Think tire pressure is an overinflated point? Sorry, bad pun there.
Tire pressure in drag racing is very important if you want consistent numbers.
Watch regular racers. They are constantly adjusting their tire pressure in the staging lanes right before a run. Why? Because in drag racing, especially in bracket racing consistency is what wins. Once you have the optimum tire pressure your car wants you want to run the same pressure from run to run. Now in order to find the right tire pressure, you have to do some experimenting. This may mean sacrificing a few race nights in an attempt to do so.
You will want to make sure your experimenting is done under very controlled conditions so as to make sure it’s the tire pressure changes causing the change in performance. As always, only change one thing at a time so you know where your performance drops or gains are coming from. Now of course temperature and track conditions can change so take all of that into consideration. Try going to the track a couple of times and run at the same time of day. Make sure to be diligent about staging the car in the same way and in the same spot on the track. Track your changes in your log book noting not only the changes in tire pressure, but time of day, lanes, weather conditions, etc. so you can get a feel for what truly caused the changes.
Check first what the manufacturer states is the optimum range. I’ll use my car for example. I have 9” slicks on a 7” rim. Not the best combination I know, but hey, I run what I can afford and that is all I have right now. I run radials and I run 13 lbs. of air pressure in them. Not a lot for radials. Radials tend to run more air pressure and some people who run the same size tire I do run upwards to 20 lbs in theirs. That’s a big difference, but I have a small rim. I came to run 13 lbs by trial and error. I lowered my pressure down in 1 or 1/2 lb increments all the way down to 10 lbs. At that low of air pressure my back end was getting loose on the top end. Not a good thing. So then I went the other way on the scale all the way up to 15 lbs. I ended up just spinning more off of the line. I played with the air pressure and studied the time slips till I found the best numbers at my current pressure. I compared 60 foot times, 1/8 and ¼ e.t. times and even mph to see where it changed. The 60 foot times would tell me if I was spinning more and I paid attention to how the car felt at the top end; like was the car drifting, getting loose, etc?
If you are currently running a certain tire pressure and feel it’s working for you try adding a pound and see what your 60 foot times do. If they get worse, try it again to make sure it was the tire pressure that caused any spin. Keep adding a pound at a time till you see the numbers get worse. Track your changes. Then go back to your original reading and then start taking air out 1 lb at a time. Track those times too including your e.t. Don’t go over or below factory recommendations for safety’s sake. Once you start to see consistent times that is where your tire pressure should be.
The other benefit of doing this experiment is you have a plan for if track conditions change or you are at a track that may not be hooking the same as your normal track. If you find yourself spinning, try lowering the pressure a pound or so and see if your 60 foot’s improve.
Some people say you should do more drastic change in tire pressures to see results. I don’t believe you need to especially in the smaller tires. If you run large slicks you can try 2 lb increments, but I don’t think you need to do much larger than that of increments to find your range. I believe most people are not that far off their optimum tire pressure. More like they just need to tweak it a little.
Once you find your optimum pressure don’t forget to check it right before a run. Heat causes expansion and you may need to take some out. Just don’t do that too soon as there may be a delay in your next run and you don’t want to have to run back to the trailer to get your air tank!
Also, don’t forget your front tires. They are very important as well and adjusting them can be a great asset as well. Some people who may be red lighting just a little can drop their tire pressure a pound or more giving them more rollout and help their lights. Just don’t go too low for safety’s sake. I see some guys in an effort to keep from red lighting take way too much air out of the front tires. They almost have flat front tires. I believe that to be too dangerous. If you are red lighting that much you need to find other ways of bringing the car to you.
Try adjusting your tire pressure as your experiment this month and see what changes in performance it causes. If you find you are right back where you started from, don’t think it was a waste of time. You now know more about what your car likes and it’s one less thing you have to wonder about. Again, keeping everything the same run after run is what consistency is all about and consistency is what wins in bracket racing.
Remember to have fun.
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