How bright should a rear fog light be?

[iroc409]

I've seen a lot of different styles of rear fog lights, from LED to small brake light bulbs to H1 or H3 bulb styles. Some of the H1 or H3 (can't remember which) almost seem like they might be too bright.

I thought I read somewhere it should be about the same intensity as the brake lights on the vehicle. Is that accurate?

 

[-Virgil-]

The photometric requirements for the US and ECE rear fog light function are identical to those of the US stop (brake) light function: 80cd to 300cd on axis, with various off-axis requirements. There's a minimum lit area requirement for the stop light function that does not apply to the rear fog function. For some reason, probably because the rear fog function is still relatively exotic and unknown in North America, many of the devices available on the North American market are just a red light with random performance characteristics, not certified to comply with SAE J1319 or type-approved to ECE R38. A good rear fog lamp, properly installed and used, can be a really effective crash-avoidance device. Pick one that's E-marked (type approved) or one from a reputable maker that's SAE-certified. Make sure to leave a distance of at least 10cm between adjacent lit edges of the rear fog and the nearest stop lamp or red turn signal, and if you install a single rear fog lamp put it on the driver's side of the vehicle.

There have been some good halogen rear fog lamps (Cibié with H2 bulbs, Kinby-Faessa with H3, etc.), and they are fireballs that will punch through the heaviest fog or snow you're likely to encounter. but now we have LEDs that consume a tenth or a twentieth of the power and have much longer lifespan. Peterson's got rectangular and round ones. Truck-Lite's got rectangular ones. Grote might have some, too.

 

[iroc409]

Wow, thanks for the info! I downloaded the whole 2011 Truck Lite catalog for something else (250MB), but never saw that fog light. Are those models any different really from the stop+tail models, but in a single mode, or are they actually brighter? I've been behind a couple older cars that were replaced with generic LED brake lights, and they are bright (LED units like Truck Lite or maybe Blazer--not replacement bulb types).

Do you know of anything suitable in a format like this?:
http://www.spectrowireandcable.com/pc/13052/LED/Red+17"+3+Wire+STT

I was looking for something to mount in the gap between the tailgate and bumper on my truck. Although I figure my chances are slim, otherwise I'm stuck cutting up the bumper or mounting something on the bottom of the bumper.

LED would be a huge bonus, as I was planning to re-purpose the factory fog light circuit--don't use those things anyway!

 

[-Virgil-]

There are no LED rear fogs in the format as shown in your link, that I'm aware of -- remember the requirements for a CHMSL (center 3rd brake light) are much lower than for the primary left/right brake lights, so don't be fooled into thinking a CHMSL will make an effective rear fog. It won't. The Peterson and Truck-Lite rear fogs are definitely photometrically different than the stop/tail lamps.

 

[iroc409]

OK, I figured it was a long shot but worth a try. Good to know those lamps are different. I suppose with the correct size hole saw, it would be relatively easy to knock out a hole for the round version (or find someone with a knock-out tool).

I was under the impression that model I linked wasn't a CHMSL, but obviously if the LED fog units are photometrically different any stop+turn model would be inappropriate. I've seen a lot of cargo trailers out there that have a bar type light that I linked to for their rear stop+turn lamps, so I thought maybe something in that realm would work.

Are there specific requirements for the lateral mounting of the light on the rear other than "on the driver's side"? I know there are height restrictions (minimum/maximum), but the only flat-ish spot on my rear bumper is probably about 18" from my license plate. It would be technically on the driver's side, but not far off center.

Edit: My main concern regarding a too-bright rear fog is from the people with cars like Mercedes and Saab that drive on clear highways with their fog lights on (because they can see better!), which also activates their rear fog lamps. Those things are no fun being behind--in clear weather. I won't be doing that, but I have been in need of a rear fog light more than once.

 

[Gregozedobe]

Edit: My main concern regarding a too-bright rear fog is from the people with cars like Mercedes and Saab that drive on clear highways with their fog lights on (because they can see better!), which also activates their rear fog lamps. Those things are no fun being behind--in clear weather. I won't be doing that, but I have been in need of a rear fog light more than once.

