Race Prep Backsliding -- Re-installing a rear windshield

[Jack Olsen]

I'll start with the bad news. Switching from Lexan to OEM glass for my rear window means 12 full pounds of additional weight, up high and in the rear half of the car -- which, from a race car's point of view, is terrible.



But my car is dual use, and I'm sick of the Lexan. I'm on my second piece already, and I the visibility is bad enough that I'm fully due for a third. In spite of carefully avoiding anything that can scratch it, the stuff just gets microscratched to death and becomes something that you can't freakin' see through.

This isn't a problem on the track, since no one, ever, overtakes me. But on the drive up to the track, it would be nice to be able to change lanes without a quick prayer.

Here's a shot of how bad it had gotten. Plastic polish no longer made things better. You can see my art-supply-store substitute for chrome trim. It has seen better days.



The old Lexan was held in place with little plastic screws. They popped out with a little pressure, leaving the fiberglass frame. (Anyone want to buy a fiberglass frame?)



The frame came out with four screws. But this left me with a problem. It'd been about eight years since I'd actually had the glass windshield in the car, and I had no memory of how it was supposed to look when it was in place.



I decided I'd figure that out when I got to it. In the meantime, I put the new seal on the glass and started inserting the trim. I went slowly with this, but didn't know the trick about using soapy water or a thin-gauge wire yet. I just pulled and fitted the rubber where it had to nest around the hook of the trim. It took some time, but it worked.



Here's the first half finished. It made things slightly easier that I had already decided not to attach the defrost. The metal on the glass had breaks in it, and the wiring harness was long gone.



But when the trim was all in, I was back at that -- 'how the heck is this thing supposed to fit in there?' point. Clearly, the trim was going to be down below the roofline in front. But it looked like the trim should be resting on the body down below that point.

I did a search on Pelican, and it kind of opened a can of worms. Some people said the rope should start at the top, some swore by the bottom. Some said it should do two complete loops inside the gasket. Pretty much everybody said it was a two-person job, unless you could press down from outside the car at the same time as you were crouching inside it, pulling out the string.

It was just me and my two toddlers here today. So the two-guy option was out. And enough people said it was something better left to a professional that I finally made a decision. I have a track day in less than a week. If I crack my piece of glass or put too much of a bend in my trim insert, I'm screwed. So I called my local glass installer and made an appointment for Monday.

[Jack Olsen]

But it kind of bugged me to give up like that. So I decided I'd give it one try.

I soaked some 3/16 rope in soapy water and decided to start at the top. Since I didn't have someone to keep the glass from slipping down (which would pull the gasket off the edge it needs to grip), I came up with the idea of a 50-lb bag of sand for downard force, and a soft paint-stirring stick down at the bottom wedged to keep pushing the window up.



This is the part where I knew I could either crack the glass or bend the trim. But I got it centered and the rope came out in one long, easy pull. It probably helped that I had new trim and gasket pieces. But let me tell you, it was pretty easy.



Nothing will change the fact that I've added weight in the worst-possible place on the car. And someone will probably tell me that there are some earlier (pre-defrost) and later (964? 993?) pieces that are lighter. But I didn't have time to order those -- and now I can see out the thing -- which is nice.

One final piece of the job was to re-attach the third brake light. I screwed it right into the sheet metal lip that the window gasket hooks into. Hiding the wire under the underside of the gasket was probably the hardest part of the whole job, since I was working around the cage, and it was getting hot in the garage.

But it's done.

There isn't a whole lot of new technical content in the post, but I figured it was worth it to get some pictures and let other guys know that it's possible to do as a one-man job.

[James Brown]

would finding thinner glass help? or is that too uber expensive.

[Geneman]

nice jack ...the chrome trim is really ghetto... you will miss that!!

can you sell me the frame? i am going to lexan and it would really help email me rauscher@wistar.org

thanks! frank

[Jeff Alton]

Jack,

Not sure where you sourced your Lexan from, but the Margaurd is extremely resistant to scratching. It is not inexpensive, but we have had very good success with it.

Cheers

[304065]

Jack,

Good decision, and good job working with the modern reproduction POS trim that is available these days. You made the best of a tough situation with that part.

Next time you are having a coffee in the company of someone with an original rear window trim, look VERY closely at the corners. The corners of the original trim are rolled into the apex so the trim seals correctly.

The modern extrusion does not roll into the apex like that- it stays flat, which causes the window to not fit properly in the corners.

