Strut Insert Dimensions

In my search for an ideal race suspension package for the AE92, I've pretty much tried out different solutions, either through my own or my friends' cars. When I first got my car, it had some cheapie Big-O brand struts with the OEM springs. I then upgraded to the Eibach Pro Kit Springs and that helped out some. Unfortunately, the cheapie struts blew out in less than a month, so I eventually got the Koni "Yellow" Sport strut inserts. I was happy for a while with those until I started autocrossing. The Pro Kit springs are great for sport touring-type driving with very little track use. After using them for half of my novice autox season, I decided that I didn't like the progressive spring rates--once the rear end broke loose, you could feel the rear spring(s) unload, soften up, then stiffen as you corrected for the oversteer. Not fun, if you ask me. I decided to try out the Ground Control coilover kit with linear spring rates that I chose myself in conjunction with the "old" Konis. Good stuff! I got nice, neutral balance that could be coaxed into very slight, but, more importantly, controllable oversteer at throttle release. Once the car was pointed in the right direction, all you had to do was get back on the gas. Easy, right?

But...

I lowered the car's ride height to effectively lower the center of gravity. Unfortunately, lowering it that small amount severely decreased the available compression travel. "How severe?" you ask? How about 1.0" in front and a little under 1.75" in back? That lack of compression travel really hurts the car's attitude in an course layout with a less-than-ideal surface. Once the corners slam onto their respective bump stops, the spring rate effectively shoots to infinity. Having a spring rate that "high" will absolutely shift the handling balance depending on which end of the car it occurs. A rate of infinity up front will cause the car to severely understeer; in back, the car will oversteer. With that little compression travel front and rear, you can see a high potential for bad handling juju.

Do we like bad handling juju when we're trying to squeeze every last bit of performance from the car? Absolutely not! Besides, it gets really old when one moderate bump fully compresses the front end and launches your car haphazardly into the air. Let's not forget--what comes up must come down, right? But, I guess any crash that you can walk away from is considered good. =)

In late Summer '02, I started to casually do some research for a new suspension setup. I had the choice of off-the-shelf coilover units from Japan like the popular Tein HAs, TRD, Bilstein, Koni, just to name a few. The biggest problem for me was, once I need to rebuild or revalve the units, how would I do it? How long would the turn-around time be? What if the parts were discontinued? Would I have to ship it back to Japan since no one state-side can properly do the job for me? Regardless, it would probably be too expensive for me.

As far as custom-built coilovers, I could choose from Truechoice (who have their own great record of building custom setups for winning autox'ers and road racers), Penske (ummm, I'd need to win the Lotto for these!), Leda (not as popular, but still great quality and workmanship), and, a relatively unknown offshoot company of Ground Control, Advance Design. If it weren't for me stumbling onto Advance Design's web site through the parent Ground Control site, I would never have known about their products.

In late '02, they expanded their universal strut/shock race inserts to fit almost any application you could think of. Now, instead of just going with one insert then getting them to shorten the body and piston shaft to suit your needs, you could choose from five variants with different strut body and stroke lengths. With that many choices, there's most likely no need for you to get a custom strut insert. What's even better is that you don't have to send out the coilovers/inserts for a revalve job. Assuming that you're comfortable disassembling things and you actually have the ability to assemble it back to proper working order, you can do it yourself!

With that said, barring a bad incident that wrecks the coilovers, the AD coilovers should last your car's competition lifetime. So, let's say you're bored with the sweet N/A motor and want to drop in a heavier (or lighter) motor and a beefier tranny in the front end. Fine! Pick the proper spring rates for the associated change in front end weight, then revalve the coilovers/inserts yourself. Cool, huh?