movieboy4fun

Looking for a bit of input on front / rear spring rates for my SBF 90NA Miata. I would like the ride to be comparable to my E46 M3, I had a ISMA mustang as a youth with aluminum bushings and 850lb springs in the front / 450lb in the rear. Rode like the axles were welded to the frame, at 48yrs old I don't need that. Car will be 95% street cruiser but will see both Friday night "instant green" 1/8th mile racing, fun event, set up like street racing with DOT tires and full exhaust, as well as a few parking lot cone events. Hopefully the new road race track is approved in Osoyoos, BC. Only be 2 hrs from house.

Any input appreciated, was going to try the Martin 450 / 165 set up to start and possibly "sebz" E36 sway bar solution for the front, just happen to have an M5 front bar.

Dean0

charchri4

The lumber wagon ride comes from shock valving far FAR more than spring rate and there are 3 factors that control that. They are bump, compression and rebound. Bump is how much force it takes to make the shock start to compress. Compression is the rate the shock compresses and rebound is the rate it rebounds back to static. Obviously the higher the bump number the harsher the ride hence the name for it but of course the other 2 are also players to ride quality.

But to answer your question consider some of the more common spring rates:

Stock NA spring rates:
164 lb/in front and 96 lb/in in the rear.

NB Mazdaspeed MX-5
215 lb/in front and 158 lb/in in rear.

The spring Monster sells with the kit:
450 lb/in front and 164 lb in rear.

The vmaxx classic and Sport:
391 lb/in front and 258 lb/in rear. The difference is the valving in the sports is adjustable to be more aggressive.

Vmaxx track:
504 lb/in front and 336 lb/in rear with more aggressive dampening yet. But if you read the info and reviews on FM they are still very much designed for the street.

Xiadas:
700 ib/in front and 300 lb/in rear.

For what it's worth I just hopped over 20,000 miles riding on 750 lb/in front and 350 lb/in rears with Billie HD shocks that are not at all valved street use. Mine can be a bit harsh on bridge seams but for 99.9% of the miles I put on I think they are just fine.

movieboy4fun

charchri4
Amazing what driving in 1/8 mile straight lines for 20 years does to the brain, LOL. Thanks for the reminder above as you have forced me to remember that YES indeed the Bone Rattle came mostly from the Formula GP Struts / Shocks that I added along with the solid upper Strut Mounts. I also remember the difference the 90/10 shocks made in the front at the track.
Happy that forums like this get the juices flowing for the DIE HARD DIY'RS like myself and many creative others. Been building boats for too long and only have shocks on the seat, remote reservoir and fresh air duct cooled too.

Thanks Again
Dean0