Apex Engineered Track Attack Spring/Shock Discussion

[baby_Carlton]

Hi HybridZ, its been a while. Took a long sabbatical from working on my S30 to finish college and get a job. For the last 6 or so months its been full steam ahead, the project is currently being rust repaired at a local body shop and I've been collecting parts as budget allows.

 

The first piece major piece of hardware to arrived is the Viking Performance Shocks from the Apex Engineered Track Attack Front/Rear Suspension kit. I noticed that Apex’s website lacks details on shock and spring selection, so I’m documenting my findings here for others and to start a discussion on their choices.

 

What's Included:

Box as it arrives from Viking Performance

 

Serial Numbers of each of the shocks (PN: C203)

 

Viking Performance Shocks Link

 

Part Numbers of Springs (600# & 700#)

 

Initial Impressions:

The car will be caged and used primarily/almost exclusively on track, so a stiffer setup is expected. However the spring rate selection still raises some concerns:

• The S30 chassis doesn’t benefit significantly from extremely high spring rates, even with a roll cage.

• The rear suspension uses inboard cantilevered shocks, which traditionally increase effective spring rate via the lever arm.

• This spring selection guide from Viking Performance indicates that the spring rate for a car with IRS and axle weights of ~1200-1400# is a lot lower than the supplied springs.

 

I'm hypothesizing that the high rates were chosen to prevent the shocks, which are short to fit the Z’s narrow frame and tight packaging within the front wheel wells, from bottoming out.

 

I’ve reached out to Apex Engineered to clarify the wheel rates for this setup and will update this thread when I hear back. Let me know if any of you have run this kit or high wheel rates.

 

 

Edited July 7 by baby_Carlton
Inclusion of spring selection guide from Viking Performance

[jhm]

Welcome back, Carlton...and congrats on the major life changes/accomplishments! 

 

Following, as I'm super interested to hear how about the installation and how you like it.  Thanks for documenting the process!  👍

[Ben280]

Good post. I was frustrated for a long time with companies not sharing spring rates on these parts. FWIW, Viking is legit, lots of fast SCCA guys run those things with good results. 

 

IF those spring rates were chosen to prevent bottoming out of the shocks, that's pretty poor design. My guess is that the motion ratio of the bellcrank will be the limiting/bottoming out feature here, and that the conversion to pushrods has resulted in some high force multipliers. My guess would be Viking starting point is mounting in a "muscle car" front end, where the motion ratio is fairly low. 

 

I'll be interested to hear what the APEX guys say!

[baby_Carlton]

On 7/7/2025 at 7:16 AM, jhm said:

Welcome back, Carlton...and congrats on the major life changes/accomplishments! 

 

Following, as I'm super interested to hear how about the installation and how you like it.  Thanks for documenting the process!  👍

Thanks for the welcome back, this car has certainly had a rollercoaster of a fate over the last 10 or so years of ownership. Excited to build it into the best version of itself (for me).

 

On 7/7/2025 at 2:15 PM, Ben280 said:

Good post. I was frustrated for a long time with companies not sharing spring rates on these parts. FWIW, Viking is legit, lots of fast SCCA guys run those things with good results. 

Thanks for the info, seems like Viking is a non-hype brand that offers shocks that do shock things, which I can appreciate. AE is slow on CS communications but that's understandable given the size of their operation. That said, for a ~$9K suspension kit, a bit more transparency and technical detail on their website would go a long way. If I can find a shock with more travel for the same dimensions or when I blow these out I'll swap. JRi's builder series and some of their GM line looks like it would bolt right in, only 0.3" longer extended length which seems negligible in terms of fitment (PN: 100-511-300). 

 

On 7/7/2025 at 2:15 PM, Ben280 said:

IF those spring rates were chosen to prevent bottoming out of the shocks, that's pretty poor design. My guess is that the motion ratio of the bellcrank will be the limiting/bottoming out feature here, and that the conversion to pushrods has resulted in some high force multipliers. My guess would be Viking starting point is mounting in a "muscle car" front end, where the motion ratio is fairly low. 

