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).

4 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.

Leave a comment

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.