Can I get a primer course in drag racing?

RevRico wrote: With street tires (half bald at that), what should I do about air pressure? Lower for a bigger contact patch or higher to ... whatever that does?

Low. Really low. Like, lower than you are comfortable with. I'd probably start with 10 or 12, and work down from there. I usually find I'm happy at about 5 psi.

It's not really about the contact patch, it's about the sidewalls. You are trying to get your street tires to act a little like drag tires- soft sidewall gives flex, and absorbs shock as you plant the gas, but then slingshots the car in the launch. It lets your tires act as part of your drivetrain (although it really doesn't work very well with street tires).

Watch slow motion shots of drag cars with wrinkle tires. That's what they do.

Don't try to drag race on autocross tires. They are really dangerous. They have stiff sidewalls, which don't let you launch, but they also get really squirrelly at high speeds.

In reply to wheels777:

Excellent!

Now, let me see... if only I could spin the tires!

Didn't Dave or JG or perhaps some other staffer write up a pretty good article on drag racing some years ago? A good bit of it as I recall was how to psyche out your opponent and do well by screwing them up. Stuff like just staring at them at the line, watching the light tree out of the corner of your eye.

What are the thoughts of autocross tires on front and drag radials on the rear?

Stampie wrote: What are the thoughts of autocross tires on front and drag radials on the rear?

Autocross slicks will steer the car well enough. It might get sketchy if you need to use the brakes hard on the drag strip, but I can't imagine common drag front skinnies would be any better for braking.

To be clear, when you guys say "autocross tires" you mean R compounds such as Hoosier A7 or similar, right? That's my experience as well, but I think we should be a little more specific for those following along. Even autocross worthy street tires (200TW) feel like drag radials by comparison. Trying to put power down on Hoosier A7s is downright scary on a drag strip.

In reply to n8:

Im curious about this because Im considering running my miata on 200tw tires at the local strip.

Just to clarify for svrex and wheels, I'm currently sitting on Goodyear rsa that are about half gone.

For the challenge, I'm eyeballing a cheap "extreme performance" sumitumo tire for the autocross and planning on keeping them up front for the drags. For the rears, well that hunt is on going.

Who sells drag tires if I can't find take offs and need to buy new? Are they sized the same as regular tires (like 225 60 16?)

In reply to RevRico:

There are drag DOTs (like hoosier A7/R7 is to a slick) and full off road drag tires. tire rack sells some DOT drag tires - and they come in standard sizes like you are used to seeing. Nitto also makes them but you have to go through someone other than tirerack to buy nittos.

Check summit racing and jegs for off road drag tires, and they are sized probably more like other off road tires (slicks, big knobby all terrains, etc "dia in inches x width in inches - rim diameter in inches").

My drag racing experience is somewhat limited, but all of it has been in very traction-challenged vehicles, so I've picked up a few things anyway.

Since drag points in the challenge are based on ET alone, maximizing traction pays dividends in much greater proportion than shifting technique or 'mild' power increases.

Since there were two minivans that 'successfully' drag raced this last Challenge and i ran one of them, i can use them as a good example. Your ultimate ET potential is basically tied to your trap speed which is a shorthand reflection of your power/weight ratio.

My van 'trapped' 90-91mph. The other van ran a best of 87 mph, i believe. Those are fairly close numbers. A car with an 87 trap could VERY easily out-ET a car trapping 91 based on a traction advantage. Assuming both were ET'ing right up to their potential, they would probably be within .3-.4 seconds of each other based only on the power difference.

However, what really happened was that my van ran 2 WHOLE SECONDS quicker because although my power/weight advantage in that state of tune was marginal, my traction advantage was massive due to using actual drag slicks. The advantage provided by the tires was so massive that i would have to miss all 3 of my upshifts (manual trans) at least once in order to screw the run up bad enough to squander it. The other van got nearly THREE TIMES as many concours points as mine did and even that was barely enough to surpass the points advantage i had simply from two tires!

My point here is that if your car is powerful enough to break traction at WOT in 1st gear (or especially so if it spins in 2nd), you will gain hugely from slicks. So much so that i wouldn't bother grinding down your synchros practicing slamming gears or street tires practicing 'launches' unless you know with certainty that you simply CANT run slicks.

n8 wrote:

Stampie wrote: What are the thoughts of autocross tires on front and drag radials on the rear?

Autocross slicks will steer the car well enough. It might get sketchy if you need to use the brakes hard on the drag strip, but I can't imagine common drag front skinnies would be any better for braking.

I'm not sure I agree with this (and would like to hear some input from someone that knows more than me).

The factor you may not be considering is the stickiness of the track surface. I don't have any science here- just memories of having run a single speed Stingray tandem bicycle on the dragstrip at the Challenge one year. Alan McCrispin and I donned oversized pants loaned from the Hong Norrs, and madly pedaled our way to a blistering 42 second pass. The thing I remember most about that ride (which we completely unexpected) is how terribly hard it was to steer. I was really confident I was going overboard the handlebars, and that it was going to cause pain that I would remember a very long time. We made it, but it was extremely difficult to keep that bike pointed in a straight line.

Sticky tires + a sticky track might not be as easy to steer was you think.

Another thought on autocross tires...

