Track Tac

Air pressures on dirt....discussion

W

W5R

New member
I had a couple new racers ask me a couple of questions last week that I honestly was not sure how to answer. We were talking about air pressures racing on dirt, and I was asked "How do you know when you have the right air pressure for the track you are racing on or track conditions?" I really wasn't sure what to say other than to use lower air for low bite tracks and higher air as the track gets more bite, since that is what has always worked for me. What do you folks say is the best way to know what the right air pressures are for a given track? Banked vs flat track I assume also is a factor, as well as how the tires were prepped, and total kart weight, but I could be wrong. I usually just guess based on what the track looks like and adjust from there based on what the kart is doing. It has me wondering if maybe I have been leaving speed on the table myself by not doing more with air, such as using higher air when I possibly should be, to help get the kart rolling better down the straits. I have heard that you can check the air pressure after coming off the track and know based on how much pressure you have gained, whether or not you need to raise or lower the air pressure from where you started, but I'm not sure what is the right amount of air to be gained in a race, or how much is too much? It seems like my tires normally gain around 1psi, sometimes less, during a run, usually with the RR gaining a little more than the rest have, and the left front gaining the least of them all....does that sound right?
 
A stop watch may never lie but it don't tell the whole story especially on air PSI
How many times have ya herd I had the fastest lap times. So what ya did not win LOL

I will take the kart that holds the line and runs the same time as the one that drifts up out of the corner on exit.
Most of the time that's the kart setup correctly and not over aired.

If you can get on a track that's good on bite and just keep round robin it and only add PSI every 5 laps you may learn a bit.
The few times I did it .In a nut shell the kart will increase lap times to a point, Then stop getting faster. Then start handling worse but run the same times. You now found your PSI for that situation that day/time of day. Not sure if that helps or not
 
We have a track here that always has good bite any given night, perfect kind of track to test and tune on. I havent played with air pressures much, i guess that is something i need to try because it sure dont seem like many want to talk about air pressures...
 
One option may be tire temps. Many use tire pressure increases but that doesn't tell you if the heat was all in the center or the edge. Take temps Immediately after exit on all four at a minimum of three places across the tire. Too much air? hot in center. But maybe that's fastest. Takes tons of time and testing eliminating the variables, and they number in the thousands.
 
Not sure they don't want to tell as much as every set-up /situation is different.
Had a tire guy help one night he adjusted each tire individually.
Think sidewall stiffness is a part of it.
 
If track has grip, go up maybe 2psi and see what happens. then you will know. try 1psi see what happens. then try 3psi or more. most people are surprised by the results. but do not try this until the track starts coming in. usually last practice. I prefer to run as much as possible and still stay on the track. a lot of karts are too tight losing speed. a free kart is faster and a little challenging to drive. as a general rule, if you can drive anywhere you want to go, you are prob tight or binding.
 
We've been on 6 and 7 before when the track is laying rubber down and when the track is good and hard, a lot folks think the track is laying rubber down but its really prep laying down on the track because its damp, just have to check the track during down time when you can...
 
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