Note: The following began as a post for another site. Unfortunately, that fell through. So, please enjoy this "exclusive" post, which I've modified and added to provide more detail than what would have ended up on the other site.
1. In
the Beginning 2. Rebuild Time 3. Factory Tour. 4. Reinstall and Impressions
1. In the Beginning
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| Rolling on the S-Tunes... |
Soon after I bought my BCNR33, seeking a more sporty ride and
wedded to the idea of “close to OEM as possible,” I replaced the OEM (“GT-R”
labeled!) shocks with Nismo’s street focused, steel bodied S-Tune shock absorbers, which looked
great and had a slightly firmer, sportier ride.
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| Like these |
After a few years however, I found performance on the track
to be a bit lacking. At the same time, I
began reading about rebuildable, customizable “proper coilovers” and then found
that Öhlins had come out with their aluminum bodied “DFV” coilovers (incorporating
their Dual Flow Valve system) for the BCNR33 and BNR34.
Developed by
Öhlins AB in Sweden, the DFV technology uses
two sub-valves, one on the compression side and the other on the rebound side,
to supplement the main piston.
These valves allow for high speed (not car velocity, but how quickly the dampers react to the road surface) damping, while the main piston handles low speed damping. This
means, while maintaining the characteristics of the main piston (which can be paired with a fairly stiff spring, as is often the case for cars that might see the track), DFV
equipped dampers respond almost immediately to minor road imperfections, thus
maximizing tire traction while giving a smooth, compliant ride.
Despite the DFV coilovers being relatively new to the market
back then,
I managed to find and buy a used set online for a great price.
The seller claimed he had bought them new and
then used them for a few thousand kilometers before switching back to something
softer, only then to have his car stolen! Thus, he was divesting himself of all
of his leftover GT-R parts.
Anyway, once
installed they were indeed like new, and I immediately noticed the difference
between the S-Tunes, with the ride being much firmer, but also, and quite
paradoxically, extremely smooth.
2. Rebuild Time
Flash forward six years and several thousand kilometers
later, the ride had gotten progressively worse, but I didn’t really think
anything was off until on a
recent journey to the back roads of Chiba Prefecture with Mr. Dalle Carbonare, when we both agreed that
something seemed off, that the suspension seemed to not have enough rebound. It was a reminder that my gold DFV coilovers were long overdue for a rebuild.
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| Looks great, but the ride was actually not as good as it should have been. |
As I don’t have the garage space to do a coilover removal
and reinstall, I asked Ninomiya-san (my
neighborhood mechanic) to do the work at his shop, “BeAmbitious.” Once removed, the actual rebuild would take
place at Öhlins’ authorized Japanese manufacturer and distributor, Labo
Carrozzeria in Adachi Ward, Tokyo. Turns out, as an ex-NISMO race team mechanic,
Ninomiya-san has plenty of contacts in the industry, and so knowing I wanted to
see how a rebuild was done, he called Labo Carrozzeria and arranged for me to
visit them for a private tour of their operations.
3. Factory Tour
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| Outside Labo Carrozzeria, where Öhlins are built and serviced. |
Upon my arrival, I was greeted by Hiroshi Shitakubo, Group
Leader for the Sales Department.
After
exchanging pleasantries (turns out we know people in common in the car world here!), he gave me a
short history lesson on
Öhlins AB and how they had begun in Sweden making
shocks for 2 wheeled vehicles. He also discussed their current product line-up,
including their
racing,
rally and offroad, and
Build To Order (BTO) applications, their
JDM-only models, and of course their DFV coilovers, now silver in color (due to
environmental concerns) and sold worldwide as their “
Road & Track” models.
One question I was curious about – the difference between
the Road & Track models versus the Öhlins models with remote-reservoir
tanks, such as the Flag-R series for GT-Rs.
Shitakubo-san explained that the remote-reservoir models do not have DFV
technology, but they do have more fluid volume and adjustability, so in a
nutshell, the Road & Tracks are more street (with the occasional track day)
focused, while the external tank models are more track oriented, given their
increased adjustability along with the smooth pavement of the race track. Plus,
he mentioned that many GT-R owners love how the reservoir tank model “looks
cool.”
