I pretty much agree with Shenrie, though as a rec cyclist and commercial driver I do like making eye contact when I can.
To answer OP's question I prefer 20% on most of my cars with a strip of 5% on the windshield.
20% or 15% matches the stock tint almost perfectly if you have a ford window van with factory tint on the rear and sides. I ALWAYS roll both windows down when backing or maneuvering though. This is important for sight AND sound.
I think I'm going with 20%. Its a good compromise between blackout and dark. I agree that seeing out is important and I don't want to regret getting something too dark, especially when I can always drop the shades/curtains if I wanted.
I also agree with the eye contact thing. Theres a lot of cyclists in my town.
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2005 E350 Chateau - V10 - Agile Offroad 4x4
2012 CTS-V Wagon - For the baby...
I ALWAYS roll both windows down when backing or maneuvering though. This is important for sight AND sound.
For the crunch sound? Of course the rule of thumb is never back up...yeah right. None of our work vehicles allow a rear site advantage and my pickup always had a camper on it so I just should have gone full tint to black out my vans rear windows. But I think reflectix helps for cold & heat. Like I said it's kind of tacky looking but who cares. Although I must admit, when I got pulled over because a girl had been abducted in town by some sleaze bag in a white van, the reflectix may have had something to do with it
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2006 Ford 6.0PSD EB-50/E-PH SMB 4X4 Rock Crawler Trailer