The suspension on my 2012 S sedan is getting tired, which isn't unexpected given the car is 12 years old and has 89k miles on it. The rear is sagging and the car uses too much suspension travel on compression. I am making this thread to document my efforts to decide on a replacement path as there are likely to be others looking to refresh their car's suspension, but aren't looking to slam the car, turn it into a track car, or have their teeth rattled out on bad roads. I am interested in a small drop, perhaps half an inch, but nothing more than that.

The newest version of these sedans is now 10+ years old, and thus some OEM parts are unavailable. The OEM Sport Tokico shocks aren't available, and neither are the OEM Sport springs. There are OEM options available, but it is the same part for both the base/Journey and Sport sedans. I do not want to "downgrade" to base/Journey sedan specs.

Aftermarket direct replacements are also available, and KYB specifically is mentioned as being a high quality option for the Sport sedans. However, the issue I am running into are springs. I can't seem to find OEM Sport-spec springs to pair with the KYB struts. There are many lowering spring options, with Swift and Eibach being the most common, but I don't want to lower the car that much. Note, the stock Sport spring rates are thought to be 8.4k/7.8k for the Sport sedan.

So, this leads me to considering going the coilover route. There are MANY coilover options out there, but most are too hardcore for my goals. This is commonly seen in spring rates that are way too high. For example, the Z1 S-Pros are 12k/10-12k progressive. This is 40% stiffer than OEM Sport spring rates. (Edit: it's more than spring rate that determines how a coilover rides. Ride is a combination of spring rate and damper specs. See post 23)

I prefer keeping the divorced rear spring setup. The car was engineered to carry the rear weight this way, although I don't seem to find anyone complaining that true coilovers have caused any issues. As I understand it, true coilovers also require replacing the OEM midlink/spring buckets.

Another issue seen is many (all?) coilover companies use the same part number for the coupe and sedan Z, coupe, and sedan, yet the sedan carries more weight on the rear axle than the coupe Z. Thus when installed on the sedan, the maximum ride height is much lower than expected. A good example of this is Fortune Auto 500 coilovers. These come with 7" rear springs, but many have found installing these on the sedan result in more drop than desired in the rear. Fortune Auto does have the option to spec an 8" rear spring to mitigate this. More details on that below.

So far, these are the coilovers I have found that seem to meet all my specs (OEM-ish ride height on a sedan, divorced rear, reasonable spring rates, come with top-hats installed, not cheap junk):

• Fortune Auto 500: I really like everything I read about these coilovers, plus they can be customized with a variety of spring rates. However, avoiding a large drop in the rear requires upgrading to Swift springs to get an 8" rear spring. That makes them $2250, which is a bit more than I am hoping to spend.
• Revel Touring Sports Damper: These are advertised as having a "comfortable" coilover ride and come with 10k/8k springs. The rear springs are 9", so they should be long enough to dial in am OEM-ish ride height. They also come with covers, which is a nice add-on. I emailed Revel and they said the middle of the damping adjuster will be an OEM-like feel with a balance of performance and comfort.

I have only found these two options that seem to meet my requirements. So, I am going to spend some more time researching true rears to make sure I am making an educated decision. In addition to understanding what else true rears require, I need to understand the impact this would have on spring rate. I plan to update this thread as I learn more.

 

going to true-style rears does remove the need for the bucket but its not a must to replace it. you can still retain it and use it as the toe adjustment point.
But replacing it with a toe rod saves weight and provides mod adjustment over the stock or SPC eccentric bolt, unless you get midlinks for a divorce setup for adjustment.
true-style setups also run a lower spring rate relative to divorce setup because of the motion ratio. definitely shouldn't run the same spring rate for both locations.

 

I think that's the second time this week I've seen a reference here to Revel's coilovers. I'd like to know more about this CO.

/subbed

 

A few more updates:

I saw that BC can do Swift springs as well. I emailed BC and the minimum drop they offer is 1 inch below stock ride height, even with Swift springs, so BC is out. There are also endless reports of clunking from BC coilovers, so I'd be very hesitant to go BC anyway.

There is very little info on the Revels from G37 owners online. Revel told me that they did install and road test their coilovers on a sedan, and that they have sold "quite a few over the years." I guess none of those cars on on the forum.

Thanks for the info. I did spend some time looking into true style coilovers, and found a similar problem, namely, they are designed for the coupe and Z, and thus result in too much of a drop on the sedan. The exception to this is Fortune Auto. For the standard price of $1850 they will build out a sedan specific set. For my goals, this is what they recommended:

• Front Suspension: 120MM front shock stroke, 270MM front shock body – Spring rate: 10kg (7-inch FA spring)
• Rear Suspension: 150MM rear shock stroke, 270MM rear shock body – Spring rate: 5k or 6kg rear (9-inch FA spring)

It's very cool that Fortune Auto coilovers are so custom. A definite advantage over the more generic, mass-produced, and cheaper options.