Shitakubo-san then invited me to tour the factory/workshop floor with
him. On entry, he pointed out that most
the workstations are dedicated to the automotive line-up, with the motorcycle section
in a segregated space in back.
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| Shitakubo-san leading me onto the workshop floor... |
Unfortunately, it turned out that they had already finished
rebuilding my DFV coilovers so I wasn’t able to watch them do that. However, I was able to witness various coilovers
at different stages of overhaul, as well as new Road & Track sets being
built.
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| The new silver colored Road & Tracks being assembled |
For rebuilds, all the incoming coilovers are thoroughly
cleaned, inspected and then disassembled.
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| Total concentration there... |
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| All disassembled, ready to be rebuilt |
Certain parts are always replaced, whether or not the wear
is obvious or not.
Those parts include
the various internal seals, and of course the oil.
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| Where the DFV magic resides |
On occasion, they will spot damage to the main piston, or
other areas including the exterior, and when this affects performance they will
change out those parts as well. Never
having seen the innards before, I was surprised to learn how many pieces make
up the valve assembly:
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| Lots of pieces... |
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| Close up of the valve |
The coilovers are then reassembled to the customer’s order,
which might include changed springs and compression/rebound rates, as well as the
addition of optional features. Finally the coilover undergoes several QC checks
before being shipped back to the customer. In my case, as you can see below, I
chose to swap out the standard pillow ball mounts with rubber mounts, but kept
everything else standard to the recommended Öhlin spec.
Here is a pair of newly rebuilt BTO DFVs for a Lexus IS-F (not mine unfortunately):
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| They really don't replace external parts for cosmetic reasons... this IS-F sees a lot of action I guess |
And a close-up of new Road & Tracks ready to get shipped out.
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| So they no longer make the gold ones... hold onto them as collectibles! |
4. Reinstall and Impressions
When my schedule finally cleared up a few weeks later, I
dropped into BeAmbitious where I had the pleasure of removing my rebuilt DFV
coilovers from their protective bubble wrap packaging.
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| The anticipation was too much... |
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| I tore off that bubble wrap in no time!! Then starting drooling. |
Interestingly, Labo Carrozzeria also sends back all the used
parts, mainly to give picky owners peace of mind that they did the rebuild.
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| Obviously I can't tell what is worn out... but I've heard it's those rubber rings... |
Here you can see how the top mounts are now rubber (compared to the old solid mounts).
Shitakubo-san told me these were developed in order to absorb the noise
that normally gets transmitted via the solid mounts, even when new. I've since learned that there might be a loss in feel but...
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Old solid mount on left, coilover now hos the rubber mount.
This photo also reminded me that the set-up uses Eibach springs too... quality throughout! |
Once re-installed on my GT-R, I could not believe how
amazing the ride was. The ride was extremely smooth, quiet and comfortable but
at the same time firm and stable, with no weird body movements, whether at low
or high speed.
The entire car feels very
tight, but without any harshness.
Loss of feel due to the rubber mounts? None that I could detect, really!
Given
that Öhlins markets the Road & Track series as improvements to the OEM
suspensions on high performance German cars, I think that gives you an idea of
the kind of performance I am trying to describe.
If you do a search on the web, I see so many comparisons between the DFVs and other very famous brands, and almost always the verdict is in favor of the DFVs. So I'm happy I stumbled onto them.
Oh, and now, after having driven the GT-R with these rebuilt, I know why Öhlins recommends a
rebuild every 2 years or 20,000 kms.
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| What I saw when I went to pick up the GT-R... |
"Anyway, now with these as-new DFV coilovers, along the
stiffened chassis and NISMO suspension links, I’m pretty happy with the
handling characteristics of the car. However,
I’m not done yet as I have several projects in mind, all aimed at seeking
further refinement on various aspects of the car, and not just in the handling
department. Thanks for reading this and
next time I hope to showcase one of those refinements."
And so with the quote above, I ended the original post... but it turned out that Ninomiya-san had spotted something odd on the car when he was doing the reinstall... stay tuned and I will post an update on that!
