This is my understanding of the bushing stackup of these trucks. Red is kingpin. Purple is baseplate and hanger. Yellow is boardside bushing. Light blue is roadside bushing. Dark blue is kingpin nut.
The baseplate has no relative motion, because it’s fixed to the deck. The hanger has no relative motion because it’s constrained by the pivot cups. The kingpin has no relative motion (when pre-loaded) because it’s constrained by the baseplate on one side and the nut on the other side.
The only part with relative motion is the kingpin nut, which can only pre-load the roadside bushing. That pre-load tension wont be transferred to the boardside bushing because the hanger is constrained.
The reason for this is the dual pivot cup design - it constrains the hanger to only move in the direction where it’s supposed to move, and this removes all slop from the system, rider input is converted to steering output much more predictably. This could be taken care of with a spherical bearing in the hanger in a conventional RKP, however those have the tendency to transfer road vibrations very well and you need to modify your bushings to fit them which is quite a hassle. (edit: and they are also notorious for breaking kingpins in half)
Couple this with the fact that the boardside bushing no longer has to support the weight of the rider like in a traditional RKP. Placing the rider weight on the boardside bushing removes a lot of the compression that you set by the kingpin nut tightness, and therefore RKPs in the center position are looser and tighten up exponentially the more you lean.
This dual pivot cup design makes sure that the bushings are only there to restrict turning, and therefore you the center is much more direct and predictable and the tension builds up linearly not exponentially.
All the stability gains from above can be traded for more turning with softer bushings, and that’s what really make these trucks magical. They are inherently so stable that no matter how loose and turny you make them they still remain stable
The trucks are a floating “kingpin” design, although technically I think it would be considered queenpin. The queenpin is custom and has a step that the washer sits on that allows the bushings to compress equally.
When I’ve been showing people the trucks, “pivot cup” feels like the wrong word… the mechanics is slightly different. Also possible I’m just being pedantic.
A pivot cup takes the normal (direction) load on the inside center of the cup
On Tito’s trucks the load is on the outside face that’s against the hanger, like a flanged brass bushing.
From what i can tell of the pictures, the pivots do not allow for any significant movement besides the intended rotation. The ability to preload both bushings is by having the kingpin float inside of the baseplate, instead of sitting on a flanged surface - basically, the kingpin is not actually retained in the baseplate, there isn’t a lip preventing it from falling out of the plate in either direction. this means it’s only retained by the bushings compressing against the hanger, and tightening it would effectively slide the kingpin up out from the baseplate towards the hanger. The baseplate just retains the kingpin from shifting out of position, not axially moving.
There is no movement only the dampening of the urethane pivots that take the edge off aka not as harsh as metal on metal
Speaking of suspension, the first prototype of the duality was on my suspension board. A cnc machined version of this with updated geometry is the ultimate goal.
Had a T-race session yesterday and got a little bit of footage
After this session I am actually feeling pretty confident that the 25/10 angles will work for the waldshut race too next weekend. That’s a DKP dominant track. These trucks turn that good.
