HKS Hipermax IV GT coilover review

[Lynxis]

So, I've got HKS Hipermax IV GT suspension that I bought used from a forum member late last year. I installed them myself in April and have driven around 3000kms on it so far between daily driving, 2 track days and 1 autocross event so I figure I'll talk about my experiences so far.

Regarding the coilovers themselves, spring rates are 6K front and 4K rear. They are monotube with inverted front struts design. They have 30 levels of damping adjustment and finally they come with camber adjustable top hats.

I know the spring rates are a little strange since most coilover kits use equal or stiffer rear springs while these are softer in the rear. I suspect they were looking to make these more comfortable on the street by doing this but I found the rear quite jarring over severe bumps and pot holes.

UPDATE: Preload was set incorrectly on mine which caused a harsh ride. It's a bit bouncy in the rear now but feels MUCH better than before.

UPDATE 2: Preload was set too loosely in the rear after my last update, tightened it to spec and now the rear is nice and compliant without being bouncy at all. Car feels great now, like OEM+.

The SPs use 7k rates square and are more track focused. Of course, this is my daily driver so I wanted something more comfortable on the street while still offering improved track performance over OEM so I felt the GTs matched my needs better than the SPs.

I installed the suspension myself with the help of a friend of mine in his garage. The install itself was an exercise in frustration because so much stuff was rusted together. Yay just 2 Canadian winters! =( The worst was the sway bar end links which had to be cut out to remove them but that didn't bother me much because the suspension came with new end links. I got the car back on the ground and started to drive home and with the alignment totally screwed up now that the car was lowered, it was pulling all over the place. My friend lives about an hour out of town so it was a hair raising trip back. Anyways, the next day, I set the ride height to 1 inch lower than stock and then got the car aligned with -2.2f/-1.7r camber and 0 toe and all was well.

When daily driving on the suspension, I need to review the front and rear separately because something like going over a pot hole gives me very different feelings in the front and rear. I played with the settings and I've put the front at 11 clicks from full soft and found this seems to be more comfortable and composed than stock to be honest. Hitting a pot hole with the front tire is certainly noticeable but doesn't feel overly jarring. Now, hitting that same pot hole with a rear wheel is very jarring at 11 clicks from full soft. I could feel my teeth vibrating whenever I hit one. I kept going softer until I got to 5 clicks from full soft. Any softer was making the car bounce around too much for comfort so I left it here. It definitely took the edge off such impacts compared to 11 clicks but it was still not nearly as comfortable as the front feels. I wonder if there is a particular reason for this. (UPDATE: There was incorrectly set spring preload. They feel very good but a bit bouncy at 16 clicks from full soft) At first, I wondered if maybe I had a problem with one of the struts so I purposely hit with the other wheels and the behaviour is pretty much the same so I don't think there is anything wrong, it is just the way it is. I'll note at this setting, it's not much worse than the stock suspension was over similar bumps so I have to give it a pass overall but I feel like it could be better. (Again, it is better)

I've had 2 track days and 1 autocross day on this suspension too. I ran the suspension at 11 clicks from full soft front and rear for all events. The autocross event was a test and tune and it was the first event I did on the new suspension. That day was mostly just me feeling out the new suspension, I could feel right away that the car was more stable and rolled way less than it did stock, I also found I could take slaloms faster because transitions didn't take as long as before. As a test and tune event, no standings were posted so I have no idea how I did relative to anyone else.

The first track day I did was very busy and I had no opportunity to do a full hot lap. That said, the suspension still felt very good and planted. Here, I was starting to get comfortable with it and push a bit harder. It was very balanced with just a hint of understeer which is the way I liked it. I managed a 2:18 at Shannonville that day with traffic.

The second track day I did was fully open and I did around 9 sessions. My first session was great and because it was much quieter this time, I was able to put down some hot laps and got a best time of 2:14 that session. Early into my second session, I broke my front passenger side end link. The slight understeer turned into slight oversteer and the car was not as stable as before. I was no longer confident to push as hard and my next session, my best time dropped to a 2:17 even though I had several completely clear laps. I ended the day with a best recorded time of 2:12 although I wonder if that would have been lower if I wasn't driven around with a broken end link for the majority of the day. I've ordered Whiteline adjustable end links and I'm waiting for them to come in. I want to get back out to the track at least one more time this year once the end link is back on and see if I can break into the 2:10s.

Overall, I'd say it's very good suspension for the money. It's reasonably comfortable but still very capable on the track to help eliminate body roll and speed up transitions. I don't regret buying it at all but I will say that I think if you are planning to go to the track frequently at all, you might be better served going for the SP kit.

