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Query about cheap TPM caps

Antaeas

Registered marching ant
While at a NAPA store, I bought some valve caps that indicate tire pressure by showing green, yellow or red behind a clear cover. It seemed like a bargain Tire Pressure Monitor system, until I noticed a flat front tire while riding one day. I found that the clear cover of the valve cap had broken off, and the air had escaped. I don't know when or how, but, after I ran my portable pump to get enough pressure, I found a plain old metal valve cap in my parts bag, and limped to a service station where I re-inflated my tire to full pressure. It has stayed inflated ever since. There was no harm done this time, but I am suspicious about these valve caps. Has anyone had a similar experience?
 
While at a NAPA store, I bought some valve caps that indicate tire pressure by showing green, yellow or red behind a clear cover. It seemed like a bargain Tire Pressure Monitor system, until I noticed a flat front tire while riding one day. I found that the clear cover of the valve cap had broken off, and the air had escaped. I don't know when or how, but, after I ran my portable pump to get enough pressure, I found a plain old metal valve cap in my parts bag, and limped to a service station where I re-inflated my tire to full pressure. It has stayed inflated ever since. There was no harm done this time, but I am suspicious about these valve caps. Has anyone had a similar experience?

I had a similar experience. Less severe, but similar. To sample the pressure they hold the reliable Schrader valve open - and then they themselves leak. I kept having low tires. I took the caps off - threw them out - and never regretted it one bit. I don't need an accessory that causes my tires to lose air.
 
Usually the valve cap just keeps dirt away from the schrader valve. The pressure
gauge type cap hold the valve open to monitor the air pressure, hence
they can be the weak link in the tire's integrity. I avoid them like the plague.
 
Do the pricey TPMs that are advertised in the ON also operate by holding the valves open?

Without seeing the TPM diagram, logic would indicate that if the TPM pressure sensor is inside the tire (i.e., on the pressure side of the Schrader valve) then the Schrader valve stays closed to hold air pressure in the tire. Conversely, if the TPM is on the non-pressure (atmospheric) side of the Schrader valve (i.e., screwed onto the valve stem), then the Schrader valve in the valve stem would have to be "held open" for the sensor to "see" the tire pressure.
 
I expect when the day comes I can no longer bend over to check my tire pressure, I'll no longer be riding........ :dunno
 
I expect when the day comes I can no longer bend over to check my tire pressure, I'll no longer be riding........ :dunno

Really? 'Cuz at that point I'll be buying a sidecar rig and start going to full service gas stations, and have the attendant check tire pressure for me!
 
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