In a coilover setup such as ksport, jic, pic all the way up to ohlins, motons...
Gas Pressure
How much nitrogen pressure is in them? How much pressure can you add or relieve from the shocks safely, and what are the determining factors of this? How will that affect the handling/ride?
Valving
What sets apart a good shock from a bad one? How does placement of the discs in the valve work? If I wanted to change how my shock responds in a certain area where would I start? And with that, is it possible to turn a shitty coilover (shitty meaning improperly set up) into something of quality that functions proplerly?
Adjusters
Since I've been told that a lot of them don't work properly anyway. How are they supposed to work? How would you tell a good adjustable shock from a bad one by looking at them? When its all apart is it possible to change the affect they have on dampening, possibly fix what was wrong with them in the first place or even disable them?
Oils
What determines what weight you should use and why? I've been told that (cheap) shocks tend to fail because the oil overheats, that would be due to improper valving correct? Assuming that cheap shocks use cheap oil, whats in expensive oil that isnt in cheap oil? What varies between oils (of the same weight) and in changing oils what should I look for or stay away from?
Springs
How do they affect what goes on inside of the shock(fluid and valving)? Why is it recommended to revalve a shock if you intend to change spring rates yet with higher end shocks this doesnt need to be done?
Instead of saying Shock A is better than Shock B. I wanna know the recipe of the two.

Modified by soulpwr at 3:53 PM 3/14/2008


Modified by soulpwr at 3:55 PM 3/14/2008

 

Gas Pressure
it depends, and for almost all of the shocks out there it isn't adjustable. JRZ, moton, Penske, Ohlins, and Advanced design are the only ones i know of that are end user adjustable. And not all shocks are pressurized. As far as pressures, it really depends: moton and JRZ both describe it in their directions as a way to add "spring rate". While it isn't exactly like it, it is close to it they say. I can't remember the specifics though
Valving
This is another "it depends" the japanese guys seem to LOVE linear valving. It doesn't make much since to me but neither does their spring rates. In the US most performance shocks have a digressive curve. This is what i like and i understand it. You would probably have to do a bit of work, and source the correct shims ect.. but sure you could. I don't think it would be easy to switch a mono-tube to a twin-tube though, but again many say that they are both good
Adjusters
I haven't heard that they don't work properly, but what i have heard and seen is that the ones with 'clicks' don't make the same adjustment for every click, and some times the adjustment just isn't there. IE total change is nothing
Oils
I don't think it has to do with improper valving. A shock creates a lot of friction and that creates heat, which breaks oil down. When i run my shocks on the dyno they get pretty warm to the touch. If you use to thick of an oil then the valving changes as the oil warms up (ie becomes more viscous(sp)) and it isn't like a motor were you can warm them up. I think that synthetic oils are what they use
Springs
The spring holds the car up, and the shock controls the movement of the car. With a stiffer spring the movement is going to need to be controlled in a different manner then with a softer spring, hence the need for re-valving. The higher end shocks don't need to be re-valved because they either have a HUGE range, or they are already valved for higher spring rates. I know with Koni 30 series and 28 series you get to pick you valving.

 

Just some added comments, all IMO, I'm no expert on dampers:

My understanding is that the main purpose of pressurisation is to reduce cavitation and oil foaming inside the damper (which is a bad thing). So why are some low and some high pressure? Not 100% sure, but at least some high pressure units can be used 'upside down', and this is related to them being high pressure dampers. Using the damper upside down reduces unsprung mass since the heaviest part (damper body) is mounted to the chassis and the lightest part (shaft and piston) is mounted to the suspension (the opposite of a 'normal' set up).

Koni and Bilstein (amonsgt other top end dampers) use digressive curves. This is a good thing (especially for a road damper) because it makes the damper effectively stiffer at low speed load inputs such as you get in body roll (important for handling), yet effectively softer with high speed shaft inputs (such as when hitting a bump), so the damper is more supple over rough surfaces. Don't misunderstand, a digressive damper is still stiffer at fast shaft inputs than slow shaft inputs, but less so than a linear damper, or even worse a progressive damper. I would avoid any damper I knew to have a linear curve, no matter how well marketed or hyped.

I can't see it being possible to 'convert' a twin tube into a mono-tube or vice versa. Typical Koni dampers are twin tube, though some of their dampers are mono-tube (I think), depending on the application. Bilsteins are I think all mono-tube (not 100% sure if all of them are, but most at least are). Twin and mono have somewhat different characteristics, with mono tubes posssibly being a little 'harsher' but providing more precise damping, especially with short stroke inputs. Mono tubes also tend to run a little cooler than twin tubes since there is only one thickness of wall between the oil and the (cooler) atmosphere.