Good man ! (or woman). This is one of my pet peeves on freeways when everyone is travelling at similar speeds (mostly on cruise control). The annoying glare irritates for a long time.

 

[Qship1996]

most {all?} factory installed rear fog lamps do NOT "automatically" illuminate when one switches on the front fogs, it is a separate step to light the rear fogs AFTER turning on the front fogs each time.

 

[-Virgil-]

Are there specific requirements for the lateral mounting of the light on the rear other than "on the driver's side"?

If only one lamp is fitted, it needs to be on or to the left of the vehicle's centerline. The farther left you can mount it the more readily it will be visible despite interceding vehicles between you and whoever might or might not see it.

Mercedes and Saab that drive on clear highways with their fog lights on (because they can see better!), which also activates their rear fog lamps.

Sorta. The rear fog switch is daisy-chained to the front fog switch so both can be left on and will then illuminate whenever the ignition and headlamps are on. This problem is (finally) being addressed in the regulations; which are changing to require that the fogs, both front and rear IIRC, must switch off and remain switched off until manually activated again if the ignition or low beams are switched off for more than 30 seconds. This is a smart requirement that should have been in the regs years ago. It'll take awhile for these new provisions to sweep the problem cars off the roads and neutralize the faulty drivers' inattention. You can set up your rear fog this way: a latching relay of the type used for back windshield defogger grids (minus the auto shutoff timer) would be fine. You push the button, and if the relevant conditions are met (front fog and/or low beams illuminated), the rear fog lamp comes on. Turn off the headlamps or turn off the ignition, and the next time you want to use the rear fog you have to push the button again. No chance of forgetting and leaving it on from now until forever.

 

[Alaric Darconville]

The Peterson and Truck-Lite rear fogs are definitely photometrically different than the stop/tail lamps.

My experience with Peterson is limited to seeing what they offer at WalMart (and maybe at NAPA). Isn't that largely rebranded stuff, à la Hella's bulbs and such? Does Peterson have a "ha, ha, you got it at WalMart" line and a *real* line of products? I've seen you recommending them, or at least mentioning them without telling us to run, run away.

Peterson's got rectangular and round ones. Truck-Lite's got rectangular ones. Grote might have some, too.

I've seen some tail/stop lamps at WalMart with the Peterson name on them, in cute "try me" packaging. I don't know if they're any good or not, but I figured one could be repurposed as a fog lamp by wiring only to the major function.

 

[iroc409]

If only one lamp is fitted, it needs to be on or to the left of the vehicle's centerline. The farther left you can mount it the more readily it will be visible despite interceding vehicles between you and whoever might or might not see it.

OK, that makes sense. I guess I could still mount something under the bumper, but just worried about it getting knocked off at some point.

Sorta. The rear fog switch is daisy-chained to the front fog switch so both can be left on and will then illuminate whenever the ignition and headlamps are on. This problem is (finally) being addressed in the regulations; which are changing to require that the fogs, both front and rear IIRC, must switch off and remain switched off until manually activated again if the ignition or low beams are switched off for more than 30 seconds. This is a smart requirement that should have been in the regs years ago. It'll take awhile for these new provisions to sweep the problem cars off the roads and neutralize the faulty drivers' inattention. You can set up your rear fog this way: a latching relay of the type used for back windshield defogger grids (minus the auto shutoff timer) would be fine. You push the button, and if the relevant conditions are met (front fog and/or low beams illuminated), the rear fog lamp comes on. Turn off the headlamps or turn off the ignition, and the next time you want to use the rear fog you have to push the button again. No chance of forgetting and leaving it on from now until forever.

A latching relay is a good idea. Maybe the owners think more lights are more better? My dad had a late model Saab for a while (until they bought it back for being a disaster) that he could activate the rear for independently of the fronts.

