By on January 16, 2012

TTAC Commentator John R writes:

What’s your opinion of aftermarket LED bulbs for signal/brake/reverse replacement?

Sajeev answers:

I like the look of aftermarket LED indicators in housings never intended for them, if the one vehicle—believe it or not, a very cool 2000 Ford Taurus–I’ve seen is any “indication.” (sorry)

The lighting certainly looked neat compared to the stock Taurus next to it, mostly because LED bulbs were just a little different. The bulbs lit up quicker, had a slightly “warmer” tone and the HID-like whiteness of LED license plate lights were rather cool. But I am just a schmuck with a keyboard and publishing rights to TTAC’s back end system.

But unlike me, Daniel Stern is a highly regarded automotive lighting genius with a somewhat famous webpage and another site for lighting analysis, Driving Vision News. My apologizes if this sounds like a pimp-atorial to some of the B&B, but contacting a lighting consultant and giving them props for their hard work is the smartest move on the table.

Daniel Stern writes:

Short answer? ABSOLUTELY NOT!!!

Long answer:  LED signalling lamps (brake, tail, turn…) are appearing on cars, and are widely used on trucks, but it really is not a “retrofit” item in the sense of dropping in an “LED bulb”. The brake, tail, parking, and signal lamps of your car rely on a point source of light (glowing filament) that radiates more or less equally in all directions — a sphere of light – collecting and distributing that light with optics in the lens and/or reflector.

An LED is a vastly different *kind* of light source.

Unlike a glowing filament, it does not produce light in an even sphere.  Instead, it projects a very narrow beam of light in ONE direction.  That’s why these so-called “LED retrofits” consisting of a 1″ diameter matrix of LEDs on a bayonet or wedge base are unsafe; there’s no way you can get enough light through a wide enough angle (horizontally and vertically) to create a safe and legally-compliant lamp. This applies even to the fancier “LED bulbs” that have side-facing as well as rear-facing emitters. The problem is not with any marketer’s particular implementation, the problem is with the concept, which does not (cannot) work.

There are other considerations, too — for any automotive lighting function, not only is it crucial that the intensity be within the proper limit through the entire relevant range of vertical and horizontal angles so as to provide a recognizable and penetrating signal to observers at any angle to  your vehicle, not only must the intensity ratio between bright and dim modes  be correct (for combination brake/tail or park/turn lamps), but the effective projected luminous lens area must not be reduced. EPLLA refers to the amount of lens area significantly lit up when the lighting device is active. With “LED bulbs” installed in lamps meant for filament t bulbs, you  tend to get a little dot of light with the rest of the lens almost completely unlit. So not only is the visibly lit area dimmer, it’s also smaller. Safety? Not so much!

Look closely at the optics of one of the newer vehicles that has LED brake/tail lamps. You’ll see optics totally different in configuration compared to those found in bulb-type devices. These special optics are necessary to coordinate the light from a large number of LEDs (relative to the overall size of the device) to get everything right in terms of brightness in both dim and bright mode, uniformity of brightness throughout the visibility angles required by law, ratio of intensity between “bright” and “dim” mode, EPLLA, etc.  These kinds of optics are not something you can kludge in your garage, let alone achieve with these unsafe “LED bulb retrofits”.

Lighting devices meant to take bulbs need to use bulbs. I’ve seen standard truck/bus LED stop/tail or turn lamps placed behind (not cut into) the lens of vehicle lights intended for use with bulbs. It can actually work fine if the LED unit is mounted close to the lens surface, and sometimes even if there’s some space between the lens and the LED unit.

The critical thing is getting the angle right; if the LED unit is tipped or tilted in any dimension, the light distribution won’t be proper. If you do this, use good quality lamp units from Grote, Signal-Stat/Truck-Lite, or Peterson — not off-brand junk. There’s an enormous variety of units to choose from. The Truck-Lite Signal-Stat “value line” units are actually quite good and they’re not very costly. Photo-illustrated discussion at: and

This guy (mention my name as a referral if interested) does custom LED conversions that work safely and effectively, but as you can see they are not cheap. He’s not profiteering…the prices actually are in line with the materials and parts cost and time and work involved to do the job right.