I agree, it seems incredibly unwise if that were the case but it wouldn't be the first time I'd seen it. I've seen similar suspension choices in GTAC (cars riding on bump stops) but that's usually done purposefully to keep the aero platform working optimally and not appropriate for a package like this. Considering the shock travel is a mere 3.6", its safe to assume this is an extremely low motion ratio design. It feels like a missed opportunity to fully leverage the bell crank inboard design (traditionally speaking) but perhaps packaging constraints of the S30 chassis left little room for alternatives.

 

I'm hoping the bottoming out feature will be at the upper A-arm which would allow me to mount a 3D printed polyurethane bump stop on top of it.  Going to email AE for an update on the wheel rates and now information motion ratios, thanks for the idea.

Edited July 9 by baby_Carlton
Grammar

[Ben280]

I'd definitely talk with Viking as well. Back when I worked at a performance race shop, they were pretty helpful. Once you get parts in hand from Apex, or just generally more information, I'd call Viking up and see what's what.

[baby_Carlton]

Update

 

From Apex:
 

     Front

          • Motion ratio: 0.92 : 1 (wheel : shock)

          • Wheel rate: 0.92² × 600 lb/in ≈ 510 lb/in

          • Wheel travel with 3.5" shock stroke: ≈ 3.2"

 

     Rear

          • Rocker motion ratio: 1.00 : 1

          • Wheel rate: 700 lb/in

          • Wheel travel with 3.5" shock stroke: 3.5"

 

Some confusing design and hardware choices here. Using a bellcrank/rocker with a 1:1 motion ratio doesn't take full advantage of the system. I will end up designing and having manufactured a new billet bellcrank/rocker with a lower motion ratio to get more shock travel. Highly likely I'll source a Hyperco spring at a different rate but that'll be handled during the bellcrank redesign and is a straight forward task. 

 

The front axle is giving me some headaches. The lack of suspension travel could be fixed by adding a bellcrank/rocker, but there isn’t enough space to fit one between the top of the strut tower and the hood. Making room would require major cutting and fabrication to the strut towers.

 

Mike Maier Inc.'s solution to a similar problem was to completely replace the original shock towers with a custom design, allowing a full-length shock to mount higher and further inboard. On the Z, moving the strut tower further inboard could create enough clearance between the upper control arm to let a coilover mount to the lower control arm. But by that point, I'm only a few steps away from designing a fully bespoke 1:1 double wishbone kit, making the OTS kit a useless purchase. I've been drawing up some concept sketches on how I could possibly do a pull rod but that would render the OEM strut tower essentially useless.

 

Alternative to implementing a front axle rocker would be to modify the upper wishbone where the bottom of the coilover mounts to be further inboard which would lower the motion ratio more but I'm not keen on trying that solution. 

 

I think I need a sanity check, I'm used to working on strut-type suspensions that have decently high shock travel to the point where coil-bind is a more pressing issue at low ride heights. Is there another solution to a short shock stroke and high spring rate I'm not considering? Or is this a case where the problem is all in my head and having 3-3.5" of shock stroke isn't that big of a deal? I've spoken to Rob Fuller from ZCarGarage regarding this problem who had some great insights on Z suspension, unfortunately he wasn't able to help me much past confirming that the wheel rates are ludicrously high. I'm aiming for a front axle wheel rate in the range of 300# to 450# and even then 450# still seems extremely high for the front axle.

 

 

Edited Thursday at 09:30 AM by baby_Carlton

[baby_Carlton]

Spoke to Mike Maier today seeing as the front suspension is most similar to that of an old Mustang. I wish I could write notes faster because holy hell that man is a wealth of knowledge. Suggested the reason for high spring rates is to prevent the upper control arm from camming over (poor arm design) and that the 3.5" of travel is definitely not enough for a road racing/track car (burms). Looks like my next steps are installing an adjustable upper ball joint that can move up/down to change the coilover angle and shock pot it at ride height looking for the lowest load value. If no substantial gains can be made there it's either back to the drawing board to make a push/pull rod cantilever or cut out the shock towers entirely and try to copy MMI's own Mod 2 strut tower modifications as well as new control arm(s) to gain the ability to mount a full length shock to the lower wishbone. This is becoming more and more of a fully custom project by the day.

