Slicks and Trap Speeds?

[Eden]

My friend's '87 GN is down about 2 mph in the 1/4 mile, with only change being MT ET streets (14 psi) instead of regular radial street tires at regular pressure. Can we assume that this trap speed reduction is due to the street slicks and low pressure? Yes, he is quicker with the tires, but we want to make sure there is no power loss. Thanks.

 

[Epitome]

There are guys on here that will better explain this, but everything sounds fine. Your ET is faster (which I assume is your goal) due to the better traction on the low end (ie better 60 ft times). The better my 60ft time is the better my ET is and my mph dips slightly.