Misaligned pivot pins

Most TKP trucks are built with their pivot pin not parallel to the pivot axis. This is most probably a design flaw that early manufacturers couldn’t care less about and later manufacturers haven’t even noticed (more on this, here). But what exactly happens with the interface pivot pin – cup when the truck turns and the pivot pin unavoidably binds with the pivot cup?

Forum member notices recurrent damage on Bennett pivot cup and pin, at exactly the spot I predicted. Installing a spherical in the hanger obviously exacerbates the problem I am describing here.

Here’s my take:

1) At the beginning of the turn, the tip of the pivot pin rotates (as intended!) at the bottom of the cup, while the upper part of the pin slides towards the lips of the cup.

2)Then, the pin’s upper part starts compressing the lips of the cup, while the tip of the pin starts sliding towards the sides of the cup away from the center.

3) Then, the “bind”: either the truck abruptly stops turning, or (more probably) the pin starts sliding out of the pivot cup (see image right; damaged pivot pin at exactly the spot where the pin collides with the lips of the pivot cup, as predicted).

4) Then, the tip of the pin reaches the lips of the pivot cup and the truck can continue turning without pressure from the sidewalls of the cup [I’d bet here is where the “dive” happens]. Simultaneously, the axle is displaced (how much depends on the pivot pin’s length and width), but I don’t know if that’s perceptible in this context.

I would be embarrassed to be a manufacturer of any one of those trucks, honestly.


Appendix
Generations of Bennett users have had to deal with the issue of recurrently damaged pivots. Here’s James Peters, widely viewed as the “godfather of LDP,” who generally doesn’t even use spherical bearings in his Bennett Vectors (because, according to him, “they dive less” with one).

Also, Griffin Skateboards boss reports seeing the same problem “a few times” (but misdiagnoses it).

10 thoughts on “Misaligned pivot pins

  1. How about replacing whole hanger with one of these (removed links to roller skate truck hangers and replacement spherical pivot pins commercial products) or making a mod alike?

    1. Thanks for reading!
      How about truck makers learned how to make trucks? 😉
      Crappy trucks are not an inevitability of life. Use your power as a consumer and reward manufacturers who at least understand the basics of logic.
      As for the specific suggestion: no, I wouldn’t say you can just replace a specific hanger with a random other hanger. The distance and the angle between the pin and the bushing seat has to be exactly the same, or else the hanger won’t sit flush with the bushing and possibly the hanger will touch the kingpin every time you turn.
      Changing the pin itself, while paying attention to the above conditions, would work better. In which case, I really must ask: do you prefer doing this instead of simply buying a non-crappy truck to begin with?
      If you’re handy enough and you own a workshop and tools and you have time and willingness to learn, you could always just build your own from scratch. I am happily riding my friend’s home made trucks, who was into this sort of thing.

      1. Sure I’d prefer buying a non-crappy truck. Could you advice a model with the same turn (LDP-related front truck characteristics) and price as Bennett? DTs are not an option for the most riders I think

      2. Thanks for your reply! You are going deeper in LDP discourse now and that’s awesome!
        I address the exact same point/question you make in my “Case against Bennett,” specifically in the third section. Let me know there what you think and let’s continue those streams of argument. Btw I’ve also looked into DT in “You tripped up again, Dont Trip!”
        Please understand I would be just copy pasting, if I answered here anything more than: your assumptions about Bennett and DT reflect widely held beliefs for which I had been unable to find well-grounded, convincing evidence. In this site you will find why. So, please do have a look around and let me know if after all you disagree. I’ll be extremely happy to start a dialogue about central issues.

  2. I want to enter in the discussion,

    I’m surfskater and tried a lot of different truck types. What surfskate makes so awsome is the ultra turny of those boards. For the turn only 2 major points are relevant: Geometry and truck dicstance (wheelbase).

