Body kits, as you well know, exist in various price levels. The variation in price usually has more to do with materials, manufacturing methods, and scale. A few years ago, body kits imported directly from Japan carried a certain cache that domestically produced kits could only emulate. You should understand that this is automotive fashion, and more exclusive body kits (much like a designer’s more exclusive dresses) simply cost more to get into the small volume manufacturing of some of these Japanese body kits afforded excellent quality with what was essentially a handlaid fiberglass construction process. Given the small manufacturing capacity, there simply weren’t that many of them on the road. In other words, there are people who cough up inordinate amounts of money to have, in effect, the dress that no else is wearing to the ball. In the process, they make their cars look like something out of an anime cartoon and remove the expensive kit two years later after the Kit Car people come to ask how they did that to a VW Type I.

Handlaying fiberglass involves laying sheets of cloth into a mold and soaking the sheets with a resin to produce the desired shape and that later hardens the sheets of fabric into a solid. As body kits grew in popularity and the visionaries in power saw that greater units could be sold to help reduce price (and increase profits), fiberglass started being sprayed from a chopper gun rather than being handlaid. This proved to be far quicker, but yielded a finished piece that was less flexible, less resistant to impact and more prone to fitment misalignments. Even larger volume production involves the use of molded polyurethane, whose greatest expense to produce rests in the expensive tooling required to mold such pieces. A urethane body component allows the greatest durability and flexibility and is actually the material used by original equipment manufactures (OEM) for bumper covers and factory sill or ground effects.

Urethane body components are the most resistant to driveway impacts and curb scrapes. Unlike fiberglass components, which are usually gel-coated and ready to paint, urethane body components require mixtures of adhesive agents to be mixed into paint for it to properly adhere. Usually paint jobs done on polyurethane do not adhere as well as on fiberglass, so they are more prone to cracking and chipping. Because of the ease with which fiberglass can be molded and manipulated by hand (and the scale on which it can be done), it is the creative canvas for body effects on a limited production basis. For the time it takes to design and manufacture one kit by hand, several kits can be produced by spraying the fiberglass into the mold. These larger volume manufacturers than pass on their savings on to consumers.

PROs and CONs:
Urethane can be quite flexible in large areas, but in smaller areas, it can rip, snap, puncture or even fold. In those scenarios, the urethane bumper is nearly impossible to repair and is completely ruined. Because of its flexible characteristics, the paint must be added with a flex agent to lessen the chances of the paint to crack, peel and spiderweb. Again, because of its flexible characteristics, it will often sag and droop over time. Heat will accelerate this process, and possibly make it worse over time. The only major advantage of having a urethane kit is when the fitment or mold was bad, it can always be flexed and forced into fitting properly.

Handlayed fiberglass is also very flexible, but not as much as urethane. In heavy impacts, it can crack, but it can always be repaired. Unlike urethane, fiberglass body kits can be repaired no matter how bad the damage is. Since handlayed fiberglass is stiffer than urethane, it doesn’t need a flex agent to be added to the paint. The paint will stick very well and has a much less chance of peeling, crack and spiderweb. Another advantage of a fiberglass kit is that it can also be modified if anyone wants it to be changed. A vent can be added, or removed… holes or mounts for foglights can be added… license plate mounts can also be added or removed. Urethane kits can be forced into a good fitment; however fiberglass kits can not be forced into fitment to the extent that urethane can. Fiberglass kits have a slightly less room for adjustment.

Some will say, “I have a urethane kit, and I can run into a wall and my bumper will still be in once piece!” Although this is true, the paint will be ruined and it will need to be repainted. Painting urethane correctly will cost a little more. A fiberglass kit in the same scenario would need to be repaired and painted. In the end, repairing the fiberglass kit came out spending slightly more. But as I mentioned above, if the urethane bumper received any permanent damage, it would be completely ruined. There is no such thing as permanent damage for a fiberglass kit.

Research, research, and then research some more. Dont aways believe the rumors and hype.