[Lynxis]

So I have to update this review a bit because I discovered some things with the rear suspension today that were negatively impacting ride quality. I asked HKS for input on my experience with these coils recently and they suggested that my alignment guy may have set ride height by adjusting preload which isn't correct with this suspension system. I looked at the preload on my rear coils and I discovered exactly what HKS suggested might be the problem. Here is the picture before I started doing anything:



So I undid the preload and watched the coil nearly unwind to the bottom of the shock before it fully loosened. Then I turned it 4 full turns to snug it up and tested. Man night and day difference! I have to say while I found bumps and dips not nearly as jarring as they were, I found the car really bouncy now. I turned up the damping setting to 16 clicks from full soft and that seemed to settle it down but it's still pretty bouncy over bad bumps and things. Anyways, I checked ride height and found the car had settled half an inch lower than it was so back up it went and this time I turned the shock body to raise the ride height and then I took this picture before I set it back down.



This is much better than it was and I no longer feel my teeth vibrating when I go over bumps or dips in the road. I kind of wish it wasn't quite so bouncy but I'm hoping that will clear up over time as the coils re-settle. If not, I'll take another crack at setting preload next week and see how it goes. I felt like I needed to update this review because my findings have changed and I can now whole-heartedly recommend these coils knowing that something was just set wrong with mine.

[x808drifter]

Wouldn't be surprised if there's something wrong with the dampening on the rears now.

[Lynxis]

Originally Posted by x808drifter

Wouldn't be surprised if there's something wrong with the dampening on the rears now.

While it's possible, I don't think it's likely because with preload that was set too high, less of the full stroke than usual would have been used so if anything I'd imagine there would be less wear. That said, I don't actually know what would happen in this case so that is just my armchair mechanic opinion.

That said, knowing how they screwed up the rear suspension, I'm concerned they may have done the same with the front which I didn't check today. While I find the fronts extremely comfortable, that doesn't necessarily mean they're right. In this case, I'm wondering if the reason it's bouncy and uncomfortable may be because the front preload is also set wrong and so the front and rear still aren't working together correctly yet. I did think to take a picture of the front coils when I was working on my brakes a few weeks ago but it's hard to tell in this case because they don't have a helper spring:

[Lynxis]

A very important update! I don't have any pictures but I have made awesome progress with the suspension today!

I found the english portion of the user manual which has suggested settings for preload and other things so I went about setting them accordingly. For the front, from top of the spring to the bottom of the spring is suggested to be 6.5 to 6.7 inches. The rear was suggested to be 7.4 inches to 8.1 inches.

I found that the front end preload was set a bit too high with the spring set at around 6.2 inches. Not nearly as bad as the rear which is probably why I thought it felt fine but even this small adjustment really helped.

While this helped the bouncy ride, it was still pretty bad so I decided to take another look at the rear preload since I had suggested specifications now. It turns out I had spring length set at 9 inches which was way too far the other way. I tightened it up to 7.8 inches and the ride quality blows me away now! It feels at least as good as OEM if not better and now the car gives me confidence to attack the corners.

Unfortunately, I ran out of light during my last test drive so there are no pictures and I think I'll need to fix my ride height again since adjusting the preload should have changed the ride height but thankfully the ride height adjustment is separate from everything else so changes to that shouldn't affect ride quality. Thankfully tomorrow is a holiday so I'll be taking a crack at fixing ride height tomorrow. If there is any change, I'll update this thread but if you don't see anything, then expect the fixed ride height to have had no affect on the ride and handling.

I will note that I have a half-track-day coming up on Thursday this week where I'll be able to put the suspension through its paces. I'll update this thread again with my experience on track.

[Lynxis]

So final update on these coils. I'll note that other than the coilovers and RLCAs, I'm still completely OEM suspension wise. No bushing replacements, no sway bars.

I got my ride heights set and an alignment for -2.2f, -1.7r. I've put many more kms on the car and I've had it to the track twice now. Overall, I think this suspension could be considered OEM+. On the street, you can feel the small bumps but they aren't upsetting or jarring at all and larger bumps are soaked up appropriately without being jarring or with excess bounce. At no point have I had the car feel unsettled or uncomfortable now that I've fixed the preload.

