What are your thoughts about external (valve cap) TPMS (tyre pressure monitoring systems) - and for tubed tyres?

Which are options are good and bad? Or are they all more or less useless for the mixed type of riding many of us do?

Checking pressure before every ride, an sometime more than once s day on 5hose long rugged days - is adviceable. I get a bit lazy sometimes...

On spoked wheels with innertubes, a puncture or a blow out can lead to losing air far more rapidly than on a tubeless. Early warning can prevent injury or bike damage. Also, an early warning can save you from having to fix a leak in a very much more iconvenient l8cation than one that is now too far behind you (where you started for the day, or a tyre repair shop that you passed...).

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There is progress to be found in some new tech... ABS, TPMS, GPS...

I travel with both bikes and cars that are 60 year old, and bikes that are brand spanking new. I don't fear new tech any more than the nostalgic old. However, if I can have the better tool for the job, I won't deny myself. I can light a fire like a caveman, but use a lighter 999 times out of a 1000 - like any wise man would. I have done trips of many thousands of kilometers on bicycle style bike seats - but prefer the ergo seats on my other rides. Each to their own I guess - but thinking that other people are doing it wrong because they improve the capabilities of their ride?

I have have been riding 30 yrs without TPMS. Stepping on the wheel, using a gauge, etc... I still want iTPMS (presupposing it is reliable). Checking tyre pressure on a heavy bike with your fingers? Yeah right! Nonsense BS!

I have had more than a few experiences where a TPMS would have saved me a lot of trouble. Only yesterday... I had just packed my car to the brim to take my family on a longer road trip. Right before leaving... I decided on an off chance to check the pressure (using a gauge and not my fingers). Only reason I did was because I had not used the car for a week, and I was killing time waiting for my family to put their shoes on. As I unscrewed the cap half a turn, it blew off from being under pressure. The valve was leaking, and must have for a while as I had lost 1 bar - though not enough to eyeball on the big wheels. The only thing preventing the air from rushing out real fast was a plastic cap, that would have shot off in the first bump I'd hit. I would most definitely have gotten a flat high up in the mountains - in the snow, in the dark, with kids... Had I not checked, and if I had TPMS, I would still have gotten an early warning and still have been ok.

It was a 30 second fix of the valve, and a quick top of with the air compressor at home. A few hours into that drive, the story would have been a lot different if I had not checked.

On another occasion, 12 hours into a high speed ride on the Autobahn, while really fatigued, I noticed I was loosing air - and just in the nick of time before things would have ended bad. That could have been and end of me, and the experience has made me far more disciplined on checking pressure - which has saved me a lot of trouble several times since.

TPMS is something I expect will become obligatory by law in not too many years - again presupposing they can be relied upon and not cause false security. It is a safety thing.

The question is rather if the valve type are any good, not if tyre pressure gadgets is a good idea or not (as long as they work).

And just so that it is known. It is very, very, very adviceable to check tyre pressure frequently and check the valve with a bit of spit. This is especially important before going on a very fast ride - and also every few hours on that ride. Also, before venturing off the beaten track (and every morning of that ride) and right after coming off the rough stuff and heading back onto the fast stuff with all the others - as well as throughout the day if your wheels are taking a beating. Also, after the bike has been standing for a while.

In fact, besides frequent brake checks, I can't think of anything more important thing to be more anal about checking than the condition of your wheels!

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How do these valve cap sensors work? Please tell me it’s not by deliberately ‘bypassing’ the actual valve to read the pressure in the tube /tyre and acting as valve and valve cap rolled into one themselves. If it is then you’re overriding a simple, time served, reliable and critical piece of safety equipment and handing the job to an unknown gadget of unknown provenance, whose only mass market testing is via Amazon star ratings and that may or may not break without warning. And you’re doing this in the expectation of greater safety? Or have I got this wrong?

My only experience of tpm systems have been the factory fit internal ones fitted to my wife’s last few (BMWGroup) cars and they have been the only things to go wrong while we’ve had those cars. On the last car we put in a warranty claim because of the tpms continuously giving us false readings and the current one still gives intermittent false readings. Not a system I have great confidence in but at least if it goes wrong it’s only an annoyance. And that’s factory fit. Excuse me if I pass on unknown Chinese valve caps where only the sticker changes between brands.

I think you have it wrong.

If you investigate TPMS systems used on heavy transport trucks (semi-trailers), most of them use a system that is connected to the inflation valve and measures pressure at the valve, by keeping the Schrader valve depressed. There is nothing wrong with that design - but the safety and reliability of it is, of course, very much dependent on good quality components and meticulous quality control during the manufacturing process.

