Evaluating the HKS Max IV SP S2000 Coilover Suspension System
by Mike Kojima
The guys at Motovicity have been singing the praises of HKS's new Max IV coilover systems to us for a while. While we have generally always been impressed with HKS's tidy OEM like engineering, it was a while since we had experienced their coilovers. In the early 2000's we had tried some of the original Hipermax suspensions on a few of our cars and although we found them to be of high quality and smooth riding, they did not have enough spring rate and damping for serious performance with big sticky tires and especially track use. We sort of regulated the brand as nice for street use only and looked toward other places for suspension for our projects.
Fast forward 10 years and 4 generations of Hipermax suspension later, plus Motovicity's raving about them made us eager to get our hands on the Hipermax or Max 4 suspension system for another review.
To give the Max IV a serious shakedown we decided that the AP1 Honda S2000 would be a good choice. The S2000 is a real fun car to drive and the AP1 is a little on a razor's edge. In addition we have our own Project S2000 that is equipped with KW's excellent Clubsport suspension to compare it to.
The Max IV coilover for the AP1 S2000 is a gas charged monotube damper. The damping is adjustable with the knob's adjustment biased toward the rebound side although adjustment does alter the compression as well. The damper is threaded and the body fork is threaded into an anodized billet aluminum body which allows ride height adjustment independent of the spring preload. The front shock assembly is shown here and you can see that it has both a main spring and tender spring with OEM like dust shields for a long service life in all weather conditions.
The rear shock is very short by the nature of the design of the S2000's suspension. Many other shock designs have issues with the shortness of the shock body as it doesn't allow for much gas volume in a monotube. This means that the gas reaction force ramps up quickly causing harshness in ride. Also pictured is the damping adjustment tool. This adjusts the damping of 3 of the 4 shocks. One of the rear shocks needs a special adjuster because the fuel filler tube block access to the top of the shock. The threaded part of the shock body is treated with a special coating called PNE. This is a special plating that is self lubricating and is 5 times more corrosion resistant than traditional zinc plating. Hopefully this will absolutely prevent seizing of the spring perches. The Hipermax IV also features a large diameter shock shaft. This helps displace more fluid under shock movement causing more fluid flow through the shock's valving. This helps create more damping force, especially critical low speed damping force, while also improving the valving sensitivity. 
The Max IV model line up has two models, the SP and GT. The GT Model is more street oriented, but can still be adjusted to work fine on the track. The SP is much more aggressively calibrated and is intended to be a daily driveable and track capable shock. The spring rates on the SPs we will be evaluating are 16kg front & rear, while their GT counterparts are 8kg front / 7kg rear. For reference, the factory spring rates for the 2001(year of our test model) S2000 are 3.9kg front / 5.2kg rear. The ST also has pillow ball bearing equipped mounts while the GT has mount with rubber mounted shafts. 
The rear shock is shown here with the flex shaft damping adjuster that is needed to bend around the fuel filler tube. The Max 4 shocks are 30 way adjustable and come delivered in the middle of their adjustment range. This way you can go 15 clicks stiffer or 15 clicks softer. HKS has spent a lot of time in calibration and ride development for each model and the shocks are supposed to be right in damping adjustment and ride height for most situations right out of the box with the owner not having to fiddle around at all with a lot of plus or minus leeway to go stiffer or softer. Most shocks we use, even the high dollar ones need some fine tuning once installed. Has HKS nailed it?
