I ran with a new set (quali, 3 heats and a final) over 2 days, ran the same set the following weekend in practise (5 sessions, 10-12 laps each on a 1km long track) and again lastly the following week. In total the tires went through 4 days of heat cycles with roughly 120km’s on them.
The final practise day I was consistently 1-2 tenths off my best pace, kart was feeling good, then inexplicably I got half a second slower in the 3rd and 4th sessions without making a change. By the 4th session I was consistently 6 tenths slower than I had been the first 2 sessions of the day, and all day the previous practise day. The kart just fell off a cliff. Comparing my data, I was carrying 2-3km/h less through multiple different corners of the track. Literally from one session to the next.
Is this to be expected from punished tires? I get time is gradually lost the older they get, but I didn’t expect such a dramatic and sudden loss. I can’t remember a practise or race day where my times fell off from one session to another so dramatically (without a change in weather) with only about 20 minutes between them, and not having changed anything on the kart.
Other than a cracked chassis or tires that died suddenly, what else could be the cause?