Tom Suddard
Tom Suddard GRM+ Memberand Director of Marketing & Digital Assets
8/25/20 9:20 a.m.

Some of the most iconic cars in history, from Fords to Ferraris, are particularly striking when viewed head-on. The nose of a car makes a powerful first impression: Whether good or bad, it becomes etched in your memory.

We have a 1987 BMW 325is in our fleet, and lately it hasn’t been making the best impression. These cars have a …

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Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
8/25/20 9:27 a.m.

What material was that spoiler made of exactly? I know this article is a decade old, but wouldn't the repair technique vary with the type of plastic?

Tom Suddard
Tom Suddard GRM+ Memberand Director of Marketing & Digital Assets
8/25/20 9:32 a.m.

I can't remember exactly what E30 spoilers are made of, but yes–it's important to match your materials to the plastic. Any body supply store will be able to give you the right stuff if you tell them what you're working on, though.

z31maniac MegaDork
8/25/20 10:29 a.m.

It's also different on the 88+ cars. There isn't that "air dam" hanging below the front bumper made of plastic. 

The later valances are metal then with an "i" or "is" spoiler attached to the metal valance below. The "is" spoiler being deeper with a raise middle profile section.

The really hip thing to do is get an '86-87, then use the later 88+ parts. You have to do some trimming on the rear bumper and bumper caps for fitment. But then you get the larger rear wheel wells of the earlier cars, with the much better looking plastic bumpers of the late cars. 

11/19/21 3:20 p.m.

Please don't use Bondo on flexible materials, it's virtually guaranteed to crack as soon as the surface flexs. There are an entire suite of flexible bodywork products you need to use when working on urethane bumpers. Bondo might do a little better on plastic, but it can still crack if the bumper is twisted enough.

Similarly, when working on bumpers, every product needs to be designed to flex, from the filler to the primer and even paint. You can easily buy flexible black paint for bumpers in a can, but any paint supply store can mix you any color you want with the required flexible additive included.

Sorry, I worked at a bumper repair shop for a number of years, and there is nothing worse then trying to repair a bumper that was previously fixed or painted with regular products meant for metal. You have to sand the whole thing down back to the urethane or it will just crack again.

05CAR New Reader
9/4/22 12:03 a.m.

In reply to Keith Tanner :indeed, and as I recall the products to fix for the na miata front bumper are completely different from the rear bumper, right?


kb58 SuperDork
9/4/22 11:54 a.m.

I read the thread title as "The repair that caused the bumper to crack."

friedgreencorrado UltimaDork
9/4/22 12:04 p.m.

I swear, if someone ever writes a book about restoring 'modern' automobiles, half of it will be about how to repair plastic.

Randy_Forbes New Reader
9/5/22 9:04 a.m.

Plus nowadays, we have more trick tools like the hot stapler* (I frickin' LOVE mine) and plastic welders that include a variety of filler materials.

If there was one (1) thing I'd change about the article, it would be to use the DX330 (wax & grease remover) more liberally; use it to clean the area BEFORE you ever touch sandpaper to the area being repaired.

* If you haven't discovered this tool yet, and there's ANY plastic on your car, you owe it to yourself to check it out (prices can range from <$100 to >$300, so shop around for what suits your needs).

The brand/model  I have has since been superseded with a cordless version (@ 2X the price) but the money saved on this one (1) taillight assembly repair would've paid for tool (working only on BMW M Coupes/Rdstrs, it's undoubtedly saved my customers thousands of dollars by repairing plastic parts versus replacing__hell, in just glovebox mounting tab repairs__let alone underbody ducting & panels).

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