Learn me: Mounting Lexan windows

I'm getting more serious about weight loss on my 190E Cosworth vintage racecar. Found a supplier of pre-cut Makrolon polycarbonate rear and door windows. The fronts even have those little sliding windows. Looks pretty good for the money.

What's the best way to mount these? All four doors on the 190E have fully supported window frames, like an E30 or early Golf.

I suppose the rears are just drilled and riveted in place with some sort of seam sealer underneath for weatherproofing. But I'll have to pop the fronts out while on track. How do I approach this?

any thoughts?

On our stock cars we mounted the windshields and quarter windows by putting adhesive foam weatherstripping down, setting the windows on top and mounting them with small countersunk Allen bolts and nyloc nuts. For the front windows could you mount them in the existing tracks and use a piece of nylon strap to raise and lower? 
 

Pretty slick! Is there a cleat that hold the strap when the window is up or what keep the window up.

In reply to pirate :

I'm not sure what holds up the one in the picture, I've seen them with small buckles that latch on the door panels to hold them in place .

Whatever you do, try to let the window "float" a bit.  Make sure the holes through the lexan are slightly bigger than the fasteners to allow it to expand.

Also, paint like a 1/2 inch strip around the inside edge of a non moveable window so it looks stock and you can't see the sheetmetal around the edges that it is mounted to.

Makes it much classier.

Check with the supplier of the windows.  From what I recall working for Bayer, Makrolon's inventor, an eon ago rivets were discouraged.  

You can use screws, but put some little rubber grommets in the Lexan so there's no screw-on-plastic action, or you'll get spider cracks. Don't use rivets as you can't control the tension properly. The superfly race car way to do it would be nutserts, rubber grommets and button head screws.

I broke the rules and riveted mine in with a bead of silicone underneath for waterproofing. They're still crack free two years later.

+1 on the black painted border (on the inside) to make them look better.

JG Pasterjak said:

You can use screws, but put some little rubber grommets in the Lexan so there's no screw-on-plastic action, or you'll get spider cracks. Don't use rivets as you can't control the tension properly. The superfly race car way to do it would be nutserts, rubber grommets and button head screws.

You don't say...

https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/1981-camaro-c-prepared-build/59501/page34/

That's exactly what I did, but I will say, doing the nutserts sucks and you should only do it where you can't get to the back side.  Along the top of my windshield, for example, I used nylocks.

I can see how you'd top-mount Lexan into a channel (as in the pics above). I can definitely do that for the rear window.

But there's no channel in the doors. I basically need to replace door glass with Lexan versions. I can't just swap them because I want to get rid of the (heavy and bulky) power window regulators.

On my 318ti, I did the front door windows like that. I pulled the factory windows out and used them as templates for the top edges, but cut the bottom off flat, leaving about an inch that extends down into the weatherstrip and door cavity. I drilled two 1/4 holes in the bottom edge so that I can pin them in place for driving around, transport, and storage, but can quickly remove them for track duty. It works great because the doors in my car have edges that surround the whole window, so the weatherstripping holds them in place.

In reply to collinskl1 :

Thanks so much! Sounds easier than I had expected.

One more (kind of stupid) question: when you remove the windows, do you slide them out the top? I suppose there's enough flex to pop them out without scratching them up. 

In reply to LanEvo :

Lower the window, rotate to nose up (to get it out of the tracks) and pull up and out.

stafford1500 said:

In reply to LanEvo :

Lower the window, rotate to nose up (to get it out of the tracks) and pull up and out.

Exactly.

Lexan does like to scratch easily. Mine are far from perfect, but I haven't exactly been dilligently careful with them either. There is a version that has a scratch resistant coating on them, but of course it costs more.

Thanks Gimp, I came in to see how to mount my windows, and am leaving feeling the need to build a racecar from the ground up.

Lanevo, any idea what weight is as it sits now? 
 

And any guess what it will be once you swap in the Lexan and get rid of the widow regulators? 

pirate said:

Pretty slick! Is there a cleat that hold the strap when the window is up or what keep the window up.

I always liked the way the Super Stock '68 Hemi Darts and 'cudas used a seatbelt with a snap for both positions to hold the lightweight Corning Glass side windows in place.