I changed the subject on this hoping somebody has an answer for me. I expected some decrease in speed, but not -5mph.

I went to the track a couple weeks ago and ran 12.5@121mph on street tires with a 2.16 60'. The weather was around 40 deg and dry with a slight tail wind. I went to the track yesterday on ET Streets and skinies, weather in the 70s and a 25 mph head wind. I only ran 11.85@116.65 with a 1.69 60'.

Could a head wind slow me down that much along with the warmer weather? I have to log for knock, but definitely didn't hear any. I launched at 5000 rpm basically side stepping the clutch.

I ran a couple of passes each day and they were all consistant.

Any help is appreciated.
Thanks
Brad Oblak

 

if the car was spinning with the street tires on it then the mph will be higher than if the car was hooking, plus i lost about 2 mph by using et streets instead of nittos

 

Depending on the air (DA) you could definately loose a couple of MPH, same with the head wind. What did others at the track say? Were they trapping lower than usual also?