3 ms·

There is also indirect method - ECU precisely comparing each wheel's rotation speed, with assumption that lower-pressure tire would have smaller outer radius, t

There is also indirect method - ECU precisely comparing each wheel's rotation speed, with assumption that lower-pressure tire would have smaller outer radius, thus slightly higher angular velocity. This method is somewhat common with European cars. It's very cheap (assuming car already has rotation sensors for ABS, and adding a software routine doesn't cost much either), and maintenance-free. But there are drawbacks, too - it doesn't detect all tires deflating at the same rate. And also, ECU has to be very conservative to avoid false-positives, average a lot, pause comparison when turning, etc. As a result, you only get the tire pressure warning like 10 minutes later that dTPMS would've flagged it.

CraigJPerry 4y ago
The VAG system circa 2014 - which i think is a Bosch system used by many manufacturers unchanged, i can’t remember the name of the system but i recall it was version 9.5 of Bosch’s system - was able to notify me of a fairly rapid puncture (hit a pothole at high speed) within around 300 yards. The tyre deflated slowly enough to continue for another 4 miles (albeit at much lower speed) so there would only have been a few PSI lost at the time it triggered. On the whole in that car (Golf R mk7) it did seem pretty switched on at noticing pressure loss from a slow leak i had after a tire replacement one time, which was handy because the tyres were pretty low profile that meant visual checks were utterly useless. It’d look perfectly fine at 10psi in a tire that should be at 34psi. One other benefit of the ABS system is that when it goes wrong and the money light comes on, the user’s probably more likely to respond to a “brake service now!” Type message than a “TP-something or was it TS or oh i dont know but the car still seems to drive fine so…”

3 ms·

There is also indirect method - ECU precisely comparing each wheel's rotation speed, with assumption that lower-pressure tire would have smaller outer radius, t

by nousermane 4y ago

CraigJPerry 4y ago
The VAG system circa 2014 - which i think is a Bosch system used by many manufacturers unchanged, i can’t remember the name of the system but i recall it was version 9.5 of Bosch’s system - was able to notify me of a fairly rapid puncture (hit a pothole at high speed) within around 300 yards. The tyre deflated slowly enough to continue for another 4 miles (albeit at much lower speed) so there would only have been a few PSI lost at the time it triggered. On the whole in that car (Golf R mk7) it did seem pretty switched on at noticing pressure loss from a slow leak i had after a tire replacement one time, which was handy because the tyres were pretty low profile that meant visual checks were utterly useless. It’d look perfectly fine at 10psi in a tire that should be at 34psi. One other benefit of the ABS system is that when it goes wrong and the money light comes on, the user’s probably more likely to respond to a “brake service now!” Type message than a “TP-something or was it TS or oh i dont know but the car still seems to drive fine so…”