www.boxertrix.com

Apologies if this has been done to death, I did a search and nowt came up. I was looking forward to the tyre pressure readout on my Garmin V allowing me to see a pressure raise and giving me the nod that they were nicely warm and ready to boogie. I'm a bit anal about tyres so my pressures have been checked on one expensive and accurate gauge on my air line and cross checked with a cheapo digi one. However, the pressures given on the SatNav bear no relation to what they actually are (it reads higher), so my question is, has the SatNav or ECU been calibrated in a different atmospheric pressure or temperature setting? It's not a big issue, I'm just curious?

I'm probably I bit more relaxed about the absolute tyre pressure, although I do try keep them at the right pressure. Riding my MV Agusta F4 1000 home after a service, an expensive one, taught me how much of a difference 20 psi makes .

My Navigator V proudly tells me the tyre pressure (in bar) to 2 decimal places but like yours it is higher than the pressure reading using a decent gauge. My assumption is the actual sensors in the wheels are not particularly accurate in the first place. That said now I know how much different they are I can mentally adjust the sat nav reading accordingly.

Should have added, the differences I see are all with cold tyres, so not due differences in air density with temperature.

I suspect you're right about their accuracy. As long as it's consistent, then mental compensation is fine - it's useful to check for slow punctures. Just for a laugh, I once put my tyre warmers on the Roadtecs and gave them a heat cycle and watched the pressure rise in quite a linear way to the temperature, just a shame you can't recalibrate the Garmin - at least for a techno 'tard like me

adam wrote: However, the pressures given on the SatNav bear no relation to what they actually are (it reads higher), so my question is, has the SatNav or ECU been calibrated in a different atmospheric pressure or temperature setting? It's not a big issue, I'm just curious?

My questions are:
is how do you know what they actually are?
Is the gauge you are comparing against accurate?
if so how do you know?

Short answer is use a gauge that's consistent and stick with that if you've got on board sensors stick with those and find the pressures that suit you. In any event I don't think we are sensitive to a pound or two either way as I'm sure you don't adjust your pressures down for cold days / wet days when your running pressure will be lower than on a hot dry day.

My reply is:
The pressure gauge on my airline in the workshop is calibrated fairly frequently.
It is cross checked with a digital one that I use at the Track.
I don't adjust my pressures for cold/wet days on my road bike - that would be silly on a Sport Touring tyre.
I use tyre pressures that suit me.
I wasn't questioning tyre pressures at all, I was curious as to why the ECU feed to the Garmin readout is different to the actual pressure in the tyre. The tyre pressure readout in my car is in the same ballpark as the actual pressures - so it is possible.