True Rear vs. Divorced spring (causes damage?)
 

So next week i'm thinking of picking up a set of True rear coilovers. HKS HIPERMAX IV GT to be exact. But yesterday at the dinner table my dad made an interesting point. The Z comes standard with a divorced spring/shock setup in the rear, so changing it to true rear coils may be bad. reason it may be bad is cause the car wasn't designed to have all the weight and load on that part of the car. Again he just said it as a thought and it did get me thinking could he be right? Only down side to not going with a true rear setup would be lack of camber adjust ability so that might suck. lets hear some of your thoughts!

I think that the HKS Hipermax only comes as a divorced setup only. I have them on my car and they are divorced just like the OEM style.

I have a divorced set up on my car, and to your dads point, I would rather play it safe than sorry. There hasn't been any definitive proof that a true set could lead to shock tower failure, and although the install was a tad more invasive comparatively, my thought process was to error on the side of caution. My two cents is I think it really comes down to personal preference and what you're comfortable with.

To your point about camber, you will need camber arms out back regardless of true type or divorced type.

You can go with an OEM-style and get camber adjustment via aftermarket parts or go with a true-style setup and get camber adjustment via aftermarket parts. The stock mounting points are fine for true-style setups as probably 50% of us have them and I've yet to see a BMW-style failure (I've been on true-style for appx 5 years now). You'll be fine either way.

This matter has been discussed before. There is no issues with switching from the stock divorced rear suspension shock/spring set up to a true type coilover. Guys have been running true type coils hard on the track for years without any issues. This isn't a BMW shock tower...

How can you get camber arms if the spring is sitting where the camber arm would go? unless I am missing something... lol

The design of the 370z rear suspension has the spring cup and camber arm divorced from each other. Where the spring sits in the stock midlink is completely different from where the camber arm is located.

https://live.staticflickr.com/65535/...80a1e2a7_c.jpg

what model HKS do you have? I want the HIPERMAX IV GT and all the photos of those I have seen are true rear...

oh, no ****. I thought they were one in the same all this time. ok so say I got a divorced rear setup for coils I'm good to order and install any rear camber arms?

Regardless of divorced or true, you will need rear camber arms. I would recommend SPL.

yes I planned on going SPL everything. toe links, camber arms and FUCAS.

If you end up with true coilovers you'll need toe arms to take the place of the stock spring buckets. I have a brand new, never opened set of SPL arms I'm selling for cheap.

To put all the answers in one place:

1) Durability

In THEORY, yes, a true coilover setup will put "more" stress on the strut towers; however, in reality this has not actually shown to be a significant enough difference to worry about. People track their cars with true coilover setups, which is a far harsher condition than bumming around down, without experiencing failure.

More to the point, if you were to run stiff enough suspension with stressful enough conditions to actually need to worry about it . . . you'd be a racing car with no DD duties and you'd have custom fabbed reinforcements in that area.

Bottom line, unless you're shooting for competitive laptimes, don't its not a problem

2) Spring Rate
Changing from a divorced to true style DOES change the geometry of the rear suspension and you should not run the same rates in a true style as in a divorced style.

Refer to this thread:
http://www.the370z.com/track-autocro...ilovers-4.html

Specifically
Summary: if you chose a "true" type setup, you will need to run a LOWER spring rate than a divorced setup

3) Alignment adjustment
There are THREE arms you need for the rear for full adjustment:
- a camber arm. SPL makes two versions, the "billet" style is just a newer design
https://www.splparts.com/products/re...-370z-g37.html
or
https://www.splparts.com/products/re...t-version.html

- a traction arm
https://www.splparts.com/products/re...-370z-g37.html

- a midlink OR toe arm
If you have a divorced setup, get this:
https://www.splparts.com/products/re...-370z-g37.html
***NOTE: The SPL midlink requires a 65mm diameter spring. Check with your coilover provider to see what diameter their rear springs are. Most good places offer Swift springs as an upgrade; Swift makes a spring with the correct 65 diameter that fits perfectly. The STOCK spring bucket is like 4.5 inches and way, WAY wider - it will not fit on the SPL bucket.***

if you have a true setup, get EITHER:
https://www.splparts.com/products/re...-370z-g37.html
or
https://www.splparts.com/products/re...t-version.html

Again, the billet version is just a newer design

NOTE:
You will also need to get an Eccentric Lockout kit:https://www.splparts.com/products/ec...-370z-g37.html

the STOCK adjustment points in the rear are eccentric bolts that may slip over time. These remove that movement, so adjustment is made purely on the arms themselves, which are more stable

Optional
Tie Rod Ends with bumpster adjustment.
https://www.splparts.com/products/bu...5-z34-q50.html


Also, they make swaybar end links which you don't NEED either

Yep, it comes in a divorced setup. OP was probably looking at generic pictures, not model specific.

