Here is the results from a Stance S13 shock on a shock dyno I found. I know they are not RX-7 specific but I'm going on the assumption that all Stance shocks of the same spec should dyno the same. What do you guys think? Good? Bad? and why?

Thanks

 

this is what i see, which is subject to correction by more knowledgeable people

good
-the clicks actually do something
-the clicks actually progress from softer to harder
-the clicks do not overlap each other (meaning a softer setting = harder damping or vice versa)
-low speed 0-4in/sec damping rises rapidly somewhere between 10-15 clicks. means it generally does what a coilover should for handling, braking etc., which is not particularly surprising

bad
-curve is more linear than digressive. high speed correlates with high force. this means the shock may tend to be harsh over bumps and rough roads
-curve at low click settings is actually very slightly progressive at up to 10 clicks, which is generally not something you want. in a progressive shock low speed is underdamped and high speed is overdamped, relative to a more ideal digressive curve.
-the clicks are not linear. meaning it is not the same 'step' in damping between each click. the higher you go, the more it increases per click.

disclaimer: i am by no means a shock expert

my buddy has these on his s14. besides the problems that many 240sx owners had (which stance has addressed rather professionally), i think they are pretty good coilovers for the price.

 

I'd say that's a very good, fair summary of them based on that dyno. It would be better to have the knee in the dyno at closer to 3 ips, but not bad.

I'd add one thing to the bad though: there's cross talk in the adjustment. Ideally with only one adjustment **** it should adjust rebound only. Here when you adjust the rebound, the compression goes up too. I know what you might think, "but it only goes up a little", it does, but it's a significant percentage increase, especially in the low speed range.

Since they seem to have good enough quality and the shocks don't dyno half bad, I'd say that it's a decent entry level coilover. I still prefer the Tein Flex though, the dynos look a little better, they're re-valveable, and they've got a much longer track record of durability.

 

most japanese coilovers suffer from crosstalk.

the stances seem progressive at the lightest setting, which is a no-no.

Seems about average for a cheap coilover though.

 

I've already had the coilovers for the last few months and I'm glad to hear that they're good at least based on shock dyno. I have been very pleased on the street and during the one track day so far. I also believe that you can send them back to Stance to have these re-valved for a host of other spring-rates.

 

IIRC you can get replacements, but no re-valves.

I'm not sure I'd call them "good", Penskes are good, JRZ's are good, they're reasonably good for the price.

 

Thats what I meant "good" for the price. I wish I had the money for the good coilovers you mentioned. I was under the impression you could have them re-valved, guess not.

 

To be frank, I'm not a fan of the valving that's pictured above.

Plus, I think there are just way too many adjustments for that range. But that's a common problem with Japanese coilovers. It's not really a problem, per se, but I'm just not a fan of it.

 

You just have to keep in mind that one click doesn't do much, and adjust several clicks at a time. The range isn't that bad, but yes, more clicks than is needed.

I could be wrong on the re-valving thing, as I'm remembering that from at least a year ago, so it may have changed, or I may have remembered wrong, but I'm pretty sure that's the case. Although, it's likely that they're using the same dampers for multiple cars, so maybe there's another one that fits that has stiffer valving?

 

fyi roen

stance is not per se japanese. it's american. the head company is touge factory, a retailer in the states. although it's possible (probable?) they outsource their manufacturing to the same companies that make stuff for japanese companies

as for the clicky range, my main complaint would be that the last 5 do more than the first 10. and the low speed rebound changes alot in those last 5 clicks.

as for how it actually works out for the car... well i just got schooled on a local forum about this same subject. without knowing crit damping we can't really make any definitive statements about under/over damping, and our observations don't really mean anything until we know what reb/comp forces we actually want.

best we can do is the generalized statements above

 

That's not bad for the money...
There's a lot of worse stuff out there.



-Ted

 

Agreed, we'd have to take into account his car, and his shock dyno, and calculate out what his critical damping numbers are, but that's too much work for a forum discussion.

Non-linear adjustment is another pet peeve I have. Then again, I don't really use my adjusters. Valve the shock correctly in the first place, and you're good to go.

I should change my verbiage from japanese, to mainstream japanese-type, contrasted to high-end japanese, american, and german.

 

I love how everyone can say certain things without any proof or even putting a "good" dyno to compare. I don't know much about shock dyno and nor care to. From what I have learned, shock tuning is like a black art. There is no such thing as perfect shock. It's very subjective. Of course thanks to taiwan and china there have been plenty of very poor quality and bad coilovers. Stance has engineers with more than 15 yrs of experience in tuning, for high performance tires and vehicles. From what I have seen they are very involved in the motor sport and had very good success. Click on this link for some of the top finishers http://stance-usa.com/news.php

Can someone explain what is a good shock? Everyone just believes what is good from information from the internet and regurgitates it. Digressive is good? Progressive is good? Haha...there are so many things involved other than just looking at the "shape". Main thing is balance, bump and rebound has to work together with the spring rates, suspension ratio, tires, front and rear balance, chassis frequency. I've ridden in cars with koni shocks which uses digressive setting. It's great for 60yr old gramps that wants their car to float around and wants to use stock springs that takes their cars out to auto cross once a year. I've ridden on koni's and I got motion sickness, haha. There is a big difference between a high performance shocks and "lets make if feel floaty and soft for guys running 15" soft tires, so they don't think our shocks are bad.

So in the end, Everyone prefers different setups and shocks. Its all what the driver wants. All this talk about JRZ and Penske shocks, Who in this thread personally runs these on their own car? I'm not talking about about quick hot laps sessions you've have "ridden" in.