Do-it-yourself is not impossible, it’s just a great deal more difficult than most people realize.


Send your queries to [email protected] . Spare no details and ask for a speedy resolution if you’re in a hurry.

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39 Comments on “Piston Slap: LED, Not For Me?...”

  • avatar

    I am not crazy about the whole LED thing either. Too ricer-ish, if you will.

    • 0 avatar

      My only problem with LED is that they don’t generate heat. That means in winter, turning the lights on will have no effect on ice buildup.

      I bought a set of LED foglight bulbs from Ebay to use on my SRT8 since I kept blowing fuses with the HID light ballasts. I haven’t had a single problem with the LED bulbs and I love the look.

      The thing that annoys me, however, are all these LED light strips being added to cars. It’s very distracting and makes the cars look like “pride parades”.

      • 0 avatar

        LEDs generate heat, but not from the emitter – the circuit board they attach to can get quite hot, depending on the type/power of LED. You should see the elaborate heat sinks, ducting and fans used to keep the circuit board behind the high output LED headlamps on the R8 and Escalade (the only 2 cars with LED headlamps I can think of at the moment) cool.

      • 0 avatar

        anything that uses energy to do work radiates heat. I should have said that the LED’s don’t generate anywhere near as much as conventional bulbs do and can’t melt ice/snow.

      • 0 avatar


        the diode itself does generate heat; in most cases for higher-power LEDs the circuit board gets hot because it is also doubling as the heatsink for the diode.

  • avatar

    Personally, I’m not buying it. In the two cars I’ve had with LED replacement “bulbs” BOTH looked brighter with the LEDs. I’ve seen pictures on forums as well that show the LEDs look brighter, from any angle the photo was taken.

    Now maybe this has to do with the vehicles’ large taillights (my old ’94 Crown Victoria & ’91 Grand Marquis). If you want to attack the failure rate of the bulbs or show me some actual, proven car-fires started by cheap aftermarket LEDs, go ahead, but I’ve never heard of any. MY eyes say the LED taillamps I bought on ebay ARE brighter (at least at night).

    I have seen many, many newer cars (mostly Chrysler/Dodge) driving around with burnt out taillights. Do taillights fail that often, I mean I’ve owned a number of cars and rarely, very rarely have I had to replace any bulbs, but these newer cars seem to come with failure-prone lights.

    What say you, other B&B?

    • 0 avatar

      If you read Daniel’s site, he talks about this “effect” when it comes to the blue headlight bulbs. It’s all about color temperature and the way your eyes process it. The blue bulbs seem brighter, but in reality they aren’t. I suspect the LEDs may work the same way – they operate in a different color-temperature range than incandescent and fool your eyes into thinking they are brighter.

      Stern also discusses another pet peeve of mine: the fallacy of using the fog lamps on your car all the time. Sure, they light up the space in between the front of the car and the headlamp beams, making things seem brighter. But by using them, you are causing your eyes to change their point of focus to closer in vs. farther out, defeating the whole point of your headlights.

      • 0 avatar

        Living in a deer-infested neighborhood, we’re finding the fog lights on our cars very useful to see deer at the sides of the street that may run out in front of us.

      • 0 avatar

        No fan of marginally useful aftermarket products myself, BUT this doesn’t make sense to me. If the LED tail lights look brighter, but actually aren’t, who cares? Isn’t the point of tail lights to be seen by humans, meaning lights that are more easily seen are better no matter what the underlying reason is?

      • 0 avatar

        As long as the bloke behind me also “perceives” the light to be brighter, I’m happy. When the car following me is being driven by a machine that is accurately measuring the luminous output and deciding whether to rear end me depending on the results, then I’ll give Daniel’s approach some consideration.

    • 0 avatar

      I guess we’ve only been comparing brightness from directly behind,

    • 0 avatar

      NO WAY ON LEDs!