I believe SPL makes a smaller diameter cup these days, you just have to order through them and not a vendor.

It's perfectly fine for the Z even hitting track curbs. Now if you had a Porsche GT3 or 4.

http://thumbsnap.com/s/yjz77U9D.jpg

sheeesh:owned:

True types are way easier to adjust than the divorced type. There aren't any real downsides especially if you are running relatively soft street rates.

If you are building the kit yourself, know that type set-ups will need to run a much softer rate spring in the rear than if you keep the oem set-up. if you are buying a kit off the shelf, that should already be taken into account.

I have the HKS HIPERMAX IV GT divorced coilovers on my 370z. Very easy install. 1st mod I did to my car.

STATIC LIFE!!:hello:

https://live.staticflickr.com/65535/...d91e274d_c.jpg

I wish I had air tho:icon14:

i hate to be the skeptic, but swapping out for a spring bucket-less "true coilover" rear setup sounds like riding the fine line of potential failure.

i ask myself: how many other cars have failed doing this, and why did nissan go this route to begin with? Also, why would i want to delete my spring bucket when A: spl makes spring bucket midlinks, B:many brands make coilovers spec'ed for Zs with spring bucket configurations as standard (you have to go looking for true rears).

i understand that others have tracked their cars on true coilover setups.. but why would the designers spend more money CAD'ing in a second load point rather than reinforce the shock mount locations? it may not snap the metal, but i can imagine that it is adding a tremendous amount of stress..

http://www.the370z.com/brakes-suspen...al-stress.html

Not agreeing or disagreeing, I think Jhill’s reply (#11) in the above thread has merit in supporting rear true type without extra reinforcement. By his explanation, if the rear bottoms up, it’s the rear shock that runs out of travel first, meaning the shock tower is still required to have the strength to bear weight and force of impact.

Haven't seen anyone report a rear tower failure yet here on the forum. The RC Nismo, the Doren and AM Performance Z's all ran the true type.

Its my understanding that getting soft springs is the cause of the failure, if you hit something really hard and spring compresses all the way, the mounting point of the car will then take the rest of the force. I've been running fortune 500 coilovers for a while now, with stiffer springs and no issues (14k/12k) iirc.

Divorced setup = + 25RWHP!!!



True coilovers :supergay: jus sayin:p

:gtfo2: :shakes head:

It's a combination of spring and valving. The oem set up has to use a stronger spring then a true style because of the leverage of the oem set up. If you use the same spring rate on a true style as the oem. You're over sprung.

:iagree: It is about wheel rate and because of where the spring located you have change the geometry so to speak and the wheel rate will be to high if you run the same springs as in a divorced setup. Ask me how I know!!! I did this with my Z and I had more offs and near offs at the track because I was way over sprung in the rear given a true setup over divorced.

Going with Fortune Auto 510's, true setup. Hyperco springs 14K front, 10K rear...my 2016 370Z is a full on track car and I have zero worries of failure. This baby has already been to WGI, VIR, LRP and many others and each have curbs that would rattle your fillings loose...no problems.

I don't know if you are running any aero or not as I have a 5" front splitter and a APR gt300 rear wing. I had my FA coilovers rebuilt to 510 with Hyperco 800lbs front and 350 rear springs. I still think your rear springs are too stiff. The should be closer to 7k. You find them to be more compliant going over curbing and bumpy tracks. You may struggle with oversteer if your rear springs are over sprung.

Sent from my SM-G965U using Tapatalk

No aero at this time...I wouldn't do aero unless I had a wind tunnel to test it in and some professional input...bad or "guess" aero could make things, much, much worse than anything I can do on my own with the suspension.

The current FA 510 setup and spring rate was professionally recommended...I provided a lot of technical detail to FA and they came up with the starting spring rate...we'll see how it goes once things thaw around here...trust me, I won't be heading out onto the track with brandie new coilovers and be whaling on the car...at least not until I know how it responds and reacts.