If your car is wearing good R-compound autocross tires, there is a very good chance (at the Challenge) that you are a top autocross contender. If so, there is also a pretty good chance you've setup the alignment to optimize the autocross, possibly with aggressive toe-out to reduce understeer and free up the car.

If you do this and DON'T change your alignment settings before hitting the dragstrip, you will have a VERY unstable car at high speeds.

This is the EXACT scenario the Texas A&M car had in 2015, when they laid down a time that totally trashed the rest of the field on the autocross (and no one was more shocked than me, because I had a VERY well prepped car).

However, when they hit the strip later that night, they were truly concerned after their first drag pass. The car was completely unmanageable.

They asked me for help, and we talked tires and alignment. They said they were running on autocross tires, with over an 1/8" toe out. They had never been on a dragstrip.

I recommended they ditch the tires for street drivers, and realign the car for neutral toe, or even opt for a little toe in. After that, they were able to lay down some reasonable times (safely), but still suffered without drag slicks (they had more power than me, and were trapping 13 mph faster than me, but our ET times were nearly identical).

My point is that tires are not a decision in a vacuum. If you have decided to wear R-compound autocross tires, you have made other choices as well. The combination of these factors can be very dangerous.

I don't care for the choice to mix them. If I had to choose, I would rather wear well worn street driver tires on the front than autocross tires.

i have 100TW NT01's on the front of the datsun because i don't take the fronts off after the autocross. they are Z rated, which i gather purpose built autocross tires are not. my car was dead straight and true at the challenge with my drag slicks on the back and i was trapping at 122.6mph. in fact, my nitrous button is on the shifter. i was making every run with one hand on the wheel and one on the button/shifter and it was easy to drive.

In reply to SVreX:

I hear you on the alignment being a potential contributor. Especially if you're running front toe out. That'll be squirrelly regardless of tire choice.

However, I can speak from experience that autocross slicks steer the car fine on the drag strip with a conservative alignment. The real challenge was keeping the rear end behind the front end, but only when using any throttle... and I mean ANY throttle. Off throttle, you could place the car wherever you wanted. That was in 2015 with used up A7s all around and zero toe.

If given the choice, I'd still recommend pretty much any street tire over autocross slicks for the drag strip on either end of the car. Used up all-seasons would still be better.

I'm curious why autox A7s are so bad at the drag strip? Don't people use them for Pro Solo launches? I used to run A6s on my SSM turbo (300rwhp) Miata, and while I never launched it on those (never did a pro solo), they didn't seem to have any problems hooking up in 1st and 2nd gears in conditions that were spin city for street tires. I've also met people who used A6s as road race qualifying tires, which suggests that they have at least some high speed stability.

Is it the surface on the drag strip that's different?

So long as they aren't insanely wide, and you aren't running an insane amount of camber/toe, autox tires aren't terrible.

We ran the drags this year with 205/45R16 Hoosier A7s on the insight, and while the launch left something to be desired, we didn't have problems with high-speed stability, trapping at 95-100.

codrus wrote: Is it the surface on the drag strip that's different?

I suspect that's most if not all of it. Autocross slicks work great on a non-prepped surface but there's something about a prepped drag strip that they don't like, such as the drag compound rubber or the traction compounds that are used to prep the surface. Maybe our resident tire engineers can chime in.

The stiff sidewalls don't help any, but I suspect that's not the entire problem since stiff sidewall 200TW street tires are still a lot grippier on the drag strip.

bentwrench wrote: .........Can you have a trans brake? Can you have a two step launch control? (megasquirt)

Yes, Yes.

I have bought a Transbrake transmission and picked up MegaSquirt for management.

Last time I drag raced, it was $10 to run all night at import / Test n Tune night at the local 1/8th mile.

That's a LOT of entertainment for $10. It's a motorsport that you can drive up to, observe, and participate in for $10. All you need is a helmet (if you can break into the 8's in the 1/8th around here) and long pants. I put some Hoosier (R6 at the time) scuffs on the back of my MR2 at 15psi and aired the front street tires up to 55psi and drove 10 miles to the drag strip. Had to borrow a helmet when I surprised myself and broke into the 8s on my first run and got scolded.

In that respect, why WOULDN'T you learn how to launch your car? Staging up next to some other random car guy or street racing bro and watching the lights count down is a rush, I don't care who you are.

All that said, I found that I had it down after about three different evenings. I knew what I could do, I knew what the car would do, and I could do it consistently. After that, not much left. It's like a road course with only 1 turn to master. I could consistent get ~.20 - .30RT, 1.6sec 60', 8.5-8.6 second ET (1/8th) ~90mph trap.

So what's the word on Saturday?

Tonight is our test-n-tune event night, if the rain holds off. I'm taking the Abarth on Yokohama S-Drive's. Somehow I feel like there's a fine line between bogging down and spinning tires in this thing. Luckily the start line/eye of an autocross is what, 10-20ft from the start? I'm also wondering if turning off traction control will do anything, good or bad?

I'm not a drag racer, will probably never do it again, but I'm curious what I can do in a quarter mile legally, and just want to get the best off the line I can.

I made other plans, because when I was looking at the weather on Tuesday it was going to be cold and wet. Now it's supposed to be 70 and sunny, but I don't know if I'll be able to make the 12 to 5 window.

They're doing test n tune days every saturday as long as the weather is nice though, so it could be doable a few more times yet this year.