I've changed the Siracs without a problem, but you absolutely must ride around for a few mins with them just about flat. This will both break the bead and warm them up for removal. It may also wreck your inner tube (if it's not already had it) though..

If you have it, squirt some WD or liquid soap into the flat tyre rim to help it slip off..

As said before: practice, practice, practice, practice and practice some more!!

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