There may be other good reasons to use twin tube in some applications and not in others, but I don't know enough to tell you what they may be. Both Koni and Bilstein are very good dampers of more or less equivalent quality and performance, even though one is twin and the other mono tube.

It's hard to design an effective adjustable valve that provides a wide range of adjustment, consistency of adjustment, linearity of adjustment, and reliability. Bilstein doesn't offer adjustable valves for this reason (adjustment only being possible by re-valving), and Koni uses only very well designed and made adjustable valves (probably patented), which are the same valves used in any of their adjustable dampers whether road or race (only the rate will differ between applications).

Other adjustable dampers (with notable high quality / expensive exceptions such as Penske, Ohlins etc, but not KYB, Tokico, Tein etc) typically have a lesser range of adjustment than Konis (despite often a dizzying multitude of 'clicks'), and often the bump adjustment range is almost zero (not really worth having). Koni dampers typically don't have bump adjustment (rebound adjustment is more important for handling purposes), but some do and any of their adjustable dampers can be retro-fitted with adjustable bump valves if desired (which I'm sure would be superior in range / quality to nearly all other adjustable bump valves).

Friction and heat from the components sliding together, and also from the oil molecules moving past each other as the oil passes through the valves. The damper effectively loses 'rate' as it gets too hot, i.e. it gets softer. Well designed valves create less friction in the oil as it passes through the valve, so less heat build up. Koni and Bilstein have the best valves in commonly available dampers, and run cooler...

In my understanding, any Koni dampers (with the exception of some of their sealed units supplied for some lower spec OE applications) can be revalved, and internal adjusters can be replaced with external adjusters if required. Bilstein of course can all be revalved too.

Dampers are the basis of any suspension set up, and as such are more important than springs, i.e. it's more important to have good quality and appropriately rated dampers than it is to have stiffer springs (and many people fit springs that are way too stiff), though this isn't to imply that correctly rated springs (for the application) are not important.

 

A high quality oil designed specifically for use in dampers will have a high viscosity index. Meaning that the viscosity of the oil stays more consistent over a wider range of temperature. A cheaper oil will have a low VI, and viscosity can vary greatly depending on the temperature of the oil, leading to inconsistent performance.

Shim thickness, diameter and proximity to the piston all factor into valving. The overall stiffness of the shim stack determines the damping force generated (stiffer shims = stiffer damping), and you can fine tune points in between by varying preload and individual shim thicknesses. It's possible to revalve a damper but why go through the trouble (do you have the tools?), just don't buy a crappy damper to begin with.


Modified by PIC Performance at 5:07 PM 3/15/2008


Modified by PIC Performance at 5:08 PM 3/15/2008

 

[QUOTE=PIC Performance]A high quality oil designed specifically for use in dampers will have a high viscosity index. Meaning that the viscosity of the oil stays more consistent over a wider range of temperature. A cheaper oil will have a low VI, and viscosity can vary greatly depending on the temperature of the oil, leading to inconsistent performance.

Shim thickness, diameter and proximity to the piston all factor into valving. The overall stiffness of the shim stack determines the damping force generated (stiffer shims = stiffer damping), and you can fine tune points in between by varying preload and individual shim thicknesses. It's possible to revalve a damper but why go through the trouble (do you have the tools?), just don't buy a crappy damper to begin with.QUOTE]

First I wanna say thanks to all of you that responded. PIC, I agree with your "Just dont buy a crappy damper to begin with." The only problem I have with that is that there is such a lack of information when it comes to shocks making that easier said than done. With that said, the price point often goes up exponentially. Because of this it is generally assumed that you get what you pay for. Thus a $2000 set of coilovers should be designed better than a $1000 set of coilovers. You would think that for that extra $1000 you are getting better internal quality/ tighter tolerances better materials.,etc. That isn't always the case though. JIC's vs. Function Forms for instance. You'd be hard pressed to find a decent shock dyno for either of these coilovers. yet their price point (for the same car is no where near the same. ( I know there are other factors that go into this as well.) There is a vast majority of end users who have purchased "crap" already, myself included. In learning from my own mistakes I wanna learn more on how to possibly make something better out of what I have already, gain better knowledge about the insides of the damper, and being able to identify a better damper rather than just paying more for the same "crap" later or buying what was believed to be good only to find out otherwise. C'mon, we all saw The Blair Witch Project after someone else said it was good and look what that turned out to be.

 

I agree 100%, you really cannot go by the "you get what you pay for" rule in this case. The price of many coilovers don't accurately reflect their actual value IMO, but companies can get away with it due to the lack of knowledge among consumers. The best thing for prospective buyers to do is to not only ask a lot of questions, but learn which are the right questions to ask, and then they will really be well equipped to make an informed decision. I tell that to people all the time.