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Tech No battery tire pressure sensor - lasts forever!

Rover Dev

Warming-Up
Jun 5, 2021
2
3
Hello! We have developed a batteryless pressure sensor for bike tires. Just thread it on your valve, pump up your tire and hold your phone up to it. The app launches and you get an instant reading as shown here. (Note that the sensor shown here is much longer than the production sensor will be).
c3dc24e6175aafe277d8563790e5e847_original.gif


The sensor is extremely accurate (+/- 0.06 psi), and lightweight (<5 g). Since there's no battery, it can last effectively forever - use it and reuse it over and over every time you change your tires.

We're currently running a Kickstarter and I've received a really high amount of contacts from Japan wanting to sell this sensor, and I'm not sure why. I'm interested in learning if the people here think this sensor would be of interest for the Japanese market. It certainly has a gadget factor, and it does work really well. Don't take my word for it though - check out this exclusive review: https://bikerumor.com/2021/05/25/ex...re-monitor-is-accurate-tubeless-battery-free/

Anyway, I'd love to hear what this group thinks about the concept. I'd also like to know if anyone has any ideas for websites we could use to advertise this sensor. If you're interested in learning more, links are:
Link to Kickstarter
Link to Rover Development
 

andywood

Maximum Pace
Apr 8, 2008
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Hello! We have developed a batteryless pressure sensor for bike tires. Just thread it on your valve, pump up your tire and hold your phone up to it. The app launches and you get an instant reading as shown here. (Note that the sensor shown here is much longer than the production sensor will be).
c3dc24e6175aafe277d8563790e5e847_original.gif


The sensor is extremely accurate (+/- 0.06 psi), and lightweight (<5 g). Since there's no battery, it can last effectively forever - use it and reuse it over and over every time you change your tires.

We're currently running a Kickstarter and I've received a really high amount of contacts from Japan wanting to sell this sensor, and I'm not sure why. I'm interested in learning if the people here think this sensor would be of interest for the Japanese market. It certainly has a gadget factor, and it does work really well. Don't take my word for it though - check out this exclusive review: https://bikerumor.com/2021/05/25/ex...re-monitor-is-accurate-tubeless-battery-free/

Anyway, I'd love to hear what this group thinks about the concept. I'd also like to know if anyone has any ideas for websites we could use to advertise this sensor. If you're interested in learning more, links are:
Link to Kickstarter
Link to Rover Development

Looks like a neat product.

In my experience most people riding road are happy to inflate their tyres before a ride or race and are happy enough with the accuracy of their floor pump.

Cyclocross, MTB and gravel riders are much more concerned about tyre pressure. Most are happy enough to go to one decimal place. For example, a guy I rode with yesterday had 1.9 bar front and rear, I had 2.4 bar rear, 1.4 bar front.

We use a portable gauge for this.

The big benefit of your product is it removes the need to carry the guage.

My concern would be the valve length. Riding off road, you get lots of branches in the spokes and valves can be broken. The shorter the valve the better. Also running, what are essentially extension valves, there is the increased chance of air leakage or other problems.

The bike radar review mentions the problem of lining up the unit aero with the spokes. I think this would be less of a concern for off road riders.

But yes, it looks like a product that would interest the Japanese market.

If you want somebody to test them and write a review in Japanese, give me a shout.

Cheers, Andy
 

Rover Dev

Warming-Up
Jun 5, 2021
2
3
My concern would be the valve length. Riding off road, you get lots of branches in the spokes and valves can be broken. The shorter the valve the better. Also running, what are essentially extension valves, there is the increased chance of air leakage or other problems.


But yes, it looks like a product that would interest the Japanese market.
Thanks, Andy. We also agree that the sensor is too long, so we cut 10 mm off the length to bring the total length to 30 mm - much smaller than the image we linked above. It's hard to get much below that with an extension because we need to have room for the pump and the antenna can't be made too much smaller. IF the extension reaches its goal, we'll develop a version that is just a valve - not an extension. This would shorten it a lot, but it would only work with tubeless tires. We built the extension first so that it would work with tubes or tubeless.

