On the fronts....the issue I ran into is the SRT wheels require the BT 5mm spacers to make them fit right on the RT's. If not, you get a slight rub when turning hard and backing up. That in mind, I didn't feel comfortable going wider than 245's up front. I did see some posts where guys were trying to stuff 275's up front and doing double spacers, etc. I hate spacers. Think they are a bad idea. No disrespect to BT....I bought their stuff and it's top notch. I'm just not a fan of them if you can avoid them. I couldn't and I believe I have a great setup but I'd still like it w/o spacers if possible.
If you have an SRT, I'd stick with a 245/45 up front. No spacers. No drama. Save a few bucks on tires too. Also, the overall size diameter works well with either 275/40's or 295/40's. Only downside is running staggered setups limit your rotation/life of tires. FYI, the Coopers can still rotate left/right.
On the rears...the 275/40's fit comfortably and within a few tenths of the "recommended" tire width for the wheel width. I will try to get a shot from the back showing the width. I really wanted the 295's myself but it's a little bigger than recommended for the 9" Alcoa rims. I've ran bigger tires than recommended before, so I might have went with the 295's if Coopers had that option. They didn't so, it made it pretty easy for me.
One last bit of info....be sure to check competing sites. I used Discount Tire for actual purchase, but had them price match another place I used in the past (also very good) called Tread Depot. I can forward you my DT sale rep's contact info if you want it. He was really easy to work with, knew his product and didn't give me crap about the price match. That was my first experience with DT and they were really awesome. I did buy online to avoid taxes and get maximum rebates. Their local shops might match, but I have a buddy hookup (know about half the guys in that garage ) at a dealership shop that was doing my oil and a few other things at the same time so that made more sense for me.
I know those prices when I bought had a rebate from Cooper, rebate from DT for tires and also another rebate from DT for using their credit card. I had cash to pay but opened an account to save a few more dollars. Will just pay in full when the bill comes in.
2014 Ram Sport QC 4x4, 8-speed
2013 Charger SXT, 8-speed
2010 Challenger RT, 6-speed (retired)