Answers from a google support the obvious; that tires goes flat when not in use, but when you read the answers carefully they allude more to that - yes a tire can still go flat when not used. My question however is it seems that tires go flat more quickly when not used compared to being used regularly, is this true and if so why?
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$\begingroup$ Can you please elaborate on your evidence that they go flat faster when unused? $\endgroup$– ChemomechanicsCommented Sep 20, 2021 at 1:00
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$\begingroup$ "Answers from a google support the obvious; that tires goes flat when not in use, but when you read the answers carefully they allude more to that - yes a tire can still go flat when not used". The last statement is the same as the first(????) $\endgroup$– Bob DCommented Sep 20, 2021 at 2:38
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$\begingroup$ he last statement is the same as the first(????) No its not and that's why google does not answer the question. Google tells me that tires go flat when not in use because leakage etc. etc. but does not the same effect happen when the tire is in use? The answers from google seem to talk about effects that would apply to both in use and not in use. I asking about affects that only apply to deflate not in use tire and do not apply when tire is in use, hence if there is a reason tires deflate more when not in use. I hope you can see the difference. $\endgroup$– Beraben SystemsCommented Sep 20, 2021 at 5:30
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$\begingroup$ Can you please elaborate on your evidence that they go flat faster when unused? its not evidence its just a seemly observation. I'm asking if its true or not? If I had a vehicle sitting for months I would always observer deflation at least 10PSI. I have not noticed that when the vehicle is in use. I don't recall having to fill up my tires for many months of daily operation. $\endgroup$– Beraben SystemsCommented Sep 20, 2021 at 5:34
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$\begingroup$ physics.stackexchange.com/q/179019 $\endgroup$– Beraben SystemsCommented Sep 20, 2021 at 10:44
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Does unused tires loose pressure more rapidly than regularly used tires? So far there seems to be a few people who have loosely observed this but I have not found anyone who has experimented to get more conclusive answers. Here are the following scenario I have found from online and my own experience.
1.1 The person who bought 2 new tires, had one fitted and in use and the other sitting unused, he/she observed that the unused tire was loosing more pressure than the one in use.
The first thing to note is why does this not seem to happen with spare tires which are usually unused for years. If tires would loose pressure at this rate, would the automotive industry not have already picked up on the spare tire mechanism as non functional and not waste money providing spares?
Few possible reasons for this scenario, the one sitting could have some minor defects etc rubber/rim etc. A more conclusive result would be found if he/she swapped the tire with the used/unused and compare the results perhaps repeated several times.
1.2 The fleet truck owner observed few trucks sitting unused lost tire pressure in the same time that another set of trucks were in use.
This scenario is more convincing since there is more than one vehicle involved that show the same result. Its is statistically unlikely that all the trucks were sitting had some defect or imperfection. Again would be more conclusive if he/she swapped the vehicles and observed the results. Also the person should note, do all tires on the vehicle deflate at a similar rate?
1.3 The same thing could be said about a single vehicle whom the owner has the means to allow the vehicle to sit for a decided amount of time, for example a motorcycle owner who has another primary form of transport. The owner could observe tyre pressure on regular use compared to left unused.
If its true that tires loose pressure more rapidly when not used there's several hypothesis as to why it would happen, here is a list I've found which I've ordered to what I believe is most likely to least likely.
2.1 A tire left sitting is subject to slight deformities around the rim seal. e.g. tires are known to deform on the surface when left sitting i.e. flat spotting. This could also be the case for the rim/tire contact point hence causing pressure loss. This would not occur when the tire is used regularly as the load point on the rim where deformities would occur don't have enough time to deform before before being reformed by driving and also having a changed load point when parked again. This however conflicts with the example 1.1 where the unused tire (is assumed) to not be fitted to a vehicle and not subject to deforming at a tire/rim point. However there is still a lot of uncertainty about 1.1. However also note that tubed tires e.g. for mountain bikes seem to also observe pressure loss with non use, the tube in the tire should negate loss through tire/rim contact.
2.2 Non used tires loose seal between tire to rim, valve seals or develop pores across the whole tire where air can escape. The heat and load cycling of regularly used tires naturally reseals the tire/rim contact, reseals valve seals and closes/seals the pores that the tire may have developed.
This might answer why non loaded tires still loose pressure, an experiment should compare tubed and tubeless tires to observe the effect of the tire/rim seal.
3.1 tires loose pressure because the air is cold? I don't believe this is relevant as it will effect both used and non used tires. One could compare the hot time e.g. 1hr per day i.e. around 4% does not match up with observed deflation rates.
Conclusion With the information thus far there is no convincing information to suggest that unused tires loose more pressure than used tire is actually a true phenomenon. Simple (documented so you don't forget) experiments however could shed more light into the direction of truth namely.
- Observation of used/unused and then swapping.
- Comparison between loaded and unloaded i.e. fitted and non fitted wheel to vehicle.
- Comparison between tubed and tubeless tires. The experiments should also take into account ambient temperatures i.e. seasons and perhaps even whether the unused tire is exposed or not exposed to sunlight.