There are seemingly endless debates about the risk of converting to true, with a lot of this coming from the Z world. Some say it's fine, others aren't so sure, and some have even gone to the effort to reinforce their rear shock towers. Personally, I have no idea, but I tend to think the Infiniti engineers knew what they were doing

 

@PDG How did you determine that the sedan carries more weight than the sedan in the rear? Recall that the coupe is heavier than the sedan.

also, I could have sworn at one point in time that Tien offered a milder spring than the S-Tech? Did they stop building those?

lastly, I looked into dampers last year and KYB offered a set for the sport sedan and coupe (same setup was offered for the G35/S, and I ran the S version), and another version for the Journey. I wonder which version they are building now?

 

@socketz67 It was based on posts such as this: https://www.myg37.com/forums/g37-sed...ml#post4315095

BUT, on re-reading, I realize I misunderstood, and the higher weight on the rear axle is compared to the Z, not the G37 coupe. Thanks for helping find my error! I am going to edit in my original post.

I'll look into more detail on the Tein springs and KYBs

 

Tein only lists two options, both with a large drop: https://www.tein.com/srch/us_search....ault&genuine=0

 

No problem. The Z is a shorter version of our FM platform, and weighs about 200lbs less if my memory serves me correctly. Coupe weight difference is negligible as I believe it comes from the adding bracing needed due to the lack of the middle pillar.

Maybe go with this KYB assembly in the front (they don't list an option for the rear?): https://www.kyb.com/catalog/

Then obtain some Coupe/Sedan Sport Springs for the rear, and add these KYB shocks: https://www.shockwarehouse.com/produ...43239862108392

 

That doesn't seem right. Hang on...

In 2013, the base model Z was 3232 pounds whereas the base model G37 Coupe was 3631 pounds. That's a 400 pound difference.

 

Dr. Google must have failed me. I took the first result I saw for each. I recall that the difference was 300lbish per several conversations here a while back, so I took the mid-lower ends of below and estimated (the ends are lower than 300lbs):

"2013 nissan 370Z curb weight"
Curb Weight: 3,245 to 3,501 lbs

"2013 infiniti g37 sedan curb weight"
Curb Weight: 3,618 to 3,701 lbs

Also, I called KYB Americas this morning and they no longer have a rear shock offering for the Sport Sedan, only the Journey and all versions of the G37 coupe (even sport models), so it seems that they have lost their way.

Good news, Koni still has an offering:
-KONI 8241 1282LSPOR Front Left Sport
-KONI 8241 1282RSPOR Front Right Sport
-KONI 8241 1283SPORT Rear Sport

Pretty pricey, but I believe several here have used this dampers with good results.

 

I'm at a place with my car where potential future mods are to replace original modifications. And one of the more eligible components for that would be my Frankenstein suspension of OEM shocks, Swift springs in the front, and Tein Basic springs in the rear.

Anyone ever research Aragosta coilovers? I've always had this vague impression that they were top shelf stuff.

 

Yes, I've seen posts about the Koni Yellows. They don't list the sedan, just the Z and coupe, but there have been people that have installed them on the sedan. But, I run into the same problem with other struts: sport springs are discontinued. https://www.z1motorsports.com/front-...d-p-13638.html

 

Check out this lengthy and detailed thread about Aragosta coilovers: https://www.myg37.com/forums/brakes-...ispreloading=1

Ape Factory ended up ordering directly from Japan to save a ton of money on them. I think sedan owners would also need to be careful with rear spring length to achieve their desired ride height.

 

I saw a TEIN EnduraPro Plus option on Concept Z's site, so I called to discuss. Not much history on these, and the kit was on backorder 3-4 months.

Then I called TEIN as they have a location in LA.

TEIN EnduraPro Plus: https://www.tein.com/srch/us_search....ault&genuine=0

Per the table on this page:
VSP92-B1MS2-L (Front Left, adjustable)
VSP92-B1MS2-R (Front Right, adjustable)

On the site, rears are just EduraPro, not adjustable per the website: VSP93-A1MS2 (Rear Shocks)

When I called TEIN (answered the phone like in the old days), they were friendly referred me to their largest partner in LA called Options Auto Salon: (626) 812-7222

They too answered the phone and then verified that the TEIN EnduroPros/Plus are made in China, but that they have not had any issues with them at all and believe that TEIN wants to move all manufacturing to China over the next couple of years and take over the spot Tokico used to occupy in the aftermarket.

Spoke to someone named Jasper, explained the Coupe vs AWD vs Journey vs Sport Sedan dilemma, and he recommended the TEIN EnduraPro setup over Koni (they sell both) as the cost of the Koni is more than double and he felt there is no difference in quality. He also said that the Koni setup only lists the coupe as an application. He thought it was odd that Infiniti killed the factory Sport replacements and now direct everyone to the journey setup. Good enough I guess?

The PN is VSP92-B1DS2 (Kit): $490, $570 shipped.
-Front and rears are adjustable

Anyway, thought I'd post my findings here as the replacement shock/strut pickings are getting slim for the Sport Sedan.

 

Another factor here: the base/Journey OEM springs are expensive. 4 new OEM springs run $1300.

Front: https://www.z1motorsports.com/front-...d-p-13638.html
Rear: https://www.z1motorsports.com/rear-s...d-p-13660.html

Add in shocks/struts, and you are looking at $1800. https://www.z1motorsports.com/shock-...t-p-17210.html

Depending on what someone chooses, decent coilovers are cheaper