Definition of FRP Composites


Not all plastics are composites. In fact, the majority of plastics today are pure plastic, like toys and soda bottles. When additional strength is needed, many types of plastics can be reinforced (usually with reinforcing fibers). This combination of plastic and reinforcement can produce some of the strongest materials for their weight that technology has ever developed...and the most versatile.

Therefore, the definition of a fiber-reinforced polymer (FRP) composite is:
A combination of

1. a polymer (plastic) matrix (either a thermoplastic or thermoset resin, such as polyester, isopolyester, vinyl ester, epoxy, phenolic)
   
2. a reinforcing agent such as glass, carbon, aramid or other reinforcing material
   
   
   such that there is a sufficient aspect ratio (length to thickness) to provide a discernable reinforcing function in one or more directions. FRP composite may also contain:
   
3. fillers
   
4. additives
   
5. core materials
   
   
   that modify and enhance the final product. The constituent elements in a composite retain their identities (they do not dissolve or merge completely into each other) while acting in concert to provide a host of benefits ideal for structural applications including:
   
6. High Strength and Stiffness Retention - composites can be designed to provide a wide range of mechanical properties including tensile, flexural, impact and compressive strengths. And, unlike traditional materials, composites can have their strengths oriented to meet specific design requirements of an application.
   
7. Light Weight/Parts Consolidation - FRP composites deliver more strength per unit of weight than most metals. In fact, FRP composites are generally 1/5th the weight of steel. The composite can also be shaped into one complex part, often times replacing assemblies of several parts and fasteners. The combination of these two benefits makes FRP composites a powerful material system- structures can be partially or completely pre-fabricated at the manufacturer's facility, delivered on-site and installed in hours.
   
8. Creep (Permanent Deflection Under Long Term Loading) - The addition of the reinforcement to the polymer matrix increases the creep resistance of the properly designed FRP part. Creep will not be a significant issue if the loads on the structure are kept below appropriate working stress levels.
   
9. Resistance to Environmental Factors - Composites display excellent resistance to the corrosive effects of:
   
   1. Freeze-thaw: because composites are not attacked by galvanic corrosion and have low water absorption, they resist the destructive expansion of freezing water.
      
   2. Weathering and Ultra-Violet Light: FRP composite structures designed for weather exposure are normally fabricated with a surface layer containing a pigmented gel coat or have an ultraviolet (UV) inhibitor included as an additive to the composite matrix. Both methods provide protection to the underlying material by screening out UV rays and minimizing water absorption along the fiber/resin interface.
      
   3. Chemicals and Temperature: Composites do not rust or corrode and can be formulated to provide long-term resistance to nearly every chemical and temperature environment. Of particular benefit, is composites ability to successfully withstand the normally destructive effects of de-icing salts and/or salt water spray of the ocean.
10. Fire Performance of Composites - FRP composites can burn under certain conditions. Composites can be designed to meet the most stringent fire regulations by the use of special resins and additives. Properly designed and formulated composites can offer fire performance approaching that of most metals.

http://www.automotiveforums.com/vbul...d.php?t=167865
http://www.mdacomposites.org/mda/frp_def.html

 

Urethane....i have a urethane lip thats wrapped with the clear bra...no chippin problems here.

Eventually all things will chip but I know if i hit something big my urethane lip isn't going to crack like a FG one would

 

Yup, I'd go with urethane. It can flex a little more and holds up better then fiberglass. Of course it costs more, but in thus case you get what you pay for.

 

When I used to race/power slide alot, I rear ended a car twice, and smashed into a curb. I still have the same front lip after 7 years of abuse. The car I'm talking about is a Civic with a Mugen front lip, lowered 2.25 inches. I never had to do any major bodywork to fix it either. If urethane is torn, punctured, or dented, its very hard, if not impossible to fix. Fiberlglass can always be repaired and modified. Anyone can just read online how to fiberglass and do it themselves.

Urethane is good... but a good handlayed fiberglass kit is unmatched imo. Look at all the high end body kit manufacturers that lean more on the racing side. They're mostly handlayed fiberglass.

IMO, Handlayed fiberglass is the best, then urethane, then choppered glass kits.