[tube80z]

Hi Carlton,

 

A lot of this has been hashed out over the years.  There are some helpful stickies available in the FAQs for selecting damper and spring rates that you may want to refer to.  Before you get too far into recommendations about springs, etc., would you tell us what you intend to use this car for (track only, dual purpose, autox, street, etc.) as this will help give you better recommendations.  It would also be helpful to know what you intend to use for tires, as this is one of the most important factors to know.  Low-profile radials will require softer springs than a higher sidewall racing tire (such as a slick, R-compound, or HP 200 TW).  The more grip the tires can generate, the higher the spring rate needed to be able to deal with the forces that take up suspension travel.

 

I'd agree with Mike Maier's criticisms of the Apex upper A-arm on the front suspension.  It is going to always limit the amount of available suspension travel that can be used.  With regards to how much travel you need, that will depend a lot on tires and the use of the car.  On my autoX/hillclimb 240 that weighed 1850 or 2050, depending on class, I ran Hoosier bias-ply racing slicks and some of their radial slicks.  The spring rates I typically used were 400 to 600 lbs/in on the front and 400 to 550 lbs/in on the rear.  This car was droop limited, and front suspension travel on the roughest hill was typically less than 2.75 inches in the front and 3.5 inches in the rear.  I experimented with softer and stiffer rates but found this range worked best.

 

A friend's street legal dual-purpose car running on 200 TW or R comp low-profile tires weighed 2400+ (LS and T-56).  This car was happier with 375 on 450 spring rates.  It was also droop limited and I found out how horrible this made the car ride on normal street drives.  So if you go down this path I'd recommend a quick disconnect when not needing the limited travel.

 

My personal feelings on the Apex upper a-arm are that it should be about 7 inches long to get adequate travel.  On my a-arm mock ups, the only reliable way I could see doing this was to use holes or pockets on the inner fender that allowed moving the inner pickup to the center of the frame rail.  Then it looks more like a '90s to 2000s Mustang strut to a-arm conversion.  The parts to do this are that bad if you use circle track components, and you can source used parts from eBay for trying out different ideas.  This requires you to have access to fab equipment, so if you don't, this isn't a road to go down.

 

Cary

[baby_Carlton]

2 hours ago, tube80z said:

Before you get too far into recommendations about springs, etc., would you tell us what you intend to use this car for (track only, dual purpose, autox, street, etc.) as this will help give you better recommendations.  It would also be helpful to know what you intend to use for tires, as this is one of the most important factors to know.

Tire selection is Nankang CRS 200TW 245/40R17 front, 275/35R17 rear, I would use their AR-1 100TW however they do not offer a 275 section tire for that model. Car will be almost exclusively a track car but despite my spine's best interests it'll probably see a very occasional Sunday drive.

 

2 hours ago, tube80z said:

On my autoX/hillclimb 240 that weighed 1850 or 2050, depending on class, I ran Hoosier bias-ply racing slicks and some of their radial slicks.  The spring rates I typically used were 400 to 600 lbs/in on the front and 400 to 550 lbs/in on the rear.  This car was droop limited, and front suspension travel on the roughest hill was typically less than 2.75 inches in the front and 3.5 inches in the rear.  I experimented with softer and stiffer rates but found this range worked best.

Were these rates with OEM-style strut type suspension? What were your wheel rates? Maier's issue with the shock travel was that unlike an autoX/hillclimb car, a road course car would see burms and 3.5" total shock stroke just isn't enough. Great insight still, thank you.

 

 

2 hours ago, tube80z said:

My personal feelings on the Apex upper a-arm are that it should be about 7 inches long to get adequate travel

The kit just shipped about 3 hours ago (for better or for worse), when it arrives I'll be able to get those measurements to see. When you say "adequate travel" I'm assuming a that refers to just enough travel for the ~3 inches of travel you've needed for your own car? I'm assuming if I want something closer to 5-6" travel, the upper arms would need to be closer to a foot long. 

 

2 hours ago, tube80z said:

On my a-arm mock ups, the only reliable way I could see doing this was to use holes or pockets on the inner fender that allowed moving the inner pickup to the center of the frame rail.  Then it looks more like a '90s to 2000s Mustang strut to a-arm conversion.

