Sunday, July 22, 2018

Project CRS Part 7 - The Underfloor

Since the very beginning I thought that being able to witness my car transformation every step of the way would not only be a once in a lifetime opportunity, but also the coolest way to learn and gain mechanical knowledge. 

So, for the past few weeks, I spent most of my Saturday mornings at Omori Factory, hanging around the workshop, inspecting parts and refining options. A special tanks goes to both Ochiai-san and Takasu-san: nothing of this would have been possible without them and their patience and hospitality have been off the scale.

Now, what I really wanted to avoid was to simply have everything replaced and the whole Nismo catalogue thrown in with no questions asked. 

I figured that being able to inspect each and every component and subsequently choose whether to refresh, replace, upgrade or customize would, not only be the best way to build something unique, but also serve educational purpose as well as avoid spending money unnecessarily (as reminded by the carbon fiber cash tray at the reception).

By the time I paid my first visit Ochiai-san had already spent a few days on my GT-R, and he surely didn’t waste any time. Taking a car apart is not a big deal for a master mechanic, but his knowledge of each and every component (including most prices and stock availability), and ability to dismantle it down to the last nut and bolt, and put it back together without the aid of any manual is absolutely impressive. I must admit that I was really adamant to see my car. Although we had already run a through condition check few weeks prior, this time he had removed all the front body panels, the engine and stripped away big chunks of the chassis. This was the moment of truth as I was about to know the actual conditions of the vehicle.

But the reality is that Ochiai-san spoiled the surprise long before we got to the workshop area as he sat me down and informed me that he couldn’t believe his eyes once he started to take the car apart. He explained that, no matter how good a car looks, once they start disassembling the chassis there is alway at least a bit (or a lot) of rust hidden somewhere, but this time he could not find any, not even a scratch, and he had seen only an handful of cars in this condition over the past several years. 

My initial reaction was skeptical, worried that I was receiving some lip service, I kept repeating myself that the car has exactly 80,000 km on the clock: to put it in perspective, it’s the equivalent of driving the distance around the Earth at the Equator, twice. However, when both him and the body specialist repeatedly insisted that I should leave the underfloor untouched (which would see Omori Factory losing a considerable amount of money), that’s when I started listening and asked to move inside the workshop area.

To my surprise, he was right: as hard as I looked all I could find was some dirt and a couple of very minor scratches, but not a hint of rust or even light surface corrosion in sight.

The car was so clean in certain areas that Ochiai-san jokingly asked if knew much about the driving habits of the previous owner (well, he used to live in Nerima...).

He showed me how the lack of rust or corrosion coming out of the drainage holes (red arrows) is also a sign of great health.

One of the true Achille’s tendon of this car subframe are the several areas where different metal sheets (usually 2 or 3) are simply pressed against each other and bent, with no sealant or protection whatsoever to prevent water from getting stuck in between. In case of rust, cutting and welding are the only options to this issue and I was so relieved to see that there was not even a hint of corrosion blossoming through the inside.

This is a cheap and fast way to assemble cars (Nissan was struggling financially in the late 90s), yet the main cause behind so many strut towers being plagued by rust, so a proper inspection of the wheel arches was due.

Again, I was quite happy to see all the four corners of the car being given a clean bill of health.

Another detail that surprised me was the complete absence of corrosion on the brake rotors, an area that is notably prone to this issue; as well as the never replaced, yet pristine Brembo calipers with no signs of fading on the red lettering.

I hope this is not coming across as a lame attempt to overly praise my car - quite the opposite: I always assumed that there was going to be rust and was ready to expect the worst, which is why my original plan was to have the underfloor treated and repainted! The idea behind it was that there is no way that modern products and materials cannot improve manufacturing technology that date as back as the late 90s. To my surprise, I was wrong.

During the original production frames are dipped in zinc and galvanized, which is one of the most rust-resistant treatment available even today. Repainting the underfloor would require sanding off the original paint - an extremely stressful process for the metal to begin with. Even if resprayed with comparable products, body shops (even the one affiliated with Nismo) don’t have access to the proprietary mass-production technology used by Nissan in its factories, which would ultimately leave the car with a - yes - shinier, yet weaker underfloor.

What about re-dipping the frame altogether? This was an option that I originally contemplated, especially after inspecting the restored white frame on display at Nismo Festival last year. However (beside the astronomical cost), it turns out that these frames are not re-dipped (and neither were the 19 Z tune models back in the days) for several reasons. To begin with, while the exterior paint can be sanded off, the same process cannot be applied to the hollow structures of the frame and, apparently, the combination of different zinc-based paints is detrimental to the metal. Additionally, the same inaccessible cavities are usually filled with dust and small debris which would prevent the fresh paint from properly adhere to the surface. Lastly, besides causing a weight increase due to more paint filling the frame again, the process would result in altered tolerances that would make refitting the parts harder and the car overall clunkier. 

So, the conclusion to this was that, when it comes to the bare metal frame, factory finish is the healthiest option possible and Ochiai-san reassured me that, if it hasn’t developed rust so far, it will probably never rust as long as I stay away from unnecessary rain and salt. This turned out great because, not only I now have full reassurance that the car is in great shape, but also saved some good money in the process! So, we picked a few options: I chose a complete underfloor clean up and decontamination, full nut and bolt restoration, ordered a few new parts that don’t look great anymore and specced a few others with additional powder coating for a bespoke touch.

This was definitely a great educational experience for me and I hope it helps owners around the world with ideas for their own cars. Thanks for stopping by today.

Until next time.


  1. That is one clean car!

    On a side note though, does Nismo have a website that sells their merchandise, like caps and jackets?

    1. Thank you!
      Yes, you can find most of their apparel here, although I’m not sure they ship outside Japan.

  2. What did they mean when they say avoid driving in unnecessary rain? Do you not drive in the rain? I became curious as to how rain affects a car's chassis in the long run.

    1. Well, rain (and too much water in general) is obviously not the best for an old car prone to rust. Driving into heavy rain makes it very easy for water to infiltrate inside the cavities of the underfloor and engine bay, not to mention, as the years progress and rubber gets harder, the risk of water infiltrating under failing window seals. That’s why it’s recommended to drive the car around a bit after a wash, to let the residual water come off. Cosmetically, rain also leave hideous water spots on the body of the car. Personally, I never enjoyed driving in the rain, even before I owned the GT-R, so not a big deal for me.

  3. Incredily clean clar. Almost too clean ;)
    And I can definitely understand why you were surprised when they told you to not touch the floor. But once you saw it in person, it easily understandable.
    Bet you are pretty happy that you bought this car after all ;)


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