Pedro,
Save yourself time and swearwords! Have old tyres removed by a truck tyre business.
I spent ages on two old cheasy tyres (40-50yrs old at least).
Tried easy things first - no good
Tried sledge hammer - no good, just bounced.
Tried crow bar WITH sledge hammer - no good, tyre laughed at me.
Tried cutting through wall with grinder - no good, just stunk to high hell and got nowhere.
Tried local truck tyre place - DONE, and they now semi hate me.
They will hate me completely when I take another two tyres there this week.
No, seriously, farm the job out!