I'm running 15#'s in a full weight car with a 6 point roll bar (if that matters).
Suspension mods are as follows: QA1 R's front and rear, front springs are 275#'s rears are stock.

Wolfe solid single anti roll bar, set up with the reccomended preload.

I'm only seeing 1.71-1.69 60's and I know I can do better. Right now I'm running a Hoosier DOT QTP (27x11.50) with 4.10 gears.

I dont remember what my shock settings are set on but I set them like Madman told me to before the anti roll bar and it started pulling the front wheels every run.

 

I've never had a set of Hoosier's but if it were an ET street (bias ply) or ET Drag , I usually start around 12psi and just see what the car likes. You didn't say if it was a manual or auto car though... Manuals it the tires harder and may like less air.

 

Sorry, I forgot my sig got moderated for being too long, its a 6 speed.
The dot QTP's are bias ply with 3 rain grooves, much like the ET streets. I started @ 18#'s and went down to 15, before the anti roll bar 15#'s made it get a little squirly on the big end. Maybe I gan get away with less now though.

 

My suggestion is a set of lower control arms, an adjustable torque arm and QA1 adjustables in the back. I have these and got a 1.58 60'.

 

In a 6 speed? I already have QA1's out back and spohn relocator brackets. An adjustable torque arm is definatly in my future but it will be awhile before I can spend the money for the Madman peice I want.

 

Dude, they're a bias ply tire... They're GOING to be squirrelly. They sacrifice sidewall stability for traction. If you were that high on air pressure, then no wonder you're spinning. Take those things down and learn to live with it, or get a D/R... I even run my radials at less air than you had in yours! You'll get used to it!

 

If you're having to drop tire pressure to the point that it's unstable on the top end, you either need to go with a wider rim for that size tire or run a tire that has a different construction, possible a stiff sidewall or radial type slick.

 

Ok, well what is the car doing? Spinning, bogging? Have you messed with your lauch RPM much?

Bias plies are going to be a little "wiggily" on the big end, dont let it scare you, just drive straight on through it, you'll be fine.

And the final question is, does your car simply have enough power to go faster in the 60'?

 

Start tire psi at 12psi and work your way up till you dont hook,usually run the Hoosiers at about 15 psi for best trade off in 60' and mph thru traps.

 

Those of you who said drop the pressure, how low have you actually gone and with what 60'? I am in the same situation as WS6Hummer, and have been as low as 1.60's @ 10 PSI. I am going to use 9 PSI the next track outing to see if the front wheels carry out the weight transfer more through out the 60'.
-Dave

 

Thanks everyone for the replies. I know they are squirley by nature, but my car is very heavy and I understand that the heavier the car is more air pressure is required. I have 27x11.50's on a 10" prostar, I think that rim width is pretty well matched for my tire. I Usually launch around 52-5500 but all the guys with good 60's are leaving @ 6k, I want to be able to do this but the tires spin @ 15#'s.

 

I have seen you say it spins at 18 and isn't stable at 15, have you tried 16 or 17 psi?

Remember there are other things to adjust other than air pressure to help the car hook.

What's the pinion angle at, what are the shocks set at, how high or low is the torque arm, what angle is the LCA running at, what spring rate are you running in the rear, what spring rate are you running in the front.

If one or more of these is off, just putting a drag tire on it and dropping the clutch at 5k+ doesn't mean it is going to hook regardless of the tire pressure.

I would take baseline measurements on everything I listen and repost them and I am sure you'll get pointed in the right direction faster.

 

I ran that tire with a M6 leaving off a two step @ 6,000rpm.
That tire like less air then a normal drag slick.
I had the best results around 11.5 to 12.
I found that a MT Drag 28x10.5 Stiff Side Wall made all difference.
It is hard to get a heavy M6 car to hook.

For a future mod, I recommend going with Madman TQ and a good double adjustable rear shock

Bob

 

Thanks Bob, I plan on getting madman's T/A as soon as I can get 700.00 together. Thunder's only an hour and a half from me so as soon as I get all my parts on I plan on getting madman to scale it and set up the pinion angle.

 

After reading all this, I would try the tires @ 12psi before the burnout and launch at 6k. It will either hook or break something!

 

Yeah that's the same conclusion I came to. Hopefully it will just pull the front wheels again instead of breaking something.