LED tail/stop bulb connundrum

[Robert Leigh]

Some time ago I fitted LED bulbs to the stop/tail and front sidelights on my 12v Ruby. Recently, as I drove into the darkened garage, I noticed that the front side lights were coming on as I braked. Eventually found that the corncob type LED tail/stop bulbs were responsible.
On investigating I found that all of the individual |LEDs in the bulbs come on for both tail and stop function - but in tail lamp mode they are all dimmer.
There seems to be some kind of internal connection between the tail and stop pips which is allowing brake lamp voltage back out onto the side lamp circuits.
I cannot detect a resistance but suspect maybe a zener diode with poor reverse resistance..I put back the the old incandescent bulbs and all's well again.
I wondered if anyone else has come across this  - or has any other theories.

I had a problem with Stop/Tail LED bulbs from a well known supplier.  I discovered that the stop and tail pips supply only ONE set of internal LEDs via two different series resistors, to achieve different current drives for the two different levels of brightness.  In my car's setup, I found this rather simple arrangement caused interaction between the brakes and other parts of the sidelight circuit due to current flowing back out of the bulbs ("back feeding").  After a lot of time wasted working out what the problem was, I had to resort to putting in series diodes (1N4001's) in both sides of both LED bulbs to prevent the back feeding.  The diodes were hidden in the wiring with the aid of black heat shrink tubing.

I found that buying cheap LED lamps from Ebay means that you get what you pay for, and back feed problems can arise. After speaking to Peter Jury at Classic Dynamo and Regulator Conversions I bought (at a higher price) some of his which apparently have diodes in their construction to prevent the back feeds, and my problem was solved. There may be other suppliers of lamps who do the same, but another good feature of the Classic Dynamo lamps is that they have colour emitting LEDs to suit the function you need, so that even with a broken rearlight cover you still have red lights at the back.