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Sun Company makes a clip-on bike thermometer that looks nice. Even the good reviews say it's hard to read tho.

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Does anyone have one? Are you able to read it without stopping?

I thought about attaching a keychain thermometer somehow but that would probably be hard to read too.

Anyone know of a better product? All could find was this one and a chinese motorcycle version that looks chintzy.

user66598
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    Personally, I would not trust more the reading of a thermometer that is exposed to the sunlight and to the elements than what I could get by looking at a weather app on the phone/watch. – Rеnаud Jan 24 '24 at 22:11
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    Not an answer to your question, but:
    • if you need a temperature value "right now", this thing will give a value as good as your gut estimates (at best);
    • if you need a temperature value "at debriefing of your ride" ... just check one of the thousand temperature historical record available in the net for your location. Unless your bike is rocket propelled going at Mach>2 for sustained times, you will be able to track temperature across different towns with enough time resolution.
     – EarlGrey Jan 24 '24 at 23:26
  • very good point about sunlight. I would think they designed it with that in mind but it's probably not a safe assumption. When I get one I'll play with moving it under my phone mount so it's shaded and see if that matters. – user66598 Jan 25 '24 at 01:42
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    I'm in the middle of nowhere and app-reported temperatures are usually wrong. That's the only reason I'm finally buying a thermometer. I finally wondered "what's the actual temp?" too many times. – user66598 Jan 25 '24 at 01:43
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    In mountains, the actual temperature may be very different from that "the cloud" reports, as it depends on the elevation. Also, mobile internet does not always work there. – nightrider Jan 25 '24 at 08:57
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    @user66598 physics says they can't possibly design a thermometer that reads a sensible air temperature in direct sunlight (the power of which varies with time, date, and latitude) le alone one that also works in shade. The black casing says they didn't even try to minimise solar heating. A thermometer placed in a light-coloured bag udder the top-tube would probably be best, then you'd have to get it out to read it – Chris H Jan 25 '24 at 11:02
  • @user66598 good point about remote areas. Getting a temperature reading is not difficult, having the correct one is another one, that's what I meant by "not trusting more": both are probably as wrong. Another point is that the concept of perceived temperature (that includes wind and humidity) is probably more important in cycling than the actual temperature. I would also not trust that they designed it with "sunlight in mind", because then you'd need irradiation measurements (how could it be able to distinguish the same temperature under cloud cover and in direct sunlight). – Rеnаud Jan 25 '24 at 12:03
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    This thing will just get hot in the sunlight. I would not trust it at all. – Vladimir F Героям слава Jan 25 '24 at 13:31
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    as an engineer I strongly suspect it would be possible to design a thermometer that would be accurate in sun or shade. It would likely need some vents, insulation and/or sun shields cleverly positioned. You could also potentially take advantage of the temp difference between black and white surfaces to correct the reading. It would almost certainly cost too much. – user66598 Jan 25 '24 at 15:26
