No-Battery Pressure Sensors For Bike Tyres

Finding out you’ve got a flat tyres halfway into a long ride is a frustrating experience for a cyclist. Maintaining the

While the epoxy does a great job of sealing the PCB to the valve extension, the overmoulding process would likely be key to producing a product with shelf-quality fit and finish. This test run was done with 3D printed ABS moulds.

correct tyre pressures is key to a good ride, whether you’re stacking up the miles on the road or tackling tricky single track in the mountains. [CaptMcAllister] has put together a device that makes keeping an eye on your tyres easy.

The device consists of an ultra low power microcontroller from Texas Instruments, paired with a pressure sensor. Set up for Near Field Communication, or NFC, it’s designed to be powered by the smartphone that queries the microcontroller for a reading. We featured a prototype back in 2015 which required mounting the device within the inner tube of the tyre itself. However, this required invasive installation and the devices tended to wear out over time due to flex damaging the delicate copper coil antenna.

The new design consists of the same microcontroller hardware, but mounted in a modified valve extension that fits to the fill valve of the bicycle tyre. The PCB is directly epoxied on to the valve extension, ensuring air can’t leak out over time. The assembly is then overmoulded in an injection moulding process to provide further sealing and protection against the elements. This should help immensely in rough-and-tumble mountain biking applications.

The new device provides a simple screw-on solution for tire pressure monitoring that’s set and forget — no batteries required. [CaptMcAllister] is currently investigating options for a production run, and given the simple design, we imagine it couldn’t be too hard to rattle off a few hundred or thousand units. We could imagine it would also pair well with a microcontroller, NFC reader, and a display setup on the handlebars to give live readings where required. We look forward in earnest to seeing where this project goes next!

53 thoughts on “No-Battery Pressure Sensors For Bike Tyres

  1. I made the mistake of installing urethane rubber strips inside my bike tires to “protect” from flats due to thorns, glass, etc. I suddenly started having more flat tires than ever because the edge/corners of the urethane strip abraded the tube enough to wear holes in it. It took me a few flat repairs before I figured out what was happening. I took out the urethane strips and the problem went away.

    You can buy tire pressure indicator valve caps for cars that just have a green indicator that tells you if the tire has pressure. I put some of those on my wife’s car once. Within a month one of them broke (maybe she hit a branch or maybe the device was poorly assembled) and left her at the side of the road with a flat tire.

    This device is interesting, but here’s the problem with anything that screws onto the valve stem: if it comes loose, it will leak air and cause a flat tire (tyre). I wouldn’t trust it.

    1. I agree. Screwing things ONTO the valve stem and depressing the valve core pin constantly is not a good idea for the reason you mention. However, this screws INTO the valve stem. You take the valve core out of the valve stem, this extension goes in place of the valve core and the valve core goes back into the top of this extension. It really presents no more risk of leaking than the valve core itself.

        1. The extension is between the valve core and the tire, so it’s exposed to the pressure inside the tire and the valve core still keeps everything in. The extension is effectively just a hollow tube that goes between the valve and the valve core. So the key is that this type of extension only works with removable valve cores, which are pretty common for Presta valve-type tubes. Not all Presta tubes have removable cores though. In the even that the core isn’t removable, you’d have to use a different type of extension that would be somewhat more prone to leaking.

      1. I don’t see how there’s much difference between screwing onto the stem and screwing into the stem. Either way you’ve added another surface exposed to the high pressure inside the tire and if whatever is screwed into or onto the stem loosens, the air is going to leak.

    2. What is this? A joke? Have you ever heared of TubeLess setup? I ride MTB bicycle, about 3000 to 5000km each season. And I just had one flat, within last 7 years I’m running tubeless , it was when I managed to cut 5cm long hole in a sidewall of my rear tire.
      StansNoTubes Race sealant is the best out there, so ditch those inserts, buy tubeless kit and perform that huge step forward from flats.
      And yeah, I’m checking pressure every time before my ride. You know, often my life depends on this simple action, especially in mountains.

