Butyl size for windshield and back glass

by Joe73 Mon Jul 23, 2018 9:16 am

Id rather not get involved in the butyl vs. urethane pros and cons.

Its been quite a while since I set front and back glass in our cars. I've always used butyl but I dont recall the size. Was it 5/16" or 3/8" ?

I took some caliper measurements and I'm doing some math.

Pinch weld (channel) depth .830
Back Glass .220
Trim .280

So .220 + .280 = .500

.830 - .500 = .330

3/8" butyl = .375
5/16" butyl = .312

I'm thinking 3/8" is the size since its only .040" (1/32") thicker than what I need and you have to compress it to set it.

Anyone recall if its 5/16" or 3/8" for the front and back glass ?

Thanks

by thatfnthing Mon Jul 23, 2018 9:34 am

I used 3/8" front and back. However, the trim fits pretty tightly, so 5/16" may work as well. 0.063" is not a huge difference.

by Mcarlo77 Mon Jul 23, 2018 9:54 am

I'm about to tackle a rear window leak and did some research on this as well. The general consensus among those who have done this numerous times is to use 5/16" if reusing the original factory glass. Since replacement glass is said to be thinner, they recommended 3/8" for those.

by Joe73 Mon Jul 23, 2018 10:09 am

Mcarlo77 wrote:I'm about to tackle a rear window leak and did some research on this as well. The general consensus among those who have done this numerous times is to use 5/16" if reusing the original factory glass. Since replacement glass is said to be thinner, they recommended 3/8" for those.

I've read that as well. I'm reusing my original factory back glass. But with my math above, I'm thinking of going with 3/8". And thats what I kind of remember from back in the day when I did a bunch of these. I dont recall buying 5/16". The difference in thickness comes to be about 1/32" but thats before tapping it down to set it. It will be going down probably more than that. And with butyl, if its a pinch high in the future, you can heat the area and tap it down with the palm of your hand.

But starting with 5/16", with my measurements, I'm already starting .017 lower even before tapping to set it.

I think 3/8" is correct for our cars going from what I remember, comment by thatfnthing, and a couple replies I've received in the facebook groups.

by S3SS Mon Jul 23, 2018 9:14 pm

3/8 just did my original rear window last year...

by Joe73 Mon Jul 23, 2018 9:51 pm

Cool. Thanks for the replies. I just ordered some 3/8". $21.80 with free shipping on ebay. 3M brand.

by Mcarlo77 Mon Jul 23, 2018 10:50 pm

Okay, then...3/8" it is for me, too. Nothing speaks better than a couple of testimonials from fellow G3ers!

by pila Tue Jul 31, 2018 2:16 pm

I used the 3/8 " "rope" for my Elco, front (new WS) and for the rear original glass. Knowing how leaks develop when the seal gets un-stuck from the glass in later years, I used a sealant around the edges, covering the glass/seal/metal joint. Did this mostly because of the rear window leaks common in El Caminos. ( those that l leak, and those that will !)

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Butyl size for windshield and back glass

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