I use the Garmin TPMS on my motorcycle, primarily because my GPS supports display and monitoring of tire pressure via Garmin supplied pressure sensor caps that fit over top of the Schrader valves. I have complete confidence in this system - I have used it for 5 years and 60,000 miles without any problem, and it did save my bacon once when I encountered a puncture from a large nail on the highway.

Like anything else, you need to be a critical consumer when purchasing equipment, particularly safety equipment. I don't purchase anything from unknown Chinese (mainland Chinese) manufacturers. Garmin makes their TPMS sensors in Taiwan, which is a totally different environment and culture from mainland China, and I have trust in Garmin as a manufacturer.

In reply to the original poster, who asked about TPMS in general, my recommendation is to purchase a system from a manufacturer that has a reputation for quality and dependability. Personally, I like the concept of TPMS integrated with the GPS because it minimizes the number of different systems on the motorcycle, and enables the manufacturer to easily update the software that operates the TPMS. The only downside that I have encountered so far is that the little batteries that go inside the sensor have a maximum life of one year, and it can be difficult to buy them when you are on the road because they are an uncommon size. This means you need to carry a couple of fresh spares with you.

Michael

I can only speak for the manufacturer I work for but this is not the case with all systems.

An external retrofit solution puts a pipe on the valve that opens it. This volume is open to a gallery where the pressure-voltage transducer is and then continues to another schrader valve. The unit is mounted on the wheel nuts so puts minimal stress on the tyre valve. In the event of failure the original valve can close.

An external solution mounting a complete P-V wireless unit on a valve tube is adding stresses to a component not designed to ta take it. Some valve stems are in metal which helps but many are not. If the original stem fails there will be an immediate and rapid loss of air. An external unit that has to be removed to put air in is permanently holding the valve open, so air is held by something potentially tested to a manufacturers internal standard not a tyre valve international one.

Internal systems either valve or strap mounted are before the valve and do not stress the stem. These will be the standard when legislation comes in. Temperature is a more useful measure in catching a blowout than pressure and you measure this off the rim not the valve air.

Personally I'm not going to screw Chinese tat onto my valve stems when two tyres can be checked in seconds with a hand held gauge. I am motivated to do this. A truck driver with 20 to do is less motivated and car drivers are incapable, hence legislation here/coming on 3+ wheeled vehicles.

Andy

I bow to greater knowledge of the subject - I'm no expert (or even much of an interested bystander) but there's a huge consequential difference between a tpms cap failure on a 32 wheeler and on a two wheeler. Especially as a trucking co is likely to be using caps with some sort of track record (to minimise failure inconvenience if nothing else) whereas the bike aftermarket is likely to be a bit of a race to the bottom minefield - especially if all you have to guide you is marketing or word of mouth. Most of the ones I've looked at since this subject came up have been heavy on marketing 'sizzle' (bluetooth this, handlebar display that, app on your phone the other) and light on independant safety assessment of the cap itself. Maybe they are a genuine advance in road safety but they - all of them - are going to have to be at least as safe and reliable as the simple time served mechanism they're bypassing to justify their place. So far I don't see any of that.

In practice what's going to happen - if your tyre and valve are functioning as they should then very little happens - no air leaks out between checks. Add a tpms and it'll tell you - nothing, and if nothing changes it'll get ignored. If it indicates something amiss you'll check a few times and it turns out to be a sensor fault (my car experience of them) through the battery going flat or it's cheap electronics or water's got in or whatever it'll get ignored ('the damn thing's playing up again'). A gadget version of the boy who cried wolf. I might come across as some kind of mechanical luddite with this but not so - I'm usually closer to an early adopter than the opposite, but aftermarket tpms's don't form a complete risk / cost / benefit circle for me at the moment. They seem like a half developed technology.

If you read in BMW or KTM forums about issues on standard TPMS it sounds sometimes similar like a half developed technology.
Riders critisize periodic connection failures to the ECU. Some complain about variable unrealistic pressure data shown in high and low environmental temperatures.
Often these issues get more frequent when the TPMS sensor had to be replaced after 40-60.000 km. Problem with the sensor is that it is nearly impossible to replace the soldered in battery. You have to invest another 70-100€ for each sensor + installation costs.

BMW and KTM plug in Schrader Motorcycle TPMS.
https://www.schradertpms.com/en-gb/o...otorcycle-tpms

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