      1. Tubeless setups are not for everyone.
        You have to have special rims and tires/tyres. The setup process is messy and needs a suitable pump.
        If you have a flat/have to reinstall your tire, you have to fill in milk, which costs quite a bit.
        Tubeless tires ar more expensive and not available in all sizes (are there TL tires in 26″? 20″?).
        One real advantage is the ability to run really low pressure, but this applies to MTBs only.
        For a commuter/cargo bike/kids bike etc. running a reasonably puncture proof tire (e.g. some variant of Schwalbe Marathon) is enough to prevent flats.

        That being said, recently I converted my tourer/gravel bike/commuter to tubeless and couldn’t be happier.
        But it takes a little dedication that the pragmatic cyclist probably lacks.

      2. This is not mutually exclusive with running a tubeless tire. You also just said you check the pressure every time.. so this device would be very useful since it lets you check it without even touching the bike. Just saying.. you’re making a good case for it :))

      3. IMO, tubeless is garbage for anything high pressure.

        I ran some tubeless specific tires with stan’s tape and sealant on my road bike years ago, when road tubeless was pretty much brand new. It seemed alright until I got a flat, and it didn’t stop it until the tire was down to 30psi or so. That was enough that I could carefully roll on it, until I got to a gas station to use their compressor, but then when I got the tire up above 60psi (still well below the minimum recommended for a 23mm road tire) the hole started losing air again. I shook it around, but it had already lost most of the sealant during the original leak down. I ended up with a tire that wouldn’t hold air, and which was virtually impossible to get off the rim (Those early ones were insanely tight fitting). I had to catch a ride home, because there was no way to fix it.

        More recently, I tried it again with some newer, easier fitting tires which are also a bit wider and run around 80psi at max. I didn’t get any flats on the road with them, but the sealant does need to be replaced every 4 months or so, which is an added expense, and both wheels eventually failed when the rim tape was eventually cut by the constant air pressure through the spoke holes, as a bonus, it blows the inside of your rim full of stanky old sealant that’s difficult to wash out. Both times it happened I wasn’t even riding the bike, it was just sitting there leaning against my wall. The second time was late at night, the night before I was getting up early to do a 100km sportif. After cleaning the smelly old sealant out, and putting a tube back in the tire after midnight so I could still make it to the ride in the morning, I decided that it’s totally not worth it.
        In the 2+ years since then, I’ve had exactly zero flat tires on that bike.

        If you want to avoid flats, get good tires and tubes, and keep them at a reasonable pressure. Forget the gimmicks.

        If you still get a lot of flats, try switching to a different brand of tires.

        I used to get flats frequently using a very popular brand of tire (probably once every couple weeks on average), and almost as often when I switched to a different model of that same brand, marketed as flat resistant. Since switching to other brands, I’ve rarely had any problems.

        In the case of large, low pressure mountain bike tires, there might be enough advantages to make it worth the faff, but on the road, there’s far more cons than pros.

    1. now where is the fun in that? no 555? no arduino. just a pump and a tire….

      for me its KISS all the way.
      Although, seeing what kind of balloon tires are placed on mere 18mm rims makes me shiver.
      Oh and of course my tire pump has a pressure meter built in. It cost me 10 euro’s…

    2. So there’s a few different use cases for this sensor that I’ve seen. For road bikers, it’s probably most useful when you get a flat and you don’t have a pressure gauge or decent pump. It tells you when you’ve pumped enough with your exhausting hand pump or when your CO2 inflator is overinflating your tire. Mountain bikers, cyclocross, and fat tire bikers often fine tune their pressure based on conditions. This allows you to adjust pressure on the trail with your hand pump.

      You can also use it as a quick check if you’re riding a road bike each day. Connecting a floor pump to the tire charges the hose with the tire pressure and it drops the pressure in the tire, forcing you to pump. 90% of the time, you could just check and go. Doesn’t save a ton of time, but if you already have the sensor installed for fine-tuning or fixing flats, it’s a nice feature.

      1. If you ride your bike every day (I’ve done that for years), then you check it once in a while. If it was good yesterday, it’s still okay today, unless there’s a leak (which will be obvious). You can also look at the deformation while riding, or give it a quick squeeze with your thumb.

