PART NUMBER: 61-1847ND
Serious performance springs for the serious street enthusiast, ENOUGH RATE for Canyons to Autocross to Track! We took a Top Time of Day with these on Koni Sport shocks at autocross event with 100+ competitors.
Tested on our ND Miata and Fiat 124 (shown here on our own Fiat 124 and a customer ND, both built on same ND chassis in Japan, same lowering effect). Stock heights were 14.25 to 14.75 (measured center of wheel up to fender lip). Lowered heights with these springs approximately 13.75 on stock shocks, settles as low as 13.25 as shown here on KONI Sport shocks which are lower pressure than stock shocks. Important to understand these are really too much rate for base trim stock shocks, the stock Bilsteins on the CLUB version handle these well, ideally used with the Koni adjustable SPORT shocks or Bilsteins with our short bump stops. 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.
Numbers here are for SOFT TOP version of MX5, these are not compatible with the RF chassis. With the additional weight of the RF the heights are incorrect.
These Miata springs feature increased spring rates for vastly upgraded handling capabilities. Certified high-tensile SAE spring wire materials. These Miata springs are cold-wound on modern CNC coiling machines, then stress relieved, pre-set, and shot-peened for maximum durability.
Rates 300 lb/ft Front, 200 lb/ft rear.
-All spring kits are powdercoated.
-Drop amount varies depending on shocks used.
BRIAN'S APPLICATION NOTES: My new favorite simple formula for around town fun that can hit the canyons or autocross/track the weekends! Enough rate to make the car MUCH more flat in the turns without making the car harsh riding. Started this project with the idea of making the perfect springs to match with KONI Sport shocks, though they also work well with factory ND1 and ND2 Bilstein shocks in CLUB editions (too much rate for the black body NON-Bilstein stock shocks). These are a great choice for those who want to replace the soggy factory springs to take out much of the crazy factory body roll. Improves handling massively without dropping the car too much, just half inch of lowering on bilsteins, total 1 inch of drop if you also add our KONI SPORT shocks. Lean on them in the turns and you will find the car is MUCH 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 THAN HALF INCH DROP than these springs provide on the Bilstein shocks, combine these springs with our KONI SPORT shocks which are lower pressure to total about an inch of drop.
INSTALL NOTES: Important 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.
These springs are manufactured to our specifications by Progress, the same makers as our standard Progress springs and RF springs, so don't be alarmed when a box of springs that say Progress arrives. Verify the part number on the box is correct for RoadsterSport springs: 40.1135.
Below is NC service manual notes, but design with ND/Fiat 124 is so similar that same rules apply.
Photos below are with KONI SPORT shocks.
Alignment depends much on what you do with the car. Assuming no autocross or track use, for pure street driving our suggestion is at least this much camber:
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 with a bias of more front than rear (because rear multi-link has more favorable camber curve) and zero toe all corners. Autocross customers will toe OUT the front, track users usually toe ZERO front and rear. Thus, more aggressive settings for customer who might autocross with stock bilsteins and these springs might look like this: front camber -1.8, rear -1.3, toe out front 1/32 per side, toe zero rear, front caster 6, and with KONI added to these springs so car sits lower and with customer going to the track and autocross often then more like -2.2 front camber, -1.7 rear camber, toe zero all around (or slight toe out front), caster 6 (caster at 6 instead of factory 7 to 8 creates more room for bigger wheel/tire combo).
BRIAN'S ADDITIONAL THOUGHTS: Our Fiat 124 took Top Time of Day at last Autocross of the 2016 season with these springs and our Koni SPORT shocks and our sway bars. That's an AMAZING result for a car that is not upgraded to serious coilovers, this setup rides well yet goes FAST, a great choice for drivers not happy with the soggy stock setup.
Great spring rate for street driving. I originally paired these with the V1 bilsteins that came on my 2016 Club. It was an okay match but a little too bouncy over big bumps. I recently replaced the V1's with Bilstein B8's and this is a great match! Firms up the car nicely but nothing too crazy.
I installed RoadsterSport springs on my 2020 MX-5 Club about a month ago with the included bump stops and the Bilstein dampers that came with the car. The springs reduce the body roll quite a bit without noticeably affecting ride quality. The car is a little lower and I have to be careful coming off of steep speed bumps because the rear of the car will bottom out because it's a little bit lower. In addition to flatter cornering, keep the inside rear tire planted when exiting sharp turns. They also reduce dive and squat during acceleration and the car feels considerably more stable when transitioning from a left to right corner. On the autobahn/expressway it feels more stable during quick maneuvers. Overall, I feel like they make the car handle more in line with what I expected when I bought it.
After lots of research, I settled on the RoadsterSport ND Springs. Installation took about 3 hours. I have put 400 miles on these springs since. My MX5 feels like the club should have felt from factory. I have much more confidence through the corners, it's much happier to turn in, it is no longer thrown off course on bumpy highways, or mid corner bumps and imperfections. The ride is a little stiffer at low speeds(as expected), but at highway speeds it's just as compliant as stock.
I am beyond happy with this product, and I haven't even had my alignment yet!