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    @user66598 if you fancy riding around with a Stevenson screen on your bike you could get something approaching decent. Even they get some solar gain (white paint being no more than about 90% reflective). The constraint of practicality was implied (with you the engineer and me the physicist, that feels like the wrong way round). – Chris H Jan 25 '24 at 16:59
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    I would rotate it scale down on the handlebars to stay in the shade. I would rotate it the scale up to read when I want, then rotate back. – nightrider Jan 25 '24 at 17:35
  • We're ignoring the effects of wind as well and they're not always negligible around here. I've designed shade structures for equipment racks I was working on in Arizona. They only needed shade during the peak hours when insolation is highest. 10 am to 2 pm. This is a more sensitive application but I do think shading the device under a phone mount or handlebar would work fine. Maybe leaving it in the sun/wind would be desireable and read as the "real feel" instead of raw temp. – user66598 Jan 25 '24 at 17:44
  • @user66598 The "real feel" under the solar radiation is hard to define (e.g. https://en.wikipedia.org/wiki/Mean_radiant_temperature or Physiologically Equivalent Temperature PET) and by no means it is indicted by just an irradiated thermometer. Some kinds of thermometers are actually not too affected by direct radiation - thin thermocouples or thermistors used on radiosondes or meteorological towers. – Vladimir F Героям слава Jan 26 '24 at 16:19
  • Don't forget the effect of wind is different on wet skin, dry skin, covered skin, and plastic (in descending order of magnitude over some relevant materials). And if you start getting into apparent temperature you have to deal with humidity as well. Measuring just air temperature is probably more consistent, then making some allowance for other factors – Chris H Jan 26 '24 at 16:46
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    Thanks for the update. I imagine this wouldn't get any better during warmer periods of the year. I use my thermometer to react to temperature changes before I get too cold or warm in changing conditions, so this might not be the product for constant monitoring if you have to flip it or stop for a reading. But for the money, it does the job, at least in certain conditions. – DoNuT Mar 02 '24 at 16:12
  • Perhaps consider this as a comparative tool, not a direct-measurement. So "it was 5 degrees at the start of the ride and now its 20 degrees, an increase of 15 degrees" Or engineer a flip-up cover like old army wrist-watches have. – Criggie Mar 02 '24 at 21:02
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    What are you trying to accomplish with such a thing in the first place? – whatsisname Mar 03 '24 at 07:09
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    seriously? first, curiosity and weather forecast validation. 2nd, I've been experimenting with biking in colder weather. It can be fun but only if I'm dressed right. I've got several outfits assembled and am using the thermometer to determine what temperature range they're each good for. Most people just look up the temperature on their phones but I'm in the middle of nowhere and phones are often totally wrong. – user66598 Mar 03 '24 at 16:16
  • @DoNuT what thermometer do you use? The Sun Company clip-on thermometer just broke on the 3rd ride. It should probably be labeled as "not compatible" with drop bars. – user66598 Mar 16 '24 at 15:54
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    @user66598 I just use my Garmin 540s thermometer. – DoNuT Mar 16 '24 at 17:10