    The Bennett looks very similar to Carver CX, but think CX is fixed reverse. I tried CX on a long Wheelbase and I figured: The longer the Wheelbase the faster you can pump. But for me: The CX is to fine for using it as a pump-truck only. If you want to compare Bennett and Carver CX (or something else), you have to mount it on the same board with the same wheelbase. I think: There is no big difference between Bennett and CX, esp. once you’re wedging it to 90°, so the geometry of Bennett and CX becomes similar.

    Just to increase the discussion here: I mounted Revenge on a long wheelbase board with 85 wheels. This is a really nice feeling. It’s surfy because front and back truck turns and you can gain easyly speed and ride fast, OK its not optimized for LDP.

    Kindly
    Me

    1. Thank you for your input, I appreciate it! I agree, for any specific use case, what matters is the overall geometry (angles and wheelbase), rather than components. If only more people understood this, consumers would waste less money and time and manufacturers would genuinely improve their offers. Oh well… 🙂

  3. There is one part that is noteworthy with these misaligned pivots, especially on the original DT-Bhanger – which initially wasn’t designed with a spherical bearing as pivot. I still own this old pivot cup version I bought in 2016 and used to be under the impression that the manufacturer was well aware about the misaligned pivot, since the design has one thing that makes it “work“ – an indentation around the pivot that prevents the pivot cup from being destroyed.
    The main factor I found interesting about this flawed design is the fact that once the pivot gets pushed out while turning, the riders own bodyweight forces it back into position, regardless of bushing durometer, that means a strong return to center. So far, I did not destroy a single pivot cup in the truck, only switched from the stock Riptide APS to their WFB cup due to less squeakyness. Maybe I didn’t destroy them because I‘m a flyweight, can’t tell.
    I‘m a bit confused about the fact that they switched to a dual spherical design, which basically removes the entire funky movement the Bennett had and makes it rather pointless since the two balls create a linear actual pivot axis. I was under the impression the Bhanger was meant to be a bad design done right kind of deal, just to replicate a flawed classic, but DT seems to be less aware of even the things they’re doing right. I can only assume the CAD-design was developed by a third party that knew what they’re doing.

    1. I’m afraid I don’t see anything but conjecture in your message, and an effort to justify a mistake that has never been corrected by anyone, let alone DontTrip. The one thing that would be a point to discuss is your claim that they sphericalized the pivot pin on the first versions of the Bhanger. I don’t want to seem too mistrustful, but would you please post a photo for us?

      1. Of course, please excuse my mediocre camera.
        https://i.imgur.com/3AS2bBr.jpg
        Not sure how noticeable it is, but the pivot is not fully spherical, the center is cylindrical and as wide as the pivot cup.
        I‘m not trying to justify this bad design and wouldn’t even recommend DT products to anyone at this point.
        I didn’t even use this truck for years after realizing the correlation between breaking kingpins and misaligned pivot axis. However, pivotcup doesn’t get damaged on this truck, but I assume it likely would be if made of rubber like the original Bennett.
        On a sidenote replaced the steel pivot with a polymer spherical by the brand Igus (which I found through your article about the Curfboard truck). Their polymer is designed to glide and as you’re probably aware the spherical glides up and down when turning, which causes damage by scratching on both the kingpin and spherical when using a steel bearing. So far this works just as good as a steel bearing without scratching or clicking (and rust) while, to my logic, also causing less stress to the kingpin.

      2. Thanks! I admit, i thought they were just reproducing the Bennet Vector blindly with a fat cylindrical pivot pin with zero tolerance. This does change things a bit, I must revise my other article a bit. I’ll use your photo, with your permission. It’s obvious from your photo they knew the pin doesn’t just rotate on its axis. The cylindrical bit is not a good idea though, but probably the pivot cup can tolerate that little part squeezing it. Not ideal, but, whatever.
        The spherical bearing of the pivot glides up and down? Would you please elaborate on this? Because a spherical on the pivot and a spherical on the hanger/KP are sufficient and necessary to define a pivot axis. So, I would think the two sphericals do remain on their respective pockets.
        Thanks for the comments Fab, i am fully intrigued now:)

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