LMAO, you have not been on the forum very long and made a handful of post. I am not sure how long you have been tracking and your depth of knowledge with the 370z platform but your post in naive. First off you don't need to do a wind tunnel for all things aero. It is common knowledge that lowering the car and adding a from splitter and having some type of rear spoiler will help. I have been dealing with FA for several years and their product is nice but some of the advise is suspect on spring rate recommendations. Lastly, because of my aero I reached out to a aero consultant to help me dial in my aero and suspension. There is a thread dedicated to that discussion in the track section of the forum if you want to increase your know and whole lot of discussion about spring rates for divorced versus true type setups. Therefore my advise is not without consulting a professional or others on this forum that have equally as much knowledge. So the rule of thumb is with a true type setup you don't want your rear spring rates to be much more than what you have for a divorced OEM spring rate, maybe slightly higher. Good luck and I hope you don't have a negative outcome because your rear spring rates are too stiff. I think the track is the best place to try out your new coils as it is a controlled environment and on the road if things go wrong it could be fatal to you or someone else. I hope it all turns out the way you want.

For reference

http://www.the370z.com/track-autocro...coilovers.html

Right on
14/10 is the standard spring rate for oem divorced type for my Aragostas

The thread linked above will explain why the rear rate should be lower on the true type

FA’s recommendation is likely based on the oem type setup

:iagree:

Yeah, might be a bit naive for sure. I don't claim to be an expert in any of this and rely pretty heavily on the experience of others. I ran about 17 track events last year with no aero. The only track where I experienced some "interesting" handling characteristics was VIR as I was able to get the car up to about 140 mph going down the back straight and into the roller coaster...I could feel the car getting a little "floaty" in the braking zone, probably due to the speed and the fact that I have neither a front splitter or a rear wing AND was running the OEM shock and spring setup.

Here's what FA asked to determine the spring rate:

Year/Make/Model
Type of Driving (i.e. 90% track 10% daily)
Track Surface - Smooth, Bumpy, Both
Brand,Model,Width Tires
Other Suspension Mods (sway bars, bushings, etc.)
Motor Swap?
If heavily modified, weight of vehicle?
Aero Mods (front splitter, rear wing, rear diffuser, flat undertray)
Roll Cage? Y/N
If roll cage, welded or bolted?

So, I answered all of those questions and they came back with 14k front, 10k rear. Now, I suppose I may need less in the rear, but changing springs can't be that expensive or that hard, no? As for trying all of this out, yes, my performance mechanic who will be performing the corner balance and alignment already warned me to take it very easy the first time out with true coilovers as the car will be completely different than the standard OEM setup. He already availed me of numerous stories of people who did not take his advice and ended up with very wrecked cars. I am lucky to have a very good track close by that offers "lapping days" where you get about 4.5 hours of track time and can go out and test various setups on the car. Definitely something I'll be doing before I even attempt to run this thing at any other tracks in my area.

I get it. There is A LOT that goes into the suspension and aero setup of a car.
You've got spring rates, swaybars, alignment (caster, camber and toe), shock compression (high and low speed), shock rebound (high and low speed), tire pressure and brake bias. All of these impact how the car handles. I don't profess to be anywhere close to an expert in all of this and also know (from experience) that even a small mistake in our "hobby" can have disasterous results.

I'm sending a followup email to FA to see how they go about determining the spring rate and if indeed need something softer in the rear. However, given everything that goes into suspension and handling, I'm guessing that one could also compensate for a slightly firmer rear spring by adjusting other areas of the suspension?

When i asked Fortune about rates they sent same questions and i answered 90%/10% pretty much same specs, sways, no roll cage, they told me 11/9. i went with 14/10 (i think) and that **** is stiff af. i will probably replace springs with 11/8.

16nz34, it’s time to get under the car and see for yourself the change in spring location, then educate yourself on advertised spring rate versus “wheel rate” (like hp vs whp).

The rear rate you have is too stiff. It’s not a matter of opinion. It’s math and physics. You just don’t run the same spring rate when the spring is relocated from inboard to closer to the wheel/hub.

Imagine using a lobster cracker....put a spring where you grip the handle vs putting there same spring closer to the joint/pivot.

You don't have a "slightly firmer rear spring". Your rear springs are way too firm.