      I learned my lesson on LEDs back in college when I followed the “Fast and Furious” crowd. I got a set of clear corners for my Toyota and filled them up with amber bulbs (along with blue xenons in the headlights which burned out in less than a year). As more kids moved to LEDs, I quickly replaced them along with adding more LEDs wherever I could. In the dark, I shined them on the garage door, and I instantly noticed that the BULBS WERE BRIGHTER! I figured out the light pattern of the bulb was better than the LED.

      Did I change them back? NO! I put so much work into wiring all the LEDs together, I left it as is! That was the first thing to go when I gave the car to my brother…

    • 0 avatar

      I’ve noticed that some LED taillights are quite bright, to the point of blinding and/or after-image. It seems that on those, the same total light is being emitted, but since it is concentrated at small points instead of diffused over the entire taillight assembly, it ‘burns’ the eyes worse.

      I have no doubt that a well-designed LED assembly is just as good as traditional set-ups (such as in traffic lights), but I would place few that I’ve seen in that category. I see little or no benefit to retrofits.

  • avatar

    Aren’t most of the aftermarket LED bulbs and housings “for off-road use only” (ie. not street legal)?

    I would LOVE to get Mr. Stern’s thoughts on headlights. I am very irritated by the drivers who plug HID bulbs into a halogen reflector housing. You also have the people who buy the extra-extra bright blue or yellow halogen bulbs, where the low beam is brighter than most high beams. Then there are the ignorant ones who drive around everywhere with their high beams on.

    I’ve also seemed to notice that Toyota and Honda low beams appear significantly brighter than other vehicles. What are the laws and regulations regarding headlight output?

  • avatar

    I’m fine with LED lights – IF they are done right. If not, I equate subpar lighting work to plastering stick-on portholes or bullet holes on one’s car – only dangerous!

    What I do not like are those blue and pink-ish headlights you see on some cars – those really annoy me, not solely due to my vision issues, but as they are substantially different in intensity from most other cars’ lighting, it draws a driver’s attention from the road – well, me a least – and I can’t afford to be distracted, especially on my morning commute, for ANY reason.

    I actually researched re-working my Impala’s rear panels to give the car a “proper” Impala treatment – THREE lights per side using aftermarket LEDs and then having to paint the rear panels to match the car color. This exercise turned out to be clearly beyond my capability to accomplish – and to make it look like it was built to be this way.

  • avatar

    My previous car had HID’s, and I hated them. Sure they were bright, but I constantly had oncoming people flash their high beams at me because they thought I had the high beams on. I was very happy to learn my Honda has good old fashioned bulbs, that don’t blind oncoming traffic.

    And don’t get me started with kids these days who intentionally put the brightest lamps they can find in their low beams (legal or not), just because they want more attention.

  • avatar

    I had a buddy who bought one of these LED retrofit kids off of eBay for his 350Z because they looked cool. He had to remove half of the rear of the car to install them, and frankly they did look pretty sharp for a Chinese made eBay special.

    Things went bad from there. His cruise control stopped working, he had fuel cutoff problems, he had problems with other electronic components of the car that didn’t seem related to the tailights.

    He fussed around with them for about a week and ended up putting the stock ones back in and behold, everything was in proper working order once again.

    Too bad he cracked the original lens putting them back in. The factory replacement tailight cost more than the stupid LED tailights did.

    An expensive lesson for sure.

  • avatar

    I think it depends on the vehicle. The LED’s are brighter and more easily visible than the equivalent incandescent and in my view offer safety for low-visibility conditions that incandescents do not. I put an LED replacement on an older motorcycle and it can actually be seen from the rear now; the advantage of the LED is that it doesn’t require replacement due to vibration nearly as frequently.

    • 0 avatar

      I used a LED “bulb” too to go into the stock stop lamp tail light housing of my scooter. I had to go on eBay twice, because the first one was much dimmer than the stock incandescent. I settled on a LED bulb replacement that packed as many LED emitters as could possibly fit in the reflector housing. There were 90 LEDs arranged in a star, and the reflector bowl would point all those rays in a range of angles. The intensity appears to approximate incandescent, and they’re very visible during a test ride.

