Urethane Vs. Fiberglass

d98gt

Founding Member
Mar 14, 2002
4,505
59
204
SE Texas
I'm currently looking at replacing some body parts since my front bumper has paint fading off and the rear bumper is beginning to get spiderweb-like cracks in it. I'm also looking into getting a hood while at it. Rather than repainting the stock parts, I figured i'd "upgrade" and change it up a bit.

Now what i'd like to know: What are the pros/cons of using fiberglass? Is fiberglass a bad idea for front/rear bumpers?

I'm checking out www.mrbodykit.com and found a few items that I am interested in, however the fiberglass vs urethane got me thinking about it. :shrug:

As for the hood, I was thinking about the s281 style hood that MBK offers
94monsters281_2.jpg
94monsters281.jpg


I'm also wanting the s-series of the front bumper
94-98-Mustang-side.jpg





Opinions? Suggestions? Advice?:shrug: :nice:
 
flexing at high speeds?

for one the stock bumpers are urethane and if its cracking when you go too fast its because the hardening agent sucks

the idea of urethane is if it does bend it flex's back if you accidently jack it up... fiberglass wont flex and hence will crack where as urethane wouldnt if it were bent slightly over a bump.

Go with urethane for front and rear bumper and fiberglass for hood.
 
well the fiberglass hood is a given, though would it really be all that bad to run FG bumpers? I understand that it'll crack rather than flex, but the car is 8+ years old and I haven't had an accident that forced the bumper to flex/bend out of shape as of yet :shrug:

Also, I believe the urethane is easier for a bodyshop to work with compared to fiberglass or am I wrong?

Thanks for the info guys :nice:
 
urethane ONLY for bumpers! go take a look at all the fox bodies with fiberglass front bumpers, they're all beat up and missing chunks. One snag or flex with fiberglass and it shreds, but urethane can twist and bend a whole lot before the paint will crack.
 
Well the GT mustangs had a problem with the fiberglass but they've been around nearly 20 years :shrug: I guess im just wanting to save some money :(

Anyone have experiences with mrbodykit? The prices seem to be good, plus the shipping also isn't all that bad.

Thanks guys :nice:
 
Just one word of advice, if your paint on the rest of the car isn't new, the new panels are going to stick out at night. I really started noticing this a few weeks ago when we were hanging out in a parking lot after doing some digs out in the country. The panel that got repaired/repainted after a hit and run earlier this year sticks out like a sore thumb on the car. It's VERY black, and the rest of the panels around it are a lighter black, faded by the last 10 years in the sun.
 
DO NOT GET FIBERGLASS it fits like garbage it takes all kinds of prep work to get it smooth and if you hit the slightest thing you will either need the whole bumper painted or a new bumper.

Urethane is designed to flex and will be fine under driving conditions.

i had a fiberglass kit on my probe gt and I hit the sidewalk that went through a parking lot that wasnt paved and totally destroyed it.:notnice:

get urethane.
 
Yeah I'd hate to be kicking myself a few months later for not paying the extra $100.

As for faded paint, I realize this will be a problem which worries me. I doubt I could afford an entire paint job so it really isn't an option.
 
You might want to see how much they'd charge just to re-clearcoat the whole car. That'd probably shine it up decent and for considerably less than a full repaint you'd think....although what do I know? nothing!
 
JaredO99x said:
IMO I would stick with fiberglass.

Ive had a bad experience with urethane wanting to flex too much at higher speeds and could possibly cause paint cracking... its up to you

Fiberglass body kits is for ricers. Urethane is the way to go. Fiberglass is fine for the hood tho
Urethan gives, and flex - important when you ever hit something like dead raccon or something(don't laugh. happened to me once). Fiberglass WILL NOT flex, there for if you hit anything, it'll crack. Plus because it does not want to flex, fit with fiberglass is usualy horrible. Nothing the competent bodyshop can't fix. But thats extra time and money out of ur pocket(if you can find competent shop at all these days)

OEM use urethan for a reason. Now i've heard story about Saleen front bumper crack paint because it flex too much under wind pressure.
That means whoever painted it, did not use sufficient amount of flex additive in paint(if at all).

My urathen bumper have ZERO issue whats so ever
 
FWIW, the body shop that painted and installed my Saleen urethane body kit said he'd never do one again. The unprepped urethane took HOURS to finish and he had a heck of a time getting bonding agents to stick. This is a guy with decades of experience. He showed me OEM urethane bumpers and they weren't a problem.

Fiberglass is a lot easier to prep and bond, but repair is much more difficult. Regardless, when someone rear ends you, the paint is gonna flake off the urethane bumper and you're still in for a huge repair bill.

As for the urethane flexing and the paint flaking off - I regularly take the car over 100 and never got so much as a crack (until the aforementioned moron that rear ended me).
 
GulfCoastMustang said:
FWIW, the body shop that painted and installed my Saleen urethane body kit said he'd never do one again. The unprepped urethane took HOURS to finish and he had a heck of a time getting bonding agents to stick. This is a guy with decades of experience. He showed me OEM urethane bumpers and they weren't a problem.

Fiberglass is a lot easier to prep and bond, but repair is much more difficult. Regardless, when someone rear ends you, the paint is gonna flake off the urethane bumper and you're still in for a huge repair bill.

As for the urethane flexing and the paint flaking off - I regularly take the car over 100 and never got so much as a crack (until the aforementioned moron that rear ended me).

You see, this is an issue mainly related to Saleen stuff. Ask around and they'll all tell you that saleen stuff comes to u as pretty much garbage. Quality of urathen itself is okay, but thats pertty much it.

Both my Saleen wing and side gill were nightmare. paint keep lifting, and pin hole kept popping up.

My Roush stuff on the other hand, was excellent. Bodyshop quoted me $400 to paint all, but charged me $200 in the end, because it was so easy to paint. required almost ZERO prep to get it ready for paint