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Does a tyre change its CIRCUMFERENCE when underinflated?
On Sat, 30 Jun 2018 06:48:18 +0100, Richard
wrote: On 29/06/18 18:41, T i m wrote: On Fri, 29 Jun 2018 13:57:07 +0200, Thomas Prufer wrote: On Fri, 29 Jun 2018 11:39:41 +0100, Andy Burns wrote: Well, my axle is 5mm closer to the road (when stationary, who know how much centrifugal [let's not have *that* discussion] force negates that when moving?) I'll inject facts into the handwaving fest:-) I'm not sure it will make any difference Tomas as 'some people' don't believe the facts, imperial evidence (millions of cars with iTPMS) and the 'experts'. empirical 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). They would prefer (if ever) to come to the exact same conclusion themselves but shroud it very carefully in a desperate attempt to make it look like they understood it all along and thinking they can hide the *fact* they are indeed 'stupid and arrogant tw*ts'. ;-) A diagonally belted tire has 5% more travel per rotation at 180km/h than at 60km/h, a radially belted tire 1% more. So, that's because of the pantographing effect (like the dragster drive wheel I linked to ages ago) as it is spun up, opposite to that of a deflation (or course). This from the German Wiki page on the subject "Abrollumfang". The article also contains the words "the dynamic rolling radius under load is greater than the distance from the wheel middle to the road r sub(s)." and a formula I can't be arsed to transcribe, but I'll toss in ;-) r sub(0): unloaded wheel radius r sub(s): static radius r sub(D): dynamic radius The left brainers will 'get' the direct stuff but won't get the stuff that requires some imagination. https://de.wikipedia.org/wiki/Abrollumfang Thanks for trying though. ;-) Cheers, T i m Cheers, T i m |
Does a tyre change its CIRCUMFERENCE when underinflated?
On Sat, 30 Jun 2018 13:15:45 +1000, "Jeff" wrote:
snip Watching TNP going from denying that the circumference changes He actually said originally that it changes by less than 1% and it turns out that he was correct about that 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? and it is now clear that the distance between the axle and the road changes by much more than that, 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? 3 times more in fact, at least with that particular car and those tyre pressures. 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 |
Does a tyre change its CIRCUMFERENCE when underinflated?
On 30/06/2018 04:15, Jeff wrote:
He actually said originally that it changes by less than 1% and it turns out that he was correct about that and it is now clear that the distance between the axle and the road changes by much more than that, 3 times more in fact, at least with that particular car and those tyre pressures. 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. |
Does a tyre change its CIRCUMFERENCE when underinflated?
"T i m" wrote in message ... On Sat, 30 Jun 2018 13:15:45 +1000, "Jeff" wrote: snip Watching TNP going from denying that the circumference changes He actually said originally that it changes by less than 1% and it turns out that he was correct about that 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? and it is now clear that the distance between the axle and the road changes by much more than that, 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? 3 times more in fact, at least with that particular car and those tyre pressures. 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 He didn't, someone else asked how it works. (and argue the accepted facts of many throughout it)? He didn't do that either. |
Does a tyre change its CIRCUMFERENCE when underinflated?
"dennis@home" wrote in message ... On 30/06/2018 04:15, Jeff wrote: He actually said originally that it changes by less than 1% and it turns out that he was correct about that and it is now clear that the distance between the axle and the road changes by much more than that, 3 times more in fact, at least with that particular car and those tyre pressures. There have been a lot of posts where he and his supporters have said it doesn't change, I dont believe he has ever said that. 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. That wasnt what the OP asked about. 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. It is unlikely that iTMPS doesnt work on any car with inflatable tyres. |
Does a tyre change its CIRCUMFERENCE when underinflated?
On Sat, 30 Jun 2018 05:07:57 +1000, cantankerous geezer Rot Speed blabbered,
again: I haven't had a flat since but there is always the chance. There is no spare on the latest car nor anywhere to put one Which car is that ? Stupid idea IMO. so the AA can fix it next time. Trouble with that approach is the annual cost of that and the much longer time for them to show up than to change it yourself. You do know what he thinks of you, don't you, senile Rot? Yet you are so miserable and lonely that you STILL need to talk to him! BG -- dennis@home to know-it-all Rot Speed: "You really should stop commenting on things you know nothing about." Message-ID: |
Does a tyre change its CIRCUMFERENCE when underinflated?
