soupcan

This thread needs boobies! Big bouncing watermelon sized boobies!

Jerry Feather

We already did boobies. I think all that is left if feet. I suppose we could do faces or even hairdos, but there might be something erotic about feet.

Neil Forn

I just went through the process of painting my front bumper. It took 3 tries to get it right. My mistake was trying to get it too perfect. I used an extremely thin layer of bondo and high build primer to eliminate the waves in the bumper. All told maybe a 1/32 of an inch in a few places. I used flex additive in the paint/primer. It looked great for a few months. Then two cracks appeared and the paint began to peel up along them. I thought it was a surface prep problem. So I sanded out the cracks and filled them in again this time using an adhesion promoter. Again it cracked! I just could not take this anymore and I swapped the bumper cover from another car. I did not do any filling on the new cover. I just sanded and primed the factory paint that was already there. I was careful not to sand through to the plastic. So far, it is looking great. Although, the cover has slight waves in the plastic. It is not really noticeable almost all of the cars are slight wavy.

Also, the flex additive is unnecessary for our cars because we don't need to bend the bumpers much to install them. Read the fine print on the bottle. It only delays the hardening of the paint so the bumpers can be installed without cracking. It is a common belief that the flex agent provides long term flexibility. This was pointed put to me by a real pro that helped me with my bumper cover.

There are epoxy fillers that bond to plastic that might work. And adhesion promoters that help bonding to plastic if you need to fair the surface. I must admit that when the bumper is perfect the car looks really sharp.

Pcplod

ABSOLUTELY!!

tveltman

Yeah, I just sanded mine until there was no flaking, and I shot paint right over it. It's been more than a year and no sign of failure of the coating. Mine was also newly purchased though, so YMMV

slate blue

Neil, a couple of things, never use a stiffer material on top the base material, there is special bumper bar filler which I did use as straight from the factory the early bars particulary have kinks etc. The filler is difficult to sand and most won't be able to do it properly, it does take a fair bit of experience or good advice.

The flex add never actually hardens, these bars are very flexible, Glasurit, the factory paint and one of the best paints in the world recommends differing amounts of flex add or "softface" for differing stiffness bars. Or at least they did when I did my jobs. Now before I bothered to do all jobs myself on my cars. The pro painter screwed up the job by not using the flex add in the primer! This earned him some rebuking by me and his boss as the job ended up free and a pain in the **** for yours truly.

The flex add is not just to put the bars on, my wife happened run my Porsche into another one of my cars, the bar was literally damaged, needed the heat gun on it to straighten it but the paint never cracked and 5 years on is still fine!

Mike take who's advice you believe, I will garantee you I am correct on this issue, been there done that. I can find the name of the plastic bar filler if you are going to get fussy with it.

Cheers Greg

By Neil Forn

James Bailey

Yes the new bumper covers are primed....I have seen many

JHowell37

Wrong.

Wrong again. It does delay the hardening slightly, but this is a by-product. It alters the chemical reaction to produce a new compound with different properties than the compound formed as a result of the reaction between the clear and hardener. Flex additive does not flash off in a few days.

Sadly, I wish more people believed it. Then I wouldn't have to debate this issue repeatedly. When I mixed the primer for my bumpers, I used the maximum amount of flex additive Glasurit recommended. I had some left over. Since I had heard your argument before, I decided to do an experiment. I left the few ounces of primer sitting in the mixing cup and then I placed the cup on the shelf and out of the way. This was in July, a time when chemicals that could flash off if left in open containers would do so rapidly. I came back a few days later. I shook the primer out of the cup and it was a rubbery block that I could fold in half without breaking it. I put it back in the cup and on the shelf. When I threw it out the following spring, I could still bend it in half without it breaking.

Post corrected.

Almost every filler on the market is polyester, not epoxy.

Adhesion promoters rely on mechanical bonding. It is an incredibly strong mechanical bond however.

The reason you had problems with the filler is probably because you used the wrong type, and you didn't apply adhesion promoter prior to using the filler. Evercoat makes a product called "Poly-flex" which is a filler for flexible materials. But I don't know if it's even flexible enough for 928 bumpers. Bumper covers turn up on e-bay all the time, especially rears. I wouldn't waste my time with one that was bad enough to require filler.

If the Glasurit technical manual says I need to use flex additive, and this tech manual was written for a product that was developed in a multi-million dollar facility, by a person with a master's in chemical engineering, who would I be better taking advice from? The engineer, or the high school drop out whose primary concerns are getting to happy hour on time and squeezing a few extra pennies of profit?

JHowell37

As far as it never hardening, I addressed that earlier. As of '07 Glasurit still recommended varying amounts of flex additive depending on the surface. I used the maximum amount allowed for both the primer and clear. I followed their plastics refinishing process exactly as specified and experienced no problems at all.

Prior to this argument, people just said it wasn't needed at all. A lot of people seem to be very opposed to the concept of flex additive. I'm not sure if it's ignorance, laziness, or simply being cheap. I've backed my car into a few things, it's been hit by a shopping cart or two, and I've driven it 50K miles in 3 years. There's not a single chip on the bumpers.

I painted my own and used Glasurit. Everything you've said is spot on. The only thing I'll add is that virtually all of the paint companies have specific processes for painting plastics that are unique to their product lines. If you don't stick to their procedure exactly as it is outlined, it will cause problems down the road.

Landseer

^^^Saw this car again last week. Looks fantastic.

Mike Simard

The grey just seems so "American". I would have expected some weird primer color from Porsche.
Jim, you yourself could have sold this! I feel it should remain in the original box for posterity, like a cabbage page doll but I have an 'idea' for it!

CatoBT

Maybe a strange question, but...

Is there a DYI thread about painting plastic parts?

As you see here, my bumper looks BAD... After somebody tried to do the paint job "at home"


Please keep in mind: Painting a car in Norway (or Scandinavia) is VERY expensive :-(

Mike Simard

I was told by my paint supplier that the flex additives sacrificed the paint somewhat and didn't use it on my racer. I now know that bumping into something will have the paint flying off in shards like ice.

Greg, what bar filler did you use? It sounds like an epoxy, no?

Thanks everyone for the advice!

Benton

I'm sure someone will try to argue with me on this, but you don't need a flex additive as long as you use the correct primer and scuff the bumper well enough. Southern Polyurethanes has a fabulous Epoxy Primer that works perfectly on our bumpers and is flexible enough to prevent paint from chipping.

On my race car, I DA'ed the front bumper bare with 60 grit and sprayed with epoxy primer. I even put filler on top of the epoxy primer to fill the headlight washer holes after they were plastic-welded shut. Guess what? Two years and 10 or so track events later (with several hits on the bumper during that period and a splitter partially mounted to the bumper cover), there are no cracks.

JHowell37

So I guess that Glasurit (owned by multi-billion dollar BASF,) multi-billion dollar DuPont, multi-billion dollar PPG, and multi-billion dollar Akzo Nobel (Lesonal is actually mentioned in the service manual) are all instructing the users of their products to utilize improper procedures and materials? How many auto manufacturers is SPI a supplier for? I'm not saying SPI is incorrect. I'm sure their procedure is spot on for their products. But it's a very bold statement to suggest that any company that calls for the stuff is somehow incorrect.

Date stamped pics please.