On 23/06/2018 07:41, The Natural Philosopher wrote:
On 23/06/18 07:08, Jeff wrote:
"The Natural Philosopher" wrote in message
news
https://www.youtube.com/watch?v=_2l5bOhHNxU
Answer. not by very much, if at all.
But the radius clearly does vary significantly.
This seems to be a perpetual urban myth.
It can't be given that Andy and others have had a number
of warnings that have turned out to be accurate every time.
It tyre pressure sensors are using this, it has to be a very very
complicated bit of software to detect - say - less than 1% change in
RPM relative to the other wheels.
Yes, but that isn't hard to measure when its relative to other wheels.
A piece of online research
[
https://one.nhtsa.gov/cars/rules/rul...prmonsys.html]
showed that relative wheel rotation was pretty crap at detecting low
tyre pressures especially in all 4 wheels or 2 wheels on the same side
(= I am going round and round in circles!)
That ruling in 2001 was in the context of what could and couldn't meet a
statutory requirement in the USA for pressure monitoring in new cars
that also alerted if more than one tyre - including all 4 tyres equally
- are 25% or more below pressure. It's no surprise that indirect
methods couldn't meet that requirement.
Hence the move to in wheel sensors.
OTOH
https://en.wikipedia.org/wiki/Tire-p...itoring_system has
"Since factory installation of TPMS became mandatory in November 2014
for all new passenger vehicles in the EU, various iTPMS [that "i"'s for
indirect] have been type-approved according to UN Regulation R64.
Examples for this are most of the VW group models, but also numerous
Volvo, Opel, Ford, Mazda, PSA, FIAT and Renault models. iTPMS are
quickly gaining market shares in the EU and are expected to become the
dominating TPMS technology in the near future.
iTPMS are regarded as inaccurate by some due to their nature, but given
that simple ambient temperature variations can lead to pressure
variations of the same magnitude as the legal detection thresholds, many
vehicle manufacturers and customers value the ease of use and tire/wheel
change higher than the theoretical accuracy of dTPMS."
--
Robin
reply-to address is (intended to be) valid