      Dirt cheap on eBay, but your mileage may vary. I didn’t bother with the turn signals, because of the need to use a large resistor (wouldn’t that defeat the power savings?) or a standalone flasher unit.

  • avatar

    On my motorcycle, I put in an LED tail light array that was produced by a forum member. The LEDs were arranged in an attempt to ensure good brightness and visibility, and replaced the reflector housing. I think it was a good job, and it helped lessen the total current draw on the electrical system. I personally wouldn’t do a straight LED bulb swap unless the light dispersion simulated an incandescent bulb, which seems not to be the case.

    Oh, and it was (RIP little bike) a Suzuki GS500E, so we’re not talking a riced out technological marvel.

  • avatar

    In the case of my xB1, I “de-riced” it by replacing the OEM white tails with cheapo ebay LED red lens units. Looks and works great.

    I admit that I’m also one of these A-holes driving around with an ebay HID headlight kit. I justify having them because I drive a lowered car. With my lights closer to the ground, and the increased risk of damaging my car on something in the road, I need the extra visibility. I re-aimed them accordingly and they are no more annoying than my 2.5RS was with the OEM fogs on. I see others on the street with them, and they don’t really bother me unless they have some crazy 14k color temperature. Don’t stare at headlights when you drive and you will be fine. I find the typical SUV much more annoying when they pull up behind me at a light and turn my interior into a tanning booth.

    The newest craze with the kids are the LED bulbs for the HEADLIGHTS. These have barely any light output and are a complete joke.

  • avatar

    I agree with Mr. Stern. I have worked with lighting design for years and have had to battle the retrofit mentality. Unlike cars, when retofitting lighting in a building it is done to reduce the use of electricity. Which is fine, but if the retrofit causes poor uniformity*** -the most critical item in lighting- the end result is a poor work environment. In cars, visibility is critical. I’ve seen some conversions that did work well, but I suspect that it was dumb luck that the conversion “lamp” and the existing optics happened to match reasonably well. I will give a nod to the more rapid light up time. Any B&B recall those older cars that had LEDs in the center mounted brake light but bulbs on the left and right? You could clearly see the difference in the speed. Like other posters here said, HID lighting is a disaster for other motorists.

    ***How important is uniformity? How bright is a moonlit night? On average, about .01 footcandles. But with a perfect uniformity of 1, the appearance is much brighter. For reference, a typical office is (should) be about 50 FC on the work surface, but uniformity is much worse…

  • avatar

    I’m down with the H-I-D as long as it’s stock. Most of the HID “mods” I’ve seen done look like straight-up ass when functioning. Obviously, this is exacerbated when they are driving behind me at night. I wish more manufacturers would consider doing the manual adjustment for load compensation.
    My GF’s 2005 Prius had the HID’s and auto-leveling. The load sensor in the rear suspension looked exceptionally simple in design and operation, but was either sealed badly or insufficiently for the location. This allowed moisture in, loss of function for the leveling, and a laser-beam quality warning light on the dashboard to sear the retinas of the Prius owner. When you wished to replace this part you found no aftermarket support, and ~$400 price tag from Toyota.
    My 2009 Mazdaspeed 3 had a knob on the dash that had 3 settings for headlight height adjustment controlled by the driver. This seemed to be a better solution vs. the Prius.
    I like the LED tails and also had them on the ‘Speed3, as part of the Grand Touring package. If I remember correctly the tails seemed identical of the cars with non-LED’s. Perhaps there was a reflector difference in the housing. But I seem to remember a few folks putting LED’s in their non-equipped cars and posting pix on that forum. My recollection was that they looked very similar to my LED’s.

  • avatar

    I hate LED taillights OEM or otherwise. I had an Audi Q7 in front of me the other day in stop-and-go traffic and I felt the need to put my sunglasses on. Those damn lights were above and beyond bright…to the point of burning my retinas…
    I understand that the main purpose of tail lights is to be seen and grab attention, but c’mon!!!