Anyways, like all the rumors you have heard.
Stance does re valve and rebuild shocks to customers specs.

 

Shock tuning is actually very objective........

Most people match the shock to the driver.

The correct way is to match the driver to the shock.

If you don't understand shock dynos, you're part of the majority. No wonder people buy suspension based on feel, it's popular opinion. It's wrong, but it's popular opinion.

I've made long posts on this subject elsewhere on this forum.

 

Yes less than 2% of forum members likely have enough experience with JRZ, Ohlins, Penske, Truesports Koni's, Moton, SD, Aragosta, etc. to comment on or compare them.

I have Stance because the pricepoint was right, my customer service experience has been excellent, and a friend won the Canadian GT Championship running Stance so I'm a believer.

I was offered Suspension Dynamics units but they were five-figures... at that price it better include time on a 7-post shaker rig...

 

I'm more into the $2.5K to $3k stuff, I don't have much experience into the $10K+ stuff.

 

lol @ shameless plug

seriously though relax man. nobody said anything bad about your coilovers.

just made some general comments that don't really mean much. all we have to go on is a PVP chart with who knows how many plots that was smoothed out and came from who knows where.

hell most people said they were pretty good in their price range.
i'd definitely put them over the silkroads i run now which as you might guess, i have never seen a shock dyno for and probably never will. however, my lower back / *** dyno tells me the valving is not very digressive.

 

What high-end coilovers have you had personal experience with? Can you provide any opinions on those if you have?

 

Mainly custom Koni's and Bilstein's.

A shock is a shock, as long as you valve the force curves right. Koni's are easier to adjust, Bilstein's (at least the ones I have) require some custom work.

 

Not a problem. I didn't take any offense.

 

I'm sorry I didn't realize you were Stance's representative till now. I did not mean to offend in the slightest, just voicing my opinion on shock tuning theory.

 

Penske - used in F1
JRZ - used in F1
Koni - used in F1
Stance - not used in F1

Koni, JRZ and Penske make better dampers than Stance, that's proven by their use by the most technically advanced, high priced motorsport in the world. They don't eff around with anything but the best. That's not to say that a Koni Yellow is an F1 level shock, but they've got the engineering know-how in the company. That's also not to say that Stances are bad, I never said anything like that. They're not ideal, but nothing in that price range is.

I'm no expert, but I've got engineering knowledge and I've read a lot of stuff written by experts on the subject.

Digressive valving has nothing to do with comfort for gramps and racing on the weekend, it's simply what gives you the best combination of body control (the steepr, low speed portion of the curve) and compliance over bumps in order to maintain traction (where it gets less steep at higher speeds). Basically, digressive is what you want for a road or track suspension, linear or progressive will either give up body control or compliance over bumps, slowing you down.

While shock tuning is partly what the driver wants, this will often end up with a car that feels good, but will be slower than a mathamatically ideal setup.

Some good reading -> http://farnorthracing.com/autocross_secrets6.html

 

To add to Black91n/a's points, the object of shock tuning is to maximize available grip, right?

That being said, two main factors play into that. The first is car's mechanical grip, the second is the amount of grip the driver can take advantage of.

The relationship is that the amount of grip the driver can take advantage of can never exceed the car's maximum mechanical grip, agreed? Pretty obvious statement here.

This is what I mean when I said, you need to match the driver to the shock, not the shock to the driver.

When most people tune shocks to balance feel or what not, they are changing the car's grip properties on either end to suit their driving style. What this does is change the car's grip, but not the driver's capabilities. The car could be giving not enough grip or giving too much grip, but something is throwing off the mesh between the driver and the car. This is what I refer to as subjective tuning. You adjust the shocks' settings until you like them.

That works fine and dandy on the street, BUT:

When you're primariliy concerned with going fast, things change.

For one, there is only one force setting per velocity that generates maximum grip. This is known as the ideal force curve. Any deviations from this ideal force curve will result in less than maximum grip.

While I'm not going to get into how to figure out this force curve, the application of this principle is of interest.

What you would want to do as a driver/tuner is tune your shocks (usually via valving) for the ideal force curve. Afterwards, get in the car, and drive it until you are comfortable with those settings. Don't change the settings, because then you will lower the car's grip capabilities.

You are, in effect, increasing the driver's capability to take advantage of the car's maximum mechanical grip, rather than decreasing grip to suit the driver. That is the key to optimal shock tuning.

 

how is the ideal force curve related to the critical damping? are they the same thing?

this is interesting

my meager background in this was a computer simulation of a shock spring pendulum system for a 300 level computer scince class back in college days

 

From the link I posted above: "Set the shocks at 65% critical damping between 0-3in/sec. Somewhere above that, digress the shock off to ~30% critical to handle the occasional high speed whack - the exact location of the knee in the force curve doesn't seem critical, as long as it doesn't happen during the chassis roll speed zone. And watch youself go faster."

As a note, that'd be wheel speed, not necessarily shock speed, as they're different depending on the motion ratio of the suspension.

His shock stuff is a good read, but the suspension stuff doesn't really seem to apply to the FC, because if we were to run his suggested ~2.2Hz front and ~2.5Hz rear natural frequencies, we'd have undrivable cars (WAAAAAAAY too much oversteer). The FC seems to like a rear frequency ~0.5Hz less than the front, and some have found more grip by going to higher frequencies (stiffer springs) because it maintains a better dynamic alignment (the front looses camber on roll).