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Stock heights on our ND were 14.25 to 14.75. Lowered heights with these springs approximately 13.5 inches front, and generally a bit over 13.5+ inches rear (measured car empty center of wheel up to fender lip, car levels once people are added since driver and passenger are almost sitting on rear suspension). Note if you add our KONI SPORT shocks they are much lower pressure because of twin tube design as compared with factory monotube and result with KONI shocks will be ANOTHER half inch lower than what we list here. Your results will vary depending on which shock you use and the age of the shocks, as shock pressure declines over time the car will settle lower.
The engineering staff at Progress has decades of experience in the design and tuning of performance suspension systems, including CART/Indy Cars, IMSA, SCCA, NASA, and SCORE competitors. These MX5 springs reflect their ability to develop a successful blend of appearance, handling capability, and ride quality. Our team works with Progress on each Miata application spring, and with nearly a decade of working with Progress we know the result will show the quality and consistent performance that we feel raises the cornering joy level of the ND platform to a new level.
STOCK spring rates are 156 front for all models, and 80 to 100 rear.
Progress Spring rates 185 Front, 135 rear.
These MX5 RF springs feature increased spring rates for upgraded handling capabilities. These springs are designed to work with OEM shocks and bumpstops but will benefit further from using high performance shocks such as Koni Sport shocks. Progress specifies only certified high-tensile SAE spring wire materials. Their MX5 springs are cold-wound on modern CNC coiling machines, then stress relieved, pre-set, and shot-peened for maximum durability.
-All spring kits are powdercoated metallic gray.
-Drop amount varies by 0.25" depending on shocks used.
BRIAN'S APPLICATION NOTES: These are a great choice for those who want to replace the soggy factory springs to take out some of the crazy factory body roll, and improve handling, without dropping the car a lot. Lean on them in the turns and you will find the car is flatter and faster because the tires stay flatter to the ground instead of rolling onto the sidewalls as happens with the soggy factory springs. For those who want MORE DROP than the the springs provide, combine these springs with our KONI SPORT shocks. For those who want the car even more flat in the turns, combine these with our Sway Bar Upgrades. I recommend our SHORT BUMPSTOPS with these springs for best ride and handling.
Shown below on our own 2017 RF on factory standard shocks and Progress Sways AND our short bumpstops.
INSTALL NOTES: As with the NC, so it also important with similar ND to not lock down the bolts to the suspension after install while the car is suspended in the air with the suspension fully extended. Bounce it on the ground, then give it a drive around the block with the bolts just snug so you get it to settle before you torque everything ON THE GROUND. Many shops will NOT know to do this...SMART CUSTOMERS PRINT ALL THIS PAGE FOR THE INSTALLER! See details in our forum installation section from NC application, thread is titled: "Spring Installation, Mazda Workshop Manual Notes" and factory TSB notes below. Once you do it right, drive it 500 miles and then do it again (which usually results in another quarter inch or more of lowering)....and then do the alignment. ROCKY'S TIPS: Our head mechanic Rocky has his own method that seems to work even better than the factory TSB. Once he finishes install at each corner he jacks up just that corner with BOTH UPPER AND LOWER LINKs loose, so the full weight of the car is compressing just that corner, then he torques the bolts...and he finds car will still settle with 500 miles but usually only another 1/8th inch.
Below is NC service manual notes, but design with ND is so similar that same rules apply.
Alignment depends much on what you do with the car. Assuming no autocross or track use, for pure street driving my suggestion is:
Front Camber -1.2
Toe IN 1/32nd per side (some shops call this 1/16th 'total' toe in).
Rear Camber -1.2
Toe IN 1/32nd per side
Racers will take much more camber and zero toe all corners (and usually full coilovers instead of just these very mild street springs). Autocross customers will toe OUT the front, track users usually toe ZERO front and rear.
/> Pictures ABOVE are on stock shocks, picture BELOW is what you get when you add our KONI SPORT Shocks. Stock shocks are monotubes, the Koni Sport shocks are lower pressure twin tubes, result is the car settles lower than before, now about 13 inches front and about 13.25 rear (about half an inch below what we were with our RF springs on stock shocks).