I have not been on the site as much as usual, getting setup back here in NV, a ton of work to do as clearing out most of what we own as decided full time RVing is going to be our lifestyle for some time to come.
Plasti Dip might not hold up for long, even plastic hub rings melt on track and some have on higher speed canyon runs, etc....high temp spray paint would be best.
Even if not autocrossing, etc...the lower the weight the better and the smaller wheel diameter brings more of the tire weight towards the center of rotation. All the gains still apply, better ride, more effective brakes which will help them hold up longer in harder use, better acceleration, better handling, better ride and less wear on the chassis and when driven accordingly better fuel mileage. The added sidewall helps protect those low weight wheels very well and helps protect the tires, suspension, mounting points, etc...
The loss of a bit of the "razor sharp response" is not always a bad thing in certain emergency circumstances, the added ability of the tires and suspension to maintain the contact patch over bumps are enough reason for the change but there are many more gains.
17's on this car are purely a style issue and Ford could of easily afforded to have 16" flow formed wheels made that were much lower in weight and as strong or stronger than the stock wheels.
The PS AS/3 is a very very good performance AS tire, the best in 17, I had them in 205/45/17 on 16.8 lb wheels, liked them just fine until I put on the 15" summer tires and wheels and noticed a huge improvement in noise reduction and ride, so much so when I put the PS tires back on my wife no longer wanted to ride in or drive the car and she likes a car that has great feedback and control as much as anybody but hated the tires so I gave them to my daughter. Now I have the 205/50/15 NeoGen, which cost around 40% less, on 11.4lb 15x8 6UL wheels, huge gain in all aspects with overall grip pretty close to the same.
I still have my even stickier 225/45/15 Rival S on 15x9 (15x8 works just fine as well) and run them this time of the year, the Rival S is far better riding and far less noisy than the PS tires.
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Tires that fit this car range in weight from 19-22lbs in most of the sizes we can use no matter the rim diameter, the lower weight option is always better if the rest of the aspects of the particular tire meet your needs.
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The most important thing in all aspects in life including wheels and tires is balance. In this case intended use, cost, weight, performance, ride, noise, reliability and even style.
Unfortunately some put style as the top priority which most often gives up a great deal of the rest which this car was designed to provide, a well balanced package for a great price and huge fun to actually drive.