Looking for feedback on Xida spring rates
 

Hey all. As im a newb, im expecting the typical miata turbo warm welcome. I did some searching around and I had a tough time finding information relating to my use.

I'm about to order a set of Xidas, and am looking for some spring rate feedback.

I live near Humboldt county, and the roads I drive on range from relatively rough backroads to long smooth open highway roads. I will primarily be running 15x8 wheels with 205 Dunlop direzza ZII's. I may be purchasing 15x9's with a 225 tire such as the BFG Rival, depending on how my car feels when it gets done with my tuner.(expecting 200whp, FM turbo kit.) I've got plenty of chassis stiffening. DIY Roadster Door Bars, Blackbird Fabworx GT3 Rollbar, Garagestar Fender Braces, FM Frame Rails + Butterfly Brace.

Im really on the fence here with 700/400 vs 550/350 rates. I've read the dampers are incredibly good at making high spring rates feel comfortable. However I am concerned that the 700/400 will be too stiff for the backroads, and thus slow me down/make the car unstable. Can anyone chime in here? Anyone running 700/400 and drive over rough roads regularly? The car isn't a daily driver, and I already have some compromises to comfort.


Thanks in advance.

Get at least 700/400. I would even get 800/500. I run mine with 900/550 and it's not bad in the street. If you plan on doing any track time or autocross at all you want at the least 700/400.

Thanks for the reply. My car won't hardly see a whole lot of track time, though it will get driven hard on the street.

I think you will be happy with 700/400. Specially if it's not a daily driver. It will be soft enough to compromise over small bumps. I assume you are getting the dual spring setup anyhow

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Yes, I went with the dual springs, as well as the sphericals. The roads I drive on quickly will be potentially rough (older, country roads) and I will be using 205's for the time being. I just don't want to run too-stiff springs that don't have enough give to handle larger more upsetting bumps.

Yea, I feel like 700 will be ok. Just don't slam your car too low. Maybe 4.5-4.75 pinch weld height

Go with 700/400 at the very least if you're planning on running 15x9s. I just bought a set with 700/400 spring rates and dual springs, installed them, and then proceeded to drive 13 hours from where I live in south florida to the Blue Ridge Parkway. They got me there with no complaints from my back or butt, and performed incredibly through the twisties. The way these dampers manage high spring rates is truly incredible. I switched to Xidas from Koni Yellow shocks and FM springs (318F/258R), and believe it or not, the Xidas ride better. They don't crash over large bumps like lesser suspension does, and they seem to almost float over small road imperfections. It's really hard to describe, but this suspension just feels fantastic. The performance is all it's chalked up to be, too. I find myself able to carry speeds 10-15MPH faster around pretty much every corner my town has to offer. Even though I'm only running 205 section width, 200tw tires, I can't drive the car to it's limit on the street anymore without at least doubling the speed limit. When I was reading reviews of these dampers, I thought that there's no way that they could actually be so capable and yet so comfortable, but they really as good as people say.

Emilio has suggested running the softest springs that will support the grip you have. Do 205 Z11s really need 700/400?

Exactly what I'm wondering here. I know everyone says that the 700/400 feel "fine" on the street, but that's not really what I'm looking at at the moment. I don't want to over spring my car, and I want the right balance.

Once you get the 225 rivals you will need the springrates. get 800/500.

The coilovers will not be comfortable on rough roads. I went from a stock suspension to 750/450 xidas, and even at full soft, the car really gets thrown around on rough or undulating roads.

However, this is just a matter of getting used to the different vehicle dynamics. Your grip is massively increased, even though you might feel unsettled by the bounciness.

To be fair, Emilio is all about getting the fastest lap time. If the softest springs that work result in the most grip... I'm not about clock at all. I daily 80 miles round trip and I just want the best driving experience possible over rural roads that are sometimes in bad condition.

It seems illogical, but I'm willing to listen to an argument that stiffer springs are more fun because they make the car more responsive. The trouble is, I haven't heard anyone say that they tried 450/300 and then switched to 700/400 and it was better (on a purely street driven Miata.) Actually, I can't remember anyone testifying to street-friendly rates with Xidas at all. I get that they defy the laws of physics and make 700/400 streetable, but what do they make 450/300 feel like with 205 tires on 15x8 6ULs?

I don't know for sure, but I think you will bottom out constantly unless you have the xidas set at maximum hight.

Try and see if there is someone near you with xidas for you to experience them. I have the 750/450 springs, and still got the 800/500 because i was increasing my power levels. I drive very long distances, and daily drive the car, I just have them set usually around 12 clicks front 10 clicks rear. Decently comfortable over all sorts of quality roads. I find that I like lower tire pressure and higher dampening rates when going over rough pavement.

I can't remember the road I was driving, but it was narrow, very curvy, and quite poor pavement. Very bumpy, lots of shallow potholes, averaged 60mph with xidas. I was playing with tire pressures, dampening, and rear end hight, based on tire temp spread and vehicle dynamics.

I guess what I'm saying is... the spring rate doesn't effect comfort to me as much as dampening rate. It is completely undriveable on regular roads at 20 clicks. super super hard. acceptably cushy with softer or taller sidewall tires and full soft.

My question is, why do you want to spend so much money on Xidas if you are going to run such low spring rates? I feel like you won't get their full use by going with those wimpy springs. They may even bottom out and ride on the bumpstops more which may make the ride worse. (I can't attest to that because I haven't tried 450/300).
If you want your car to ride well over bumps and still be soft why don't you build a bilsteins setup?
I just don't see the logic, it's like driving a formula 1 car on street tires.
Additionally, I think with 225s and 200whp your soft springs will make the car less easy to drive when applying that much power. I've driven a 600/350 +250whp car on the track and it was very wobbly (with bilsteins)

You can always just swap springs later. Go with your gut and get the wimpy springs. You might be happy with them for a long time. Then you might get into track stuff more often and then figure out why everyone said to get the 700/400 at the very least.

I would ask emilio point blank what the lowest rates his suspension was TESTED to work ok with, and not run any less. This way you get a decent compromise. You don't want to be limited to a smaller damping range by the springs.
He posted this info somewhere here but it was a while ago and I don't remember anymore.

Directly from the 949 Racing site:
Assuming that these guidelines are accurate, it seems to me that OP's intended use straddles the line between Sport and Touring. With the upgraded power and possibility of running a grippier wheel/tire later, it would seem to make sense to round up and get the 700s.

I went with the 700/400's. Will be reporting back.

Did you get the billet coaxial top mounts?

I sure did.

How heavy is your car? I've had good experience with 800/500 and 225 Rival S on MSM with full Interior. I called 949 before I ordered and after describing my car and intention to have a decent autocross/street-able car was recommend that spring rate. I thought that might be too much when I ordered but was surprised how well they ride. Overall stiffer, harder, and more communicative on street (isn't that why we get them) but actually takes potholes better in the sense that the car feels less fragile and unsettled than the original bilsteins. Setting dampers at 6 or 8 on street can handle some rough roads and that's with a pretty low 4.25 pinch weld height. You might want to contact 949 and describe your vehicle and intentions and see what they recommend.