D2 Coilover Install
By Dave Clements (4/13/01)
With the height and spring set, the spanners were employed in tandem to lock the perches into place and everything was again checked for tightness and fit. Wheels back on, lugs set, time to see what the results were.
Wow. Not much overall difference in height, but definitely a bit lower. Fortunately the difference is almost identical from front to back, so it looks the same, just lower.
Time for a test drive.
First impressions were that the dampening was set to it's maximum soft, as small dips made a lot of motion in rebound. The springs were very stiff, but the car is heavy and the shocks weren't set up to hold them back. Regardless, the springs really did the job in corners, keeping the body roll to a very minimum and surprising me with the amount of steering accuracy I could now wield.
Two days of adjustments have me now on maximum hard, and considering what I need to do to tune the spring compression to get more from them. I am at max hard and it's good, but it should be much, much stiffer. The theory of what's happening is sorta complex, but makes sense if you think it through.
Right now the spring is barely compressed from it's relaxed state. It's got enough load to keep it from moving around when fully decompressed over bumps and whatnot. A spring that is slightly compressed will more easily compress more than one that is more compressed before compression. She sells sea shells by the seashore. Let me put this in numbers:
If a spring is compressed 10% from its relaxed state, it takes less force to compress it another 10% than if it were at 20%. The more the spring is initially compressed, the harder it is to compress it more. This is linear, sort of. Other spring types will dramatically increase in stiffness with compression based on their design. These are not that design.
Currently I have the shocks dialed so that they're counteracting the natural motion of the springs to bounce back as quickly as possible from compression. This means I need to apply more compression to the springs so that they'll not compress as much with pressure and and will have less to travel when that pressure is released. This should stiffen up the ride noticeably. I'll append further changes when I've found more information.
After talking to Chris at TRi, we tried removing all preloading from the springs to remove the bounciness with no success, or ill effects. Perhaps a slightly lower ride height was gained from this however. The perch is just tight enough to keep the spring from moving, about 7.175".
Upon installing the front T properly and adding the washer, the ride has improved substantially. It now feels very overdampened, bobbing over hard surfaces and not harsh but VERY firm. In all, an incredible improvement. Further discussion and experimentation will follow. Ride height in front dropped as a result of proper installation as well, so 19" front is advisable for a set height. Also of note is that camber adjustments need to be dialed almost all the way out for the lower settings. While not extreme, the negative camber is noticeable and will affect tire wear if allowed to continue.
Additional information on pages six and seven!