    3. What about when you’re just nipping to the shops? It’s only a 10 minute ride, you’d spend a good chunk of that checking the pressure. I think that’s where I see the most use, utility bikes where a process too long to bother with for short hops can be replaced by a quick check with a phone.

    4. Exactly. An invention for a non-existing issue. Realtime pressure sensors would be neat (not need), though, assuming the battery life was any good (and no, not a week or two, but like a year).

      1. If it does become an issue, it’s not so hard to construct a basic plastic truss that goes to the nearest spokes. Bam now it’s structural, mjrippe’s scenario abated.

        Nice work on the sealing around the sensor!

  2. Its not a product I would make use of (my three year old checks my bike tyres before I go out on my bike, if he says there ok Im good to go ) of but I could see some potential particularly if you were into optimizing tyre pressure in the field.

    The injection molding bit was interesting – using mold made of of 3d Printed ABS does work!

    1. Nice work – I can think of a number of scenarios this would be useful in.

      I don’t understand all the critical comments. Even if this isn’t product worthy as some commenters imply it should be, it’s still interesting.

      To all the naysayers, I guess the saying is true: it’s easier to destroy than to create.

  3. This is neat I suppose… But road bike tires rarely hold pressure sufficient to ride without pinchflatting more than a few days. This strikes me as more of a mtb thing. Or maybe ebike. Or rental City bike? Would only be useful at low speeds I’m home, as it would seriously unballance my tire/wheel at my common descent speeds of 30-50 mph.

      1. Yeah, unless you’re on latex tubes, that’s a bit of an exaggeration, but the point is still valid.
        On skinny road tires, I find that they’ve usually lost enough air that I’d want to top them up roughly weekly. (from ~100PSI down to ~85)
        I think it would be another week before it would be low enough for much danger of pinch flats unless you’re bashing curbs on a regular basis.

    1. 30-50 mph is up to 80km/h I thought the device is intended for bicycles, not motorbikes. Or do you ride an overpowerded e-bike (more than 25 km/h for an e-bike would not be street legal here)

      1. “Descent speeds,” as in speeds attainable while riding down a long, steep hill. I hit 30 mph for short stretches on most of my rides around here, and there are a couple hills where I can get over 40 mph pretty easily.

    1. This isn’t really intended to be a real time monitor. There are other, much more expensive (and heavier!) products for that. This is a way to do quick spot checks before a ride, on the road, or on the trail. It enables you to spot check your pressure with the one thing you carry with you everywhere – your phone.

  4. aw, part of me thought that maybe a tiny pinwheel powered by the rushing air was providing just enough generated electricity to run a microcontroller for a few seconds.

    1. Now that’s a good question. My opinion is that expensive, battery powered sensors that pair via Bluetooth or ANT+ are just unnecessary. As many snarky comments here have said, why do you need to know your pressure WHILE you’re riding? Most people I’ve talked to think you don’t need real time monitoring. I do think a cost-effective pre-ride spot check to fine-tune pressure when you don’t have your floor pump is an unmet need though. That’s why I developed this sensor.

    1. Heh, you could say that about so much bike equipment: carbon fiber? Clipless pedals? Bike computers? If you need those you should not be riding /s

      I ride and my pressure gauge is on the pump itself. So even if I don’t need air, I’ve already gone to the trouble of getting it hooked up. When it comes to the use case, would be nice to do a quick scan with my phone and see if I need to get the pump out. (Incidentally, yes I need a top off every single ride.)

      On the technological standpoint, this is the first time I’ve seen an opportunity to use one of these NFC sensors in any part of my day-to-day. That’s pretty neat. I find the manufacturing technique even cooler!

      1. Incidentally, the reason you always need a topoff when you hook up the pump is because hooking up the pump charges the pump hose with pressure, depressurizing the tire slightly. So if you use your pump to check the pressure, you HAVE to put some air in or just live with the depressurization. Most of the time, you really don’t need to even hook up the pump, and checking the pressure without hooking up the pump is what I’d use this for the most. But what I’d VALUE the most is being able to confidently fix a flat and keep riding. Several people have said just pump the flat, pinch test it, and ride home, and that’s fine if I want to ride home slowly and carefully. But I want to keep riding confidently, and this allows me to do that. I developed the concept during a 100 mile ride after I got a flat on mile 6. That day, I did just pump up as much as I felt like and struggled through the next 5 miles on a tire that only had about 60 psi in it (those hand pumps are exhausting), until I could get to a rest stop with a floor pump to know my real pressure – fortunately that one was a supported ride.

