what size drag

hey i was wondering what was a better drag tire i mean do i go to 15 and get tall tires to make up the difference for the a bit of flex in the side wall or 17 are just as good wiht a drag tire.... any one know what size slick would fit a 17 rim and if you know what 15 rim would fit my car that make skinnies let me know any advice would be great thank you

not to sound real dumb but that what i want to do can you lol tell me what size rim 15x? and i have a 5 lug lol whats the bolt pattern and what size tire do i need to keep my speedo the same sorry i got a 150 shot on a motor and i just cant grip good till after 4th gear hard to believe but i got 4.88 rear end and just want to spray out of the whole..... thank you also what skinnies size i need