Is there any reason you wouldn't replace it with a factory part? You can find the part number from realoem. http://www.realoem.com/bmw/select.do?kind=P&series=E39&arch=0
Factory are moderately priced, look good and a new set is like a fresh detail job. In fact once you put them in you WILL detail your car from the inspiring look of having new fogs again!
I want to replace my fog lights with a more brighter and white bulb. Was wondering if I could just replace the bulb I have now with a PIAA Xtreme White Bulbs - H-8 or do I replace the whole fog light?
I don't know what model car and style of your fogs, but you can put a higher watt bulb in, or go with a whiter bulb as you suggested. Just get the proper bulb style/number.
Be very careful about putting in higher wattage bulbs Putting in bulbs with a wattage higher than 55 watts could melt your housings as well as possibly damage your electrical wiring, as the stock wires were probably not designed to handle that much power. One option you may want to take a look at are HiR bulbs. No that's not a typo. See the weblink for more details. http://hirheadlights.com/
Ya, no BMW owners have ever upgraded tires, suspension components, audio, engine management, lighting...
At the risk of being flamed by the purists, I believe the OP has identified the same issue I've noticed. The xenon headlamps look great, but the driving lights look sadly yellow when they're used at the same time. It's not a good look and as a result, I don't use the driving lights. I know, I know: It's not about "the look". Catbert Mine: 2003 530i Daily Driver: Toyota Avalon Mrs. Catbert: 2003 325xit
The simple answer to your question is that you don't have to replace your foglight housing, the bulbs are designed to be replaceable. The safest path is to replace with bulbs of the same wattage, or equivalent current draw, as stock, regardless of which brand and type of bulb. If you start upping the ante with wattages, the more above stock you go, the more you risk an issue, worst case scenario being a wiring short, possibly even from melting the wire insulation, resulting in a underhood fire or wiring meltdown. That's more likely if you did something like going to 110w bulbs (or higher) over the stock 55w, and swapping in higher amp fuses on the headlight circuits to handle the additional current draw, without changing the wiring. I have PIAA's on my E34 - happy w/ them, but the HIR's look intriguing.
I'd say that's a moot statement.... ...considering BMW doesn't MAKE either component. +1 on CR Krieger's statement on Daniel Stern Lighting. Anyone who's read his site would realize the man knows his stuff.
Get these http://www.ddmtuning.com/Products/DDM-HID-Kit-Slim-Ballast-35W-or-55W in H8 fitment in the range of 4300K-6000K color 35W. You will be quite happy with them. They are easy to install and look great. If you get tired of a particular color, a new pair of bulbs by themselves are only $30 including shipping. I've got the 6000K in mine and at night, I can leave my headlights off and still light up the road very well, just a bit lower cutoff than the headlights.