mat in tn Posted March 19 Share Posted March 19 I did the alignment this morning. After setting the toe to 1/32" in each side for 1/16" total I measured caster and camber. Driver side camber is .5 degrees positive and 1.5 degrees positive caster. Passenger side is 1 degree positive camber and 2 degrees positive caster. That explains the lack of steering return to center. Truck drives good but on flat roads sometimes has a slight drift to the left due to the caster differential so I may adjust the passenger side radius arm bushings to take a little differential out. Drives straight as an arrow on most crowned roads though. Drives well other than the crappy return to center and it is a LOT smoother than it used to be up front and bump steer is all gone. I take it the I beams need bent to correct the caster issue. the signature says 86 year model. king pins?? the best way to correct caster is with offset radius bushings and you have done that. this lowers the rear of the radius arm pivot point. the second is to use shorter springs. I know. not a good thing to say. but that will raise the front within the geometry range and bring in the caster and camber. Link to comment Share on other sites More sharing options...
FordFETruck Posted March 19 Share Posted March 19 the signature says 86 year model. king pins?? the best way to correct caster is with offset radius bushings and you have done that. this lowers the rear of the radius arm pivot point. the second is to use shorter springs. I know. not a good thing to say. but that will raise the front within the geometry range and bring in the caster and camber. Yes, 86 F250 and F350 4X2 had king pins, last year for them. From all the reading I have done, raising the ride height should add positive caster and camber, and lower ride height should reduce the caster and camber. I can definitely tell a difference in how it steers with the higher ride height, it's better than it was before but still not what it should be. The last few years the front end kept sitting lower and lower, return to center becoming worse with the lower ride height. Link to comment Share on other sites More sharing options...
mat in tn Posted March 19 Share Posted March 19 Yes, 86 F250 and F350 4X2 had king pins, last year for them. From all the reading I have done, raising the ride height should add positive caster and camber, and lower ride height should reduce the caster and camber. I can definitely tell a difference in how it steers with the higher ride height, it's better than it was before but still not what it should be. The last few years the front end kept sitting lower and lower, return to center becoming worse with the lower ride height. the majority of what I deal with are f150s. however I do have an f250 4x2. on the way the geometry works, there is an arc of movement centering at the radius arm bracket. with the forward/ I beam end clamps the I beam like a c clamp. picture the swinging of a hammer, as it is in an upward angle the head tilts backward at the top yet as the radius arm swings downward at the front, the head tilts forward at the top. if by lifting the trucks stance the radius arm was to tilt lower at the front then positive caster is the result. the same point is made about the sideways swing of the I beam too. so, by lifting the truck at the spring and keeping the factory axle pivot point, positive camber is increased. essentially if you lift the truck off the axle by the spring alone all adjustments get disturbed Link to comment Share on other sites More sharing options...
85lebaront2 Posted March 19 Share Posted March 19 the majority of what I deal with are f150s. however I do have an f250 4x2. on the way the geometry works, there is an arc of movement centering at the radius arm bracket. with the forward/ I beam end clamps the I beam like a c clamp. picture the swinging of a hammer, as it is in an upward angle the head tilts backward at the top yet as the radius arm swings downward at the front, the head tilts forward at the top. if by lifting the trucks stance the radius arm was to tilt lower at the front then positive caster is the result. the same point is made about the sideways swing of the I beam too. so, by lifting the truck at the spring and keeping the factory axle pivot point, positive camber is increased. essentially if you lift the truck off the axle by the spring alone all adjustments get disturbed Unfortunately if the ride height is correct, but caster and camber are off (FWIW, rear ride height needs to be factored in as it affects caster) the only permanent solution is what I had to have done on my 1977 F150 and Darth. The actual I-beams need to be bent. After either was done, the difference was amazing. Darth wears the front tires completely even across the tread and directional stability is excellent. There is the normal king pin stiffness fully returning to center (even had that on our Packard Patrician) on a flat road leading to a slight wander. Link to comment Share on other sites More sharing options...
Nothing Special Posted March 19 Share Posted March 19 .... From all the reading I have done, raising the ride height should add positive caster and camber, and lower ride height should reduce the caster and camber.... .... if by lifting the trucks stance the radius arm was to tilt lower at the front then positive caster is the result.... Maybe I'm thinking about this wrong, but I believe that if you lift a Twin I-Beam (or TTB) front suspension by increasing spring height you will reduce caster and increase camber. I believe that positive caster means the line through the king pins or ball joints is leaning back at the top. As the spring gets longer the front of the radius arm will move down with respect to the pivot point, so the top of the knuckle will lean farther forward, giving less positive caster (and eventually negative caster). And I believe that positive camber means the line through the king pins or ball joints is tipping out at the top. As the spring gets longer the tire end of the I-beam goes down with respect to the pivot point and the top of knuckle leans out more. So that gives more positive camber. Link to comment Share on other sites More sharing options...
