arse_sidewards
Red Skull Member
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On a leaf sprung D50 yes.
On anything with radius arms no. The line about which the arm swings is different.
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On anything with radius arms no. The line about which the arm swings is different.
iadr
Member
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Sorry didn't see replies to this
So you are saying, "pointing the pinion at the T-case yoke", you mean pointing it "up"? If they did that, they end up with negative caster? AFIAK all the braketry is new and custom, so the suspension geometry is separate from the pinion angle. But anyway, sure, if they get it wrong, that is what I am asking. So in theory, if you wanted to check for sufficient caster, that can be done on anything from a flat surface and DIY, to simply getting it on an alignment machine. What caster is good? 7-8 deg for pavement and small tire vehicles. More in this case? I thought if you get too much caster, you get caster wobble? And I thought caster wobble is death wobble.
OK, so a super stiff frame mount, no rubber in the bar ends (Jeep XJ, and IIIRC, ZJ & WK). And caster.
665.0coupe
Red Skull Member
It's my understanding that caster wobble is from negative caster, like a shopping cart wheel. When you push the cart fast the wheel starts to wobble. That's from lots of negative caster.
Tiha
Red Skull Member
Caster is what causes the steering wheel to center itself after a turn.
You always want negative caster. (Top ball joint farther back than the bottom)
3 degrees should be enough. Anymore than that and you are putting undue stress on steering components.
With more negative caster it is harder to turn the wheel, Imagine, with negative or positive caster, when you turn the steering wheel you are trying to lift the front of the truck up.
The ride is worse, draw a line between the upper and lower ball joint. That is where all the road force is pointed. (the driver's seat)
With big tires especially Zero caster is the easiest to turn. But you have to do all kinds of other things to get the truck to drive straight and not get death wobble.
I’m a big proponent of 8° minimum and up to 12° for bigger unbalanced tires. That’s often a point of contention between myself and engineers. You CAN get Deathwobble with 100% tight suspension and 0° of caster. You can’t hardly create Deathwobble with shot rod ends slopped out link mounts and 12° of caster. If you want self centering (return to center) steering you need at least 8°.
See what I mean about contention. Tiha above proclaiming not to go more than 3°. 3 is as good as 0 and with radius arms 3 becomes zero through suspension modulation easily.
Tiha
Red Skull Member
That is a good point. I am thinking of leaf springs. Coil springs have much more travel and change under normal driving conditions.
I don't deal with coil springs, too girly for me
iadr
Member
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- Jan 12, 2023
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Well in the case of a shopping cart, they wobble while still having the wheel way behind the pivot...? I'm mashing together lead and caster as being the same, which they are and aren't. Also how relative it is, they operate with caster opposite of road vehicles.
In a completely different vein, I know in Mercedes they use huge caster- 14* was their standard for decades, and I was told don't operate it without its steering dampener. Maybe they're unrelated, and the dampener is only to add to a "luxury feel".
In muscle car applications you want to run about 7-8, as in a turn it helps the outer tire stay vertical...otherwise you end up needing to run (even more) static negative. Again, that's crutching badly designed geometry. OR geometry designed for vastly different tires and usage cases, which amounts to the same thing.
I'm a car car more than a truck guy, but I am a parts manager at a car dealer, and a pretty dedicated performance oriented DIY modder. I may have gotten the terminology backward- I'll have to check which is negative and positive. So much of what Tiha wrote is preaching to the converted. And I felt the details petered out at the last minute with " you have to do all kinds of other things to get the truck to drive straight and not get death wobble." ha Always leave them wanting more? ;) What kinds of other things?
So I did a Google search caster wobble - Google Search
and boy the dancing around and double talk even in theoretical attribution is pretty.. heavy. From assembly line carts to wheels chairs, there are a lot of wiggle words used.
They all do say add more lead. Caster would be our equivalent, though in reverse, like a bicycle fork.
They also say "Castor Wheel Flutter is caused by harmonic excitation of the castor wheel. Simply put, when the wheel tread deforms and rebounds, due to force"
Oooo, OK. Well, a 37" on 10 psi has a ton more deformation that a 205/40r17 at 38psi and with VR-rating style sidewalls. But logically, observationally how do you separate that from weight and suspension layouts? No a Civic is not going to get death wobble, but tires are not per se why.
Seem to throw a decent amount of science without getting too jargony. Suggestion of the spinning of the casters paragraphs is to me a steering dampener isn't just a crutch but a part of the primary working package. And that the rubber mounted drag link was always a risky thing to put in.
Interestingly rolling friction actually is beneficial.
In a completely different vein, I know in Mercedes they use huge caster- 14* was their standard for decades, and I was told don't operate it without its steering dampener. Maybe they're unrelated, and the dampener is only to add to a "luxury feel".
In muscle car applications you want to run about 7-8, as in a turn it helps the outer tire stay vertical...otherwise you end up needing to run (even more) static negative. Again, that's crutching badly designed geometry. OR geometry designed for vastly different tires and usage cases, which amounts to the same thing.
I'm a car car more than a truck guy, but I am a parts manager at a car dealer, and a pretty dedicated performance oriented DIY modder. I may have gotten the terminology backward- I'll have to check which is negative and positive. So much of what Tiha wrote is preaching to the converted. And I felt the details petered out at the last minute with " you have to do all kinds of other things to get the truck to drive straight and not get death wobble." ha Always leave them wanting more? ;) What kinds of other things?
