You're right. This is what happens when you type from memory. I was impressed that I was close on the frequencies. You generally want the rear NF slightly higher than the front.

Another really technical point, but why do you shoot for subcritical damping? I would think the ideal damping would be 70.71%.

 

I do think that part of the reason Zzyzx was not as popular in the Evo community is that there were multiple high profile options available at a lower price point.

Now that Zzyzx is putting out a new line of products that give us the sort of options and performance of big money systems at KW/JIC prices I think we will see some things change.

I would also point out that Steve is the person who actually lays hands on these systems and as such can help tailor your system just for you... this is the reason why I just stepped up to get one of the first sets of these new dampers and why I can't wait to be one of the very first Evos with this new product.

On the JIC failure issues. I considered them very seriously as they provide great bang for the buck and never found any such reports of serious problems with their quality and safety. I did however find endless numbers of folks going fast.

 

robispec all the way i have the kw club sports and man are the freaking sick car drives smoother then stock to

 

Yeah for chrissake!
I've run a 1:13 in a 750hp Evo 10 at the big track.
What, Need For Speed Pro Street doesn't count?

 

It took awhile for the EVO community as well. It wasn't until 2005 that good (relatively) inexpensive coilover setups started to come about IMO.

 

I'm not sure I understand, 70% is already below c-crit no? Or do you mean, why not any higher than 70%?

 

This was sort of answered in the ultimate suspension engineering thread. 70.71 is the Q for a critically damped 2nd order system (1/sqrt(2)). It means that the system responds as quickly as possible without overshoot. In this case it would mean the body would roll and set without bouncing. I think the difference is to account for friction losses in the system.

Joe pointed out in the suspension engineering thread that you get more and more underdamped as natural frequency increases. I'm wondering if this is to increase the response time of the suspension at the cost of letting it bounce a little.

 

As I understand it, C-crit is when the damping coefficient = 1. So when I saw a percentage, I thought that it was also sub-critical damping, no?

also, can you link me to the thread where Joe mentions the increase in underdamping as NF goes up?

 

It's been a while since my Linear Control class. The basis of all this is spring on the mass (old news) and the governing equation is a second order differential equation. This format of equation is the same as second order filter (i.e. as in your audio system)....just change a few variables.

Anyway, damping factor is 1 for critically damped system. Less than one is underdamped. Over one is overdamped.

0.707 (or as you would call 70.7%) is the magnitude (DC) response at the resonance (natural) frequency for critically damped system. The "magnitude" in this case is the position of the mass on the spring (in other word, the relative position between the 2 shock mounting points). In this case, the magnitude is the percentage relative to "resting" (or DC) state, i.e. suspension at rest.

Electrical engineers would call natural frequency "cut off" or "minus 3dB" frequency. Sometime, this is also called resonance frequency.

To simply put, resonance frequency is the frequency that the system will generate (in our case, mass on the spring) if we were to push the spring in and let the mass/spring bounce (or resonate). This is the same concept (but in wave theory) how you can get certain frequency out of musical instruments (guitar strings, organs, piano).

If the system is underdamped, it will overshoot. So at the resonance (natural) frequency, the shock position will be above 70.7%.....and will have ringing characteristic. In short, the shock doesn't damp the spring enough.....resulting cars bouncing through the corner.

If it's overdamped, it'll undershoot. The system will be slow in response....and shock position will be under 70.7%.

We're talking about the rebound cycle by the way.....which means if the shock/spring is at rest....that's at 100%. Now the suspension hits a bump...not it goes to 0% at the end of the travel......and now the shock/spring is decompressing.

You two are talking about the same thing.....except one is talking about the damping factor....the other is talking about the result of the damping factor.

If you want to know the math:

http://en.wikipedia.org/wiki/Damping

See the Zeta chart (thirde pic down)....shows the graph of 3 types of damping.

 

why explain it myself when someone else has already done the work?

http://optimumg.com/documents/techti...Tech_Tip_3.pdf
http://optimumg.com/documents/techti...Tech_Tip_4.pdf

 

My problem is I'm thinking in terms of Q, not zeta. It's been a while since I've seen these equations. I worked a lot more with root-locus type stuff in my EE courses.

 

https://www.evolutionm.net/forums/sh...54#post3194854

You were posting in it, so I assume you've seen it before.

 

I couldn't come to a decision, so I had John set up my car with the stock shocks for now. I think I'd be happier with the +$4k stuff, but I can't afford it right now. After doing a bunch more research, a lot of what was written here is making more sense to me. I wanna thank you guys for taking the time to give your detailed responses. GtLocke13, thank you for writing the list of specific brands/models and what your impressions were of them. I might just get a set of MR Bilsteins for now, or leave it alone, and go with the Motons or Flags when I can afford them. I'm an Ohlins dealer(bikes), so considering I can buy the Flags at dealer cost, I might just go with them. I wanna make sure John can set them up though...
Once again, Thanx!

 

Just so you know, those weren't my personal impressions from actually driving on any of those (aside from the Konis, which feel pretty nice from the driver's seat). It's just what I've soaked up through lots of reading. The stuff I listed is pretty much what everyone can agree on as being good stuff.

BTW, if you can get the Ohlins at cost, that should be a no-brainer.

 

Ohlins dealer cost is based off how much you buy from them, and as you can figure, being Ohlins, there isn't much discount. I'm a small Kawi dealership, and don't buy tens-of-thousands of $$ from them at once. I do however, have a secret agent who works for KMC working a deeper discount than I can get.:-). I don't want him to burn a favor on my behalf though..
BTW.. regardless of the content of what you wrote coming from what you've read, you, and all the rest of the posters took the time to give me important (to me)info. This is the internet afterall, and you don't know me from Adam. Taking the time to help e is greatly appreciated.