You can correct this by taking a rubber pad or something that won't mar the anodized finish and a hammer, and tap, tap, tapping on the inside of the corners to "roll" the metal so the locking barb on the extrusion locks into the windshield gasket.

Don't even get me started on the finish on the modern trim-- comparing it to the old stuff it looks like it was polished with 80 grit.

Call me a perfectionist (go ahead!) but I am on the lookout for some unscratched original trim that I will send to Marcos for re-anodize.

We spent probably 10 hours total and seven or eight round trips of the rear glass, plus TWO different brand-new in the Porsche bag $140 factory (not OEM) seals before we figured this out.

The fact that you have achieved what appears to be a very nice result is a testament to your patience and craftsmanship. Well done Jack.

[Hnichols]

Wow -- when you said you were going to try it w/o a helper I was expecting an unhappy ending. ...
I just did this job: it took three installations, multiple attempts, getting the positioning just right. By far the easiest part was installing the brake light (which I did 3x).
I'm envious!

[Jack Olsen]

Originally Posted by James Brown

would finding thinner glass help? or is that too uber expensive.

It's expensive. I'll keep an eye out for it, from this point on. But it'll have to be a (relative) bargain. I'm thrifty.

Originally Posted by Geneman

nice jack ...the chrome trim is really ghetto... you will miss that!!

can you sell me the frame? i am going to lexan and it would really help email me.

I will miss the ghetto tape. I love that stuff. In fact, you can see the track-day-only wing in these pictures. I made it last week, and it's EPS foam (the stuff beer coolers are made out of) covered in leftover tape that I'd previously used to wrap the padding on my roll cage.





Ghetto? Yep.

I'll email you on the frame.

Originally Posted by Jeff Alton

Not sure where you sourced your Lexan from, but the Margaurd is extremely resistant to scratching. It is not inexpensive, but we have had very good success with it.

I put the original piece on in 2004. I think it got replaced after an incident...



...at Sears Point in 2005. So if I'm right about that, this piece has been in there for 8 years. I don't know if scratched is even the right way to describe the damage. It just slowly got cloudy over time.

Originally Posted by 304065

Good decision, and good job working with the modern reproduction POS trim that is available these days. You made the best of a tough situation with that part.

Next time you are having a coffee in the company of someone with an original rear window trim, look VERY closely at the corners. The corners of the original trim are rolled into the apex so the trim seals correctly.

The modern extrusion does not roll into the apex like that- it stays flat, which causes the window to not fit properly in the corners.

You can correct this by taking a rubber pad or something that won't mar the anodized finish and a hammer, and tap, tap, tapping on the inside of the corners to "roll" the metal so the locking barb on the extrusion locks into the windshield gasket.

Don't even get me started on the finish on the modern trim-- comparing it to the old stuff it looks like it was polished with 80 grit.

Call me a perfectionist (go ahead!) but I am on the lookout for some unscratched original trim that I will send to Marcos for re-anodize.

We spent probably 10 hours total and seven or eight round trips of the rear glass, plus TWO different brand-new in the Porsche bag $140 factory (not OEM) seals before we figured this out.

The fact that you have achieved what appears to be a very nice result is a testament to your patience and craftsmanship. Well done Jack.

Well, as the chrome-tape will indicate -- 'craftsman' might not be the best word for me. But thanks for the compliment. I know that Wayne at Pelican spent a long time working to source the best of the currently-made trim pieces. And you're right, it's still not as good as the original stuff. But for this car, it's a home run.

Originally Posted by Hnichols

Wow -- when you said you were going to try it w/o a helper I was expecting an unhappy ending. ...
I just did this job: it took three installations, multiple attempts, getting the positioning just right. By far the easiest part was installing the brake light (which I did 3x).
I'm envious!

I was lucky -- the kid who picks up a basketball on the side of the court and makes his very first shot. I think if I had to do this same job ten times, I'd have three pieces of cracked glass and five sets of bent trim. But once I got it centered and pressed down, it popped in pretty precisely.

[wayner]

Originally Posted by Jack Olsen

.

Jack, don't do that...

BTW,
Nice job on the rear glass. For my next attempt I hired a pro.
That was a stupid idea, now that he is done I have to order new trim and seal (again).

So much for the pro. I'm bookmarking this thread and for father's day I'm asking for a sand bag...

[Jack Olsen]

An old dog's bed is also an essential tool.

[wayner]

Originally Posted by Jack Olsen

An old dog's bed is also an essential tool.