On Sat, 30 Jun 2018 05:11:02 +1000, cantankerous geezer Rot Speed blabbered,
again: It might be but unless you can measure it under the dynamic conditions it is just a guess. I think it would be hard to get an accurate measurement while driving Not really, shouldnąt be hard to have a laser mounted on an arm outside the car, from the roof rack and a rolling road isn't going to help either. Correct. I don't suppose you have a laser you can exactly centre on the wheel and suspend a measure down from the wheel arch with a slow mo camera to record what actually happens? Not serious BTW. It wouldnąt be hard to do. You haven't yet realized that all these good people here prefer to ignore your pesky trolls, Rot? You just don't give up easily, especially as most people in real life seem to ignore you too! BG -- dennis@home to know-it-all Rot Speed: "You really should stop commenting on things you know nothing about." Message-ID: |
Does a tyre change its CIRCUMFERENCE when underinflated?
On Sat, 30 Jun 2018 04:00:36 +1000, cantankerous geezer Rot Speed blabbered,
again: You, TNP, and harry have that in common. I guess thats why you still support brexit as you can't see the problems that it is producing and will keep you "solutions" in your mind no matter how wrong they are proven to be. They just donąt see They ALL see what the matter is with you, Rot! -- dennis@home to know-it-all Rot Speed: "You really should stop commenting on things you know nothing about." Message-ID: |
Does a tyre change its CIRCUMFERENCE when underinflated?
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Does a tyre change its CIRCUMFERENCE when underinflated?
On 30/06/2018 10:36, Tim Streater wrote:
TNP can speak for himself but I've always accepted that it may change 1% or so between inflated and flat. But that difference is not what is being argued about, as I have said before. I'm not arguing about anything. I just stated the obvious, that it does change and why it changes. I haven't got the computer model that would be needed to work out what change you would get from a particular tyre/wheel/car/road combination and at what speeds and what pressures. It is far from a simple exercise to work it out. |
Does a tyre change its CIRCUMFERENCE when underinflated?
On Sat, 30 Jun 2018 19:29:02 +1000, "Jeff" wrote:
"dennis@home" wrote in message ... On 30/06/2018 04:15, Jeff wrote: He actually said originally that it changes by less than 1% and it turns out that he was correct about that and it is now clear that the distance between the axle and the road changes by much more than that, 3 times more in fact, at least with that particular car and those tyre pressures. There have been a lot of posts where he and his supporters have said it doesn't change, I dont believe he has ever said that. 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)? 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. That wasnt what the OP asked about. 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). ;-( 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. 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. It is unlikely that iTMPS doesnt work on any car with inflatable tyres. 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 |
Does a tyre change its CIRCUMFERENCE when underinflated?
On 30/06/2018 11:56, Tim Streater wrote:
In article , "dennis@home" wrote: On 30/06/2018 10:36, Tim Streater wrote: TNP can speak for himself but I've always accepted that it may change 1% or so between inflated and flat. But that difference is not what is being argued about, as I have said before. I'm not arguing about anything. I just stated the obvious, that it does change and why it changes. No it doesn't (apart from the 1%). And you haven't presented any evidence or arguments to the contrary. If you say so. However what you say is not true, but IME it seldom is. |
Does a tyre change its CIRCUMFERENCE when underinflated?
"dennis@home" wrote in message ... On 29/06/2018 08:51, Andy Burns wrote: Tim Streater wrote: It can change *shape* but not *length* (except by 1% or so, which no one is disputing), and that is what I say above. Now that we know that we're talking about detecting speed changes under 0.5% you can't discount a circumference change of 1% A flat will change by more than 0.5% as shown empirically by another poster. Its also fairly obvious that it will from the destruction of one twin wheel tyre on a lorry. If it only changed by say 1% the tyre wouldn't generate enough heat to destroy it and its the heat that does it. It isnt heat that sees the entire tread come off on a twin wheel tyre, that is due to the retread coming off. On single wheels the friction between the slower moving inner bit of the tyre and the outer will generate plenty of heat and wear to destroy the tyre. The twin wheel one won't have this contact so the heat generated in compressing and stretching the tread is what does it. |
Does a tyre change its CIRCUMFERENCE when underinflated?
