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I have a Trek Incite 8i wireless bike computer, which I have had for some years working perfectly. Both batteries are new. Recently, on my usual ride, I have found the speedometer reading speeds in excess of 150 mph in a certain street of say 100m length. Leaving that street, speed reduces to normal correct reading. I removed the head unit and stationery in the affected street, the same excess speed readings are shown. So I deduce that my head unit is being affected by radio transmissions from this street, and only this street. I cannot find out if the Incite 8i is analogue or digital? If the former, it sounds like I should buy a digital replacement. If the latter though, I don't know. Should I worry about excessive levels of radiation in that street? It would be good to know what is causing it of course.

Any pointers/advice welcomed Thanks Jonathan

Jonathan Ling
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  • I’m not sure what you mean by analog vs digital in this case. If digital means modern GPS-based head units, maybe analog is the older style of wired computer? – Weiwen Ng Jul 18 '23 at 15:49
  • I'm not sure either, but was picking up from a previous post on the same subject here https://bicycles.stackexchange.com/questions/71817/identifying-extra-triggers-in-a-speedometer where they make that point. The trek Incite 8i is not GPS, just a basic but good quality bike computer. – Jonathan Ling Jul 18 '23 at 16:37
  • There are two causes of extra counts: Reed switch double closure Radio interference (in an analog radio based wireless cyclocomputer) – Jonathan Ling Jul 18 '23 at 16:39

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Yes - EMF interference is absolutely a thing and can mess up the signal between a wireless sensor and the head unit.

  • A fresh battery in the sender/sensor can help with a "louder" transmission, but you've done that.
  • Slide the spoke magnet and sensor up the fork, closer to the head unit. Downside, the magnet is further out and undergoes more centripetal force and can turn easier. plus its further away from the fork tine so the sensor has to be further out.
  • Adjust the position of the head unit a tiny amount. If you move it to the side of the bike where the sensor is and not on centerline, it may help. Also if the head unit is over your handlebar, try moving it in front or behind to see if the bar is masking it. Just hold it there and see if it helps.
  • Check your manual and see if this sender/head unit has switchable channels it can use. Another channel may work better here.
    Sadly this Manual makes no mention of changing wireless channel.
  • Change your route - stop riding through this area?
  • Upgrade to a wired unit? I have a $30 cateye velo-7 and it does speed, clock, ride duration, and odometer. Those are about the only things I really ever look at. Sure, its got a wire, but on the other hand it is immune to wireless interference

Last option is to ignore the speedo readings in this road. That's probably the easiest solution, but also the most annoying.

Criggie
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  • Story Time: I once had a broken reed switch in a wired sensor, and it occasionally reported 2x and 3x my speed because a loose wire was bouncing. Was amusing to jump from 20 km/h to 40 to 60 all at the same effort levels. But that got old fast, and a 10c replacement reed switch along with some hot glue and solder fixed it properly. – Criggie Jul 18 '23 at 22:32
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    Thanks Criggie. I think the RFI or whatever it is causing this behaviour does not relate to the connection between the sender & head unit; reason being that when I am stationery in the affected street, the head unit displays 156 mph (fluctuating). And the same if I remove the head unit and move away from the bike. So the RFI is being picked up by the head unit direct from the airwaves I think. Which is a bit scary. – Jonathan Ling Jul 19 '23 at 16:04
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    I don't want to be beaten by this and have to change my behaviour like avoiding the area, as it is part of my training run (in London) and I don't want to go wired which is a backward step for convenience and looks. I can't ignore the readings either! Changing channel would be good, but as you say Trek give no indication of being able to do that. – Jonathan Ling Jul 19 '23 at 16:04
  • @JonathanLing I wonder what the source is - perhaps there's a ham radio operator living there with a large transmitter? There may be some kind of local council "report a problem" service which could benefit from being informed, perhaps ? – Criggie Jul 19 '23 at 19:29
  • Thanks again Criggie. I had thought the same. I was wondering if I purchased a cheap RFI detector and then could perhaps get a measurement of the amount of radiation in that area and then take that to the local council. It just doesn't seem 'right' to me to have such strong RFI in a street occupied by dozens of people. – Jonathan Ling Jul 19 '23 at 20:53
  • @JonathanLing Its not your problem to fix or ID the cause, and those detectors are not cheap. https://www.snapsendsolve.com/ might be useful here - it directs reports to the appropriate authority for that location. Ask to be kept up to date in the problem report, and see what happens. – Criggie Jul 19 '23 at 22:51
  • I agree that it's not my responsibility; I think that however my local council will not be bothered to investigate without some sort of evidence to demonstrate the issue. I looked at snapsendsolve.com but it appears to be only for Australia and New Zealand. I am in London UK. I will try the council next but you might not hear the outcome for several weeks if their past performance on say potholes is anything to go by! – Jonathan Ling Jul 20 '23 at 10:30