I write this as a separate topic from Tom Stones current thread of
similar subject. I do this for the archives.

The high wattage bulbs that get installed  as back-up lights, turn
signals, brake lights, and tail lights - produce a lot of heat. The
plastic materials used in the fixtures for these lights soften and
distort at the temperatures the bulbs produce. How do I know? BTDT!!
Yup! melted my tail lights. Actually distorted the plastics and rendered
one of them unusable and I had to replace it. Maybe could have started a
fire - but it didn't, and I'm grateful for that. I first realized there
was a problem when one night I was looking at a tail light and saw the
distortion in the pattern in the plastic. It was clearly distorted. Next
day I removed the fixture and took a look and discovered the damage. I
went back to the old bulb for all except the backup lights. I kept the
50 bulbs there, because those bulb don't stay on long enough to do any
damage, but to use them you must understand that. Put it in revers, back
up, take it out of reverse. Don't dilly-dally - you will over heat the
plastic. If you get on with the business of backing up then get out of
reverse quickly, you can enjoy the benefits of the brighter light
without the hazard of over heating. But that backup light is the only
one I would use in a 50W bulb .

Regards,

John Rodgers
88 GL Driver