O.T. tyre pressure sensors - how do they work?

[Bob Eager]

I had a spate of flattening tyres a few years ago. Turned out to be peeling varnish on the allow wheels, spoiling the seal.

[The Natural Philosopher]

It would if a flat tyre was circular.

Since it isn't, you are talking relative bollocks

What is the radius of a tank track?

[Andy Burns]

Varied ...

Several (yellow warning) times when tyres had just gradually lost pressure without a puncture, maybe 43 down to 38psi, which would be detected at about the same level as when I started to notice going over speed humps was a bit softer than usual.

Several normal slow punctures from nails/screws (also yellow warning)

Once (red warning) where it picked up a fast puncture on the motorway before I had noticed it, and by the time I had come to rest on the hard shoulder the tyre was completely flat.

Overall I think 5 were punctures (all except one were repairable) two were from kerbs, the rest were just reminders to top-up pressures.

Several of the punctures occurred in the first year of buying the car, I was half convinced there were nail-magnets fitted.

[Michael Chare]

I thought I was prone to getting punctures but not as bad as that. I had one wheel which vibrated a bit so I fitted it to the rear. Even then I noticed a vibration at about 75mph. Eventually I had to stop for a flat tyre and found that the tyre had developed a bulge say a couple of inches in diameter which had then worn completely through. I wonder if the pressure sensors in the tyres of my new car would have noticed that before the tyre became completely flat.

[Michael Chare]

I do wonder about the benefits of alloy wheels. There was a recent thread about the tyres on them sometimes not staying inflated and they are quite easy to damage.

[T i m]

Just how distortable is a tank track, how many ply is it?

Do the lay of the plies form a mobile parallelogram allowing the tracks themselves to change size under different circumstances (including load bearing rotation)?

Cheers, T i m

[harry]

Improves ride and handling.

[Harry Bloomfield]

harry brought next idea :

Actually alloy does neither. The weight is about the same and alloy is sometimes even heavier than steel. The use of alloy is more about design and fashion.

[T i m]

On Sun, 24 Jun 2018 01:06:05 +0200, Peeler

[Michael Chare]

I agree although I think the original alloy wheels 50-60 years ago on rally cars were to reduce the unsprung weight. Also it does appear that reducing the unsprung mass does increase cabin noise and vibration which is not what you want on a normal road car.

[Tim Watts]

I agree - alloys are a pointless gimmick. Nickable so need locking nuts, easily damaged by kerb grinding, expensive.

Why they couldn't just get the "look" by careful design of a full sized "hub cap" beats me.

[Halmyre]

I used to have a Rover 416 which had alloy-look wheel trims. One went missi ng and I went to the dealer's for a replacement. "What type is it?" asked t he chap behind the spares counter. "One like those", I said, pointing out t he door to my car, which was parked so that the two fully-shod wheels were visible. "But those are alloys" he insisted, and wouldn't change his opinio n until he'd gone outside to see the bare steel wheel.

[Tim Streater]

I had a Stag with "full sized hub caps". They looked OK but vibrated and thus generated unwanted noise.

[Vir Campestris]

The unsprung mass of a fat tyre is only the mass of the bit of tyre on the road - at least for small bumps. Modern skinny tyres have almost no give, so the suspension has to do all the work. And the result is a harsher ride, poorer handling, and vulnerability to potholes.

Some think they look better. Which overrides the other three.

Andy

[Vir Campestris]

I'll take this slowly, but only once.

Imagine a wheel that was flat at the bottom so that it had half its original radius. The rolling radius of the wheel is the radius where it touches the ground - half the normal radius.

This bit at the bottom is the only bit that counts. The rest is not on the road.

A tank track doesn't have a radius. It isn't a circle. The effective rolling radius of tank wheels is exactly the same as it would be if the track wasn't there - it's just they are rolling along a track, not the road. This is why it is called a track laying vehicle.

Andy

[Tim Streater]

The tank track (or any similar one) is in any case not relevant to this discussion, as we are talking about a wheel and tire where the tire is in contact with the whole rim of the wheel at all times.

Only a small part of a tank track is ever in contact with any of the tank's wheels.

[dennis]

It wouldn't be actually. Its driven by the big sprocketed wheel so its radius (assuming negligible stretching) would be the radius of the sprocket plus whatever extra the track thickness adds.

