Considering Rejoining the FJR Ranks - Question for 2016 ES owners

[AdamK]

Also, the sensors on the valve stems seem to be inordinately sensitive to ambient, the colder it is, the lower the reported pressure. As a result, I don't use these as an indicator of accurate tire pressure, I check with a pencil gauge before each ride. On super-slab rides I run 38F, 42R and on twisties combat runs, 36F, 40R. I look at the TPMS for delta between front and back (always shows 4 PSI difference) and for deflation indicating a puncture. I can also see the pressure rise delta as a percentage of initial reported pressure due to the warming of the tires but that is really not on my radar screen

Are you saying the pencil gauge reads higher relative to this system before you even start riding? That is strange?? My readings are lower at colder temps or higher altitude, but the external gauge and the sensors always report the same lower values.

The indicated temps always rise when the tire gets warmer. Sometimes quite a bit more in high heat and in the twisties or at high speed. I can set upper and lower limits on the TP Checker but they are absolute limits. They are not adjusted for temperature. The Smartire is one of the only systems which compensates for temperature. ie, it calculates what the pressure should be since launch based on the temp increase. It won't alarm unless the change in pressure doesn't compute relative to the temp change.

 

[RossKean]

My readings are lower at colder temps or higher altitude, but the external gauge and the sensors always report the same lower values.

Cooler temperature should definitely make the TPMS (or other gauge) read lower (Boyle's Law) but it should read higher at higher altitude. A pressure gauge reads the DIFFERENCE between what's in the tire and the ambient (outside tire) pressure (relative pressure). The absolute pressure inside the tire does not change at higher elevation (except by stretching) but the outside pressure is lower resulting in a higher differential. (Higher RELATIVE pressure)

 

[bergmen]

Are you saying the pencil gauge reads higher relative to this system before you even start riding? That is strange?? My readings are lower at colder temps or higher altitude, but the external gauge and the sensors always report the same lower values.
The indicated temps always rise when the tire gets warmer. Sometimes quite a bit more in high heat and in the twisties or at high speed. I can set upper and lower limits on the TP Checker but they are absolute limits. They are not adjusted for temperature. The Smartire is one of the only systems which compensates for temperature. ie, it calculates what the pressure should be since launch based on the temp increase. It won't alarm unless the change in pressure doesn't compute relative to the temp change.

Yes, that is the case (pencil gauge reads higher than sensor pressure). When I check before each ride, I may have to add a pound or two depending on ambient or how long it has been since I've ridden (to bring to my 38/42 pressure). Once underway, my front can read as low as 34-25, rear 38-39. The readings are consistent and seem to read lower if it is cold out, higher if warmer.

At first I was concerned about this since I didn't trust the system. But after using it for a few thousand miles realized that the sensors are just temperature sensitive and not a source of accurate pressures for the purposes of confirming ready-to-go pressures.

Dan

 

[AdamK]

My readings are lower at colder temps or higher altitude, but the external gauge and the sensors always report the same lower values.

Cooler temperature should definitely make the TPMS (or other gauge) read lower (Boyle's Law) but it should read higher at higher altitude. A pressure gauge reads the DIFFERENCE between what's in the tire and the ambient (outside tire) pressure (relative pressure). The absolute pressure inside the tire does not change at higher elevation (except by stretching) but the outside pressure is lower resulting in a higher differential. (Higher RELATIVE pressure)

Sorry, yes you are correct, the pressure increases. I experienced this during two trip to Colorado this past summer. Had to readjust after returning to Seattle.

 

[AdamK]

Are you saying the pencil gauge reads higher relative to this system before you even start riding? That is strange?? My readings are lower at colder temps or higher altitude, but the external gauge and the sensors always report the same lower values.
The indicated temps always rise when the tire gets warmer. Sometimes quite a bit more in high heat and in the twisties or at high speed. I can set upper and lower limits on the TP Checker but they are absolute limits. They are not adjusted for temperature. The Smartire is one of the only systems which compensates for temperature. ie, it calculates what the pressure should be since launch based on the temp increase. It won't alarm unless the change in pressure doesn't compute relative to the temp change.

Yes, that is the case (pencil gauge reads higher than sensor pressure). When I check before each ride, I may have to add a pound or two depending on ambient or how long it has been since I've ridden (to bring to my 38/42 pressure). Once underway, my front can read as low as 34-25, rear 38-39. The readings are consistent and seem to read lower if it is cold out, higher if warmer.

At first I was concerned about this since I didn't trust the system. But after using it for a few thousand miles realized that the sensors are just temperature sensitive and not a source of accurate pressures for the purposes of confirming ready-to-go pressures.

Dan

Both of my systems were/are accurate relative to a high quality gauge. I haven't had to rely on my gauge anymore. I just carry it for backup now.

 

[Birdman2010]

Thank you for mentioning TPMS on this thread! I researched and purchased the FOBO Bike TPMS. I bought two T-Valves with the system. On most photos, I noticed that the T-Valves are mounted sideways like this photo. However, I want to mount the T-Valves so they point straight out so I can add air more easily. Is there a clearance problem with T-Valves? Do they have to be installed sideways like this photo, or can I have the T-Valves installed at a 90 degree angle so they point straight out?