher your caster, the higher it is, the lower your caster is. When we set up jeeps I like 6.2-6.5 personally and I’ll adjust it as needed after a test drive.

brett

 

[Iggy]

Look up rock krawlers instructions and take the measurements that have for their lift that replaces the LCA.

To put it easy, the closer your front pinion is to the ground the higher your caster, the higher it is, the lower your caster is. When we set up jeeps I like 6.2-6.5 personally and I’ll adjust it as needed after a test drive.

brett

A good comfortable caster setting for a solid axle Jeep is right around +6.0 degrees +/- 0.5 degrees. The steering will be a bit heavier, but you've got power steering. The main benefit will be a more solid feel on the highway. The steering will want to track straighter. By having adjustable LCAs you can have your alignment tech compensate for the road crown degree and then it really will be straight.

Also, braking is better as mass transfer under braking will be reduced because the increased caster will be using the springs to reduce the transfer. This allows the rear brakes to add more to braking than before and gives the fronts a little break.

 

[jeepingib]

Caster is the self centering characteristic of your steering. This stabilizes the steering at speed. When you don't have enough caster then your steering will feel touchy as it doesn't have that tendency to go straight. The steering engineer for the JK and JL should be ashamed of themselves. Previous straight axle Jeeps had caster in the range of 7 degrees. So long as you stay under 7.5 you will be fine. But I would start at 6 and go from there. Too much caster tends to feather tires when they aren't rotated frequently enough.

 

[CptFloridaMan]

In cause you’re a visual person such as myself



When i first started learning about suspension and cars years ago my brother sent me this video.

 

[Roky]

There are ten million threads regarding caster and bad steering that all seems to wander off track without getting to the point. Can some help this simpleton out so I can understand it. I am running a 2.5" lift with 35" tires and I do have adjustable LCA's. My current caster is at 3.1 even on both sides top of the knuckle and 92.1* on the dif. With my current setup what are you guys running with this type of setup?

Remember back riding a tricycle, and how it steered, (twitchy) now remember getting on a bicycle and the steering was easier, to the point of letting go of the handlebars. That’s the difference between low and high caster. Now if you ever rode a bicycle or motorcycle with extended forks (chopper) and the way that steers, that’s what over 6 degrees of caster would be.......

 

[Cthehentz]

Your current caster is way too low, try to get it in the 6 degree range, probably an additional 3/8" to 1/2" in length to get you there.

Thanks for all the replies, I typically over think the simple things haha.

 

[AnnDee4444]

I'll try to simplify this as much as possible.

• Caster is the angle of the ball joints when compared to vertical
• The steering is forced to rotate around the ball joint center-line
• The ball joint center-line intersects the ground at a certain point
• Between this point and the tire's center-line makes a lever arm
• The longer this lever arm, the more force exists to keep the steering pointed in it's neutral state (straight ahead)

Think of it like a trailer: A trailer with the axle in the center wouldn't be as stable as one with the axle towards the rear. (the hitch would be the ball joint center-line, and the axle is the center-line of the tire)

 

[Cthehentz]

Well I got everything adjusted within spec, steering wander is down to about one inch per side from center. The only other thing I can think of is the steering gear box needs adjusted or replaced.

 

[jeepingib]

Well I got everything adjusted within spec, steering wander is down to about one inch per side from center. The only other thing I can think of is the steering gear box needs adjusted or replaced.

When you say within spec, what exactly are you referring to? The "spec" for caster on the JL is too low. So even a Wrangler that is within the specifications according to the alignment settings in the machine, will still drive poorly.

 

[blnewt]

When you say within spec, what exactly are you referring to? The "spec" for caster on the JL is too low. So even a Wrangler that is within the specifications according to the alignment settings in the machine, will still drive poorly.

Actually the spec is such a wide range that there is good caster & bad caster across the JL line.
The Sports 5.35° +/- 1.00°
Sahara 5.05° +/- 1.00°
Rubicon & Diesel Sport/Sahara 4.80° +/- 1.00°

Since these all use the same Lower Control Arms the Sports & Saharas tend to be on the +1% for Caster in the 6 degree range, and the Rubicon w/ the added lift (which naturally lowers Caster) is more on the -1% for a Caster in the 3.8 to 4 range.

So with the spec written as-is they can get away w/ such a wide range without resorting to actually changing the LCAs for the vehicles in their line that truly need it
Shame on you FCA!

 

[jeepingib]

Actually the spec is such a wide range that there is good caster & bad caster across the JL line.
The Sports 5.35° +/- 1.00°
Sahara 5.05° +/- 1.00°
Rubicon & Diesel Sport/Sahara 4.80° +/- 1.00°

Since these all use the same Lower Control Arms the Sports & Saharas tend to be on the +1% for Caster in the 6 degree range, and the Rubicon w/ the added lift (which naturally lowers Caster) is more on the -1% for a Caster in the 3.8 to 4 range.

So with the spec written as-is they can get away w/ such a wide range without resorting to actually changing the LCAs for the vehicles in their line that truly need it
Shame on you FCA!

Agreed. What I had seen on a printout from an alignment shop was the caster setting was 5° +/- .5° across the board. Which gives it much less range, but still not a very effective caster angle for a solid axle vehicle. And I still can't fathom why they are built like this. Adding just a degree of caster from the factory would improve the steering substantially across the line. They already have the parts on the shelf. Just put the Mopar lift LCAs on as standard. There is no downside to doing this.

 

[Cthehentz]

Sorry for the late reply, I got the caster set to close to 6 but I may add one more turn this weekend when I install the compressor. Something I noticed when I posted the earlier reply steering was better but still loose, last night I took a drive and it was tighter after things cooled down.

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