On track, it's great! The car still feels neutral like OEM with an understeer bias. I dialed some of it out by softening up the front suspension a bit compared to the rear (front at 11 from soft, rear at 16 from soft) but the front still gives up well before the rear does but it's not bad, I can still steer with the throttle and kick the rear out under power if I'm not paying attention. Anyways, for me, this is very comfortable and predictable so I'm happy with it. The spring rates result in a car that still rolls just enough that you can feel it but it doesn't dive as much under braking and transitions are quicker. Also, I can feel very early, even before the car visibly slides when I am breaking traction now. I do think this is as much my own ability to actually feel these things coming in as it is the suspension communicating the situation to me but it's pretty awesome none the less that I can recover from slides that sent me spinning out just at the beginning of this season.

Overall, I'm extremely satisfied with the suspension now that it's working right and I don't have any plans to replace it anytime soon.

[Clipdat]

Nice! Sounds like you are extremely satisfied with them!

I've been interested in these since I first heard/read about them. Everyone who I discuss coilovers gives me a WTF look when I mention I'm thinking about getting HKS.

[Lynxis]

Originally Posted by Clipdat

Nice! Sounds like you are extremely satisfied with them!

I've been interested in these since I first heard/read about them. Everyone who I discuss coilovers gives me a WTF look when I mention I'm thinking about getting HKS.

Yeah I am. They just aren't well known I'm guessing because they're Japanese. Most people know of the brand and know they aren't junk but nothing beyond that. I made it a point to talk about my experiences with these coils to increase peoples awareness of them. A very good mid-entry level kit for the money.

[sugoi]

Originally Posted by Lynxis

Yeah I am. They just aren't well known I'm guessing because they're Japanese. Most people know of the brand and know they aren't junk but nothing beyond that. I made it a point to talk about my experiences with these coils to increase peoples awareness of them. A very good mid-entry level kit for the money.

I don't think it's because they're Japanese, I think people just aren't aware HKS makes parts other than exhausts.

[Lynxis]

Originally Posted by baorz

I don't think it's because they're Japanese, I think people just aren't aware HKS makes parts other than exhausts.

This is also a possibility. Many companies that make different types of parts often don't excel at any of them and have issues gaining traction as a result and HKS may also be a victim of that.

I said the issue might be because they're Japanese mostly because they seem to be a really popular brand in Japan for everything they do but they haven't gained a lot of traction over here for anything. Honestly, I knew they did superchargers before I knew they did anything else.

[scmil95eg]

+1 for GTs.

I've had them on my Evo for the last 60,000 miles and still live the way they make the car feel.

[Lynxis]

A long term update for those interested.

Nearly 3 years and 40000kms later, I'm still running these coilovers and they're doing fine. I mentioned I got them used from a forum member but I don't think I ever mentioned that he sold them to me with around 25000kms on them already so they have a total of ~65000kms on them and tons of abuse during my ownership including but not limited to: Daily driving for ~3 years on terrible Canadian roads including 2 and a half Canadian winters. An average of 4 track days and 40 autocross runs per year. Both a front end AND a separate rear end collision. Full disclosure, the front end collision was on the passenger side and I've been experiencing spring bind on that side since then. I suspect the thrust bearing took damage in the hit but it's just a popping noise and it doesn't affect the handling or operation of the car at all.

In terms of how they have held up: I set the preload and ride-height as mentioned in the original post and other than dampening adjustments based on what I'm doing, these haven't been touched since. Operationally, these are still running fine. No oil leaks and the ride still feels firm and controlled. There is a layer of surface rust on the threads which I'm confident a suitable solvent could remove but I'm not going to bother as it doesn't seem to be hurting anything. No other rust to speak of.

I'm very happy with them after 3 years of ownership although I am a bit concerned when it comes time for a rebuild which I suspect will be sooner rather than later, considering their age and how I (ab)use them. I confirmed that HKS USA will no longer rebuild their suspension about 2 years ago. I was told I could either send the suspension to HKS Japan or I could try to find an independent suspension service centre that will work on them. I confirmed this situation with Scott at HKS maybe 2 years ago now so it's possible it has changed now but there doesn't appear to be any new information on their site.

Hope this helps anyone trying to decide if they want to get a set of these.

[ayoshioka1]

go figure, HKS USA in Arizona is just a distribution hub / USA office. They don't have the time, nor man power to perform such tasks. Probably at most 3-4 people working the office/warehouse at a time. From a business standpoint its probably a good idea that they don't partake in suspension rebuilds as their US market for these is incredibly small.

I almost went with HKS IV GT's. i guess im sticking with my original plan and go with FA.

[WC-BRZ]

And this is why FA is winning so much business in North America. I remember when FA was just another random coilover but how they've turned the business around recently could probably be a case study for business schools lol