315 Falken RT615k will it work?

I just picked up a mostly stock low millage 04 Cobra. I got lucky and found some 18x10.5" AFS Cobra replica wheels. These are actually made by Detroit. I found the 18x9's on amazon and a few other places.
But on to my question. I want the same front and rear tire. 275/35 & 315/30. I know the R888 works in a 315/30 18. As gorgeous as the tread pattern is and my experience with NT01's on my S2000 do not want an R compound tire for casual driving. I know tire sizes differ from manufacturer. Does anyone know if the Falken RT615K runs wider or narrow? H&R sport springs and low profile IRS bolt are on the way. Not rolling the fenders.

my 315 30 18 615s were narrower than my 305 35 18 r888. same wheels and same everything. hope this helps

What makes you think your AFS wheels are made by Detroit? AFS stands for Autumn Fleet Sales. They're a company located in Canoga Park, CA, and their wheels are manufactured overseas (China).

If you want RT615K, I recommend to wait few more months.
Falken tires will sell new tire, RT615K+ on this March.
But tire sizes are still unknown...

The Falkens will be narrower and honestly go with the R888. I have the 615k in 315 and they barely hook more then my hold BFG KDW 295. I originally wanted the R888 but they were BO at the time.

i dunno about running 315 in the front. I did run in the past a 285 and that worked well. As far as tires for the rear id go with the r888. Im sure someone will chime in as far as a 315 working in the front.