Why do tires have small extrusions?
November 21st, 2011 | 
Author: Question by Oliver: Why do tires have small extrusions?
Every tire I have seen has small, cylindrical extrusions all around the tire. They are located on the tread of the tire. Why are these here? Are they left over from the injection mold process or something?
Best answer:
Answer by Dennis
Yes.
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see tire manufacturing videos on youtube
here’s one I found with google. I haven’t watched it though, but I’m sure there will be related video links if it’s insufficient
http://www.youtube.com/watch?v=dYoItDN2gb0
They are from the molding process. They also indicate that the tire has not been used.
Its the bit of rubber moulding that keeps the rest or the rubber in situ during the injection process.