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Project VA WRX: Improving the Suspension With Tein Flex-Z Coilovers

by Mike Kojima

Many of our MotoIQ Project Cars feature top of the line or even exotic suspension parts, exactly the kind of stuff you want to use in cars that see mixed track/street use with a heavy track bias. However, not all of our cars are set up like this, some of our cars are more street oriented and set up towards hassle free daily use. 

We decided that Project VA WRX would take this route. Since track duty is the domain of the more powerful and expensive STI we will be building the VA WRX to be more street oriented. It will still perform pretty well but have less compromise in daily driver practicality.

For selecting a suspension, we decided that super trick two and 3 way adjustable dampers were not the way we wanted to go.  We wanted a suspension that would work well yet be affordable and durable. After doing some research we decided to give the new Tein Flex Z a try.

The Flex Z is Tein's new lower priced but high performance line of coilovers designed to compete toe to toe price wise with the tons of crappy cheap coilover sold on Ebay and such that are flooding the market. Although the Flex Z suspension line is built from the ground up to be inexpensive, it doesn't mean it sacrifices performance or durability. Read on and let us show you how it does that and how well it works.

Read more about Project VA WRX here!

 

The Tein Flex Z is not a cheaply made in China re-labeled shock, but a high quality unit made in Yokohama Japan.  It has a lower cost not so much due to using worse materials or shoddy construction, but rather due to Tein investing in OEM high volume assembly methods that reduce unit costs. The costs are mitigated by the use of a sealed damper unit that contains the rod and piston but is valved per application. The damper is adapted to various chassis with removable mounts. A WRX specific McPherson strut lower mount is used with the damper with a WRX specific camber plate for the front shock.  The removable mounts also allow ride height adjustment independent of shock travel and spring preload.  Since the damper is the same dimensions across many different applications, there is economy of scale and production costs are greatly reduced. 
The Flex Z is 16 way adjustable with close to equal linear adjustment steps.  The adjustments mostly affect rebound damping although compression damping is affected slightly. The camber plate is made of lower cost powder coated steel which is not trick like anodized billet aluminum but perfectly fine for the job.  The powder coating is a highly corrosion resistant 2 layer process. The damper unit itself is a twin tube design with a drawn tube and a non-rebuildable swedged and crimped top seal. This sort of manufacturing is much cheaper than a typical racing shock that is assembled with many machined parts. This is just like how stock replacement and OEM parts are made. The damper unit is gas pressurized to reduce foaming and cavitation in the valves.  The innovative universal damper system allows Tein to make a high performing but durable low cost coil over.  When the suspension needs to be serviced, just the inexpensive damper unit is replaced.  Custom valved dampers can also be special ordered per application. 
Just because the camber plate is steel and cheaper doesn't mean it's not durable. High quality bearings are used and all steel hardware parts are highly corrosion resistant yellow chromate coated.  The Type Z has a full length dust boot to keep dirt and water away from the seals. 
The rear shock is much like the front part. The lower ride height adjustable mount and the top mount are application specific. The threaded  body of the dampers is coated with Tein's proprietary highly corrosion and wear resistant ZT coating. This coating greatly helps prevent the ride height and preload adjusters from becoming stuck to the shock body even in corrosive environments like winter salty roads.
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Comments
touge
tougelink
Monday, December 21, 2015 5:41 AM
How do these compare with fortune auto 500, especially the valving? Not necessarily specific to the VA platform, but in general.

Thanks
Van_1986
Van_1986link
Monday, December 21, 2015 8:59 AM
Just installed a set of Bilstein PSS into my friends BRZ. Haven't tested them much yet but they ride better than stock. Would be cool to compare with these, since they are both around a grand. PSS has no adjustment, but they are a monotube design.
Mike Kojima
Mike Kojimalink
Monday, December 21, 2015 9:24 AM
We are getting some Fortune Auto 500's very soon to test. We are very eager. Not having adjustment is a huge disadvantage right off the start for a car that is going to be driven on the track at all.
warmmilk
warmmilklink
Monday, December 21, 2015 2:00 PM
Mike, which car are you going to be testing the FA500 on?
warmmilk
warmmilklink
Monday, December 21, 2015 2:08 PM
Mike,
I have a general suspension engineer question for you. The OEM front strut assembly has a very big diameter spring thats not centered on the strut and is kinda mounted at an angle. I noticed this is common (every one I've seen anyway) on front MacPherson strut cars stock. Is there a reason for this?

Looking at how the spring is angled I remembered the Hypercoil perches I saw and the load axis line. Is keeping that load axis line straight what the OEMs are doing?

http://www.hypercoils.com/perches
Mike Kojima
Mike Kojimalink
Monday, December 21, 2015 2:23 PM
@warmmilk, it will be on a future B13 SE-R project.

It is probably to reduce off center spring kinking forces out of it, or for clearance of something.
Fabrik8
Fabrik8link
Monday, December 21, 2015 3:43 PM
@warmmilk, just like Mike said, it's for clearance and to get the spring axis somewhat acceptable while keeping the large diameter away from the tire. The large spring diameter is to lower the stress by reducing curvature, and also to keep the ratio of spring length to spring diameter (the slenderness ratio) at a good level to prevent bending/deflection. Coilover springs that are long but skinny don't have as much of a problem with that because they're somewhat "guided" by the coilover body when they bend. OEM springs are all about long life and being as cheap to produce as possible...
warmmilk
warmmilklink
Monday, December 21, 2015 4:01 PM
@Mike
I was really looking forward to it when you said EP3 cause I had FA500's on my RSX that I tracked (sold for soon to be acquired s2k)... but then you went and changed it to B13... btw, its a little not fair that only mods can edit their post...

