Ford View on Caster Angle
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Senior User
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From: CT
Ford View on Caster Angle
So this thread is not about any interaction I have had with the dealer or Ford. It is intended to be more of an approach to front suspension specifications, specifically the effect of caster angle on wheel stability.
Over the last week I have read several technical articles on the subject. They all suggest that wheel stability increases with caster angle(that should not be read to mean that there is no limit, just that there be some positive caster angle). Then I read Ford TSB 05-22-1 and spoke with the service manager who directed the installation of caster shims to reduce the amount of caster angle my truck left the factory with from 3.8 to 2.3. He was adamant, Ford wants the caster setting to be near 0, which I found interesting because that is not how it left the factory but would seem to be in accordance with the direction provided in the TSB(which applies to 05 and 06 MY trucks, however it would seem there really is not much different in the front end since 2005).
If I had to guess I would say that there maybe is a balance established between the two extremes. Having too much caster would tend to wear out the components which keep the wheel aligned since the moment arm that exists between the contact patch and the steering axis established by the upper and lower ball joints is longer, therefore any forces imparted by the road and the weight of the vehicle tend to be amplified even though the wheel is relatively more stable whereas near neutral all of those components do more work to stabilize the wheel.
For the purpose of this discussion assume that all components are tight in the front end.
Just wondering if there were any thoughts. My feeling is that the perspective of TSB 05-22-1 is that the starting point of the caster angle is somewhere north of 4 degrees, hence the bushings to reduce the angle. According to Bill over at PSH, 1 degree is too little. He states that from 05 on that the factory setting was near 1 degree, I know mine was 3.8....
Over the last week I have read several technical articles on the subject. They all suggest that wheel stability increases with caster angle(that should not be read to mean that there is no limit, just that there be some positive caster angle). Then I read Ford TSB 05-22-1 and spoke with the service manager who directed the installation of caster shims to reduce the amount of caster angle my truck left the factory with from 3.8 to 2.3. He was adamant, Ford wants the caster setting to be near 0, which I found interesting because that is not how it left the factory but would seem to be in accordance with the direction provided in the TSB(which applies to 05 and 06 MY trucks, however it would seem there really is not much different in the front end since 2005).
If I had to guess I would say that there maybe is a balance established between the two extremes. Having too much caster would tend to wear out the components which keep the wheel aligned since the moment arm that exists between the contact patch and the steering axis established by the upper and lower ball joints is longer, therefore any forces imparted by the road and the weight of the vehicle tend to be amplified even though the wheel is relatively more stable whereas near neutral all of those components do more work to stabilize the wheel.
For the purpose of this discussion assume that all components are tight in the front end.
Just wondering if there were any thoughts. My feeling is that the perspective of TSB 05-22-1 is that the starting point of the caster angle is somewhere north of 4 degrees, hence the bushings to reduce the angle. According to Bill over at PSH, 1 degree is too little. He states that from 05 on that the factory setting was near 1 degree, I know mine was 3.8....
Logistics Pro
Joined: Apr 2017
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From: SoCal
Seems like most guys have the best luck around 4* of caster. Personally I have 2.3-2.0 caster and it drives pretty good to me. I'm eventually going to get some adjustable 3-link radius arms so I can tune it to my exact liking...but for now, all of my bumpsteer and wheel hop/oscilation went away when I put my Fox 2.5's on, so I never really pursued it any further than that.
In my head, I can certainly see the stock shocks just not being able to handle that front end hitting something at speed. I could feel the front end hop and shudder going over pavement to concrete overpasses, or raised man-hole covers, and its not hard to imagine a bad wheel oscillation getting out of control from there. I've never had DW in my life, but I've also never had stock shocks for more than a couple thousand miles.
In my head, I can certainly see the stock shocks just not being able to handle that front end hitting something at speed. I could feel the front end hop and shudder going over pavement to concrete overpasses, or raised man-hole covers, and its not hard to imagine a bad wheel oscillation getting out of control from there. I've never had DW in my life, but I've also never had stock shocks for more than a couple thousand miles.
Posting Guru
Joined: Apr 2006
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I've lifted to many to count trucks in the last 25 years and setting the caster on any particular truck that had been lifted/larger tires needs to be done knowing that some trucks need a bit more positive caster to help those bigger tires run straight down the road.
Some trucks need a bit more toe in as well. I start with adding about 3 degrees. Decreasing caster makes zero sense. What are they thinking? Larger tires need a bit more toe as well.
Caster does indeed cause wobble. This is a fact. Another thing you have to accept is no solid axle truck is going to have the same spec left to right or from truck to truck.
Lifting a truck is a lot more involved than just bolting on parts. The fine tuning is where the real time is spent.
Find a shop that lifts trucks and will work with you as far as sorting it out. Bolting on a kit is easy. Getting it right is not.