A tyre is similar to a track anyway as the contact area of the driven wheels will move in relation to the axle due to the forces acting on it to move the vehicle. Likewise it will move under breaking too.

[The Natural Philosopher]

Oh dear...

Oh dear

Neither is your example above.

The effective

Right. And that is exactly the same effect as a tyre that has completely lost its sidewall and is in fact just got a tread left.

So what we have, if you can picture it, is the rim rolling long inside a tread that is ciurcular and bugger than te rim diameter,.

Ok so far? Now this is a ring gear and pnion in effect - a reduction gera where the tyre is turning slower than the wheel

How can the tyre be turning slower than the wheel *if it has a sidewall connecting them*

It cant.

What happens is taht all te other nbits of te tuyre connected to te rim are actually pusing the ytrye tread around faster than the rim is going so there is a relaticive angulra velocity between the flattened part of te tyre and the rim above it.

This is wahy your 'bit at the bottom is the only bit that counts' is so completely and utterly WRONG..

The bit at the bottom is not bolted to the rim. Its attached via a flexible elastic medium, and its the flexing of that medium that allows motion from all parts of the wheel and tyre to be transferred to the contact patch.

Nothing says that the instantaneous angular velocity of the tread has to match the instantaneous angular velocity of the rim, and in fact it doesn't at the contact patch. All that has to happen is that the AVERAGE angular velocity of the whole tyre has to match the angular velocity of the wheel.

And that is where your thinking is totally flawed. You learned the mechanics of solid wheels at O level, you failed to learn the mechanics of more complex rotating systems thereafter.

Worse, you think you understand when you do not. Like dennmis, Huge, harry T i m and all the other remooaners who run on received wisdom and cannot actually think for themselves

[The Natural Philosopher]

I introduced tehe idea of te tank track as an extreme example of a tread that is much bigger than the wheels driving it, and rotates much much slower.

It is the counter example - the case where the twits get it right, but them you have to say what happens if te track IS rotating at the same speed as the wheel driving it?

Because a tyre is a track/tread that *is* rotating at wheel speed. Even thoiugh its a greater diamter than the wheel rim

The intention was to show that simple thinking leads to a paradox in which the tyre is obviously rotating at the same speed as the wheel, and yet their 'logic' says it must be rotating slower or the circumference must somehow *contract* massively under load!

It's a fascinating example of scientific denial so to speak. Like climate change they must 'save the theory' even when the data lead to contradictory results.

Judging by here, its likely a technical problem that well over half the population would get wrong...

Which also gives some degree of value to the false claim that '97% of scientists say' meme.

And eplains wihy 47% of those with opinions voted to remain in the EU.

And a very high proportion of those with secondary education.

What we find is that undeducated people see things pretty much as they are and dont pretend to understand them.

People with education who have been *told* how to use more copmplex models *think they are smarter than they are*. It is in the end only a small proportion of top brains that can actually think for themselves that can puzzle it out and get to the right answer.

The rest might as well memorise te Koran by heart, because they never will think independently. Radical Islam. Socialism. Climate change. The EU. They will beleive in whatever they are told to believe by people they consider to be their intellectual superiors - the authorities to which they appeal.

That is why the remoaner class - funadmentally the over educated and less intelligent middle class, are in fact the most gullible.

At the bottom the uneducated expect that people are talking shit to them. They just dont believe anything except cash in hand and how much a pint costs. At the very top people who can really think for themselves understand much of what is going on, but are either not going to let on, or are actively told to shut up.

Blairs triumph was to capture the imaginations of the over educated and less intelligent middle class, increase their numbers by borrowing money and giving it to them to go to 'uni' on the absurd proposition that since people who were bright enough to get to university made more money, sending people to university who were frankly thick as pigshit would in the end get them more salary.

The odd thing is how many believed him.

But since this little experiment, Perhaps its not so odd. Thats how self important stupid people behave it seems.

[T i m]

Bwhahahaha .... I love it, *exactly* as predicted the Turnip has now basically accepted what some of us have been saying from the beginning but 'of course' he will try to obfuscate the point by trying to wrap it all up in his bs waffle!

Actually I feel sorry for him ... because he can't help it. ;-(

Cheers, T i m