mat in tn Posted March 19 Share Posted March 19 Unfortunately if the ride height is correct, but caster and camber are off (FWIW, rear ride height needs to be factored in as it affects caster) the only permanent solution is what I had to have done on my 1977 F150 and Darth. The actual I-beams need to be bent. After either was done, the difference was amazing. Darth wears the front tires completely even across the tread and directional stability is excellent. There is the normal king pin stiffness fully returning to center (even had that on our Packard Patrician) on a flat road leading to a slight wander. there is certainly more "wander" with the kingpins. but if well-greased, they can last a very long time. it's no accident that they were used in so many heavy-duty designs. absence of caster is the only reason I can think of for this. beyond that they rely heavily on good pivot bushings and radius arm bushings to keep things aligned. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 19 Author Share Posted March 19 .... From all the reading I have done, raising the ride height should add positive caster and camber, and lower ride height should reduce the caster and camber.... .... if by lifting the trucks stance the radius arm was to tilt lower at the front then positive caster is the result.... Maybe I'm thinking about this wrong, but I believe that if you lift a Twin I-Beam (or TTB) front suspension by increasing spring height you will reduce caster and increase camber. I believe that positive caster means the line through the king pins or ball joints is leaning back at the top. As the spring gets longer the front of the radius arm will move down with respect to the pivot point, so the top of the knuckle will lean farther forward, giving less positive caster (and eventually negative caster). And I believe that positive camber means the line through the king pins or ball joints is tipping out at the top. As the spring gets longer the tire end of the I-beam goes down with respect to the pivot point and the top of knuckle leans out more. So that gives more positive camber. Bob - I think there's a difference between types of springs. I'm assuming that the specified caster at a given ride height is what Ford expected there to be with new components. And it looks to me like: Caster goes down as the ride height goes up on a 4x2 truck. Caster goes down as the ride height goes up on a 4x4 truck on coil springs, meaning an F150 or Bronco. Caster goes up with ride height on a 4x4 truck with leaf springs, meaning an F250 or 350. Am I reading that correctly? If so, why is that? Link to comment Share on other sites More sharing options...
mat in tn Posted March 19 Share Posted March 19 there is certainly more "wander" with the kingpins. but if well-greased, they can last a very long time. it's no accident that they were used in so many heavy-duty designs. absence of caster is the only reason I can think of for this. beyond that they rely heavily on good pivot bushings and radius arm bushings to keep things aligned. the way you explain is clear and correct. sorry if I got something transposed. but the point is that the wheel axis needs to be trailing the trucks suspension. so that the weighted mass pulls against the friction contact of the road. this is the force which centers the truck while in motion. like the front wheels of a shopping cart. think of pulling a trailer vs backing one up. each behaves drastically different. backing one up, the trailer tries to get out of your way and move to a side yet pulling one it just gets in line and follows. centers. if the radius arm is set where the axis is forward at all, the wheels will be pulled left and right with the variations of the road. if it is zero caster, it will be the easiest for you to turn yet also turn too much (no feel feedback). Link to comment Share on other sites More sharing options...
Nothing Special Posted March 19 Share Posted March 19 Caster goes down as the ride height goes up on a 4x2 truck. Caster goes down as the ride height goes up on a 4x4 truck on coil springs, meaning an F150 or Bronco. Caster goes up with ride height on a 4x4 truck with leaf springs, meaning an F250 or 350. Am I reading that correctly? If so, why is that?.... Sorry, I missed that we were talking about a leaf spring TTB (F-250/F-350 4WD). With the coil spring suspensions there's a solid radius arm behind the axle. As the front end of the radius arm goes down with respect to the pivot point (meaning the ride height goes up) the top of the knuckle leans more forward and caster goes down. With the leaf springs the "radius arm" (the fixed end of the spring, the end without the shackle) is still behind the axle. But it's not a solid radius arm. It bends. So as the ride height increases the "radius arm effect" would have the top of the knuckle lean more forward, making caster go down (just like the coil spring version). But as the spring flexes there would be the opposite effect, bringing the top of the knuckle back. It's not clear to me which effect would win out, but I can see that it would be different (and less pronounced, as those graphs show). Link to comment Share on other sites More sharing options...
FordFETruck Posted March 19 Share Posted March 19 Unfortunately if the ride height is correct, but caster and camber are off (FWIW, rear ride height needs to be factored in as it affects caster) the only permanent solution is what I had to have done on my 1977 F150 and Darth. The actual I-beams need to be bent. After either was done, the difference was amazing. Darth wears the front tires completely even across the tread and directional stability is excellent. There is the normal king pin stiffness fully returning to center (even had that on our Packard Patrician) on a flat road leading to a slight wander. I think I'll try and find a place around here that can bend the I beams someday. I know nothing is binding in the steering/suspension as when I had the truck up on my turn plates the steering turns lock to lock with the engine off extremely smooth and effortlessly. One thing I will say, the truck has always had really exceptional tire wear. I've always heard about twin I beam being hard on tires, well I can't say that's been the case with this one. I do have to grease the kingpins about every 1000 miles for optimum steering I have noticed. Switching to Schaeffer 274 aluminum complex grease also made a very noticeable difference in how it steers and stays in the king pins a lot longer. Where the pins used to take 3-4 pumps of grease to see anything come out now only takes 1-2 pumps of grease. The truck doesn't really wander much at all, either. Link to comment Share on other sites More sharing options...
Recommended Posts