Plastic rear window on a streetable 911

[WP0ZZZ]

I've been looking at plexiglas/lexan rear windows and the prospect of losing 5 kg at the back of the car and so high is very appealing.

I'm wondering if any of you have one of these on a road-going 911 and if you have problems with fogging when it's cold and humid.

[Hi_Fi_Guy]

I ran a polycarbonate windshield on an old “street legal” vintage racer. No issues as long as you only use Lexan to clean. Order the piece in the same thickness as the glass you are replacing to ensure a good fit with existing seals. If it is thinner, or designed for racing vs street use you may need to add additional hardware to secure it. If you have a rear wiper either remove the wiper arm or remember not to use it. Any tiny debris trapped or dragged by the wiper blade will scratch the polycarbonate rear screen.

[Jjm4life]

Had one on my 964. No issues at all

[WP0ZZZ]

Nice to know. Thanks!

I guess that since a plastic window has a lower thermal conductivity it's less prone to fogging.

[KRLocke]

I've seen cars with plastic rear windows also have 2 aluminum bars running down them. Are those only for the track?

[WP0ZZZ]

Originally Posted by KRLocke

I've seen cars with plastic rear windows also have 2 aluminum bars running down them. Are those only for the track?

I think that's only for very thin track-only windows.

[Noah930]

If you’re still in Hawaii, this won’t be a problem. But if you live where there’s frost and you happen to park outside, you can’t scrape frost off lexan. As we realized on a friend’s (normally garaged) car on a rally one spring.

[Mahler9th]

Years ago there was a company that made a really nice ABS frame and plastic window for flush mounted 911 application... no longer in business.

He used Vivak (PETG) instead of Lexan/polycarbonate-- easier to keep clear but with better impact resistance than cast acrylic.

I made my own frame (ABS) and window (PETG).

I used 1/8 thick material, but of course could have used 3/16 instead-- not much weight difference.

I did some mild heat forming on mine.

My 911 has primarily been a race car, but it is also street "legal."

I have never had an issue with rear window fogging, even on colder race mornings.

You should remember I live in Northern California.

When I bought my car, the rear window was plastic (I think polycarbonate), and it was installed in a 911 rubber gasket instead of glass.

The car is a '75 and I cannot remember which type of gasket was used (that is from which 911 model).

I decided later that I wanted a project which is why I made my frame and flush mounted window.

[Mahler9th]

Here is a picture of the rear window of my '75 with its simple 1/8 inch thick plastic in place of glass:




Not sure which rubber gasket was used, but it was a stock part (perhaps 993?).

The plastic window was very likely from Five Star in Wisconsin. I don't remember whether it was slightly formed, but it was 1/8 inch thick.

So in this case the weight savings over stock was modest.

The ABS flush-mount frame I made is lighter than the rubber gasket by just a tiny bit, and the PETG window I made was ever so slightly heat formed.

[gled49]

Raced for 20 yrs with polycarbonate rear window with straps.
Later, converted to the street with the same rear window, now without straps, no issues.

[Jjm4life]

no issue for years on my old 964. might swap one in on my '83 eventualy. i was alwasy warned to be careful when washing the car but it was never a problem. no weird visabilities issues with poly v glass either imy experience

[chapo]

My polarized sunglasses make my poly window a kaleidoscope