We may take you up on the review offer when we have more sensors. In the meantime, do you have any suggestions of websites or forums that we could reach potential Japanese Kickstarter backers? We're trending toward barely meeting our goal right now. If we don't get funded, I'm not sure we'd try to keep building this. We have virtually no backers from Japan currently, so maybe we could find some to bring us over the goal.
 

andywood

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Apr 8, 2008
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Thanks, Andy. We also agree that the sensor is too long, so we cut 10 mm off the length to bring the total length to 30 mm - much smaller than the image we linked above. It's hard to get much below that with an extension because we need to have room for the pump and the antenna can't be made too much smaller. IF the extension reaches its goal, we'll develop a version that is just a valve - not an extension. This would shorten it a lot, but it would only work with tubeless tires. We built the extension first so that it would work with tubes or tubeless.

We may take you up on the review offer when we have more sensors. In the meantime, do you have any suggestions of websites or forums that we could reach potential Japanese Kickstarter backers? We're trending toward barely meeting our goal right now. If we don't get funded, I'm not sure we'd try to keep building this. We have virtually no backers from Japan currently, so maybe we could find some to bring us over the goal.
I thought about having it as a tubeless valve, but is it not a problem that you have insert the valve from inside the rim? Unless the unit is detachable?

For reaching a Japanese audience and kickstarter backers, the best way may be to try to get a review (either the bikeromor one translated, or an independent one) on the cyclingtime website.

Andy

 

OreoCookie

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Dec 2, 2017
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A few comments:

- The price seems good (about $30 per sensor on Kickstarter). If that is close to the retail price, you’ll definitely have a market even with the limitations.
- I think you should offer an aero cover. The sensor will produce a shirtload of drag otherwise. Personally, this kills the product for me.
- I’m not sure how practical it would be to use the pressure gauge with a portable pump — I need both hands just for the pump, so a riding buddy would have to hold it.
- I am not sure whether it is smart to permanently affix it to a valve stem. I have average depth aero wheels on my road bike (45 mm deep), and I need valve stems of specific length (I run my tires tubeless).
- I wonder how compatible the system really is with tubeless tires: usually refilling sealant requires you to remove the valve core. Is that even possible with your stem? If not, that would pose a serious challenge for your product.
- The pressure ranges do not seem to make much sense: the LP model has its limit at 40 psi, the HP model goes up to 400 psi. Even hard core old school roadies wouldn’t inflate their tires past 130 psi. Perhaps this is a limitation of the sensors available to you, but I’d want more accuracy than 0.7 psi.
- I think it’d be nice to have pressure stats while riding so that you can check whether you have a slow leak. I know that this requires a battery, etc., but I think this might really be useful.

Despite the limitations, I think this is an interesting product, not least because of the price. If you offered an aero cover, I’d probably buy two. Without ero cover, this is a no go for my and many others’s road bikes, though, which is the majority of the Japanese market. But I might buy two for my mountain bike. Also, I’d be happy to review your sensors if you are interested in that.

If you are interested in getting professional reviewers, you should reach out to GPLama and dcrainmaker. They are the premier sports and cycling gadget reviewers.

We have virtually no backers from Japan currently, so maybe we could find some to bring us over the goal.
Most Japanese do not speak any foreign language, and there is a huge language barrier. I don’t know how many Japanese even know what kickstarter is. But I think this is a product that would appeal to the Japanese market.
 

andywood

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Apr 8, 2008
2,978
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A few comments:

- The price seems good (about $30 per sensor on Kickstarter). If that is close to the retail price, you’ll definitely have a market even with the limitations.
- I think you should offer an aero cover. The sensor will produce a shirtload of drag otherwise. Personally, this kills the product for me.
- I’m not sure how practical it would be to use the pressure gauge with a portable pump — I need both hands just for the pump, so a riding buddy would have to hold it.
- I am not sure whether it is smart to permanently affix it to a valve stem. I have average depth aero wheels on my road bike (45 mm deep), and I need valve stems of specific length (I run my tires tubeless).
- I wonder how compatible the system really is with tubeless tires: usually refilling sealant requires you to remove the valve core. Is that even possible with your stem? If not, that would pose a serious challenge for your product.
- The pressure ranges do not seem to make much sense: the LP model has its limit at 40 psi, the HP model goes up to 400 psi. Even hard core old school roadies wouldn’t inflate their tires past 130 psi. Perhaps this is a limitation of the sensors available to you, but I’d want more accuracy than 0.7 psi.
- I think it’d be nice to have pressure stats while riding so that you can check whether you have a slow leak. I know that this requires a battery, etc., but I think this might really be useful.

