As usual I read too much, thought too much and possibly even ended up making too much of the wrong decision, but I thought I would document my questions and experience below in case it is of any assistance to anyone.
Before reading below, its probably worth noting that I am a little particular with my handling, so my idea of things might be totally different to yours. I also have limited knowledge, so much of what I write might be utter crap, so digest at your own discretion.
For interests sake - my car has LSD, front and rear strut braces, a H brace, 20mm front and rear swaybars with new bushes, new nolethane control arm bushes (which removed a lot of understeer I had) and yet degrading all this I have 18" wheels with 35 profile tyres.
At the time of purchasing the coilovers I didn't really have the budget for the high end (and predominantly track spec) Tein and Cusco items, so I opted for the BC Racing BR Gold - as many others on here have. Based on all I had read and heard, these were the only budget coilovers worth buying.
From talking to people, reading and going for a spin in a few cars with coilovers, I decided that I really wanted to have mine a little softer than normal, because from what I could tell most of the out of the box coilover kits I read about and drove on were far too hardcore for Australian roads and more than anything degraded usable performance. Sure they might go ok on a track, but there has to be a nice compromise which can be achieved somewhere along the line.
The question was, how much lower spring rate should I choose and (assuming the BC damping was matched with much firmer spring rates ) would it have the range of adjustability and damping quality to cope with lower spring rates?
In the end, I opted for 4kg front/3kg rear, significantly less than the 7kg/5kg than BC Racing usually provides the FTO with.
Due to a booking fail, I had these installed at 10.30 the night before I needed to go to Albury so I didn't even get a chance to play around and test them. I had them set on about 3/4 hard (22 clicks) and the following morning set off on my way to Albury (not down the highway). Not knowing what to expect from coilovers, I was immediately pretty unhappy. They didn't feel terribly hard, but it was very bouncy, very skittish over bad sections of road and I felt EVERYTHING. My car had rattles and vibrations it never had before and just felt like a bitch. Was easily the worst 6 hour trip I have ever had. Yes I am a goose for not just stopping and changing the damper settigns, but I just wanted to get there ok lol.
Eventually, I had time to play around with the full range of damping available and drive repeatedly around the same long loop of road across different surfaces to see the difference each change made.
After much testing I tried to figure out why I still wasn't getting the results I wanted and came back across what I think is a great summary of damping.
After lots of testing, I think(I don't really have enough knowledge to say definitely) I can achieve something close to "critical damping" at about 5 clicks below full soft. This is also the setting that feels most settled and comfortable on normal roads. However, when you take a mate for a drive in your FTO and he describes it as comfortable, you know you have failed in your quest for a mildly aggressive performance setup.The way you tell whether a system (such as a car's suspension) is under or overdamped (or "critically damped" which means the perfect amount of damping) is by looking at how it oscillates.
Damping absorbs and dissipates the energy put into the suspension (in the form of heat) to control oscillations. A damper resists movement and therefore controls the speed at which the suspension can move. For example you could move a shock absorber very slowly and not feel it but if you moved it quickly you would feel resistance to that movement. This is caused by the shock pushing oil through small holes in the shock...move slow and oil flows fine, move fast and there is resistance.
An underdamped suspension (e.g., if there were no shocks on the car) would oscillate up and down for many cycles before settling down. So if your car is still bobbing two or three oscillations after a bump it is a bit underdamped.
An overdamped suspension would have too much resistance to movement. This is a bad thing because a suspension needs to keep the wheels in contact with the ground at all times. If you have a very aggressive shock on a lightly sprung car and hit a bump, the shock will prevent the wheel from rebounding and coming back into contact with the ground...obviously a bad thing. Your car may not oscillate but it will be skipping over the pavement.
The idea is to achieve critical damping where the suspension is allowed to move to keep contact with the ground but stops any oscillations after the bumps. Critical damping is a function of both spring rates and damping rates so you have to match the shocks to the springs to get it right. In general the stiffer the spring the more damping is required.
This isn't to say I am totally unhappy with this current setup. I am now able to get the ride stance I want (even though I haven't lowered it properly yet, I will shortly), I have the camber adjustability without spring binding, all the while having a reasonable performance/comfort compromise.
The disheartening aspect of all this is that I spent $1200 + fitment on suspension which (when set to best alround settings) feels almost exactly the same as Tein Springs/KYB Shocks/Cusco Pillowmounts it replaced.
On current settings mentioned above (5 clicks below soft), the handling is still reasonable, but there is still the slight sponginess to the suspension feel when pushed hard - something I was hoping to move beyond.
This sponginess is replaced by responsiveness the harder I set the damping, however the actual real world handling deteriorates markedy as it becomes crazy bouncy and skittish. Even going around the block, a hard acceleration out of a corner with slight imperfections turned the car into a real handful skipping and then suddenly gripping and tugging the wheel hard.
I suspect that by going down so far with the spring rates, I have made my suspension too easily "over damped". I suspect anything over about halfway hardness results in virtually riding on the shock, which I can't imagine being a good thing.
I'm not sure what it would like being in an overdamped car on a track. On smooth roads the hard damping settings feel reasonably good, but I guess it could be seriously degrading shock life?
So I am left with the dilemma as to whether I should leave it as is and just be happy with the all round compromise I have, or go another 1 - 1.5 kg higher in the spring rates to see if there is a happy medium which can be struck on the BC's.
Ideally, I would like to bump the "critical damping" level up to somewhere around the middle of the damping range (15-20 clicks) so that it could be nice and responsive, yet not overly harsh and skittish on normal roads.
However, I don't know if merely increasing the spring rate a bit more will achieve this or keep things predominantly the same, just firmer.
Would appreciate input or suggestions on this as I'm not really sure.
My uneducated conclusion is this;
- Don't drop your spring rates too far below recommend settings for the damper.
- Depending on how hard/soft your coilovers are, similar handling characteristics can be achieved with a good shock/spring combo. Just because you have coilovers doesn't instantly mean your car handles better than one which doesn't. As long as the spring and shock compliment each other and the car you will have good handling.
- Don't buy coilovers if you think they will magically turn your car into a handling masterpiece. There are many variables (road conditions being one) which affect how they will perform. If they are over damped, they will suck, if they are over sprung, they will suck. If you drive on crap roads like Parra road all the time, they will still suck as they are not Camry spec.
- Wanting to set your own ride height/stance, needing wheel clearance, wanting more camber adjustability (without dicking around with camber pins), wanting to track your car a lot, are all valid reason for coilovers. Up to you if you think that is worth $1300+