Some trucks need a bit more toe in as well. I start with adding about 3 degrees. Decreasing caster makes zero sense. What are they thinking? Larger tires need a bit more toe as well.
Caster does indeed cause wobble. This is a fact. Another thing you have to accept is no solid axle truck is going to have the same spec left to right or from truck to truck.
Lifting a truck is a lot more involved than just bolting on parts. The fine tuning is where the real time is spent.
Find a shop that lifts trucks and will work with you as far as sorting it out. Bolting on a kit is easy. Getting it right is not.
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Senior User
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From: CT
I've lifted to many to count trucks in the last 25 years and setting the caster on any particular truck that had been lifted/larger tires needs to be done knowing that some trucks need a bit more positive caster to help those bigger tires run straight down the road.
Some trucks need a bit more toe in as well. I start with adding about 3 degrees. Decreasing caster makes zero sense. What are they thinking? Larger tires need a bit more toe as well.
Caster does indeed cause wobble. This is a fact. Another thing you have to accept is no solid axle truck is going to have the same spec left to right or from truck to truck.
Lifting a truck is a lot more involved than just bolting on parts. The fine tuning is where the real time is spent.
Find a shop that lifts trucks and will work with you as far as sorting it out. Bolting on a kit is easy. Getting it right is not.
Some trucks need a bit more toe in as well. I start with adding about 3 degrees. Decreasing caster makes zero sense. What are they thinking? Larger tires need a bit more toe as well.
Caster does indeed cause wobble. This is a fact. Another thing you have to accept is no solid axle truck is going to have the same spec left to right or from truck to truck.
Lifting a truck is a lot more involved than just bolting on parts. The fine tuning is where the real time is spent.
Find a shop that lifts trucks and will work with you as far as sorting it out. Bolting on a kit is easy. Getting it right is not.
Just to be clear, my truck is completely stock.
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Posting Guru
Joined: Apr 2006
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Well, then to sum up my view on this I think when you add a lift and larger tires you need to add positive caster as well.
Going the other was makes no sense. That would be like pushing a shopping cart backwards.
Going the other was makes no sense. That would be like pushing a shopping cart backwards.
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Again, these trucks (or any solid axle for that matter) are never identical. While they share the same components (tie rod, panhard/trac bar, etc.) they all while differ slightly. As mentioned above, Ford’s alignment specs in that TSB are a bunch of horse pucky! No two trucks are the same and castor immeasurably helps keep oscillation and vibes down. Any component bolted/attaches to your axle has the potential to create unwanted drivability issues, which is why you’ll hear of folks swapping out eccentric cams for added castor, replacing factory shocks with aftermarket (King/Fox/Bilstein), replacing steering stabilizers, replacing entire suspensions (3-4 links) or replacing control arms with ones with adjustability, and finally, mix-matching/custom tuning each of these components until you find what works for you.
Lets face it- most of us want a certain look. To achieve this, modifications need to be made, but not every “shoe” fits. Yes, it can be a frustrating process to sometimes get it dialed in. I recall and old Jeep of mine that had DW so bad, I never drove it on the streets. I later sold it to a young kid; whom I’d seen driving down the Hwy in my old Jeep. I wanted to know why he wasn’t experiencing DW as I did. He replaced the coil spring isolators (previously rubber) to urethane. I wish all these issues we experience could be fixed that easily!
The bottom line- yes, we spend lots of $$$ on these trucks. Then some of us insist on dumping more $$$ to make them “ours.” Even with a blank canvas, some of you folks will have these issues without ANY mods. Those who purposely modify (leveling/lift kits) have to accept that what works for you might not work for me; meaning if Tricon used Fox 2.5 shocks and has no problems and someone else followed his example and still has issues— keep fine tuning. These are all just suggestive measures that work for some, but not the all-in-all cure for suspension woes...
Sorry for the long rant...
Lets face it- most of us want a certain look. To achieve this, modifications need to be made, but not every “shoe” fits. Yes, it can be a frustrating process to sometimes get it dialed in. I recall and old Jeep of mine that had DW so bad, I never drove it on the streets. I later sold it to a young kid; whom I’d seen driving down the Hwy in my old Jeep. I wanted to know why he wasn’t experiencing DW as I did. He replaced the coil spring isolators (previously rubber) to urethane. I wish all these issues we experience could be fixed that easily!
The bottom line- yes, we spend lots of $$$ on these trucks. Then some of us insist on dumping more $$$ to make them “ours.” Even with a blank canvas, some of you folks will have these issues without ANY mods. Those who purposely modify (leveling/lift kits) have to accept that what works for you might not work for me; meaning if Tricon used Fox 2.5 shocks and has no problems and someone else followed his example and still has issues— keep fine tuning. These are all just suggestive measures that work for some, but not the all-in-all cure for suspension woes...
Sorry for the long rant...
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