I posted this elsewhere thought you guys may want to read it
2015 Mustang S550 Performance Pack Review And Thoughts
Yesterday I had a chance to spend some quality time with the S550. Drove it around for a bit, put it up on the lift, took some stuff apart, poked around for a while. Keep in mind I have a 2012 GT Vert Brembo with a M6 that is pretty much stock and a 2007 GT that is a full blown out of control 1000hp “roadrace” car. All my friends have S197’s in one state of tune or another too. I get lots of seat time in S197’s and my fair share of open track events. Here are my thoughts:
Driving-
The car drives really really nice. S197’s feel like they were put together with a nail gun in comparison to the S550 which feels like it is carved out of billet (the chassis). It’s very quiet and refined. Over bumps and road imperfections it just thump, thumps through the entire chassis. Very BMW like. Not the “worn out” feeling that the S197’s have. I’m not even sure if it can really be called a muscle car anymore. It is a lot closer to my buddy’s Aston Martin Vantage (but the Mustang is faster) than maybe even a S197, certainly closer to the Aston than a SN95. You can still probably call it a Pony car, but Muscle car I’m not to sure about. And I am perfectly OK with that. I like refinement, balance, control, handling, nice ride, etc. Overall I liked it a lot. I sure wouldn’t mind daily driving one and that is saying a lot. I don’t DD my other stuff. They are pretty much pulled out when the weather is nice. I DD a F-150 4x4.
I wasn’t able to push the car real hard in the corners because I didn’t have time to take it out to my favorite twisty roads. Well at least not hard enough to get the front end to plow in and the whole car loose through the apex. I did some “spirited” driving though. I hung the back end out a few times on exit. So, pretty spirited. The chassis and suspension work good. It seems to have more base spring rate than the S197 (all of them) which is nice. It gives a good feel without being harsh. This is helped out by the dampers which are valved pretty good for stock stuff. The compression isn’t real stiff but it has plenty of rebound which is severely lacking in most cars, especially S197’s. It corners real flat, it’s pretty neutral and if you trail brake to the apex, roll the center and accelerate out like you are supposed to the car does what it was told.
The IRS is a huge improvement over the stick axle in the S197’s. All you have to do is accelerate through a corner exit with some bumps/ripples and you will be in love. It does its thing and just drives on down the road. The S197’s, no matter how well set up liked to tie the rear end up under the same conditions and you could find yourself getting out of shape because of it. The IRS even worked with the tail hung out over bumps/ripples. That would have had a S197 all out of shape and maybe trying to kill you.
The rear end of the car is a lot more precise than the S197’s. The S197’s with stock control arms will flex all the bushings, etc sideways when you’re loading it up entering a corner. This gives it a “loose rear axle” feel to it as the entire rear end moves sideways under the chassis. You can drive around that but it takes a certain smoothness. And if on a S197 you break traction while the rear end is loaded up it will unwind like a spring and try to get sideways on you (snap oversteer). The S550 does none of this. It makes it easier for an expert driver to drive fast and will help novice drivers not get themselves in trouble and find their way into a ditch…… backward.
The steering is a bit goofy and doesn’t want to self center on corner exit. This may be a EPAS thing or maybe not enough caster, or both. My 2012 does the same thing. None of the “race car” stuff (none of them have EPAS) I drive/work on do it. I’m not really sure what the cause is and some people may not even notice. It’s not a problem, just a trait. That said I would like to make it go away.
The brakes work. Pretty much the end of the story there. If you can kill them on the street you’re a psychopath.
All in all I am real happy with the chassis/driving aspect. It is much better than any S197 and as good as your standard springs/dampers/control arm/swaybar modded S197. And the modded S197 will never be as refined and easy to drive. I think the S550 is a pretty big leap forward.
Packaging-
The entire car is a lot better thought out. From stuff like weather stripping to where things were placed in the car. It’s just plain nicer than the S197’s
Cool Features-
I am 100% in love with the airbox/ram air. Yeah, the car has real ram air. Air enters the grill and is directed to the airbox though a HUGE diameter tube. It’s absolutely awesome. This will help out with NA cars for sure, but it will be huge for the guys running blowers. Nice cool air from outside the engine compartment, WIN! I’ve been planning on making something just like it for my race car, but it’s a huge project. It sure is nice that the S550 already has it. Anyone going with a CAI or removing the airbox is flat out retarded. I could see going with a bigger intake tube (between the airbox and TB) but using a custom airbox lid that retains the stock filter (or drop in unit) and the ram air/airbox base. That would not change the function of the ram air at all. If going with a blower I wouldn’t even consider something with an open to the engine compartment air filter (what would normally be done). If the blower doesn’t come with a new airbox lid that retains the stock airbox function skip it. There is no blower on the planet that is so good that it will outweigh the loss you would see by opening the air cleaner to engine compartment temps. I’ve done a lot of testing on engine compartment temps. They usually run 50-80deg above ambient. You DO NOT want to feed your motor with air that hot when the factory gave you a way to feed it nice cool (relatively) outside air temps.
I’m as giddy as school girl about this whole airbox thing!
Tires/wheels-
As far as I can tell after a few quick measurements the wheel offsets are the same as S197’s. So you should be able to use any S197 wheel. That said, the S550 has 14mm wheels studs compared to the S197’s ½” studs. I’m not sure if you can simply drill out the S197 wheels to work with the bigger studs or not. I’ll have to look into that.
The front PP wheel/tire weighs 60.5lb
The rear PP wheel/tire weighs 64lb
The front end is a little tighter than that S197’s when it comes to stuffing wheels in there. You can get a 275 in there without much trouble. Maybe a 285 with just the right offset. But the overall diameter can’t be much bigger than 27.5ish inches. Any bigger and it will get into the spring perch on the strut. Someone will figure this out with coilovers, but it may be a while before you can run really fat rubber. The GT350 has 305’s on the front. I think they pulled that off with wider fenders though.
The rear end is about the same as a S197. It will take a 11” wheel with a 315mm tire without too much trouble. But that is it. We did figure out how to get 345mm tires and appropriately sized rims on the rear, but that is going to take a little fabrication trickery, which is what we do. We may be able to come up with a bolt on kit that will allow the use of those HUGE tires for not much money. So if you want really fat rubber (who doesn’t???) back there don’t go out and plunk your money down on 315’s just yet.
Weight-
A lot of people are complaining about the car weighing 180lb more. Well, most of that is sound deadening material. It’s EVERYWHERE! Maybe not 180lb, but a LOT. This is a lot of the reason the car feels so refined. There are also a few easy weight loss areas. The exhaust being one. The S197 stuff was lighter stock. How much, IDK. But enough. I would guess 25lb. If one were “sporty” and wanted to drop some weight there is a lot more low hanging fruit than on a S197.
