Bike lights and wireless cycle computers

I had an email from a reader about a month ago enquiring about an issue he had with his new Smart Lunar 35 lux light interfering with his wireless cycle computer, a Sigma 1009 STS. Unfortunately, it’s quite a common problem that LED bike lights and other electrical equipment such as electric bike motors can make wireless bike computers go haywire.

Various things can be tried to rectify the problem from moving the light or computer (or both). I’ve also seen it suggested that wrapping the light in aluminium foil or tape can help though I think it somewhat  ruins the look. It may be that the lights made completely of metal are less prone to interfere.

Ultimately people who suffer from this problem usually end up switching to a wired computer which will always fix the issue. I like to use one with a temperature display which I find particularly handy as it gives me some idea of the likelihood of ice on those chilly mornings when I might have forgotten to check the weather forecast.

I think it would be useful to gather further data on compatibility between bike lights and wireless computers. I’d greatly appreciate it if you could post a comment below with make and model of your light and computer and whether or not you’ve experienced problems.

7 Replies to “Bike lights and wireless cycle computers”

  1. I have two bikes with 2 different wireless trip meters (1 made by bell &1 made by rsp)
    And when used with my smart lunar 15 front lights in half power or flashing mode it sends my trip computers mad and read speeds of upto 25 mph when stationary.
    If I use my electron nano 1 light with the same trip computers they behave perfectly normal.

    I took the lights back to Evans where I bought them from and they just told me it is a problem with the trip meters. I explained I am on trip meter number 3 all being of different makes and models, and each behaved badly when combined with my smart lights. Again no problem with either my electron light or a £2 cheepo light from a bargain basement store.

    Still Evans would not accept there is a problem with the shielding of the light and just offerred to sell me another trip meter.

    In my opinion the smart lights have a problem and not necessarily the trip meters

    Advice greatly appreciated

  2. OK Faith has been restored in Evans, thanks to some freindly staff at head office customer relations, who actually took the time to listen and undertsand my concerns. Unlike the guy in my local store.

    They have now taken a few sets of the same light, and various trip meters to conduct their own tests, only to find some of the lights worked with all computers no problem, and then some did not and caused the interference issue.

    So it appears that not all lights do it, and that it may not be after all just poor quality shielding of teh trip meters, and maybe a combination of the two, or just the production tolerences of the lights?

    Either way, the staff at Evans HQ are at least now working with me to find a suitable solution.

    Having now experienced this I will make sure that any future purchases are made only after testing, especially if I was going to consider a remote buy over the internet.

    I would still go wireless every time, and would probably use Evans again, just not my local store, I pass enough on my travels and there is always Evans online.

    1. Hi Steven, Thanks very much for taking the time to post regarding your experience. Do let us know what combination of light(s) and computer you end up using if you find a combination that works and if you get any feedback from Evans on specific models they’ve tried.

  3. I have two Sigma computers, none are wireless because I got tired of the short life expectancy of wireless computers, the longest life I got out of one was 4 years and that was out of 3 different brands! All the units that failed were due to the sending unit failing.

    In addition the interference with bar mounted lights causing strange problems, high powered electrical overhead lines doing weird stuff, they were very prone to not working in cold weather compared to wired jobs, and a minor nuisance was the sending unit battery would last about 6 to 8 months.

    I haven’t ever tried a Sigma brand wireless and I won’t, but I really like their wired 1609 computer, it has all the features I could ever use, and it’s been very reliable even in down pouring rain and cold weather, plus no interference issues whatsoever and no sending unit battery to replace.

    Some people don’t care about reliability because they want the clean wireless look, but I’m the kind of person that can’t logically think of a reason why I should have to buy a new computer every 3 years vs every 15 years or more and pay more money and get less features with a wireless. That just doesn’t compute!

  4. I hope this is a usefull addition to the information you are gathering. I too have had light/wireless computer interference problems. I am using two different Lezyne micro-drive front lights and a Sigma 8.12 computer. The symptoms are the same: computer freezes with the readings at the point of switching on the light. The computer display is about two inches from the light. I tried moving it further away but the symptoms persist with the light positioned anywhere on the handlebars.

    On my Brompton, the Lezyne lights were fine with my Cateye computer but this changed when I converted my Brompton to electric assist and the front-hub motor played havoc with the wireless setup! The speed readout stayed at zero.

    I have now gone to i-Phone in a tube bag and reverted to a Cateye wired computer for the Brompton.

    I hope that the light, computer and electric motor designers start colluding soon because, in the shops I have tried, it is getting harder to find wired computers in the UK (loads in Japan). That said, I hope I don’t need to buy any more computers – properly designed computers should last the life of the bike they are fitted to.

    Does anyone still remember those odometer mechanical counters fitted on the front forks?…………………..

  5. I have had the Smart lux 35 light for a while and got no interference in my Cateye Micro wireless computer. I have recently bought a second front light of the same make and model and this causes my speed display to zero. It only happens when I use the new light. I have tried moving it further away from the cateye and changing sides but to no avail. The original light causes no issues what so ever.

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