"Andy Burns" wrote in message ... On 28/06/2018 22:28, T i m wrote: dennis quite clearly stated the scenario with a twin wheel lorry where the 'effective circumferences' can become substantially different if one tyre becomes deflated Aren't twin lorry tyres linked by a pipe between the tyres? So they're inflated as one? 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. |
Does a tyre change its CIRCUMFERENCE when underinflated?
Jeff wrote:
Andy Burns wrote Aren't twin lorry tyres linked by a pipe between the tyres? So they're inflated as one? The inner one usually just has a much longer filler pipe so it can be pumped up from outside the outer wheel 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. |
Does a tyre change its CIRCUMFERENCE when underinflated?
On 01/07/2018 07:01, Jeff wrote:
"dennis@home" wrote in message ... On 29/06/2018 08:51, Andy Burns wrote: Tim Streater wrote: It can change *shape* but not *length* (except by 1% or so, which no one is disputing), and that is what I say above. Now that we know that we're talking about detecting speed changes under 0.5% you can't discount a circumference change of 1% A flat will change by more than 0.5% as shown empirically by another poster. Its also fairly obvious that it will from the destruction of one twin wheel tyre on a lorry. If it only changed by say 1% the tyre wouldn't generate enough heat to destroy it and its the heat that does it. It isnt heat that sees the entire tread come off on a twin wheel tyre, that is due to the retread coming off. 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. |
Does a tyre change its CIRCUMFERENCE when underinflated?
"Andy Burns" wrote in message ... Jeff wrote: Andy Burns wrote Aren't twin lorry tyres linked by a pipe between the tyres? So they're inflated as one? The inner one usually just has a much longer filler pipe so it can be pumped up from outside the outer wheel 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. 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. |
Does a tyre change its CIRCUMFERENCE when underinflated?
"dennis@home" wrote in message ... On 01/07/2018 07:01, Jeff wrote: "dennis@home" wrote in message ... On 29/06/2018 08:51, Andy Burns wrote: Tim Streater wrote: It can change *shape* but not *length* (except by 1% or so, which no one is disputing), and that is what I say above. Now that we know that we're talking about detecting speed changes under 0.5% you can't discount a circumference change of 1% A flat will change by more than 0.5% as shown empirically by another poster. Its also fairly obvious that it will from the destruction of one twin wheel tyre on a lorry. If it only changed by say 1% the tyre wouldn't generate enough heat to destroy it and its the heat that does it. It isnt heat that sees the entire tread come off on a twin wheel tyre, that is due to the retread coming off. Well why do you think it comes off? Because trucks still use retreads. Anyway quite often its the entire carcass too. Hardly ever. If you have driven million miles on motorways you tend to see a lot of this stuff. Hardly ever the entire carcass. |
Does a tyre change its CIRCUMFERENCE when underinflated?
On 01/07/2018 07:01, Jeff wrote:
"dennis@home" wrote in message ... On 29/06/2018 08:51, Andy Burns wrote: Tim Streater wrote: It can change *shape* but not *length* (except by 1% or so, which no one is disputing), and that is what I say above. Now that we know that we're talking about detecting speed changes under 0.5% you can't discount a circumference change of 1% A flat will change by more than 0.5% as shown empirically by another poster. Its also fairly obvious that it will from the destruction of one twin wheel tyre on a lorry. If it only changed by say 1% the tyre wouldn't generate enough heat to destroy it and its the heat that does it. It isnt heat that sees the entire tread come off on a twin wheel tyre, that is due to the retread coming off. Then some clown reports that they have seen a crocodile on the motorway. -- Max Demian |
Does a tyre change its CIRCUMFERENCE when underinflated?
On Sun, 1 Jul 2018 08:43:32 +0100, Andy Burns
wrote: Jeff wrote: Andy Burns wrote Aren't twin lorry tyres linked by a pipe between the tyres? So they're inflated as one? The inner one usually just has a much longer filler pipe so it can be pumped up from outside the outer wheel 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. 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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