I've seen some tail/stop lamps at WalMart with the Peterson name on them, in cute "try me" packaging. I don't know if they're any good or not, but I figured one could be repurposed as a fog lamp by wiring only to the major function.

That's kind of what I was hoping for. I was playing with the Blazer units at WalMart in one of those packages while trying to find some fuses. They seemed pretty bright in the store (enough I couldn't comfortably look straight at them :duh2, and would be more streamlined, but sounds like that won't quite work.

 

[Alaric Darconville]

That's kind of what I was hoping for. I was playing with the Blazer units at WalMart in one of those packages while trying to find some fuses. They seemed pretty bright in the store (enough I couldn't comfortably look straight at them :duh2, and would be more streamlined, but sounds like that won't quite work.

If my Corolla's reverse lamps are far enough away from any lit edge of a brake lamp (10cm or greater), and the photometrics of the reverse lamp are equal to a brake lamp once the lens is reddened, it could possibly make a good rear fog lamp. I'd lose a reverse lamp, though It'd be a way to have a rear fog lamp without body modification.

As I've said before, a rear fog lamp is much more useful than a front one. In the fog, I drive like I want to get there; others often drive like they want to rear-end everyone on the road.

 

[-Virgil-]

My experience with Peterson is limited to seeing what they offer at WalMart

Interesting. I wasn't aware they sell stuff at WalMart -- mainly because I don't shop there. I have no idea what they might be selling there, and whether it's genuine Peterson product or what I guess we might call "PINO", Peterson In Name Only. I would have to guess at an answer to that question, and I wouldn't be able to do so without pushing this thread well off topic into political and economic areas that are not the subject of this board.

I've seen some tail/stop lamps at WalMart with the Peterson name on them, in cute "try me" packaging.

That might factor into my guess; when you buy Peterson's stuff from a real parts source, you generally don't get cutesy packaging.

I figured one could be repurposed as a fog lamp by wiring only to the major function.

Not optimal. Get an actual rear fog lamp.

 

[-Virgil-]

If my Corolla's reverse lamps are far enough away from any lit edge of a brake lamp (10cm or greater), and the photometrics of the reverse lamp are equal to a brake lamp once the lens is reddened

They aren't. Not even slightly close. This idea is popular with some of the young Euro-enthusiast fanboys, but it does not work. The photometric spec for a reversing lamp is quite different from the photometric spec for any other function.

 

[iroc409]

Interesting. I wasn't aware they sell stuff at WalMart -- mainly because I don't shop there. I have no idea what they might be selling there, and whether it's genuine Peterson product or what I guess we might call "PINO", Peterson In Name Only. I would have to guess at an answer to that question, and I wouldn't be able to do so without pushing this thread well off topic into political and economic areas that are not the subject of this board.

That might factor into my guess; when you buy Peterson's stuff from a real parts source, you generally don't get cutesy packaging.

Not optimal. Get an actual rear fog lamp.

I try to avoid WalMart for the most part, for a plethora of reasons. It's hard to find a fuse kit with certain requirements locally (including at WalMart, as they didn't have it either).

The only Peterson I've seen at WalMart is the tractor/utility lights. They did not appear to be sub-par in quality, and if I remember right may have even been manufactured in the USA.

All of the other misc. lights they carry that I saw recently are Blazer brand, but I don't know if they are a sub-brand of another company or what.

 

[-Virgil-]

Blazer is an American brand of lighting equipment mostly imported from the Pacific Rim. Most of their stuff is prioritized on being as cheap as possible. They have supplied complete fog lamps to GM, and during Guide's death throes Blazer supplied headlamp subcomponents for certain Guide headlamps.

 

[Diesel_Bomber]

I've purchased and installed Peterson LED 6" ovals and their Piranha line of marker lights from both a real parts store and from Wally World. The packaging is the only difference as far as I can tell. I would have no concerns with the quality of Peterson products from Walmart.

That said, I buy at my preferred parts store, despite the higher cost, for a variety of reasons.

