So I just have some information to share through me ending up ordering two different wheels sets and one set of tires for my new 2016 Scat Pack. Circumstances beyond my control led me to ending up with both sets and I want to sell at least one set - the MRRs/tires or the Forgestars, which can be bought with tires since they are still at my dealer. You can find individual posts for those + the stock Scat wheels/tires in the classifieds section. On to the info to share.
As I ordered my car, I knew I wanted to get a little more footprint. I didn't care to go with a staggered setup and felt I would do well with the improvement to a 275 section width vs. a 245, especially I was able to pick one of the best tires vs. the Goodyear summer tires which are pretty much not the best choice, even at the same size. I like being able to front-back rotate as well.
For a summer tire, it seems hard to beat the Continental DW. It is the lowest weigh summer tire, at least in a 275-40-20. (275-40-20 is identical height to stock 245-45-20s) Tire rack shows the tire at 30lbs while Continental's site has 27.7. Despite Continental insisting (I sent them a note) 27.7 is right, my dealer's scale, which I believe to very close to on the money, showed them at 29.05.
Here's the stock wheel/tire tread (Goodyear RSA 2s) next to the Continental DWs:
From what I've read, there is savings, even with this bigger tire vs. the Goodyear but I only have independent info on the Conti and the stock wheel/tire assembly together.
On to wheels. Stock looks like this:
And weight comes in at 62.0, probably a few tenths lower, from what I saw by holding it in my arms and subtracting my weight:
On to wheels. There are a number of wheels that use 'Flow Forged' technology and many of them use apparently the same plant in Taiwan. I liked what I saw in TSW, the Bathurst in particular, but they can't be had in correct offset and also require re-drilling of the lug holes. I pursued and ordered Forgestar first. I had a slight preference for the CF10 but it wasn't available in my fitment. I ordered the CF5Vs, again in 20x9.5. The offset is +20, which is pretty much ideal for a 9.5" wheel on our cars (at least Scat Packs/392s/Hellcats) Lead time is 4-6 weeks (mine took about 7) as they apparently start with wheels that are already come out of Taiwan with the correct offset. They machine the lug holes and do the finishes in the US. They do full quality control in the US. Their wheels are not hubcentric, though they are close so you use these with a fairly slip hubcentric ring.
Forgestar CF5V, 25.2lbs on the scale. The finish is Gunmetal:
If you went with the Continentals, I believe you would be right around 55lbs with tire sensor and balancing weights.
I learned about the MRRs on this forum despite my dealer also being a major dealer for them. I ordered the MRRs because I was lead to believe I would save 3.5+ lbs. as compared to the Forgestars. It turns out the difference is just less than 1 pound. Identical specs, 20x9.5, +20 offset. MRRs are made hubcentric. MRR lead time is closer to just two weeks, as I understand they stock wheels with a thick "center pad" and machine away the pad for higher offset wheels. In addition, similar to Forgestar, they drill the lug holes, do the finishing and quality control in the US. MRR calls their finish for what I picked "Gloss Gunmetal"
MRR mounted with the Continental tire:
MRR wheel on dealer's scale, 24.3lbs:
MRR/Continental on the scale, 53.8 lbs:
Aftermarket lugs will also save you about 1lb. for the whole car:
So with either 'cousin' wheel set, at least with the Continental tires, you can save either side of 30lbs of un-sprung, rotating weight. Unburdening your drivetrain of that weight should be worth the equivalent of freeing up 10 horsepower or more. And at the same putting more rubber on the road. There could be a hair bit of loss from extra frictional losses with the bigger footprint.
When I first considered new wheels, I was trying hard to figure out a 18" fitment. But I was used to the previously typical tire height at around 26". At 28.7", our stock tire height offers more footprint for a given width and a 20" wheel offers a much more reasonable amount of sidewall for compliance as compared to a 20" with a 26" tire that at least used to be typical on Camaros, Mustangs Corvettes that I worked with.