Clutch issues while hunting better 60' times.

[stepqhen]

Just got back from a test and tune at MIR and had a major issue. I started off leaving the light at 1500rpm and was turning 2.2 - 2.4 60' times. I started raising my RPMs and when I got up to about 3000 RPMs before my times started dropping. When I left at 4000 rpm my clutch peddle pulls away from my foot and then the clutch slips badly. Before the clutch started slipping the best 60' time I could cut was a 1.95. I never had traction issues tires never even chirpped, the clutch was letting go before the tires.
The last straw before I left was when the burnout box was mostly dry and I started a burnout and the tires didn't spin (bailed out and left after that)
tires are 305/40/18 nt555rs running 18psi
clutch is ACT FM13-HDG6, first time drag racing on it, >7k miles on it daily driving.
I also changed gears down to 3:55s from 3:73s (I autocross more than drag race, and needed a little more MPH/RPM)

I was trapping at 115+ at 12.5 or so even with the lousy launches.
so WTF, the tires are drag radials, it isn't like I am running on full on slicks. Am I running to0 much tire, too big/heavy/wide/etc?
Is this just a fact of life and I have to learn to deal with poor 60's
is this all my doing, am I doing something horribly wrong?
does the clutch spring removal trick address this issue at all?

Any input/advice/random facts and sea bass recipes appreciated.

 

[Five Oh Brian]

I had problems launching my '11 GT. It would bog with the factory 3.73's and drag radials. Bad on the clutch! Went with 4.56 gears and cured my launches. Sixties dropped into the 1.69-1.75 range. My 1/4 mile ET's didn't improve due to the extra shift, but the launches were simple and consistent.


Sent from SYNC in my '14 Mustang GT...