I have an interesting question about bmx grinding.?

Question

are the sparks created because of the surface you are grinding on or the type of peg you use? sometimes when i grind there are sparks and sometimes there are not. i thought that was a little odd.

Answer 1

It's the same concept as starting a fire with flint and steel....or pretty much the same concept as a cigarette lighter that you turn the little wheel with your thumb.  If you have steel with a decent amount of carbon in it and it rubs with pressure and speed against something with silica/quartz in it, you get sparks.  Whether or not you get sparks when you grind depends on the surface of what you're grinding on and on how your pegs hit it.  When you try to catch a spark with flint and steel, it's a low-ratio success for most people...you don't always get a spark at all, and sometimes not a good enough spark to catch the tinder.  

That's all I know about it...you got me curious about the actual science involved in the spark, though.  I'd assume it's the silica that is sparking, not the metal, but I don't know.   It'd be interesting to learn exactly what is going on when the spark occurs.