Going through those comments, I see a few familiar names, but I thought this one was definitely worth posting here for anyone that didn't watch the video and read all the comments.
Mog
8 hours ago
Ok, so I’m an engineer who’s been skating since 87 so what I’m saying comes from a place of understanding what’s going on here. To understand it better don’t look at the truck with the hanger pointing up, turn it the way round it actually is when you’re skating it, with the hanger to the ground.
When a truck is turning two things are constant: the hanger is parallel to the surface you’re riding on, and the baseplate is oriented in the direction you’re riding. When you lean to one side the base plate tilts on a fulcrum made up of an invisible line between the inside of the pivot cup and where the bottom bushing meets the hanger. Measure the angle between those two and you’ve got a true indication of what’s turning on your truck. Because the position of the base plate is fixed relative to your board, tilting the base plate by leaning forces the angle of the wheels to change.
The angle of the pivot cup/bottom bushing changes how much a certain angle of tilt on the base plate translates into changing the angle of your hanger and wheels on the plane of the riding surface. If you had pivot cup/bottom bushing angle that was parallel with the bottom of your baseplate then the truck could move back and forth without changing the angle of the wheels, so you could get wheel bite without turning, that’s not what you want. The other extreme would be if the angle was really steep, which would mean that a small lean of the baseplate would translate to a huge amount of turn, that would result in really twitchy trucks that would also be really hard to turn, because you would be using a really small lever to try to move it. Finding the sweet spot where the right amount of lean translates to the right amount of turn is the science behind truck turning, and it’s also complicated by the fact that as you turn your bushings compress, which changes the angle slightly. Your kingpin angle relative to the fulcrum angle changes how progressively the bushings compress also, so if this angle is greater the resistance will increase the more you turn. Conical vs cylindrical bottom bushings also effect this.
You can play around a bit with changing the fulcrum angle by changing the height of your bottom bushings or adding or removing washers from underneath them, but this can mess up other things in the geometry like the angle the hanger sits in the pivot cup. This is why indy pivot cups click until they’re broken in when you swap the bushings out for bones ones.
There’s also where your wheels are positioned relative to the fulcrum which changes the way trucks turn, which is one (but not the only) reason why different width trucks with the same baseplate geometry feel like they turn different. On top of all that if the axles are closer in together the same hanger angle describes an arc with a smaller radius, ie a sharper turn.
Anyway I hope anyone who’s gotten this far in has learnt some things about truck geometry and sorry about the essay. In case you’re wondering, no I don’t post on slap and no I don’t have truck madness any more, ace classic 55s suit how I skate pretty perfectly.
Anggita
8 hours ago
You need to make a video about this, Professor 🙇🏻
Mog
7 hours ago
@Anggita making videos isn’t really my thing, but I’m happy for anyone else to use this info to make one
Topic: Truck set-ups (Read 1229203 times)