Detailed differences between aftermarket and Porsche windshield seals

[universeman]

All,

In one of the windshield threads I talked about doing a detailed overview of the differences between Genuine Porsche and aftermarket (URO) windshield seals. I now have both here in my garage, so I looked at them closely, took a bunch of pictures, and am posting my findings here for reference later, for those looking to decide which seal to buy.

Commonly read here on Pelican forums is the fact that the Porsche seals have the corners molded into them and the aftermarkets do not. This is said to cause "bunching" at the corners on the aftermarket seals. I have to say that I did not see this in the seals I have. Neither seal appears to have corners molded in. To the contrary, the old seal from my car that I removed (which I think is original Porsche, or at least a P replacement) does have those corners clearly visible. That could be that the windshield's weight and shape formed corners in the seal after decades (?) of being on the car. It is possible that the aftermarket seals will "bunch" instead of forming corners over time; I can't comment on that because I'm not going to install the URO seal.

What I can say about the URO seal compared to the P seal is the following:

1. it weighs about the same as the P seal
2. it is roughly the same overall size in profile (though slightly different shape), and exactly the same length
3. the seam connecting the two extruded ends is very different and much rougher, and contains a metal insert
4. the trim slot is much wider and rougher
5. the rubber itself feels less 'silky' and more stiff
6. surprisingly, the profile (cross-section) is different, in what appears to be meaningful ways

Below are some pictures of the seals laying on my table, along with a diagram I made to try and show the differences in the profile. Hopefully this is helpful to those of you considering which seal to buy. Based on holding both in my hands and doing this analysis, I can tell you that the Porsche seal is much higher-quality and designed and manufactured in a more-refined way, based on the way the seals look and feel in your hand. Probably 15-20% (if that type of thing can be quantified) more quality in the Porsche seal.

Whether that translates to less water leakage is another matter entirely, and I will try and update this post later once I have had some experience with that.

Regarding the cross section -- I don't know what the purpose of the closed lip is on the P seal, but it appears to be molded so as to grip tightly against the gap it's covering, probably for water-tightness. The URO seal simply does not have this lip, and I have no idea what that means -- but I bet someone here does. Also, with one fewer retaining ridge (3 instead of 4) it's possible the URO seal moves more in its channel than the P seal does. Again, hard to know for sure, but the engineering appeal of extra rubber molding to hold the windshield where it's supposed to be, is clear.

While I have these seals out and can do the comparison, let me know if there's anything you'd like to see!

[wayner]

Fantastic!
Thanks for documenting that!

[DerkPerk]

Crystal clear. Thanks for the info!

[KTL]

Very well done job explaining your observed differences in the seals. Thanks very much for sharing!

What's also noteworthy is that original Porsche or OEM vs. URO is where the differences lie. I have an "OEM" brand seal I recently bought from Pelican, which has the details like the genuine seal you describe, and therefore I think the OEM seal is basically identical to the old seal I recently took out of my friend's '86. The old seal I have is at least 16 yrs old, as it has been in the car since 1999 when my friend first acquired the car.

[78-911SC]

Jason great job. What was the cost difference and what made you go with the Porsche seal. Any difference in the density?

[universeman]

Thanks everyone for the feedback!

The seal in my car right now is the "OEM" branded seal (i.e., the "middle" quality), once I have it out I'll compare it to the other two.

The cost difference between URO and Porsche is big: ~$35 for URO, ~$60 for OEM, ~$135 for genuine Porsche. Yikes! But what I decided was an extra $100 was nothing, if it keeps my interior dry in the rain for 10 years or more.

PJ: Density-wise I think they're about equal, since they weigh about the same and are the same size. However, the rubber that the P seal is made from is far more supple, noticeably so, than the stiff URO seal. Again, not sure if that matters.

[Uwon]

Many thanks for the write up Jason. Very apt for me as I'm soon going to be installing all the glass into my project.
Cheers,
Johan

[javadog]

Excellent post. Thanks for taking the time to document this.

I tend to use original Porsche parts when I can, as you just can't know ahead of time if an aftermarket part will be different in some significant way. It's not worth the risk, to me.

JR

[wachuko]

Excellent post. Thank you for taking the time to share it.

[universeman]

Was just thinking about the lip on the interior of the P seal.

If rainwater were to conduct through the frame by gravity and capillary action, it would most likely be caught by that lip and perhaps even get 'sucked' into the gap. The same would probably happen with the URO seal, however the URO seal does not have a lip to keep water that gets into the top and sides in, and it would likely drip into the car. Whereas once water gets behind the flap in the P seal, it would run to the bottom edge, stay contained by the lip, and probably evaporate over time rather than leaking in the car or sitting on the metal frame. Obviously there is a limit to how much water can be held this way.

I'm theorizing here, about the reason this lip was molded into the seal (there has to be a reason, as it adds cost/complexity to the manufacture to have it there. Since it's inside the car, I can only think it has to do with stopping water from entering that has passed the main part of the seal.

[redstack]

Thanks for your efforts, and thanks for the search function. I'm just going to buy one tonight, and I guess i'll spend the extra $100.