40 vs. 35 Profile Tire?

I think you'll hear different opinions on this. My opinion is that with street radial tires, sidewall flex while launching is negligible in the first place. I think the actual brand / compound is far more important than a 5 point bump in sidewall height.

+1

No. Treadwear and compound are going to be the most important things. What other mods do you have on your car? Gears? What HP do you plan to be at?

285/35/18 = H25.85 W11.22
275/40/18 = H26.66 W10.83

You are getting a taller in the 275, but less contact area. Street tires at normal PSI in these sizes are not going to flex much. You might see a better 60ft if you dropped the PSI down and got the car to launch on a prepped track.

Not sure what you do with your car, but I am going to be running running toyo r888's(r coupound though) on the street, and Hoosiers at the track at around 625rwhp. Another 2 good tires to look at might be the NT05 and Invos.