Despite the limitations, I think this is an interesting product, not least because of the price. If you offered an aero cover, I’d probably buy two. Without ero cover, this is a no go for my and many others’s road bikes, though, which is the majority of the Japanese market. But I might buy two for my mountain bike. Also, I’d be happy to review your sensors if you are interested in that.

If you are interested in getting professional reviewers, you should reach out to GPLama and dcrainmaker. They are the premier sports and cycling gadget reviewers.


Most Japanese do not speak any foreign language, and there is a huge language barrier. I don’t know how many Japanese even know what kickstarter is. But I think this is a product that would appeal to the Japanese market.

Good points as always.

For points 3 & 4/5,

You would inflate the tyre higher than desired pressure, then let the air out to your desired pressure.

The device would be like an extension valve. For tubeless, it would effectively be your core. However, the base valve would have to extend out of the rim to add sealant with the tyre in situ. This is why I would be concerned about the valve being too long.

Andy
 

OreoCookie

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Dec 2, 2017
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You would inflate the tyre higher than desired pressure, then let the air out to your desired pressure.
You’re right, didn’t think about that.
The device would be like an extension valve. For tubeless, it would effectively be your core. However, the base valve would have to extend out of the rim to add sealant with the tyre in situ. This is why I would be concerned about the valve being too long.
I see. I double checked and this is also how the only other product of the kind I am aware of, Quarq’s Tirewiz (the name was not my idea), works. It is more expensive (MRSP is about 2x of this sensor), but features continuous measurement.

I noticed that Quarq has quick tire pressure calculator. That’d be a nice addition to the app.

Oh, and one more thing about the pressure cutoff between LP and HP models: this is right in the pressure range of gravel bikes and very close to the pressure range of modern rims. (I currently run 50–60 psi on my road wheels.)
 

joewein

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Oct 25, 2011
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Oh, and one more thing about the pressure cutoff between LP and HP models: this is right in the pressure range of gravel bikes and very close to the pressure range of modern rims. (I currently run 50–60 psi on my road wheels.)
Yeah, I also found that an odd value. I run my 42 mm tyres at 3 bar (42 psi) and always considered that low pressure, compared to most other people's tyres for road rides.

OTOH, the 0.7 psi precision for the HP model is 0.05 bar, which to me is plenty. I agree with @andywood, most riders wouldn't care about more than one decimal place, if that. At different times, I will have anything between 3.2 and 2.8 bar in my tyres and definitely won't be able to tell the difference between 3.0 and 3.1. So the only real benefit of a more precise readout to me is to determine the rate of slow air loss over a short period.

My concerns would be that any valve extensions adds a point of failure where leaks can occur (I once had a slow lead from what turned out to be a removable valve core that was loose), plus it makes it mechanically more vulnerable to tree branches and other debris.

My pump has a small extension hose, so not much risk of damaging a longer valve while pumping, but that may be a worry with other pumps. I'd be less concerned about air resistance, but it may be a concern for faster riders.

When I was still using tubeless with sealant, I had issues with clogged valves from sealant refills through the valve but as I've gone back to tubes that's no longer an issue.

Both my floor pump and my bike pump have built-in pressure gauges. The readout from the small pump may not be that precise, but it doesn't really matter for me. I only check the tyre pressure every week or two so this is probably not the product for me.
 

