Moto IQ: Industry Insider-Seibon Carbon

In Moto IQ’s words:

Seibon invited us to their headquarters to take a closer look at some of their products and answer some of our question on how they are made.  We know Seibon’s quality has improved by leaps and bounds over the past few years.  Our Project FR-S has a Seibon hood and decklid and we were very impressed with their fit and finish – which is flawless.  No ripples or warps and the gaps to the OEM panels were actually tighter than stock!  Let us show you some of the stuff we saw during our visit.

We first looked carefully at Seibon’s standard wet carbon parts.  Wet carbon isn’t sexy but it makes up the bulk of the carbon part market and if done well, wet carbon makes for a strong, light and functional performance part.  A wet layup is just that.  The mold is first sprayed with a gel coat, a thicker resin that serves as the part’s smooth surface finish.  Then carbon and fiberglass cloth are layered in the mold and brushed with resin which is usually polyester based.  The resin is rolled into the cloth and the excess is squeegeed out.  This method is how most aftermarket composites are made and is perfectly adequate.  Seibon’s wet carbon parts are produced using proprietary techniques for the wet layup which minimize weight, improve appearance and maximize strength.IMG_7220-L



Let’s take a look at Seibon’s wet carbon Nissan GT-R door as an example of wet carbon done right.

At 10.8 lbs each, Seibon’s wet carbon GT-R doors are much lighter than the stock parts, saving over 40 lbs per door! On the front surface, the first layer of the door is made of carbon backed by two plys of fiberglass cloth. The carbon gives cosmetic looks and strength while the fiberglass gives stiffness while being much more cost effective than carbon. One thing to note is that Seibon uses fiberglass cloth, not mat or chopper gun fiberglass.  Cloth is much stronger and uses less resin, but it is more labor intensive to apply.  Look at some of the cheaper carbon parts on the market and you can see that the carbon is backed by unidirectional mat or a criss cross matrix of chopped fiberglass soaked with lots of resin.  Some of these cheaper parts can weigh more than stock!IMG_7222-L



The back sides of the doors are made of fiberglass and are perfect replicas of the stock doors.  This means that the inner door panels, hinges, locks, handles, speakers and even window regulators and tracks can all be kept in place and functional.  Even the areas where the seals mount are functional. We don’t think street cars should be driven with these doors without a cage as they are lacking the OEM door’s steel side impact beams, but the doors save much of the weight that a cage adds!  The Seibon doors do have molded ribbed internal supports for strength though, so the door is not a weak floppy part.

The hinge areas of the doors are reinforced to reduce door flop.  Look at the detail here!IMG_7225-L

The lock and door handle areas are also reinforced with more cloth.  All the stock interior parts can go on and you would never know that this is a composite door.  Of course if you have a race car, you can cut much of the inner parts out to make clearance for NASCAR style door bars.IMG_7223-L

We looked at some of Seibon’s other wet layup parts. How about a 9.4 pound chair?



Sweet knives with ceramic blades and carbon handles. We think these were prototypes.  We want some of these.  They were super lightweight.

CaIMG_7262-Lrbon framed sunglasses!  The ones without lenses are for hipsters.

Saving the best for last, let’s take a look at Seibon’s high end dry carbon parts. Seibon uses carbon cloth that is pre impregnated with epoxy resin called pre-preg for short.  Epoxy has superior structural strength and toughness over polyester resin but is not as crystal clear and pretty.  For function it rules however.  With pre-preg, the amount of resin used is very precisely controlled and you get just what is needed for the matrix to bond together. This dry carbon GT-R hood only weighs 17 lbs and is strong enough to shrug off blows from a hammer without cracking.  Look at the detailed vents.  The top of the hood is made of three plys of pre-preg. No fiberglass!IMG_7244-L





The area where the hood latch bolts is reinforced with extra layers of dry carbon for added strength. This is an area where many hoods fall short. Check out the surface finish of the underside structure, it is very nice.


All of the holes are present for OEM trim and seals.  Note how the weave of the cloth is not distorted even with the complex geometry of the part, not even in the corners,   No black paint masking cosmetic flaws here! The edge finish is very nice.


The weave in the louvers is very straight and nice as well. Look at many other carbon parts and you will see subtitle fogging of black paint in the corners to hide flaws. Not Seibon parts.


Seibon’s GT-R dry carbon door is another nice piece of work. The dry carbon door is 100% carbon/epoxy pre-preg, no fiberglass here.  This surface finish and fit is still excellent.  Carbon and epoxy make for a much stronger part than carbon/polyester/fiberglass.

IMG_7257-LLike the wet carbon door, the carbon part is compatible with the stock components.IMG_7250-L


The dry carbon door shows the weave straightness even with tight bends much like aircraft of high end race car stuff. Look how little the carbon weave is distorted even in areas of 3D contouring and sharp edges.IMG_7256-L

Look at the detail of the doors. All stock interior panels, window regulators, speakers, locks, handles and seals bolt right up.

The door is highly finished. Note the holes for the seals and the water drains. A lot of lower priced “dry” carbon is simply wet carbon with a flattening agent in the gel coat to make the part dull. Seibon’s dry carbon is the real deal.

Look closely in areas that you will never see. Look at the lack of weave distortion and the nice edge finish.IMG_7253-L




Seibon’s quality has evolved as well from typical low priced stuff to top class in their latest offerings.  For example, the fit of the Seibon stuff on our project FR-S is amazing. Seibon’s quality has improved so much that they are now producing parts for other high end aero kit companies and are even making some composite parts for OEM manufacturers!

For Moto IQ’s complete write up visit:–seibon-carbon.aspx