Thanks for the advice about the dog's bed Jack, you saved me from another mistake that I was just about to make. I'm going to start over and ask my neighbour if he has a dog instead...

[Mahler9th]

One trick for those wishing to have a lighter plastic rear window is to use Vivak (or similar PETG) plastic instead of Lexan (or similar polycarbonate). The PETG is close enough to polycarbonate in terms of impact resistance and closer to acrylic when it comes to scratching. I got this tip from the company that used to make shaped rear windows for 911s with ABS frames (it was a "drop in" solution).

I have a polycarbonate rear window and a PETG rear window. The latter is much more clear (nearly crystal) and resists scratching. It polishes better than polycarbonate as well.

[mjshira]

Didn't the rear lexan fly out on the freeway once? Can't remember if that was BB2 or scrappy.

[Jack Olsen]

Originally Posted by Mahler9th

I have a polycarbonate rear window and a PETG rear window. The latter is much more clear (nearly crystal) and resists scratching. It polishes better than polycarbonate as well.

Do you have a source?

Originally Posted by wayner

I've got to say -- what a great-looking 911! (And my cat says he prefers your approach.)

Originally Posted by mjshira

Didn't the rear lexan fly out on the freeway once? Can't remember if that was BB2 or scrappy.

Not BB2. I've lost a couple of windshields, but the back one always stayed in place. So far.

[Rodsrsr]

I switched from Lexan to glass last year and haven't looked back. Lexan is simply a poor material for a car that sees any type of street use. The windshield is available two versions, an original German or an aftermarket one that is made in China. I went with the China piece which was 50% less weight compared to the German one... Low budget RS glass. I dont know if its available for the rear glass but its likely.

[Mahler9th]

You can buy PETG/Vivak sheet from lots of places. I bought some from Interstate Plastics. Again, it is more like acrylic in terms of scratch resistance, and more like polycarbonate in terms of impact resistance. Relatively inexpensive and easy to shape with heat, or let it shape itself. You can buy several pieces for what some of the vendors charge for fancy polycarbonate rear windows.

It is also easy to cut and shape... similar to the other plastics.

[Danish Dynamite]

Hey Jack

This Dutch guy has a lot of nice stuff. Including polycarbonate windows: Lightweight Windows

/Christian

[PcarPhil]

Originally Posted by Jack Olsen

I soaked some 3/16 rope in soapy water and decided to start at the top. Since I didn't have someone to keep the glass from slipping down (which would pull the gasket off the edge it needs to grip), I came up with the idea of a 50-lb bag of sand for downard force, and a soft paint-stirring stick down at the bottom wedged to keep pushing the window up.



This is the part where I knew I could either crack the glass or bend the trim. But I got it centered and the rope came out in one long, easy pull. It probably helped that I had new trim and gasket pieces. But let me tell you, it was pretty easy.

Jack,

I want to thank you for sharing this post. I needed to change the rear window trim of my '87 turbo due to a poor previous window installation attempt. Of course this means I needed to remove and reinstall the window. Not fun!

I've done a few of these in the past with the 2-3 person team approach however I liked the idea of constant pressure from 50 lb bag pushing down on the glass along with me taking care of everything else. It seems very controllable --- as long as the glass doesn't break from the bag!

In my case I ended up using a 40 lb bag of wood pellets as I have these readily available. The weight seemed to be enough and I didn't feel like the glass was going to break. I started at the top and when I was halfway done I moved the bag down towards the bottom of the glass. I only roped the gasket once and working slowly everything fell into place the first time with no major issues. I'm sure the new genuine Porsche trim and gasket helped.

Thanks again for sharing this info. Here's a pic when I'm just about done (I just need to tap down the corners of the trim at this point).

[ganun]

Had it done on my car, an 87, now with metal trim; ....wood shim as used in construction with the corners rounded as needed then tap tap tap the corners until flat like the factory, it worked.

My tip, since your Lexan is toast you can try this, we did it to clean off scratches on many polycarbonate ( trade name Dupont Lexan, IIRC) pieces, ...with a propane torch go over it lightly not to burn or bubble it but to reflow the surface so it cryslal clear, no abrasives needed.

[Kobalt]

Old thread, sorry.

Just want to send my thanks to Jack and other contributors that helped me repair the defroster and also installing it.

Roping it in was actually surprisingly easy compared to the windshield. (1970 body)

Well - I have not tested it for leaks yet so I can’t really claim success yet.


18 kg sack in my case.