[Damping Debug - 3rd Time?] Chasing the bug where the Avenir's rear feels 'bouncy'! Finding the 'sweet spot' of the Largus 32-way adjustable coilovers

Hello! This is Re:NISSAN from Re:Tech Japan. Thank you for reading as always.

The Avenir, also known as 'Abe-san,' has returned to my garage after a long time.

Perhaps because the weather has warmed up, or maybe because I haven't been behind the wheel in a while, I've started to feel something off about the 'damping' of the suspension.

For now, I tightened the front by 5 clicks (set to -9/32), and yeah, the front feels a bit better.

However, the behavior of the rear when going over bumps is still 'bouncy,' undulating and failing to settle.

Is this a point that every Avenir owner would agree on? ...This car's rear suspension adjustment is seriously a nightmare (a bug). It just won't settle.

This time, I'm bringing you a life log of my gritty, repetitive adjustments to put an end to this 'hellish damping debug' of the rear.

Ryoucyan's damping adjustment record. This was helpful.
Largus Coilovers (Nissan Avenir W11) by Ryoucyan - Minkara

(Actually, this is after the adjustment lol) There were details on the Minkara page of Ryoucyan, a senior Avenir owner! This page... I should have seen it before... If I had realized sooner that the damping adjustments were written in such detail... I might not have had to remove and reinstall the rear three times. But it gave me a strong push, confirming, 'It was fine around here! My adjustment direction wasn't wrong!' Thank you very much.

🛠️ [Damping Debug] Chasing the bug where the Avenir's rear feels 'bouncy'! Finding the 'sweet spot' of the Largus 32-way adjustable coilovers

📐 [Specification Verification] The extreme leverage ratio of 7kg front and 12kg rear

Installed on Abe-san are the 'LARGUS Spec S' coilovers, which are among the cheapest in the country. This is the second time in my life I've deployed brand-new Largus coilovers.

Actually, the manufacturer's default spring rates for these coilovers are as follows.

• Front: $7\text{ kgf/mm}$

• Rear: $12\text{ kgf/mm}$

The rear springs are overwhelmingly stiffer than the front. As you can see from these figures, the Avenir has a special architecture where the rear leverage ratio (the mounting angle and action point of the suspension) is significantly different. (My previous car seemed to be F6k-R4k. Since spring rate depends on the structure, you can't tell if the actual ride will be hard or soft just from the numbers.)

The stock shocks themselves were also quite stiff, so it might have been an unavoidable fate (specification) that the behavior would become even more peaky (harsh) once converted to coilovers.

💔 [A Troubled Past] Gratitude to the shop, and choosing 'DIY Hard Mode' after a trust error

'What is the manufacturer's recommended (out-of-the-box) damping force?'

I could just ask the professional shop that did the initial installation, but it's highly likely they've forgotten the details of the February work by now.

After all, I entrusted the coilover installation to that shop with deep gratitude and respect, as they were the ones who correctly identified that the 'clunking noise' from the front, which had been bothering me since the car was delivered, was caused by the upper mounts.

As a result, while the clunking noise was completely resolved (debug successful), I was dissatisfied with the quality of the coilover installation, which caused an error in our relationship (please refer to past logs for the complaints regarding the subcontracted work).

Consequently, I ended up choosing the DIY hard mode protocol where I do all subsequent work myself. I can't help but feel I'm choosing the thorny path on purpose (lol).

📊 [Log Analysis] Damping force adjustment history from February to July

Here is my debug log (adjustment history) where I kept adjusting the click count by trial and error after losing track of the initial settings.

Adjustment Period
MileageRear Damping SettingTrigger / Notes for AdjustmentFebruary36,388 km
-32 clicksInitial setting at shop installation (softest side)May38,628 km
-11 clicksFirst DIY adjustmentJune39,025 km
-16 clicksAdjusted to the median range based on a senior's adviceJuly (this time)39,463 km-10 clicksDebugging by trial and error alone

🚗 [Road Test] 'Hey, hey, hey, this isn't bad!' Finally found a best setup that is actually rideable

With the rear at -10 clicks (the front was confirmed to be -9/32), I headed out to my usual 5km test course.

The moment I started driving, I had a gut feeling, 'Oh, this might actually be pretty good this time.'

Looking back at the past logs, I've actually returned to almost the same setting as in May ( -11 clicks) (lol). Perhaps the ride height setting was slightly different back then, or the synchronization (compatibility) with the front side (-9 clicks) just clicked into place.

I continued through the local mountains (Kashikirina Mountain) and did a lap around the wide oval course.

I deliberately drove the Avenir into a sector with rough, bumpy road surfaces, but...

'Hey, hey, hey, this is actually pretty good!'

The unpleasant 'bouncy' excess pitching was suppressed in one go, and I felt like the tires were firmly gripping the road. It might be fine to go even stiffer (low double digits), but this state that retains 'suppleness' is extremely pleasant. I'll commute with this for a while and test if my colleagues notice the change.

What I realized through this debugging is that 'even if there are 32 levels of damping force, the usable 'sweet spot' for that spring is only within a few clicks.' Moreover, it seems the manufacturer's initial recommended position is actually quite stiff for the Largus factory-set springs. (Probably lol)

If you make the damping too soft relative to the spring in an attempt to improve ride comfort, the damper cannot control the spring's movement, which conversely triggers the 'bouncy' unpleasant ride bug.

⚙️ [Future Updates] Want to lower the initial rate. Introducing Swift springs and the 'Spring ID' trap

I am satisfied with the current damping balance for now, but in the future, I am thinking of 'wanting to make the springs themselves one rank softer'.

Swift springs, which have a lower initial rate and move flexibly, have long been very popular among DIYers.

However, this is where the specific specification limitations (bugs) of Largus stand in the way.

It seems that the 'ID (spring inner diameter)' of Largus coilovers is slightly different from general standards, and it appears that a dedicated adapter is required when trying to bolt on and deploy straight-wound springs from other manufacturers.

Precisely because it is one of the cheapest coilovers in the country, 'trial fitting' these expansion parts is the real thrill of DIY. I don't intend to push it too hard (lol), but aiming for comfortable street cruising with Abe-san, I will enjoy debugging the suspension little by little!

I feel like I want to aim for the rear to be even softer than stock, in particular.

[Regarding Re:Tech Japan's product and information verification]

The equipment and analysis data introduced on the Re:Tech Japan blog are life logs that Re:NISSAN has researched and experienced through trial fitting by allocating his own time and brain memory while going through the bypass of general theory, mainly for the maintenance of garage life and the life extension of his own chassis (living environment/beloved car). The equipment introduced on the Re:Tech Japan blog was mainly purchased, installed, and verified by Re:NISSAN at his own expense. Re:Tech Japan earns income through qualifying purchases as an Amazon Associate.

※Warning: Always follow the instruction manual for correct usage. The challenge known as DIY is always performed at one's own risk.

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