Think you guys could tell me how I broke my kingpin?

**Irrationalist** · 03-02-2010 03:31 AM

So I was doing a quick nightly run on campus and half way down I felt like I hit a huge rock which turned out to be this.

I kept going thinking that I was lucky that rock didn't stop me and then at the bottom of the run tried to do a coleman which just sent my hanger off my board and me to the ground. Thankfully scuffing up my baseplate rather than my new Supermodel. After getting up I found the other piece.

So does anyone have any ideas why this happened? I hadn't done anything I hadn't done a million times before. Was a little surprised that my kingpin broke in half to say the least.

**gavmck** · 03-02-2010 04:04 AM

It was probably weakened by something earlier. I snapped a randal kingpin just cruising to the shops after about 3 years of riding. Now all me boards are setup with grade-8 kingpins flipped from stock randal position. Haven't broken one since...

**Big Mike** · 03-02-2010 06:56 AM

Originally Posted by Irrationalist

I hadn't done anything I hadn't done a million times before.

Metal can only flex and return x number of times before it fatigues and snaps.

Find yourself a shouldered (not threaded all the way to the head) grade 8 bolt the same length and put 'er back together.

gavmck gives us a good tip above - flipping the kingpin on a Randal baseplate puts the shouldered part of the kingpin in the base, instead of the threaded part. That way the stress is borne by a solid cylinder of steel instead of a cylinder that has had threads cut in it. Much stronger that way...

**Ogre** · 03-02-2010 07:03 AM

they will also break where the threads are cut (creating a stress riser) Try and get a grade 8 and flip it.

**Irrationalist** · 03-02-2010 01:28 PM

Haha, thanks for all the input guys. I was just a lil stunned to run over my kingpin.

One last thing, how do you tell a bolts grade?

**Ogre** · 03-02-2010 01:31 PM

Grade 8 will have 5 hash marks on the head (I know..weird huh) Grade 5 will have 3 Grade 8 are normally goldish in color

**Mile_High_Mark** · 03-02-2010 01:35 PM

Hex Bolt Identification Guide - Engineers Edge

**TIMORNE** · 03-02-2010 01:39 PM

hydrogen embrittlement!!

**fuzzy_nickels** · 03-02-2010 01:47 PM

on my street board i noticed destruction of king pins were directly corrilated to the hardness of my bushings, so i wenr to grade 8 hard ware and i ended up snapping the base plate, never heard of it happening on a long board, but thought it was worth mentioning, the stress has to go some where, guess the bolt was more rigid than the base plate.