So I did a Google search caster wobble - Google Search
and boy the dancing around and double talk even in theoretical attribution is pretty.. heavy. From assembly line carts to wheels chairs, there are a lot of wiggle words used.
They all do say add more lead. Caster would be our equivalent, though in reverse, like a bicycle fork.
They also say "Castor Wheel Flutter is caused by harmonic excitation of the castor wheel. Simply put, when the wheel tread deforms and rebounds, due to force"
Oooo, OK. Well, a 37" on 10 psi has a ton more deformation that a 205/40r17 at 38psi and with VR-rating style sidewalls. But logically, observationally how do you separate that from weight and suspension layouts? No a Civic is not going to get death wobble, but tires are not per se why.
Castor Wheel Flutter - Bulldog Castors Blog
What is Castor Wheel Flutter? Castor Wheel Flutter is a phenomenon whereby a Castor Wheel attached to a piece of equipment, for example a Trolley, shakes or rotates uncontrollably from side to side. Many people will have experienced Castor Flutter at the supermarket. Ever noticed how one of the...
www.bulldogcastors.co.uk
Interestingly rolling friction actually is beneficial.
SHARPMACHINE
Web Wheeler
I really like this idea.Made them.
Current stupid duty.
F***roads
Well-known member
long story short, did an at home alignment, drove well. finally got a real alignment, dude said I had "too much" caster. and set it to 4.5. hated that BS and dialed it back to about 8 and it drove nice again. SD60 for reference. will always run more then "spec"
iadr - solid axles w/leafs typically have no caster adjustment per the FSM. (Most alignment shops will blindly parrot that.) Collapsed bushings, sagged leafs, shims, and/or other suspension mods often erase the scant few degrees (1-3ish) the factory built for; and then the trouble starts. Modern IFS and strut suspensions also have very low caster settings which makes the idea of 5-10 degrees (for a solid axle) seem outrageous.
That factory spec, which is some enginerd bs to begin with. On a Superduty that is meant for 245/70/17 10 ply tires with 70 psi of air in it.
I’ll never understand the mentality of a people who throw away 99% of factory engineering because it didn’t work for what we’re doing. And then want to fight to the death over a few degree’s of caster when we’re running bigger tires on usually a much lighter vehicle with far stronger steering.
Time to highjack a thread. bdkw1, I’ve never built go fast TTB. I’m a geometry snob and I strive for perfect. I know it would require swingers, but how do you go about figuring out exactly where to put all the pivot points to completely eliminate crazy toe change in suspension cycling? These guys are good guys, they try hard, I’m not bashing them. Where would a guy start to clean this up?
Draw a line through the radius arm pivot and the beam pivot. The inner tie rod needs to be inline with this pivot axis. moving it forward or backwards to clear stuff will also move it in and out. It's not hard to figure out once you look at it.
Moving the radius arm pivots in towards the center of the truck can help shorten up the tierods and get rid of some caster change.
Moving the radius arm pivots in towards the center of the truck can help shorten up the tierods and get rid of some caster change.
Does doing equal length beams make it more difficult or less difficult when positioning the swing set? Seems like it would only be easier but on an OE frame I could see it adding a level of difficulty
'84 Bronco II
El Chingón
Obviously some sort of swing set or cross-over setup is the best answer, but here's my 90% low-effort solution. You still get some bumpsteer, but it actually toes out at full droop which helps suck the suspension down when running soft springs. When the suspension toes in during droop, that is what causes the crazy jacking effect TTB is notorious for. I measured mine when I was building the steering and I think it toed out 1/8-1/4"at full droop, but I don't remember exactly. Personally, I think it is a lot better than a K-link setup like Ryeder is running in his Ranger.
Here's a decent picture showing the steering linkage:
Flexed:
Unfortunately I did't take this picture head-on, but the tires are not toed in:
Equal length doesn't make much of a difference. The frame will be in the way no matter what, it's kind of a Murphys law deal. On TTB's, the P side lines up pretty close with the steering box. Close enough not to fuck with it. Single swinger work well on these. Drop Dien brackets are the devil. They create a lot of bumpsteer. I think the largest drop pitman is 2"? So anything more than that is bad.
Going with the longer D side tierod makes the inner pivot move up and down more. Probably not that much change in bumpsteer from stock. Go single swing, not hard to do. Look at Autofabs steering and copy it.Obviously some sort of swing set or cross-over setup is the best answer, but here's my 90% low-effort solution. You still get some bumpsteer, but it actually toes out at full droop which helps suck the suspension down when running soft springs. When the suspension toes in during droop, that is what causes the crazy jacking effect TTB is notorious for. I measured mine when I was building the steering and I think it toed out 1/8-1/4"at full droop, but I don't remember exactly. Personally, I think it is a lot better than a K-link setup like Ryeder is running in his Ranger.
Here's a decent picture showing the steering linkage:
Flexed:
Unfortunately I did't take this picture head-on, but the tires are not toed in:
'84 Bronco II
El Chingón
Certainly not ideal, but my setup is far better than stock and pretty much as easy as building steering linkage for a solid axle. The truck was undrivable with the stock steering linkage and these soft springs. I do still have bump steer, but it is way better than factory and I don't get the jacking from toe in anymore.
Stock linkage with a drop pitman arm and the same springs and shock from the first set of pictures:
TTMotorsports
Red Skull Member
If you swapped the heims so the tie rods pivot from point furthest from the wheel it would help. Still would be far from good.