OreoCookie

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Dec 2, 2017
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OTOH, the 0.7 psi precision for the HP model is 0.05 bar, which to me is plenty. I agree with @andywood, most riders wouldn't care about more than one decimal place, if that. At different times, I will have anything between 3.2 and 2.8 bar in my tyres and definitely won't be able to tell the difference between 3.0 and 3.1. So the only real benefit of a more precise readout to me is to determine the rate of slow air loss over a short period.
I can definitely feel smaller pressure differences on my mountain bike. But there the LP variant would work perfectly.

On my road bike, an error of 0.7 psi is borderline — it isn’t unusable, but just a little on the high side. I try to inflate my tires up to +/- 2 psi, which is roughly of the same order of magnitude as the error. If I think from the perspective of a customer that this would appeal to, they are the persnickety type who want to dial in their tire pressures exactly. I’d just be nicer if the HP sensor went up to, say, 150 psi and had only 4 x the error of the LP unit.
 

joewein

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On my road bike, an error of 0.7 psi is borderline — it isn’t unusable, but just a little on the high side.
(I currently run 50–60 psi on my road wheels.)
I'm not sure I understand - you're setting your pressure somewhere within a 10 psi (0.7 bar) range but if the precise value is off by 0.7 psi (0.05 bar) it's is a big deal? Could you please explain! I think a lot of road cyclists, unless they're running quite wide tires, will be running pressures higher than 5 bar / 70 psi, making 0.7 psi an error of less than 1%. We're talking the weight of one full water bottle relative to cyclist weight.
 

OreoCookie

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Just think of the following common scenario: you want to add slightly higher pressures on the rear than the front. I usually run about +2 or +3 psi in the rear. Can I feel the absolute pressure difference, distributed evenly? No. But I think I can tell whether my tire pressures front and rear are balanced (to account for the fact that the rear tire has to carry slightly more load).

More importantly, if I were that kind of person who is interested in a tire pressure sensor, I’d want that dialed in within 1 psi. That’s why I am saying an error of 0.7 psi is borderline, because even if they can‘t tell the difference, they’d like to have their pressures dialed in within 1 psi. Does this arcane unit psi also contribute? Yes.

Also, most newer rims require much lower pressures than 5-6 bar/70+ psi. If you look at the recommended pressure tables by Enve or Zipp for wheels of same size and internal width as mine (e. g. Enve 4.5 AR and Zipp 303S), then their recommendation at my body weight is 3.4–3.8/50–57 psi for the road and 10–15 psi lower on gravel (depending on tire width). This will become the norm and the tire pressures in the product shots of 100+ psi will become the exception. Like I wrote, the cutoff of 40 psi is very unfortunate given where modern rims and tires are going.
 

joewein

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Just think of the following common scenario: you want to add slightly higher pressures on the rear than the front. I usually run about +2 or +3 psi in the rear. Can I feel the absolute pressure difference, distributed evenly? No. But I think I can tell whether my tire pressures front and rear are balanced (to account for the fact that the rear tire has to carry slightly more load).

The purpose of the tire pressure is to sustain the load on the tire, which is by no means the same at the front and the rear. There are actually two scenarios to consider, regular riding (including cornering) and braking.

In regular riding, the load will be proportional to weight distribution. Depending on geometry, rider position and luggage carried, this will normally result in anywhere from 30:70 to 40:60 front/rear distribution. This would allow a significantly lower pressure at the front. We have a similar (but opposite) situation in cars, where the engine at the front results in a front weight bias, which is reflected in recommended higher tire pressures for the front.

Against that we have to consider what happens under braking, where load will shift to the front wheel. This is where things are quite different from cars, partly due to the higher center of gravity relative to vehicle length in a bike. As you apply the brakes, the friction between the pads and the rims or disk brake rotor tries to move the frame and rider in the same forward direction of the wheel being braked. This takes weight off the rear wheel and shifts it onto the front wheel. Counteracting it is air resistance on the frontal area of the bike (largely the cyclist) which pushes in the opposite direction and adds weight to the rear (a little bit like a spoiler on the trunk of a sports car that generates down force for high speed cornering). As speed drops, the rear brake becomes less effective and eventually the rear wheel of the bike may even lift up. At that point you need to quickly ease off on the front brake!

