Tire pressure for drag racing Mickey Thompson et tires
07-29-2016, 11:50 AM
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Tire pressure for drag racing Mickey Thompson et tires
I have 08 vet with super charger needing to know what air pressure to run in Mickey Thompson et 305-30-19.. For drag racing.......--- Any info apreciated...
08-04-2016, 01:19 AM
#5
Drifting
I don't think there is a magic number. it depends on track prep and also very dependent on how hard you launch and how much you let the clutch slip.
Have you already tried them?
Assuming your burnout it well done (often overlooked and or overdone)
I would start them at 18-20psi hot (already a run or 2 with burnouts in them)
launch the car with what you are comfortable with.
did it hook? NO! either slip a bit more, and repeat or drop 1psi
did it hook ? YES! now you can try moving up say 200rpm or increasing tire pressure by 1 psi if you don't feel like increasing rpm launch.
It's not always "X" you need to read the track, the weather and depending if you change anything on your approach.
I'm assuming its a manual but it would be a bit different for an auto but follow the same principle. Feel the car slip, lower pressure, feel the car hook, then launch harder or add some pressure. The more pressure you can apply with good results can help you pick up a bit of trap speed at the end
Have you already tried them?
Assuming your burnout it well done (often overlooked and or overdone)
I would start them at 18-20psi hot (already a run or 2 with burnouts in them)
launch the car with what you are comfortable with.
did it hook? NO! either slip a bit more, and repeat or drop 1psi
did it hook ? YES! now you can try moving up say 200rpm or increasing tire pressure by 1 psi if you don't feel like increasing rpm launch.
It's not always "X" you need to read the track, the weather and depending if you change anything on your approach.
I'm assuming its a manual but it would be a bit different for an auto but follow the same principle. Feel the car slip, lower pressure, feel the car hook, then launch harder or add some pressure. The more pressure you can apply with good results can help you pick up a bit of trap speed at the end
08-04-2016, 01:23 PM
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Tire pressure is only one factor in the launch and it can change during the course of a day. The best pressure is the highest you can get and still hook. In ideal conditions, I've been as high as 32 psi, but never below 17 with a 275/40x17 on a 9.5" wheel. The contact patch wants to be longer (front to rear) than wider. A tall sidewall and lower pressures add length during the launch as the car's center of gravity shifts to the rear and then reverts back to nearly the length of a static patch when downtrack. Tire/wheel weight is important, particularly in the rate of recovery when slippage occurs. Smaller diameter wheels and thinner tire treads keep the weight low to reduce the centrifugal forces.
Prior to your first pass, watch closely as other cars with DR's launch. Notice the length of the burnout and the size of the sidewall. If the car's nose lifts considerably upon launch without noticeable spin, then you can run higher pressures on your first pass, assuming you have similar tires and burnout. If they spin, run lower than normal pressure. Consider 20 psi as your initial normal.
Now look how the lane director is pulling cars from the staging lanes. This is important as you don't want to follow a car running street tires. When you are directed out, pay close attention to where the car in front of you does his burnout and follow his tracks to the starting line.
On your first pass, turn the TC off, drive around the water box and back into it, then in Sport mode paddle shift to 2nd gear and do a 3-5 burnout with the speedometer reading 60-70 MPH. Then shift into Drive and back into Sport as you pull up to stage. Foot brake to 1200 RPM for the launch. If you only spin slightly at WOT (aka controllably) you'll need to either reduce pressure, do a more aggressive burnout, or roll into the throttle. If you spin too much or the backend steps out more than a foot, just abort the pass, since you can't learn any more by continuing. Before the next pass, reduce tire pressure and do a better burnout. If you continue to spin, it's likely that the track prep is not sufficient for your tire/wheel/hp combination and you'll just need to roll into the throttle.
Track conditions (prep, air and track temperature, humidity) will change throughout the day. If you pay close attention to that relationship and your results, you'll start the learning process that will let you make adjustments to compensate before the fact.
Prior to your first pass, watch closely as other cars with DR's launch. Notice the length of the burnout and the size of the sidewall. If the car's nose lifts considerably upon launch without noticeable spin, then you can run higher pressures on your first pass, assuming you have similar tires and burnout. If they spin, run lower than normal pressure. Consider 20 psi as your initial normal.
Now look how the lane director is pulling cars from the staging lanes. This is important as you don't want to follow a car running street tires. When you are directed out, pay close attention to where the car in front of you does his burnout and follow his tracks to the starting line.
On your first pass, turn the TC off, drive around the water box and back into it, then in Sport mode paddle shift to 2nd gear and do a 3-5 burnout with the speedometer reading 60-70 MPH. Then shift into Drive and back into Sport as you pull up to stage. Foot brake to 1200 RPM for the launch. If you only spin slightly at WOT (aka controllably) you'll need to either reduce pressure, do a more aggressive burnout, or roll into the throttle. If you spin too much or the backend steps out more than a foot, just abort the pass, since you can't learn any more by continuing. Before the next pass, reduce tire pressure and do a better burnout. If you continue to spin, it's likely that the track prep is not sufficient for your tire/wheel/hp combination and you'll just need to roll into the throttle.
Track conditions (prep, air and track temperature, humidity) will change throughout the day. If you pay close attention to that relationship and your results, you'll start the learning process that will let you make adjustments to compensate before the fact.
Last edited by HOXXOH; 08-04-2016 at 01:23 PM.