That's what I'm finding as well just looking at Maier's Mod 2 front axle suspension kit. Complete replacement of the front strut towers moving the pickup points slightly upward and a few inches inward to increase clearance between the coilover and upper control arm. I'm not opposed to doing this and I could even keep most of the Apex kit except for probably both the wishbones. 

 

2 hours ago, tube80z said:

The parts to do this are that bad if you use circle track components, and you can source used parts from eBay for trying out different ideas.  This requires you to have access to fab equipment, so if you don't, this isn't a road to go down.

Ah yes, old stockcar components on eBay, a true goldmine for (hopefully) decent parts. Definitely have looked at sourcing a fuel cell and oil coolers from there. Luckily I have access to rapid prototyping equipment and fabrication tools so I'm good to go. Not the best welder or anything but I know a few. Thanks for your help tube80z. 

 

Only other gripe I have with this design is on the rear subframe; the differential and control arms mount on the same structure and that seems like an exceptionally suboptimal design choice. Time will tell I suppose. 

Edited 15 hours ago by baby_Carlton

[tube80z]

1 hour ago, baby_Carlton said:

Tire selection is Nankang CRS 200TW 245/40R17 front, 275/35R17 rear, I would use their AR-1 100TW however they do not offer a 275 section tire for that model. Car will be almost exclusively a track car but despite my spine's best interests it'll probably see a very occasional Sunday drive.

 

I'd probably start in the 400 to 450 range given the tires then.  

 

1 hour ago, baby_Carlton said:

Were these rates with OEM-style strut type suspension? What were your wheel rates? Maier's issue with the shock travel was that unlike an autoX/hillclimb car, a road course car would see burms and 3.5" total shock stroke just isn't enough. Great insight still, thank you.

 

The kit just shipped about 3 hours ago (for better or for worse), when it arrives I'll be able to get those measurements to see. When you say "adequate travel" I'm assuming a that refers to just enough travel for the ~3 inches of travel you've needed for your own car? I'm assuming if I want something closer to 5-6" travel, the upper arms would need to be closer to a foot long. 

 

 

The struts were stock-style reinforced 280Z bodies.  Spring rates were for springs but if I remember correctly MR should be 0.97 or close.  I can't find my notebook at the moment.  It's all detailed in buried threads on this site.  There's a lot of it in the shock/unsprung weight FAQ 

 

I think 5 inches should easily be enough for a track car.  By burm do you mean a banked corner?  I know a few people on this site run their cars at tracks with high oval-style corners, and perhaps they can chime in on what they see for travel.  

 

1 hour ago, baby_Carlton said:

 

That's what I'm finding as well just looking at Maier's Mod 2 front axle suspension kit. Complete replacement of the front strut towers moving the pickup points slightly upward and a few inches inward to increase clearance between the coilover and upper control arm. I'm not opposed to doing this and I could even keep most of the

Apex kit except for probably both the wishbones. 

 

My wife has a '65 Mustang.  That's a sweet kit from the look of it.  My mock was very similar, except it used a Joe's style front 2-piece a-arm.  So you only needed to have two holes for the A-arm to poke through.  I was doing the upper mount similar to what Griggs uses on their Fox body conversion.  It comes down from the stock Datsun upper strut mount.

 

[baby_Carlton]

1 hour ago, tube80z said:

start in the 400 to 450 range given the tires

I agree, I reached out to Apex earlier this week asking about feasibility using the existing shock stroke with 400-450# springs.

 

1 hour ago, tube80z said:

I think 5 inches should easily be enough for a track car.  By burm do you mean a banked corner?

Yes, loading the outside tire on burm and then hitting an imperfection on the track seems like it would decimate one of these shocks (same with hitting kerbs/rumble strips) unless I find a way to get more travel. If I could get 5inches of travel I would be very happy but I will try for a full length (~6.5") shock design if I end up copying MMI's Mod 2.

 

2 hours ago, tube80z said:

Joe's style front 2-piece a-arm

Very interesting, would definitely prefer welded to bolt-on but if everything fits up right I could end up using it as a way to test different upper wishbone lengths.  The Griggs conversion looks like a pretty strong structure but I don't want to jump to conclusions quite yet. Do you have any photos of your work? Interested to see what your mounting solution looks like. If I can avoid trimming the strut tower and still get the full stroke shock I will.