Öhlins DFV Rebuild (Part 2) and Factory Tour!

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. 

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.

Image may be NSFW. Clik here to view.

From: http://www.roadandtrackbyohlins.com

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.

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.

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.

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.

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.

For rebuilds, all the incoming coilovers are thoroughly cleaned, inspected and then disassembled.

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:

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):

And a close-up of new Road & Tracks ready to get shipped out.

Image may be NSFW. Clik here to view.

So they no longer make the gold ones... hold onto them as collectibles!

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.

Interestingly, Labo Carrozzeria also sends back all the used parts, mainly to give picky owners peace of mind that they did the rebuild.

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...

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.

"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!