I drag (weekend footbrake) my 2003 Touring Z on weekends and have a question about launching. The car is totally stock and an automatic.

I recently switched the back tires from Bridgestone to MICHELIN PILOT SPORT A/S (235/50ZR-17) because I was told they were sticker and would result in a better launch.

I now get more tire spin at gitgo than before, and my times are about the same as before.

Would it be better to launch at a lower RPM or lower Tire pressure? (I currently launch at 2000rpm and 35psi on the tires (recommended pressure)?

Thanks in advance for the advise.

 

Some recent time slips would be helpful.

 

1/8th slips from this past Friday:

60ft.....2.196
330ft....6.196
1/8mi....9.44
mph......74.71

Those times are pretty much what I had with the Bridgestones, although I did pop a couple of 9.1's and a few 9.5's with them.

 

It's hard to say. It depends on the tires and I know little about your tires. 35 psi seems high though. I always got best results with 25-30 psi and 3k launch with all street radials I used. You need a little bit of spin to get the rolling inertia, just not too much. No spin = bog. I also always did a little burnout while in pre-stage to warm up the tires. experiment around and find your sweet spot.

Oh, this was also a manual tranny. I've never used auto so I don't know if you'd launch the same or not.

 

Street tires, as opposed to slicks, have a sturdy side wall. They will never flex like a slick. That said, I have raced with several brands of street tires. 35-30 PSI works well for me.

 

You are welcome.

 

+1 I always run my street tires at about 35 psi.

 

3 problems with what you say: (my opinion of course)
1 - 30-35 is great, I like 35 or so cold for my runs.
2 - You don't want to really spin the tires much, the suspension is too prone to wheel hop to try that. Learn to stay on the limit of grip and the mild wheel spin you want will come. My best runs usually have no spin, but some of my very good runs will and the car feels faster (and traps higher) because of the spin. But saying to try for a little spin is setting a first time to the track driver up for failure
3 - The burnout on street tires is important, but not for heat. You want to keep the burnout short, maybe 3 seconds and while rolling forward. You do this to get any dirt, chemicals, water, rocs, etc. off your tires. You pick up a lot of crap in the staging area and the waiting lines.

Nothing major, and I know that wheel spin works in some cars, solid axle especially, but from my experience the transition from slip to wheel hop is too hard to predict to aim for that hair of wheel spin.

 

I run 18-19psi when drag racing. The reason why you want to run so low of a psi is to increase contact patch. You want the sidewall to flex and create a greater contact patch. With our low profile tires, which come with stiff sidewalls, 30-35 psi is not nearly enough to get any decent flex, You've got to go below 20, and even then they hardly look flat.

 

Don't make me go into it again - just trust me that you are getting less patch because the stiff sidewall (which you seem to be aware of) carries more of the cars weight than the air in the tire as you decrease the air pressure (to an extent usable in motorsports).

 

Reducing the air pressure still allows the sidewall to flex more, regardless of how stiff it already is. Therefore it still helps increasing contact patch.

I mean, don't quite understand why this is even an argument when I've tried running stock tire pressure, 30psi, 25psi, 20psi, 18psi, and the latter has always worked best for me.

I think a lot of people are paranoid about running that low of a tire pressure in fear of losing control of the car, but I've never had a problem.

Do whatever is best for you I guess.

 

Because - if you have full pressure the design contact patch of the tire will hold the car with little support vertically from the sidewall. If you lower the pressure, the sidewall starts to compensate, the tire looks like a saddle and has 2 high pressure points and the center disconnects from the pavement.

So down to about 20 psi or so (depends on the tire) the contact patch is actually less than at the design pressure (in our case 35 psi) and you get less grip. I've noted this at the track, when driving through a wet spot and looking at the tread pattern left by my tire, etc.

Also note - Veetec and warmmilk are running the same. Davidv agrees with us, etc. Its not one guy saying run stock pressure on the potenzas, but rather a decided group who has seen good success from it.

 

Like I said, whatever works for you, do it. Not everyone's car is exactly the same.

I'll run 18-19psi because this is what has worked best for me. Not only do I get my best 60' times at that tire pressure, but it also eliminates wheelhop since there is more cushion underneath the rims.

 

Are you by chance running a goodyear tire?

 

I run Continental Contiextremes during the cold months
and run Nitto Neogens during the summer.


Lowering the pressure on both tires at the track have yielded better 60' times for me. Though the continentals are much softer and do not respond as well to the pressure drop. It's a pretty drastic difference with the Nittos.

 

I'm not familiar with the nitto's. I know goodyears don't respond the same because they have a softer sidewall. IIRC the Nitto has a softer sidewall than the Toyo (T1-R at least) and so it would probably like a bit less pressure (before it buckles). I've noticed that changes I make have little correlation to my improvments. Changing my driving style improved my results considerably.

The conti's shouldn't like lower pressure - they have a pretty stiff sidewall.

 

I agree with Peak350. The lower you try to go, the worse your times will get. Been there, done that, and seen my friends do it (which I tried to tell them not to, but they didn't listen).

 

27psi worked for me when stock, all 3 measly runs lol