Edit: An idea occurs to me. If someone really wanted LED lighting, what about mounting 6" ovals or 4" round lights in a car's existing lighting fixtures? These lights are already photometrically tested and approved as both safe and legally compliant.

 

[Alaric Darconville]

Interesting. I wasn't aware they sell stuff at WalMart -- mainly because I don't shop there. I have no idea what they might be selling there, and whether it's genuine Peterson product or what I guess we might call "PINO", Peterson In Name Only. I would have to guess at an answer to that question, and I wouldn't be able to do so without pushing this thread well off topic into political and economic areas that are not the subject of this board.



That might factor into my guess; when you buy Peterson's stuff from a real parts source, you generally don't get cutesy packaging.

I could have SWORN it had the same PM-in-octagon logo, but maybe it was the "Blazer" stuff. I do remember that at one time Atwood's carried their plug-in magnetic rotating beacons in the automotive section (the Model 771). Those things weren't very well made, and looked exactly like the Blazer offerings on Walmart.com (but I think it used an 1141, not a #67 bulb). The beacon shape and the fluting at the base is identical.

Part of their problem was that the rubber ring would glaze and harden, and also develop indentations where the drive 'gear' rested, so that they'd stop spinning.

They aren't. Not even slightly close. This idea is popular with some of the young Euro-enthusiast fanboys, but it does not work. The photometric spec for a reversing lamp is quite different from the photometric spec for any other function.

At first glance it seemed "close", but I did more research and decided it was a ridiculous idea, and did bear all the hallmarks of being a mod for the "JDM" and "Euro"-type fanpersons doing it to look "kewl" or to "keeps it REAL" or whatever the big time phrase that is so money is nowadays.

 

[Alaric Darconville]

I've purchased and installed Peterson LED 6" ovals and their Piranha line of marker lights from both a real parts store and from Wally World. The packaging is the only difference as far as I can tell. I would have no concerns with the quality of Peterson products from Walmart.

So I'm not the only one

That said, I buy at my preferred parts store, despite the higher cost, for a variety of reasons.

For example, having someone behind the counter that might understand a little about cars.

Edit: An idea occurs to me. If someone really wanted LED lighting, what about mounting 6" ovals or 4" round lights in a car's existing lighting fixtures? These lights are already photometrically tested and approved as both safe and legally compliant.

Most people want LED lighting *AND* for it to look like it was factory installed. Those ovals and rounds would look decidedly odd mounted within the fixtures; it would require complete removal of the lenses or for the lenses to be cut out so the ovals and rounds could be sunk into them. Placing them in the fixtures with the factory lenses over them would detract from their photometric performance.

 

[iroc409]

At first glance it seemed "close", but I did more research and decided it was a ridiculous idea, and did bear all the hallmarks of being a mod for the "JDM" and "Euro"-type fanpersons doing it to look "kewl" or to "keeps it REAL" or whatever the big time phrase that is so money is nowadays.

I saw a thread some time back where someone used the unused filament in the turn signal bulbs on the back of a Tacoma for rear fog lights. It was a neat idea--except, they're amber and he wired up both sides.

 

[Alaric Darconville]

I saw a thread some time back where someone used the unused filament in the turn signal bulbs on the back of a Tacoma for rear fog lights. It was a neat idea--except, they're amber and he wired up both sides.

I'm sure it was somewhat *visible*, but it probably also could lead to confusion for other drivers.

Steady yellow lights could be interpreted as a car driving toward you, especially in the limited visibility of fog-- and especially because the unused filaments would be the *minor* filaments, and therefore have parking lamp intensity. Sometimes "noticeable" or "glaringly obvious" is detrimental; part of vehicle lighting functions are to provide unambiguous indication of a vehicle's position and direction, not just driver's intent or to provide visibility for the driver.

Doing that to supplement reverse lamps for backing in less-than-advantageous conditions might be a neat idea (but I'd rather use the major filaments), but using them as a "rear fog" is iffy (not to mention contrary to the requirement that rear fog lamps are required to be red).