Regardless of air or track temp, you should be aiming to have the tire come in at a certain lap. For me it’s usually 4-ish laps into the run. This may vary for you depending on the race length or track.
If the tire starts to go away at the end of the run (usually overheating) then you need to drop pressure. If the tire comes in after your target lap, raise pressure.
On that thought… how do you tell, exactly, when a tire has come in to the ideal.
For me, it’s just that after a few laps it feels like it got to temp and is behaving. The tire works and holds as expected and I’m able to go fast. When cold, I feel little bits of push that progressively diminish as tire warms.
I ask because I don’t think I’ve gotten to feel what overheating late in heat feels like. May be a function of hard tires.
My son’s fastest laps are always his last lap or two, almost regardless of length of race. Does the tire coming in correlate to the fastest lap? I also wonder if it just takes him that long to get into a rhythm.
This weekend should be interesting, as Saturday has a high of 70 and Sunday a high of 86.
I did a 22 lap stint last Friday and the tire was “in” on lap 4 but my best was lap 21. So it depends on how long the tire stays in the working temp window. You might nail a lap right when the tire comes in or you might take 15 laps to nail a lap.
Given that I know what pressure you’re running, I would say some of that is why your best laps come at the end. But of course it could be just Blake finding the rhythm late in the run too.
Harder tires will typically come in slower and take longer to over heat. So maybe if you are on hard rental tires vs the Evinco Blues/MG Reds???
Climate where you are matters. We are going to be racing in triple digit temperatures in TX where the asphalt is hot enough to burn bare skin. In those conditions, you can most definitely over cook the tires by the end of the run and have to balance how soon tires come in versus where they fall off.
Also, track layout matters. We have a small club track to liked to run when we were in 206. It put huge amounts of load on the tires and felt like you were always turning. It was also the most physically demanding track my son drove on. We had to run our lowest pressures there to avoid cooking tires by the end of a race. By comparison, we run a couple larger flowing tracks that need more pressure because they just don’t build heat as quickly in the tire over a lap.
Of late I’ve been indoors where it’s cool and the earth doesn’t add heat to the racing surface (which is wood). I have yet to see if overheating is possible, in that to date, the kart just keeps getting faster and faster with more laps. The problem is the longest sessions are only about 15 laps so it’s more about getting to the ideal before the race heat is done.
Someday I will experience greasy hards, but not indoors.
Yes and No…I generally understood what you are saying but more specifically how much adjustment in air pressure is required for say a sunny vs cloudy session, or 70* vs 80*. With the old tire, it didn’t seem to change much but the new tire, 1lb seems to make a difference.
KA100. Ran a set of new mg reds with a 49.96. 56 laps later ran a 50.38. Happy with them so far. that was after 5 heat cycles. Going to use them for one more practice day before i ditch them, but happy so far. Not sure what everyone else has done with them
At the USPKS race in Happy Hour, I went about 0.3 slower than the top guys on new tires and mine were down to the cords. They feel pretty consistent for me.
Glad to know others are getting the same. 49.85 is currently the track record for KA so to be half a tenth off after 60 laps is pretty much as good as anyone could ask.
have you found an ideal pressure for these tires? they don’t seem to get super hot from what i’ve seen. I only went from 11psi to 13psi after 12 hot laps
There is no ideal pressure, only ideal temperature. Depending on weather, grip level, track surface and conditions, they have been found to work anywhere from 8-25 psi cold.
I ran 15 psi at USPKS Dousman. I ran 20 yesterday at Dousman with cooler temps and less rubber down.
In terms of “spring rate” of the tire, they are designed to work in the 10-15 range, but if you can’t get heat into the tire at that pressure you need to go higher.
oh wow. 20 starting pressure or warm temp? I definitely need to do some experimenting now. thanks! would having a temp gun to shoot the tires after sessions help get a consistent pressure?
Yes, I have a temp gun but the batteries are always dead when I remember to use it.
Put some lithium batteries in there and you can forget about that for a couple of seasons.
I’m currently experimenting with how these fall off. Today wasn’t my greatest driving, so that was a significant factor, but I have noticed they need more heat to generate grip as they age, which means higher pressure and aggressive attack. It makes sense but it also is a little counterintuitive to me since the thinner carcass of a worn tire should build tire pressure faster, but the lower grip when cold means less heat buildup. It is like they need a head start building heat, and then they get fast. As they cycle out, the difference between “off” and “on” seems way more pronounced.
I’m at 21 cycles now on this set with an all-time PR at cycle 12. All cycles on a new-to-me used kart, so there’s a LOT of very unscientific variation in this experiment, haha. PR was also with a strong draft from chasing a faster driver. Still, it feels like they do still turn on, but it is now taking a couple sessions. Trying to gently approach the limit doesn’t work anymore when running “reasonable” pressures; you just run out of time before they turn on. I’ve not pushed my pressures much higher yet, but that’s the next step.
TL;DR: even after 20 cycles they can run pretty well, not nearly the falloff of the SH for me, but it is taking a lot of work to get pace out of them. I have no doubt the fast guys can be quick on old tires, but us fledgling guys will see more drop off.
I would agree these tires stay consistent through multiple cycles. They do seem to wear a little quicker than the old SH. Maybe its me, but they don’t seem to be happy being rotated and like to be spinning only in their intended direction
21 cycles seems really high. Is the track high on tire wear? Im on cycle 7 right now and wondering when I’m going to see a significant drop.
Depends on the layout. Main layout isn’t too bad for wear. I’ve been flipping the fronts a couple times.
I am running too many heat cycles because, with the summer heat, they were coming in pretty strong before the last race, and I hadn’t sat down and counted the cycles. Considering that one day can be five cycles, it can sneak up quickly.
I have a race next weekend, so I’m just still running them now to send them off and learn what I can about pressures, temps, etc. New tires go on soon.
So here’s my situation I got a race tomorrow at T4. I normally race on Vega Reds in the 206 legends class. I am very familiar with the Vega tires and know that there is a difference in qualifying on brand new tires as compared to used tires probably .2 seconds. Wanted to know if there was much of a difference between brand new MG red and used. I bought a brand new set and didn’t know if I should use them in morning warm up or save them for qualifying. Thinking about tire pressure around 12 psi. Temps are high down here in Tampa