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-   -   Tire pressure monitor... (http://www.horizonsunlimited.com/hubb/equipping-bike-whats-best-gear/tire-pressure-monitor-43055)

Ness 27 May 2009 16:10

Tire pressure monitor...
 
Does anyone have one? Make? R U happy with it?
normness at gmail dot com

Threewheelbonnie 27 May 2009 17:01

Are we talking about a red/yellow/green thing that screws on the valve caps?

They are dangerous. Your life is depending on a 0.02p Chinese O-ring in a dynamic seal where no o-ring should ever be. The German TUV took one look and banned the things. As someone whose worked with pneumatic seals for 15 years I'm with the TUV: cheap nasty dangerous garbage.

Now, if we are talking a direct system where a pressure sensor is mounted on the rim, or an indirect system that uses the ABS sensors to detect the speed up as a tyre goes down, I didn't know they'd been set up for bikes yet and would like to see more.

Andy

Stephano 2 Sep 2009 19:55

2 Attachment(s)
Quote:

Originally Posted by Threewheelbonnie (Post 243606)
Are we talking about a red/yellow/green thing that screws on the valve caps?

They are dangerous.

Andy is right. I used these for the convenience of knowing my tyres pressures. The first time one failed, it appeared to develop a pinprick hole in the top of the clear plastic and left me with a flat tyre in the garage.

I wrote to the manufacturer expressing my concern and they sent me a new one without comment.

More worryingly, this summer I took out my bike to ride and a second one of these monitors had failed and sprung apart (see photos). However, a thin black membrane was keeping the air in the tyre at full pressure. I barely touched it with my hand and the membrane popped letting the air rush out. If what you can see in the photo had happened when riding, I dread to think of the possible consequences.

I advise anyone to avoid using these.
Stephan

devildiver 2 Sep 2009 21:06

Digital or stick pressure checker, on a major tour check once a week.

Job done.

Warthog 2 Sep 2009 21:25

I had used those pressure tyre caps too. I got rid when I heard about alleged concerns.

There was also talk of the centrifugal forces exerted by a wheel spinning at speed combined the added weight of these valve caps (they are significantly heavire than a normal valve cap) possibly causing a valve failure when moving.

Rapid decompression: rapid problems

electric_monk 3 Sep 2009 11:54

Aside from the concerns listed previously I would have to ask if they really do save you anything?

To me they just appear to be another gadget for gadgets sake.

A friend has fitted ones to his bike that use bluetooth to send the pressures to a little receiver the size of a pager.

I remember being told years ago not to trust anything other than the pencil type gauges because anything else has some form of electronics incorporated into it which may fail.

Threewheelbonnie 4 Sep 2009 08:11

In a past life I sold truck systems like the one you describe. These could monitor 24 tyres to an accuracy of about 0.1 PSI and would bring on a yellow light when the pressure was down by about 2%.

We also did ABS systems that can monitor each axle end and bring on the light when one wheel speeded up by about 5%.

With both you get the driver to react before the tyre is damaged, which at £200 plus a tyre, maybe £10000 if they close a motorway lane to fix a blowout and millions if your petrol tanker crashes, it's well worth it. In the direct system you get single pressures without the driver spending maybe 30 minutes checking. Indirect is a tiny bit of software in the ABS, so is almost free.

With a bike I can see the advantages if they are OEM fitted. Retrofit, does it really take that long to take two pressures? For say a police bike I can see it'd pay for itself in tyres and the safety's for free, but on a private bike?

I now sell gauges

A pencil type gauge has an o-ring which wears, sticks and generally misbehaves. They are highly innacurate but repeatable if used by the same person. A bourdon type gauge (round) is typically accurate to 1% and should be repeatable, but will go out of calibration if you carry them about and vibrate the tube. A digital gauge is both reliable, accurate and repeatable, but best of all doesn't go out of calibration so long as the battery is good and it is allowed to zero to the atmosphere on start up. I'd always go digital on a tyre gauge to carry with maybe a bourdon in the garage if the odd half PSI worries you.

Andy


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