Re: Coker whitewalls

Posted by Bob J On 2023/8/23 21:22:28

Absolutely, those are 'gates', where the material fills into the mould around the core. On the whitewall they are trimmed close, leaving nubs, quite often they are left long on the tread's black sidewalls. You will notice a number of them arrayed around the entire surface. The synthetic rubber is quite viscous and does not flow easily so they use a whole series of small gates to ensure a complete fill of the tool. I am sure as hard as they try there is still 'short shots' that either leave areas unfilled, called 'voids' or areas that are not completely packed out leaving the tire unusable as it cannot be balanced properly. Unlike a lot of moulding processes there is no way to recover the material once vulcanized so any tires that are unusable have to be thrown into a machine to be ground into pellets that are used in other lower grade products, which explains their relatively high cost for the ones that work, as well as the tool having so many gates to try and avoid any issues.
BTW, your wheels look fantastic!
Bob J.