DMS 40mm "Gold" Coilovers
by Dave Clements
Ok, so i've had coilovers on my car for 13 months. They were the TRi Race coilovers i purchased from TRI Tuning, and while they were an improvement in many ways over the KYB GR2/Stock spring setup i had, it was a compromise in ride quality.
Late last year, when installing my STI top mounts, i also discovered that the front right was leaking. This progressed until hard bumps made that corner actually knock due to the lack of dampening. A rebuild kit was ordered from TRI, but it's been a month from this date (May '02), and no sign of it yet. I'm not holding my breath.
To be honest, i'd always wanted what i could call a "quality" coilover. In many ways, the TRi setup didn't fit the bill. It was made by some unknown company, sold by a company with a shady rep, and was ill suited for my car. The dampening wasn't sufficient, even at full-hard, and the springs were very, very linear. This setup would probably work perfectly for a GC8 Impreza, but...
Several brands come to mind when shopping for coilovers: TEIN, CUSCO, ZEAL, HKS, Apex-i and DMS. All of these brands have a tried-and-true installed base, and can be counted on for a measure of quality and support. These were attributes i was looking for.
Being patient sometimes pays off. I'd had several chances to pick up a set of several of these brands' products, but for one reason or other, it never quite worked out. In this case, everything did.
DMS has a fairly devout following in the Subaru community, being a popular track and rally setup that compromises nothing when driven on the street. The 40mm version is a downscale and slightly less expensive version of the popular 50mm product. It keeps the same tri-progressive spring but has only one-way rebound/dampening adjustment. The build quality is excellent as well, and the unit is suprisingly light for using a steel body.
My expectations of the 40mm was to give me a more European ride: smooth and supple until pressed, then very firm. This is different from the Japanese approach, which generally over-springs everything with astronomical rates. Dampening is also dialed in very high. The ride is choppy, and well suited to a smooth circuit, but not so much for the street. Utah streets are terrible, so i decided to look towards a compromise.
Having installed and experienced the 50mm setup in a GF8 Impreza wagon, i was instantly impressed. Even with the lighter weight of the Impreza, it drove exactly how i'd wanted my car to: smooth then firm. Over bumps there was no drama, no clunking, no bouncing.
DMS Coilovers Installation.
Installation was pretty straightforward, especially since I'd done a fair share of suspension installations prior to this one, including a set of DSM 50s on a GF8 Impreza. That experience had tought me that the DMS product did indeed live up to the hype, and that one must be careful with wheel offset and tire width because of the length of the springs.
At my disposal was a garage full of tools, manual and pneumatic. Due to my desire to get the suspension on as quickly as possible, I ended up installing it myself. While it's not exactly a hard job, I was experienced.
The front set went on first, but not without some head scratching and tinkering. The front assembly has to be put together in a very precise way, or it won't sit together right and will not work properly. At the top of the strut cylinder, the shaft flattens out, then goes straight up, flattens out again, then starts on the threads. As much as I looked at this and tried to fit everything together, it wouldn't sit right. When I put it all on, and clamped it down, the top hat would shift, causing it to rub against the top mounts, inhibiting it's motion. This wasn't the way it was supposed to fit.
Closer examination revealed that the top had wasn't sitting on the proper perch. It hand't fit onto the first, flat ledge due to a prior misinstallation. The hat had apparently crept up and was instead resting on the 2nd ledge, causing a number of grooves to be dug into the bottom of the hat. Puzzled, but certain that the hat was supposed to go on the bottommost ledge, I flipped it over and literally beat on it with a hammer around the rim, till the deformed aluminum was reset, letting the hat rest properly.
That done, I assembled everything else as it came, with the two washers between the hat and mount giving just enough space to eliminate interference, and promptly zipped it down tight with the impact wrench. Both sides proved this troublesome, but succumbed to my determination eventually.
The rear proved a bit more interesting, however, as I'd previously read about the interesting way DMS had to deal with the rear springs interfering with the tires, and the older Sti top mounts that many people are using with the WRX. An aluminum disc, with an angled, circular depression on the top, and a spring perch on the bottom, was all that went between the spring and mount. It turns out that this setup, with the top depression made eccentric to the center, lets the installer move the spring in or outward by rotating it. This solves some of the problems people have had with clearance in the rear, primarily with high-offset wheels and very wide tires.
The rear also features an interesting way to enable camber adjustment on the strut itself, without using an aftermarket top mount (which probably wouldn't work anyway). On both sides, the top two holes have removable washers, set into the strut itself. These washers have eccentric, offset holes which can be rotated to promote positive or negative camber, relative to the setting of the assembly. This gives the installer two ways to adjust the relationship of the wheel to the spring, so that one can run more negative camber but not worry about contact with the spring. I only received one set of these washers, which adjust 0.7 degrees, but a larger offset one is normally included as well.
After spending about 6 hours in the garage, I was ready to give it a whirl. I set all of the dampers to full hardness, and cranked up the height about 2" in the back (bottom perch relative to bottom thread) and about an inch in the front. Lowering it from the jackstands revealed that it was indeed very low.
The first drive was also revelatory: I needed a good deal more height. I was rubbing, a lot, but the ride was very nice for being on full stiffness all the way around. A trip back to the garage and a few more cranks on the springs gave me enough height no get me home for the night.
The next day I took a trip to Salt Lake City, with two guys in the back totaling more than 500lbs. It rubbed in corners, a lot, but not nearly as bad as if I hadn't adjusted it before leaving the previous night.
More adjustments, up to 3", netted more improvement, but further adjustments to 3.5" and 4" brought me to the realization that I wasn't going to solve the rubbing and get proper camber at the same time. In fact, I was getting positive camber, not something anyone wants in most situations.
I resolved to look at the camber washers and see what was going on. It turns out that I was dialed to the full positive settings, keeping the tire as far away from the springs as possible. While this was a noteworthy cause, it wasn't necessary, as I realistically had plenty of space. Getting positive camber, however, proved to be a bit more troublesome than I had hoped.
The camber washers are a great system, but when the spring is pushing down hard on the control arm assembly, negotiating the bolt into the holes on the spindle isn't a simple task. While the assembly does rotate, it doesn't do so without vigorous effort. One person, even with my strength, could barely do the job. Compounding this problem was the small amount of force required to unseat the washers. I do wish they were keyed somehow to keep them in place.
Eventually I did indeed get everything set to full negative camber, and set the rear springs down to 3.5". This closed the fender gap a little bit, removed the negative camber present before and replaced it with an almost neutral setting.
By now, I was getting used to the firm, but smooth feeling of this new suspension. The differences between the two setups were startling in many regards. A few noteworthy themes come to mind:
High-rate, linear springs may be fine for the track, but they're ill suited for most of the roads in the world. The jarring ride that this setup gives is also better suited to a lightweight car, rather than a heavy one. With proper dampening, the ride can be tolerable, but it's really numbing and uncomfortable for most people.
Spring length matters! I never took measurements, but the DMS springs are more than twice the overall length of the the ones on the previous setup.
At this point, I think I'm going to lower the car a bit more, the front especially, as the car seems to track better and handle bumps better when the front is lower than the back. Lowering it will also increase the negative camber in the rear, possibly ridding me entirely of the rubbing when going through corners very hard.
They're worth it. I know that there are other worthy systems available, but the DMS setup seems to satisfy me very well. Again, it's all about what kind of ride a person wants from their car, road quality, car usage, etc but in the end, a well made and designed setup will suit more of those situations and with better results. The DMS 40 does just that.