  • avatar
    Carlson Fan

    Best thing to happen to trailer lighting in a long time. Did one of my boat trailers last summer and the snowmobile trailer is next. Neither of our vehicles have LED lights and I wouldn’t waste my time or money putting them in. But for trailers that seem to constantly have a burn’t out running or marker light, it’s money well spent.

  • avatar

    High end crossovers with HID’s seem to be the worst offenders of blinding me while driving. It’s really annoying when one of them is following you on the interstate. I point all my mirrors directly back at the vehicle.

  • avatar

    I’ve noticed lots of burned out factory LEDs in the past couple of years, ranging from a few dark diodes on a third brake light to two late model Audis in the past week with only one DRL array lit. Conventional bulbs die too, particularly on VWAG products. Still, unless they’re unreachable fog lights in a Camaro, conventional bulbs are a cheap fix. It isn’t like I’ve ever worried about the performance of my running lights. At least with HID there is a visibility enhancement to go with the cost excesses. Having experienced what can go wrong with HIDs on a Mini Cooper, I wouldn’t go out of my way to buy another car with them. I wouldn’t avoid one where they were standard though, and strangely there have been no unpleasant surprises on our TSX, which is now as old as the Mini Cooper was when we gave up on it. Taking on LEDs the way a little girl puts on an Easter Bonnet and shrieks, ‘Look at me Mom!’ in a cry for attention isn’t something that appeals to me.

  • avatar

    Have to admit the idea that pre-LED brake light assemblies had ANY significant amount of thought put into their optical design is enormously entertaining as fiction goes. There’s an enormous variability in incandescent lamp construction and no real detailed effort at consistency of emission patterns from the different filament configurations and orientations. Incandescent lamps DON’T emit as point sources but as extended sources. Computational power for careful reflector design didn’t exist until about 20 years ago and that was lavished on headlamp design, seldom or never on turn signal and brake light design.

    This discussion reminds me of nothing so much as the rejection of digital sound recordings by vinyl-and-tube-amp enthusiasts, or of the bias tire old guard who insisted that putting modern radial tires on an older car would wreak havoc on the car’s handling because the old cars had been “optimized” for bias ply tires.

    Like or dislike LED retrofits as a fashion statement as you like. But for most reasonable retrofits there’s no reason to believe that the functionality is any worse than that of a replacement incandescent bulb, and a few qualities that are clearly superior (activation time, life expectancy, current draw).

    • 0 avatar

      No, Sajeev’s right and you’re…well, you’re not. Your claim that “there’s no real detailed effort at consistency of emission patterns” is not only inaccurate as stated, but also inapplicable. Any vehicle lamp is designed to take _one_ kind of light bulb (1157, 3157, etc.) and each of those light bulbs’ design, construction, and performance is highly and specifically standardized. It’s not at all random or “variable”. And even plain, basic, simple vehicle lights (parabolic reflectors + pillow or Fresnel optics in the lens) are specifically calculated to work with only one specific light bulb. Don’t believe me? Find an old brake light or turn signal and shift its bulb a few millimeters in or out relative to where it’s supposed to be. This isn’t hard; there are sockets available with a whole bunch of different light center lengths. Point the light at a wall since you probably lack the proper measuring equipment to back up your opinions, and compare the light distribution with correct bulb placement vs. incorrect. No comparison at all. Now compare the light distribution with correct bulb type versus LED bulb retrofit. Again, no comparison at all.

      The only thing that can reasonably be disagreed with is Sajeev’s failure to _edit_ Daniel Stern’s unnecessarily wordy way of putting it. The whole thing can accurately be presented much more concisely, in just three sentences: Car lights are heavily and precisely regulated. They work correctly only when equipped with the type of bulb for which they were designed. LED bulb retrofits do not work.

  • avatar

    I always felt that the factory LED tail lights used on the ’05-’07 Accord were somehow not within regulations as they always seemed WAY too bright. Honda fixed the problem by decontenting LEDs out of the next gen Accord. :/

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