Project 200SX – Overhauling the suspension…
By Wes Dumalski
We're not going to lie, our old Ground Control and KYB AGX combo might have been good back in the day, but after too much autocross and track time it was showing its years. The time has come to replace it with something worthwhile, the big question we had was what do we replace it with?
The B14 Chassis Sentra and 200SX are plagued with very little suspension travel from the factory. Take that and reduce it by lowering the car with OEM length dampers and you have a recipe for smashing bump stops, frequently. We knew that we needed to go with a shortened strut setup, and without spending big money it left us with one option… KONI. Koni offers damper inserts for the B13, B14, and B15 chassis. These dampers insert in to modified OEM housings. Many people are afraid or are not even aware of this option, but honestly it is one of the best available, and perhaps the best part is that it is a very cost effective.
Since Koni offers Both red (street) and yellow (sport) inserts for our application we did some research to determine what would work best for us. We knew we would want to run a maximum spring rate of around 425 and as such we wound up using the B15 yellow sport inserts for our application. The front inserts (Part # 8610-1409) are singly adjustable for rebound and damping via a dial on the top of the strut. The rears (Part # 80-2838) are singly adjustable as well, however the damper must be fully compressed in order to adjust it. This is primarily done before assembly and installation, however our resr suspension is very easy to remove and reinstall in the event was want to change damper settings.
Given that we already had Ground Control coilovers we had a choice to make, re-use the GC sleeves and perches, or go full tilt and use the ones that Koni offers. Because we were building a new setup we chose to use the Koni units. The Koni sleeves and perches are high quality units and are used by other aftermarket suppliers in their coilover applications. We paired the Koni sport dampers and coilover parts with Eibach Race Springs. The ERS are available in nearly infinite diameter, length and rate. For our application we chose 2.5″ diameter, 7″ length, 350lb rating for the front and a 2.5″ diameter, 6″ length, 300lb rating for the rear. These rates are on the lower end of the spectrum but they will allow for a good balance between street comfort and track performance. The nice part about this setup is that our dampers will support stiffer springs in the future.
With the parts sourced it was time to set about installing this setup. Now bare in mind there are many ways to go about installing the inserts in to the OEM front housings. Many people take the minimal approach and simply remove the OEM damper tube assembly and insert the Koni, leaving the factory finish and spring perch. Because we wanted a sano setup, we chose to take it a few steps further.
The first step in this process is to find a pair of donor housings. If you only have the ones on your car many people will choose to buy a set of blown OEM used dampers or something very inexpensive to use. This allows them to build the new setup and still have a usable car. In our case we had an extra set of OEM dampers lying around that were perfect for the job. We started by laying out the front damper insert parts and busting out the good old instructions. In this case it pays to read them FIRST. This process involves drilling and cutting in to a pressurized shock absorber so be careful here. Before you begn cutting the damper tube Koni suggests you drill a small hole in the center of the bottom of the damper, this will relieve the pressure and allow you to drain the fluid.
|Here you can see the bottom of the strut. We drilled a pilot hole and then used a step bit to enlarge it. The bottom of the Koni insert will pass through this hole.|
Once you have done this on both front struts it is time to cut the OEM housing. There are two reasons for cutting the housing. The first is to facilitate the removal of the damper assembly, the second is to shorten the housing itself. The Koni insert will provide the full range of factory travel, but because it gets mounted in a shortened housing it allows you to lower the car without loosing travel. This is CRITICAL if you want to keep the car off the bump stops and still have a lowered center of gravity. Koni recommends you cut 55mm off of the factory housing for which we used a cut off tool. Ideally you want to keep the cut as straight as possible, however because the insert does not rest on top of your cut it is not imperative.
|Here you can see the cut housing with the strut body being removed. When you cut the housing do not attempt to cut straight through as you will hit the strut shaft.|
Once cut through you can remove the strut assembly and discard it. We then cut off the factory spring perch but before we did, we measured and noted their position so that we could weld on machined hats in their place. We took the time to grind off the welds and clean the rough edges up. We also then enlarged the hole we previously drilled in the bottom. This is important to do correctly because the Koni insert has a threaded protrusion on the bottom that will pass through the bottom of the OEM housing.
|After trimming our housings we chose to completely remove the OEM spring perch in favor of a custom welded on piece.|