3 Answers3

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Probably worth noting, some bike computers (can) have temperature sensors, even if it is not advertised on the product pages or listed among the available sensors. Based on the comments of DoNuT and Vladimir F, the presence of a barometer is a serious hint of the presence of a thermometer (necessary to correct barometric measures).

On the existing products:

  • Some "basic" computers offer temperature readings (Sigma seems to include temperature quite fast — even on 30€ wired computers, Cateye reserves it to the top of the range).
  • looks like all Wahoo have one (the most basic has one, so I'm assuming others have one as well).
  • Garmin Edge Explore 2, Edge 510 upwards have one (and probably the higher models as well) — thanks to the commenters for the info.
  • Garmin sells an external temperature sensor — wireless (which allows to place it on a better location than the handlebar).

If you already have a bike computer, it may be worth investing the available fields that can be displayed, and if there's a temperature sensor, temperature should be listed among the data to be displayed.

It can be the case of other brands as well, I haven't done an extensive research.

DoNuT
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Rеnаud
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    Garmin definitely has internal sensors, I think the external one is mostly used as addon for devices that have none or of which you don't get realistic readings from, for example because you carry your GPS tracker in the backpack and still want to pair it with the external sensor somewhere exposed on the outside. – DoNuT Jan 25 '24 at 10:43
  • @DoNuT Good to know, I looked at the specs list of some Garmin computers (520+, 1030, 1040) and drew my conclusion based on the absence of temperature sensor in the specs. But if you have one with temperature sensors, might be useful to list the model (Wahoo doesn't list it either in the spec sheet). – Rеnаud Jan 25 '24 at 10:59
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    Also the Explore 2 does have a temperature sensor. These days the (often Bosch, e.g. BMP 280) miniature sensors used to measure the air pressure usually also measure the air temperature and/or air humidity. – Vladimir F Героям слава Jan 25 '24 at 13:28
  • well now you're bringing up a whole separate question. I use an old smartphone with the Supercycle bike computer app to record my rides and then upload them to Strava. I send the author money once a year and it's still much cheaper than using the Strava app. The app does almost everything imaginable. What's the benefit of a real bike computer? – user66598 Jan 25 '24 at 15:28
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    @user66598 it's indeed a totally different question, and it depends obviously on the bike computer. This question may interest you: https://bicycles.stackexchange.com/questions/62502/dedicated-bike-gps-computer-over-smartphone/82121#82121 (but it's mostly about advanced bike computers, not the basic ones) – Rеnаud Jan 25 '24 at 15:55
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    Most microcontrollers have temperature reading built in, chargeable devices often have a second one in power management IC, and air pressure sensors typically have another one. So it's just a question whether to show the temperature in UI. – ojs Jan 25 '24 at 20:25
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    @ojs Yeah but on a bike computer, you would expect temperature readings to be from a purpose-built sensor and not just some sensor that shows an internal value impacted by factors like charging or warming circuits. It is a design decision to show values and in the end, users somewhat rely on the readings and it should at least be in the right ballpark. My feeling is that at least while riding, Garmin computers do a decent job but you have to take readings with a grain of salt initially (lets say the first 5 minutes in cold conditions) or after you stopped in sunlight.... – DoNuT Jan 26 '24 at 09:25
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    @DoNuT I understand the concern, but in practice the built in temperature readings are surprisingly accurate. For example, I have two cheap Sigma bike computers that very probably don't have a dedicated temperature sensor. They both show temperatures within 0.5 celsius from a calibrated thermometer, which actually closer than a non-calibrated dedicated thermometer. The battery-powered bike computers run for months on a coin cell so I doubt there is much heat from power dissipation, but direct sunlight and remaining heat after taking the device out of house are of course error sources. – ojs Jan 26 '24 at 16:59
  • @ojs Those sensors are to protect the device and don't measure ambient temp. Most lithium batteries also have temp sensors to shut off the charger in the event of thermal runaway. Otherwise they explode. Every smartphone has numerous temperature sensors in it but it's rare to find one that has a sensor measuring ambient temperature. – user66598 Jan 26 '24 at 17:01
  • @user66598 please read my previous comment. – ojs Jan 26 '24 at 17:03
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I do not think it would be hard to read as there are many readings on E bike display that have very comparable size and you only need to spot where the arrow is. Gear indicator, if present, is also about of this size and easily readable.

In any case it is not something you would look at very often, but if very hot or very cold, may be interesting to talk about later.

nightrider
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  • Thanks for a 2nd opinion. We agree! On my ride earlier I decided that I'd probably only look at the thermometer once or twice per hour, and even if I have to duck my head a few inches to read it that won't be a big deal. – user66598 Jan 25 '24 at 01:40
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I took this thing and my most accurate thermometer on a ride to compare readings. Even in winter the mid-day sun caused the clip-on thermometer to read more than 10 degrees above the actual temperature. Twisting the thermometer so the handlebar shades it and then flipping it up to read solved that problem and the thermometers were within a degree or two of each other after that.

Having to flip it up like that means it's not really readable while riding (cables are in the way so it takes two hands) but having to stop makes the fact that it's a bit tiny less of a problem.

A bigger concern might be that it's made for bars of 1" diameter or less. My gravel bike's bares are 1" on the ends but larger in the center. The thermometer barely fits on the bar right where the tape starts.

Ultimately it's a usable product and I think will be more or less worth the price (˜$13 I think).

user66598
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    it broke. i got about 3.75 rides out of it for $13. The first ride it read 10 degrees high due to being in the sun. The 2nd ride I used an accurate thermometer to determine that this thermometer was accurate if kept in the shade by twisting it. 3/4 thru the 3rd ride it broke from catching on the brake cable when I twisted it. I have drop bars on this gravel bike and the thermometer barely fit between the end of the bar tape and where the bar increases in size. It might last longer on flat bars with nothing in the way. – user66598 Mar 16 '24 at 15:26