It's the rubber that burns the wheels and engine blocks. Aluminum liquefies at 1200 degrees. Rubber ignites at about 600-700 degrees but burns at very high temps, 2500 degrees or more.

https://nbcmontana.com/news/local/tire-depot-fire-could-burn-for-several-days_20160512151138618

https://www.youtube.com/watch?v=xvrntMh-eCw

It's the rubber that burns the wheels and engine blocks. Aluminum liquefies at 1200 degrees. Rubber ignites at about 600-700 degrees but burns at very high temps, 1400 degrees or more.

https://www.youtube.com/watch?v=xvrntMh-eCw