An example is a track I frequent. The track is normally VERY good with Maxxis being the go to tire. So there was a large race the weekend this happened. Lots of UAS coming, Small blocks and such. Friday night was practice and sort of a drag race bracket style. Wed and Thursday we got an exceptional amount of rain and and the track was ran in for friday and it was very wet, tacky, also incredibly fast. The track record reportedly broken more than once unofficially. On prepped up Vega running low 11 second lap times. The official record stil stands at 11.66. Tales of 11.5, 11.4, even an 11.3 were spreading through the pits.
Come Sat morning it was quite cool, the track was ran in and prepped according to the Owners normal routine, calcium was put down, and everything went as normal. Well, with all the moisture from the previous night, the calcium on top sealed the track off. Everyone was struggling early thinking the track was going to carry over with the moisture and that the calcium would hold all that moisture in and it would be like friday night. Well, it did hold it in, but it sealed off and it was mid 60's and the track just got dry slick. No one could get a handle on it. I've seen this happen a few times, and everyone said, "oh you'll never get anything to hook up on this, we'll just have to wait it out till it starts to get good."
Just before qualifying I made the decision to abandon Vega and Maxxis and go with a Burris for a few reasons. One, prepping wasn't getting the tires in the track, just making them slide. So that told me no amount of prep or soft tire was going to get the job done. Two, the kart was driving off the corner decent if you backed up the entry. It wasn't getting in and then four wheel sliding through the center, but if you backed it up enough it would drive off as good as you could hope. Not fast, but better than sliding everywhere. Going to the harder natural rubber done two things. Still had good grip for drive off, decent roll speed, and could prep them and still actually get bite. But ultimately it solve ALOT, but not all of the issues of driving in and through the corner. Where everyone was suffering was the side walls were just too stiff and the tires couldn't grip through the corners. They needed side bite, and the softer sidewalls of the Burris was just that, it gave side bite. Dropping air can only accomplish this so much on a stiffer sidewall tire. You needed Burris at the end of practice into the first and second wave of Qualifying. By the end of qualifying into the first Consi's the track had started to come around enough the normal tire of choice for this track was starting to come back into play. Mainly due to the amount of karts getting on the track.
The track was harder, which normally would go to a lower 3-4psi Maxxis in the low 50's. But, turns out during that specific event of the track transitioning. It was dry slick and needed a softer sidewall to make enough side bite. Now we weren't setting any records, but it was enough to get the kart back on track for the day. We had decent qualifying positions for most of the races we ran that day and later that night we all went back to Maxxis as the track started to come around and get decently fast in the high 11's again. But, during the day it was way different than normal. But, it was all due to weather and chance. This is one example of many that could warrant a softer sidewall. It's not always about how hard or soft the track is. In this example the track turned out harder than everyone expected. But, it generally comes down to side bite, and I know not everyone can completely change brands.