Taillight bulb question. P21/5W vs 1157?
 

What's the difference. The taillight says <a href="http://www.donsbulbs.com/cgi-bin/r/b.pl/p21%7c5w.html">P21/5W</a> on it, but for some reason I had been looking for an <a href="http://www.donsbulbs.com/cgi-bin/r/b.pl/1157.html">1157</a> (I guess I got the info here?) According to <a href="http://www.donsbulbs.com/">Don's Bulbs</a> they have the same base (BAY15D), so what's the difference? I guess looking @ the list below, the 1157 is supposed to be brighter, but the P21 lasts longer. The 1157 also draws a bit more juice. Though the reason I am curious about this is cos I found some <a href="http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=8041594133">1157 LED bulbs</a> (yeah, I know, they won't be bright enough, yadda yadda yadda) that I would like to try, which actually makes me less worried about the amperage.


<blockquote><b>P21-5W/12V/21W/5W/BAY15D ECE bulb specifications:</b>
category: MINIATURE
volt: 12
amp: 1.75 / .417
watt: 21 / 5
base: BAY15d - Double Contact Index Bayonet
glass: S8
filament: C6/C6
fil.res.: 6.86 / 28.8 ohm
m.o.l.: 2 inches
l.c.l.: 1.25 inches
i.lumens: 264 / 75.4
cp: 21 / 6
d.hours: 1000 / 200
notes:
automobile lamp
clear glass
FOR 6 VOLT USE: 1154 USA
FOR NEAR SUBSTITUTION USE: 1034 USA
indicator lamp
incandescent
stop lamp
tail lamp

<b>1157 USA bulb specifications:</b>
category: MINIATURE
volt: 12.8 / 14
amp: 2.5 / .214
watt: 32 / 3
base: BAY15d - Double Contact Index Bayonet
glass: S8
filament: C6/C6
fil.res.: 5.12 / 65.4 ohm
m.o.l.: 2 inches
l.c.l.: 1.25 inches
i.lumens: 402 / 37.7
cp: 32 / 3
d.hours: 600 / 5000
notes:
automobile lamp
clear glass
incandescent
motorcycle
stop lamp
tail lamp</blockquote>

They're the same, only different...
 

1157 is a US designation, P21/5W is a European designation. They're slightly different in specs, but interchangable for this application.

A closer US cross is a 7528, but that's probably less common in the US than a real P21/5W.

Note that the usual LED bulbs will NOT work properly with reflectors designed for incandescent bulbs.

Actually I think these may...
 

<center><img src="http://www.maxspeed-motorsports.com/maximages/360LED10.jpg"></center><p>They have an omni directional design to them. Having played with LEDs I know that even supposed 'wide angle' LEDS aren't, but these bulbs are actually cylindrical in shape with the LEDs mounted around the outside and on the end.

Better, but...
 

still don't get anywhere near the small source of a bulb. Still, probably OK for taillamps or other non-beam applications.

True, I expect they will still have an odd speckly directional effect.
 

Oh &amp; thanks for the info. Glad to know they won't explode or anything. ;^)

hijack: is that taillight on purpose in your sig, or did it just show up there?

Heh...it's on purpose. If you look closely you can see the silhouette of the car.
 

Just kind of a carryover from previous sigs.<ul><li><a href="http://homepage.mac.com/maxhedrm/TTSigs.html">http://homepage.mac.com/maxhedrm/TTSigs.html</a</li></ul>