@Mike and @Fabrik8
ok, so it basically is the same deal as what the Hypercoil perches are accomplishing... but lower cost OEM version
Wrecked
Wreckedlink
Monday, December 21, 2015 4:36 PM
Would love to see a test of BC Racing coilovers.
Fabrik8
Fabrik8link
Monday, December 21, 2015 5:12 PM
@warmmilk, the Hyperco perches are all about reducing friction in the damper. This really doesn't have much to do with the OEM stuff, because reducing damper friction isn't as important in OEM passenger car applications (at least for the added cost it would add) with such soft spring rates and low natural frequencies compared to race applications. You also have soft rubber strut tops that locate the upper spring, etc., all of which change the load distribution of the spring.

So no, I don't think you could really correlate the OEM springs with what the Hyperco perches aim to accomplish.
Mike Kojima
Mike Kojimalink
Monday, December 21, 2015 5:35 PM
Hyperco perches are also super high maintenance, not applicable to OEM or even most grassroots racers.
warmmilk
warmmilklink
Tuesday, December 22, 2015 10:51 AM
@Mike
what kind of maintenance do they require?
Mike Kojima
Mike Kojimalink
Tuesday, December 22, 2015 11:00 AM
@warmmilk, you have to inspect and possibly rebuild them every race weekend. They are super susceptible to dirt damage. They work amazingly well and someone should refine the design so they are more robust. I think Hyperco came out with their carbon disc springs to get around this.
Fabrik8
Fabrik8link
Tuesday, December 22, 2015 11:28 AM
I've always wondered about retrofitting a light duty gaiter or bellows to help with the dirt ingress problem. There's barely any relative travel between the perch parts, so very little motion capability is required for bellows, etc. There are probably a few ways to keep dirt out with little or no difficulty.
Mike Kojima
Mike Kojimalink
Tuesday, December 22, 2015 12:19 PM
We use Dirtbags but enough still gets in there to mess stuff up.
warmmilk
warmmilklink
Tuesday, December 22, 2015 1:45 PM
@Mike (or anyone else that gets this)
So am I not understanding something or are the carbon springs $150 each?
http://www.hypercoils.com/carbon-composite-springs

I'm gonna bet on me not understanding something, otherwise why aren't all mid to high end coilovers not running carbon springs...
warmmilk
warmmilklink
Tuesday, December 22, 2015 1:47 PM
or is each one of those carbon disks $150?
Fabrik8
Fabrik8link
Tuesday, December 22, 2015 2:46 PM
The "$150 per rate" claim assumes that you buy a kit of different discs which can be combined to make up an inventory of spring rates. It's really a price per permutation from the kit that you would get instead of buying an inventory of different rate steel springs, not the price per spring stack for each corner. Supposedly you can get the price somewhere between steel and titanium springs, but there's all the problems with dirt and fretting and lower fatigue life than steel or Ti springs too. So again, it's a case of suitability for race cars but not street cars. Steel springs are cheap and last a really long time, so they're still the thing to beat.
Fabrik8
Fabrik8link
Tuesday, December 22, 2015 2:49 PM
There's a huge amount of low hanging fruit that can be picked when doing suspension tuning before needing anything close to composite belleville springs. When everything else is optimized and characterized and you're chasing that last 1%, then start thinking along those lines...
Mike Kojima
Mike Kojimalink
Tuesday, December 22, 2015 4:12 PM
@fabrik8, my understanding is that carbon has better fatigue properties than steel but is notch sensitive.

I would think the carbon disk packs are less dirt sensitive the HLC's? HLC's are super dirt damage prone and they can easily make about 1-2 seconds a lap difference. You can actually feel the difference with a car that has them. I don't do it for my personal race car, too much work! I recommend them for my customers and if they want to pay, yes I use them a lot.
Fabrik8
Fabrik8link
Tuesday, December 22, 2015 5:29 PM
Supposedly they have better fatigue life than titanium but less than good spring steel from what I remember. I mis-worded that before. I'm just going off of memory from what I've been told in the past, admittedly maybe not the most accurate info.
The carbon belleville springs should be far less dirt sensitive than the hydraulic perches, definitely. I'm comparing them to traditional coil springs, which are insensitive to damage from being dirty. Dirt would likely not degrade the spring performance of carbon bellevilles at all, but I could see it decreasing their lifespan from abrasion between the mating surfaces, etc., and there is also the weakening effects of moisture absorption along the fiber axis between the fibers and resin matrix. Shouldn't ever be a problem on a race car. This is likely not something you'd want to run long-term on a street car is what I'm getting at. It's a really cool product though, and I would love to try them out on something. I'm sure some of my colleagues in the same racing series have tried them, but I haven't seen them in use and I don't tend to ask around about things like that because of the sensitive nature of racing...
Mike Kojima
Mike Kojimalink
Wednesday, December 23, 2015 12:51 AM
I think the biggest advantage of the carbon springs is the elimination of the need for HLCs.
warmmilk
warmmilklink
Wednesday, December 23, 2015 12:05 PM
@Fabrik8
you can use a spring sock like the offroad guys use to prolong life
http://www.csishocks.com/store/csi-armor-coil-shock-cover-pair

but you're right, overall it doesn't really sound like a feasible product for a street car...

Which racing series do you run in?


@Mike
Does Dai's drift car have HLC's?
Mike Kojima
Mike Kojimalink
Wednesday, December 23, 2015 12:17 PM
I use HLC's in any race series where the customer is willing to pay for the maintenance and parts. I do a few other things to them too to make them work even better. I use a dirtbag but the small amount of dirt that gets through still can mess them up.
Fabrik8
Fabrik8link
Wednesday, December 23, 2015 6:35 PM
@warmmilk: The series on TV every weekend where the cars turn left, mostly.
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