Not very interesting but...

[bluetone]

I guess bulb manufacturers must work to a pretty consistent standard and/or tight tolerances: My Mk1, which, must have seen it's fair share of new bulbs over the last 14 years, had both sidelight bulbs go pop within a week of each other (I hadn't had to replace one previously in 3.5 years of ownership). I had the same thing happen with the headlight bulbs a while a go.

Anyway, as you were

[rfn]

Either that, or, during the time when your first headlight/sidelight bulb blew, more pressure (current, I assume) was put on the currently working bulb, which contributed to its demise soon after?

[NeoVR]

Your probably right..
Ive had several "uprated" sets of headlight bulbs on my previous cars.. and generally they tend to go within a few days of each other.. once even within 2 hours of each other!

[dylan0451]

i believe it's a current spike - when the first one blows, that side goes open circuit, and momentarily puts a huge load on the remaining bulb.

sometimes you'll find a large'ish resistor somewhere in the circuit which i assume is there to try to dampen the effect, though i assume nowdays more complicated electro trickery keeps tight reins on everything electrical

[bluetone]

These theories very much make sense; when I was changing sidelight bulb 1 I did think to myself "fk me, the other one is very dim and can't be longer for this world" - getting the current for two bulbs, even just momentarily won't do 'em any good am sure so thanks for the input fellas

Aren't t'internet fora great?

[dylan0451]

i find the same thing with halogen/high output kitchen spot lights - they're all fine for 3 years, one goes then you end up replacing the other 2 a week or so down the line

forums are great, if you can ensure the info you're getting is right, bit like the early days of wikipedia, sadly i doubt it'll ever knock off everyones assumption that it's just a joke