First post! I know every kart and driver is different, with that said what have you guys been successful with when temps go from sunny and 80 to misty/damp and 55* regarding tire pressure?
Lower same, higher?
We have a pretty good running kart, nice weather tire pressure I have a good number for us, but the weather change I tried to drop them a bit( potentially given bad advice) and this poor kid was understeering and over steering all over. No other changes.
Kid Kart, MG Red’s. we have max dia. allowed normally ( not this last race)
Higher pressure will make the tire stiffer and reduce the contact patch, so in damp conditions it will ‘cut’ through the moisture better and generate surface temperature better. So generally you will go higher when the track is cool or damp.
Lower pressures will help the tire flex and fold better, but reduces the stiffness of the tire overall, so the tire surface won’t be worked as hard. It also increases your contact patch, requiring more work to heat the tire up. But if the tire flexes more, it will generate core tire temp as you run on it.
In general, I would imagine a KK is going to want higher pressures, almost all the time, since it doesn’t produce enough force to actually work the tire as it’s designed.
Tire temp is the thing you’re really going for when adjusting pressures. If the rubber does not heat up sufficiently, it will not be in it’s peak zone of traction and performance will suffer. When the track is cold, the tire does not have enough lateral load potential to flex and generate core temperature, because the track surface is slippery and can’t provide friction. In that case, you’d go to a higher pressure to get higher temps on the surface of the tire and try to generate grip that way.
If the track is very hot or sticky, you need to be careful not to flash-heat the tire surface by raising pressures too much. If you overheat the surface of the tire, it will also lose traction. In these cases you are looking to manage surface temp, while letting the tire flex enough that it heats up internally.
In the end it’s a balancing act, but generally the cooler the track temp, the higher tire pressure.
thank you! That makes sense. To add some salt in our own wound and I think proves your point aswell we are nearly 50lb over the minimum weight. That adds to the tire flexing more with less pressure which would only hurts the situation. We usually run 22frt and 28 rear and the tires will tack to the return road when I lift it onto the stand and it performs well overall. Next cool day in 2 weeks I will ry the same or slightly higher then we usually have.
The other fun aspect with KK is that many series and clubs have tire pressure and circumference limitations for the tire. Too many parents trying to play games with rolling diameters to overcome the fixed gear ratios. Lol…
So you can be a bit limited in just how high you can go in the cold and wet conditions if you run in a series or club that check for that.
For example: TSRS has a 20psi HOT pressure limit all corners with a maximum 33.75” rear circumference limit.
Yeah but this is an absolute must. KK is good for getting started, but I am ready to move on as soon as my kid is remotely ready. There’s far more speed to be gained with a big diameter than you lose with handling. The corners are just too slow in KK and too far apart (time-wise because of the low top speed) to truly build heat and get the tire into a window where pressure matters. The best evidence I have for this is that I have to scrape my daughter’s tires when she runs KK but not when she runs a green slide and 6k limiter. Same driver, same track, same tires, same weight. She does prefer the flex you get with lower pressure, so I run lower in the front (obviously) but I’ve ran 50+ psi and saw improved times in practice.
On purpose, I tried to see if there’s a limit, and there’s not: bigger tire = lower times. As long as she can keep it pointed straight, haha. With KK, top speed is king because it is also the easiest pass. The worst part of KK is when a kid has a run on another through a corner but their positions just freeze and hold on the chip until the next corner. It forces some pretty sketchy passes unless you have even a 0.1 mph advantage.