I'll do it in parts, as it'll end up being quite long, and i doubt ill get it all written at once.
Maybe when done, ill re-edit and turn it into one big write up.
I'll first say that im no pro. I dont re-valve my dampers, i dont have suspension travel data logging gear (one day maybe), i don't have a mechanical engineering degree, etc, etc.
What i know is from my experience and reading as much as i can on this topic over the years.
So don't take what i write as fact, how i my modify my suspension as being fool-proof, it being the best way to go about it, or that its safe to follow.
It'll be a bit random, with some general information why cheap coilovers are crap, why what im doing i believe is decent, etc, etc.
Why i'm doing this...
I *love* hills driving!!!
I live in a decent sized city, that is surround on two sides by comparatively low mountain ranges with lots of twisty, challenging roads, that are often quite bumpy and unpredictable.
Occasionally some of these roads also get closed off for rally, sprint and hill climb competitions that i compete in when i can.
An example of one of our fun roads: https://www.youtube.com/watch?v=M31hXZ339hk
Me competing in a hillclimb last year: https://www.youtube.com/watch?v=DNqdvFOQDco
The bumpy and unpredictable nature of the roads (and most public roads in general) means you need quite compliant suspension that wont give you any surprises.
You should be able to hook around a corner almost at the limit, hit a bump in the road, pothole, etc, and not be thrown into the other lane, or worse, off the side of the road.
Suspension like this is what we should all aim for: https://www.youtube.com/watch?v=zZQKepbGKiI
What we commonly use...
There is generally three problems that come up with the type of suspension modifications we do.
Not enough bump travel - you hit a bump, the suspension travels all the way to its limit hitting the bump stop (bad!).
Springs that are too stiff - stiff springs are great for a smooth track, but not for normal bumpy road driving.
Dampers (shock absorbers) don't match the springs/car - causes a lot of problems, like making the car bounce and not settle after hitting a bump.
Off the shelf lowering springs actually do the job reasonably well for the price. They normally use variable rate springs that lower the car, but also increase the spring stiffness as they are compressed.
The downsides of them is the reduced suspension bump travel, and not having a damper that is matched to the variable spring rate.
Cheap aftermarket coilovers have a bunch of problems (it appears the Japanese tuning market is mostly to blame. "Its Japanese, it must be good!", nope!).
Tein, JIC, and then later the other aftermarket Asian brands like BC, etc make coilovers that look pretty, have high spring rates that make the car feel like a go-kart, but actually do a pretty bad job of providing more grip on the road.
Basically they hide the poor quality of the product by using a high spring rate. A super high spring rate means dampers don't have to work as hard (so they can be cheap and crappy), and the normal suspension travel issues are not a problem.
Those million-way damper adjustment levels they provide are very unpredictable and inconsistent.
Alloy housings, no thanks! Even steel housings have been known to crack. Trusting your life on cheap alloy housings is a really bad idea (in my opinion).
Just think about it... say you are paying $1200 for a set. That's $300 a corner for a blingy housing, the strut top, the spring, the damper, etc. It's too cheap, its just not going to work that well.
Even at twice that price you may not get decent quality springs, quality dampers that are matched, and damping rates that are setup to suit the specific car.
For decent coilovers that use decent quality parts, are made to suit the specific car (to some degree), etc start at around $3000 a set.
If you think that's expensive... top end, professional racing team coilovers are often worth >$40,000 (like in that what we should aim for youtube video above).
Home made coilover conversions can do the job well if done right (like hopefully i am).
Doing it properly is quite a challenge though. Simply fitting a sleeve to the existing housing, and sliding in a damper that will fit is not ideal (sorry rear AGX conversion thread, but this applies to you).
Next up, my plans...
BTW, comments are very welcome
It may be some time between instalments.