 

With intense and extreme driving, I think handlayed fiberglass holds up better than urethane. Urethane can flex... but sometimes flex too much for the paint job to hold on... causing alot of cracking and spiderwebbing. Handlayed is also flexible, but only to a certain extent. Because of its surface, and its more stable build, the paint will not be as prone to spiderwebbing/cracking.

As for "getting what you pay for". Thats not always the case. A price tag doesnt always parallel the worth or value. I saw "bottled fart" being sold on Ebay for $25

**EDIT**

Here is some new information I learend from G352NV about a product called One Choice by PPG.

 

I updated my orignal post with "PROs and CONs" about urethane, and good quality handlayed fiberglass.

 

good information. would you mind explaining how FRP is made?

 

To be honest, I dont know too much about FRP or PFRP. All I know is that FRP (fiberglass reinforced plastic) is a very hard and durable plastic that has tiny glass fibers embedded in the plastic.

Theres also PFRP which is poly fiber reinforced plastic, which is supposed to be more flexible that FRP. I really dont know much about this either.

 

**UPDATED**

Definition of FRP

 

Of course different material has different characteristics. But if OEM uses Urethane as their prime material when making parts such as front or rear bumpers over FRP or PFRP, then I think there has to be a reason why they pick URETHANE despite FRP is much cheaper. You pay for what you get, urethane has much better quality.

 

There are some very good points made here but I would like to mention a couple things that were omitted.

Urethane (or ABS or any plastic based) parts are made by casting or injection into a mold, so the quality and fitment is very uniform from piece to piece. Whereas the methods listed for fiberglass production tend to allow for a higher variance rate in piece to piece. The difference being, a misfitment on a fiberglass piece can sometimes be reshaped to the proper design by a shop skilled in fiberglass, while a urethane piece is much harder and must be forced to shape (as mentioned).

The advantage to urethane is that when a mold is designed that is considered to be "perfect", it is very cost effective for high volume processing. When the OE manufacturer produces 20,000 front bumpers a year, its very inexpensive for them on a per unit basis. When a small company has to front the costs of designing the mold and may only make several hundred pieces a year, they must charge much more per piece while trying to recoup development costs similar to the OE manufacturer and achieve profitability. Due to the cost and complexity of trying to create entire front ends and replacement bumpers in a mold, this is why most uerthane components tend to be smaller add-on trim such as rocker panels or lips. These are the least expensive pieces to design for urethane production. Being that they tend to be the pieces that are most commonly rammed into curbs, potholes or other road hazards, it makes sense to keep a highly flexible piece that can be removed and repainted if the paint cracks but the part is still in one piece. But because no aftermarket manufacturer will ever be able to produce a single body kit that appeals to thousands of customers, the odds of seeing aftermarket full replacement bumpers in urethane is low. So in low volume production (which all aftermarket parts are), fiberglass is more cost effective than urethane for development and resale.

 

helldorado, you have some very good points too. If you dont mind, I'll add your post to the top one. That way, no one will overlook your reply to the thread.

Also, welcome to G35Driver.com! Hope you enjoy your stay

**edit**
Nevermind, theres not enough room to fit your reply into the top post.

 

Trust me on this. go with fiberglass but have the whole back of the front bumper coated in carbon. it'll be a couple hundred but next generation in Cali can get it done. did it to my ken style... perfect. hit that thing you pull uo to a 7/11 so f*ckin hard i thought it shattered, barely even a mark in my paint. anything else on my word would have cracked including stock
sawdigga
check my pics in the coupe general forum

 

it really all comes down to you, urethane may be stronger but like mentioned before its really difficult to repair if you actually damage it, but if you are a pretty careful driver in general that go with the urethane, even small dips and driveways can make a difference compared to fiberglass since it can flex too well.

 

IMO, because fiberglass doesnt flex too much, its actually a good thing. It keeps its form so that the paint doesnt crack, spiderweb, or peal. My house has a steep driveway with a deep drain gutter thing, I've gone over countless speedbumps and dips for over 7 years, I've gotten into around 3 accidents... I still have the same fiberglass bodykit Also, in the long run, urethane tends to sag and start drooping. The only way to minimize this effect is to use alot of mounting points to hold it up.