The 'nibs' or 'spikes' serve 2 purposes during manufacture, firstly the holes the are formed in allow any air present in the mould to escape and secondly they give an indication of how full the mould was on curing, they all have to be at least 3mm long to prove that the mould was full. they then serve no purpose and will probably be worn off the first time they are 'gently brushed against a kerb!)
Technial name 'sypes'
I think you are referring to sipes (Sypes) which are the little slots in winter rubber.
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