In any case, the front wheel handles much more load during braking and that needs to be taken into account when setting the tire pressures. If you were to simply apply the for example, 30:70 ratio from the normal weight distribution to give both tires the same wheel drop when loaded, it would optimise overall efficiency by minimising tire deformation but it would not work well for braking. The front tire would start to collapse and squirm, as it could easily have to handle triple the load of regular steady state riding. When the load on your front wheel goes up to 300 percent of normal while braking, does it really make sense to be concerned about being able to measure the pressure down to less than 1 percent?

There is no simple scientific formula for picking the right tire pressure for front and rear. You will need to find a compromise between pressure by weight distribution (which will give you the most comfortable ride) and a similar pressure front/rear based on the braking scenario (for safety). It is best found through experimentation but I think convenience counts more than precision.


This will become the norm and the tire pressures in the product shots of 100+ psi will become the exception. Like I wrote, the cutoff of 40 psi is very unfortunate given where modern rims and tires are going.
Yes, as road tires become wider, from 23 to 25 to 28 mm and beyond, the need for high pressures decreases as the same load is spread over a wider contact patch. We will see more and more people ride tires with pressures around 40 psi (2.75 bar).
 

OreoCookie

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The purpose of the tire pressure is to sustain the load on the tire, which is by no means the same at the front and the rear. There are actually two scenarios to consider, regular riding (including cornering) and braking.
Excellent points, as always.
I think you should add a third factor: suspension performance. On rigid bikes especially, tires are the softest part of the virtual spring that sits between you and the road. To maximize traction and comfort, I'd opt for a slightly higher pressure in the rear.

But you are totally right, braking shifts weight distribution towards the front (which you can mitigate somewhat with body and toe position).
In any case, the front wheel handles much more load during braking and that needs to be taken into account when setting the tire pressures. If you were to simply apply the for example, 30:70 ratio from the normal weight distribution to give both tires the same wheel drop when loaded, it would optimise overall efficiency by minimising tire deformation but it would not work well for braking. The front tire would start to collapse and squirm, as it could easily have to handle triple the load of regular steady state riding. When the load on your front wheel goes up to 300 percent of normal while braking, does it really make sense to be concerned about being able to measure the pressure down to less than 1 percent?
I certainly would not want to ride a bike where the tires pressures are chosen so as distribute the load more evenly during max braking efforts. When you optimize for handling micro bumps and potholes, putting more pressure in the rear makes sense. Humans on bikes are more like mid-engined cars, on a road bike the center of gravity is close to the bottom bracket.

Neverheless, I think smaller pressure differences are noticeable when it comes to comfort. And small pressure differences become more noticeable the lower the tire pressure is. At 50 psi, 1 psi is already 2 %.
There is no simple scientific formula for picking the right tire pressure for front and rear. You will need to find a compromise between pressure by weight distribution (which will give you the most comfortable ride) and a similar pressure front/rear based on the braking scenario (for safety). It is best found through experimentation but I think convenience counts more than precision.
No, there is no recipe, not least because tire pressure recommendations do not take things like leg length into account: if you have longer legs, you need to raise your seat post, which puts your rumpus — and thus, your center of gravity — further back. Nevertheless, separate pressure recommendations for front and rear tires are IMHO a good starting point (and Zipp does this, for example). Like you wrote, you need to experiment a little. Honestly, a much bigger issue for consistency right now is that every time I check my tire pressure with my floor pump, air escapes, which lowers the pressure. (I am cheap, I haven't spent the ¥¥¥ for a tire pressure gauge.)
Yes, as road tires become wider, from 23 to 25 to 28 mm and beyond, the need for high pressures decreases as the same load is spread over a wider contact patch. We will see more and more people ride tires with pressures around 40 psi (2.75 bar).
Agreed. On mountain bikes, tire inserts have become common, which allow you to run even lower pressures. AFAIK many people haggle over 0.1 bar very easily, so a resolution of <0.05 bar is really a must. (I realize that the LP variant has more than sufficient accuracy.) As tire inserts are becoming more common for people riding gravel, I reckon this will motivate people to ride lower pressures still.
 
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