        It seems like a lot of commenters either think real-time pressure monitoring is not necessary (I agree, and that’s why this isn’t real-time), or maybe are just happy riding with a large range of tire pressure. I don’t think that’s true for all of us who ride, and this concept would be for those people.

        Plus, I really did have a lot of fun coming up with the manufacturing concept. Who knew that you could injection mold into FDM printed ABS?

        1. I don’t mean this in a negative way, as I’ve done plenty of impractical projects myself, just for fun, but I don’t think there’s much practical point to this. I still think it’s cool, and has some neat techniques, even if I don’t see it as particularly useful, though.

          If you’re using low volume high pressure road bike tires, they lose air pretty quickly on their own, and not just because of the pump.
          I would top up my tires before any time I’m planning a long ride, because if I haven’t filled them lately, they’re probably a little low, and I’ll see that from the gauge on my pump when I connect it.
          For normal day to day riding, I’m not super picky, but I would tend to pump the tires up once a week or so from the 85psi or so they would end up at, back to 100 (On a tire that feels best at 90-95)
          If I forget, I’ll feel it before they get low enough that I would be worried about pinch flats.
          If I get a flat, I just fill it up until it feels right when I ride. If it’s too soft, I’ll just stop and put a little more pressure in.
          I’ve never been super picky, though, nor do I think there’s any reason to be. Generally tires are rated for considerably more pressure than will be ideal for rolling resistance, so If I just fill them until they’re hard enough (by feel after riding a little bit, not a “pinch test”), they’re close enough to finish the ride without any significant performance/safety penalty.

          BTW, I would suggest trying a few different hand pumps and finding one that’s much lower volume. On a road bike with skinny 23/25mm tires, I typically want something that will take a couple hundred pumps to fill the tire to 100PSI. it might take a tiny bit longer, but it’s easy to do, and you won’t end up with “only 60 psi”
          Some hand pumps are definitely more suited to big mountain bike tires. If you’re filling a big tire to 15-20PSI, you want a high volume so you can fill that large volume quickly, and you’re never filling it to a high enough pressure for the pump to get hard to push.
          Fill a mountain bike tire with a road bike pump and you’ll be pumping for 5 min to get it filled.
          Fill a road bike tire with a mountain bike pump and you’ll have trouble getting enough pressure, and you’ll tire your arms out.

  5. Combine this with the speed/odometer’s that are already widely available… trip the NFC the first rotation of the wheel, turn it off once it gets a reading to save power, throw an alarm if the pressure is low…

    Net effect, check your tires automatically when you are slowly rolling the bike out of the garage, or back off the bike rack, get a notification of some sort if the pressure is low, otherwise, go for a ride, and not be pumping milliamps into the NFC system all the time for a real time read out.

  6. This is pretty cool. I race enduro and DH mtb and I pump my tires above desired inflation, then deflate using an accurate analog gauge to reach my desired psi before each ride. It’d be nice if there was an led somewhere to indicate if your psi is within 1-2 of desired and an alarm function if psi drops suddenly.

    You probably know there is already a commercial solution from Sram/Quark called Tirewiz, but it does require batteries. Does it handle tubeless sealant ok? You’d probably also want to balance the weight of these with a counterweight, especially on lightweight road wheel/tires.

  7. I’m always excited by gizmos, even when the actual need is not yet obvious, or when a suitable target demographic has not yet been identified. Keep going with pushing concepts like this, and let the market (not closed minds) decide if it’s useful or not.

    NFC is very short range: a few inches at most.
    Slightly longer range could allow your smart gps unit to warn you of slow punctures, or track your performance against tyre pressure (as well as heart rate, cadence, speed, sleep, biorhythms,…).

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