Amazing video today.... the best way to understand why is to read their email:
Hi, I have had this project influence by iceroadracing and ice speedway what is normal motorsport in here Finland. So i did spike tyres on my old hybrid tires 37mm with screws and put inside 28mm tyre to protect tubes. Tires rolling resistance sucks at the moment but biking on ice velodrome is lot off fun, corners can go as fast as straight with 7mm spikes.
Here is link to video what i did made for first test day on ice.
Thanks a lot Tuomas, enjoy your ice!