Dicky, thank's for that (that's what I was intending to type but the spell checker changed and the character size is pretty small on that dialogue box, especially when my eyes are tired).
Do us a favour though, if you are only going to correct one word in a post, snip all the stuff that follows that ... (the rest left in to demonstrate the point).
Cheers, T i m
But he also said in his OP:
"Does a tyre change its CIRCUMFERENCE when under inflated?
Answer. not by very much, if at all.
This seems to be a perpetual urban myth."
'If at all' and *a perpetual urban myth* that is making millions of iTPMS systems work every day (as he finally comes to accept)?
However, because he is a tortured mind, he went on to say:
"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."
He then spent the rest of the thread denying the concept of terms like 'rolling radius' when it was patently obvious to everyone who understood how a tyres 'effective circumference' was less than it's unloaded one so there must also be a 'loaded radius' that went with that. Except he's a left brainer so he can't grasp things he can't actually measure with a rule (but could easily calculate).
Are you looking to become one of his pet goblins, like Streater?
Doh ... who said it didn't? Stop press, if you reduce the pressure in a loaded tyre, the distance between the axle and the road drops!!! Who would have thought eh?
Quite ... you can't draw any real conclusion re the actual distance till you know all the other factors (like tirewall stiffness, pressure drop and overall load etc).
If Turnip accepted how and why iTPMS systems worked, why did he post a question about it (and argue the accepted facts of many throughout it)?
Cheers, T i m
There have been a lot of posts where he and his supporters have said it doesn't change, some where they have defined it as not changing as though they think it doesn't obey the laws of physics.
Also there hasn't been any proof that it changes by less than 1% on a flat tyre. We do know that some TPMS can detect a very small change when the pressure drops from 39 to about 31 on one car from measurements done.
He didn't, someone else asked how it works.
(and argue the accepted facts of many throughout
He didn't do that either.
I don?t believe he has ever said that.
some where they have defined it as not changing as
That wasn?t what the OP asked about.
We do know that some TPMS can detect a very small change when
It is unlikely that iTMPS doesn?t work on any car with inflatable tyres.
Are you in denial or something? What part of:
Turnip: "Does a tyre change its CIRCUMFERENCE when under inflated?
Answer. not by very much, if at all.
This seems to be a perpetual urban myth."
... don't you understand (that Turnip wrote)?
Again, that was *exactly* what he was asking about:
Turnip: "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.
(Ok, the fact that it starts with a typo where Turnips 'It' should have been an 'If' but I'd hope even you could work that one out). ;-(
Yes, *we* know that direct TPMS's can detect fairly small increments in pressure change whereas we also know that iTPMs systems can't. This is why several car manufacturers don't use iTPMS.
True, however iTPMS systems do need more driver intervention re resetting (another reason why they are / were shunned by some manufacturers) and rely on the vehicle having wheel rotation sensors installed.
Cheers, T i m
Did you realise you were replying to Rod?
It isnt heat that sees the entire tread come off on a twin wheel tyre, that is due to the retread coming off.
The inner one usually just has a much longer filler pipe so it can be pumped up from outside the outer wheel, and that is from a mate of mine that drives them for a living and you can check that by looking at them.
That's the pipe I'd seen and assumed linked them ... seems you /can/ get kits to link them, but that's not the norm.
Well why do you think it comes off? Anyway quite often its the entire carcass too.
If you have driven >million miles on motorways you tend to see a lot of this stuff.
Yeah, you can have central electric systems that allow you to change the pressure in all of them at once too, but again, not the norm.
Because trucks still use retreads.
Hardly ever.
Hardly ever the entire carcass.
Then some clown reports that they have seen a crocodile on the motorway.
As confirmed by my mate the HGV driver > transport manager and another (current) HGV driver. ;-)
A mate did a physical experiment with one of his spare tyres.
He pumped the tyre (Pirelli P6000 195/65 15) up to 50 PSI and ran some galvanised steel wire around the central groove and twisted the ends together till he could still feel a tiny amount of slack. Then he let the tyre down to 10 PSI and noted that the slack had increased significantly.
Now, whilst that confirms a tyre will 'expand' (or change profile) under pressure, it doesn't go any way to confirming (or demonstrating as we would see it) that the effective circumference is reduced at the cord created by the distortion of the tyre under load.
Cheers, T i m
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