Thanks in advance for taking your time to read this!

I am wondering if I can use 245/40-17 Front and 275/40-17 rear tires. There is a -4.84% or -1.25inch difference on the Front tires from what I am running now there is a -3.82% or -1.02inch difference on the Rear tires from what i am running now. My other option is to use 245/40-18 Front with -.99% or -.25inc difference and 275/35-18 rear which is -4.13% or -1.10inch. I will use these for autocross only so I don't care about the speedo readings. Will either set will work with correct offset 17" or 18" rims? Any other suggestions or combos of these sizes that would be better?