I recently got a cheap Maplins wireless bike computer, and I thought it was pretty neat for the money. However, just recently I've been having some trouble with it - it sometimes measures my speed as being much faster than it actually is. Today I worked out the what the problem is. My bike computer is sat right next to a Cateye 3 LED front light on my bars, and when I have the Cateye turned on (I tend to have it turned on to blink mode), I get an extra 32Mph added to my speed, even when I'm stationary. I'm not sure what frequency the wireless sensor on my computer uses, but it's quite evident that when in use my Cateye produces pulses at a similar frequency. I guess I'll have to move my computer over to the other side of my bars now!