rear tyre pressure

[AdyB]

A question from England. Going to put a Toyo Proxes TR1 225/50/15 car tyre on the rear of my 2016 Spyder RT Limited.Usually ride 2 up, I weigh 80 kilos and my wife weighs 60 kilos. Reading others posts, people use anything from 18 psi to 28 psi pressure. Would appreciate replies stating what pressure you use so I can start off with the most popular. Thanks in advance.

 

[Peteoz]

I think you’ll find around 18 is the most popular for both front and rear aftermarket tyres, Ady, regardless of rider/passenger weight as car tyres are so strongly built, but some are happy with the other end of the spectrum too, say 28/30. You need to find what best suits YOUR riding style. There is no issue with running at 14, and one rider accidentally ran at 8 for a couple of hundred miles, with zero issues. I don’t use high pressures based on some of the excellent advice on best grip from experienced tyre testers on here (not just tyre Installers). Start at say 24, and gradually lower the pressure until you find one that feels the most effective and comfortable for your riding style and comfort. The lower pressures don’t impact tyre wear. Others will chime in soon ��

Pete

 

[missouriboy]

I think the only useful answers you'd get would have to be from someone using the exact same tyre with a similar load.

Here's my theory on pressure with radial tyres: this type of construction is designed to perform best when the sidewall flexes a little bit while in motion. So... apply your typical load, then air the tyre until it shows a bulge similar to any regular vehicles: no bulge is too much air, fat bulge is not enough. My idea is that when the proper amount of bulge shows, that's the right amount of pressure for THAT particular radial tyre on THAT particular vehicle. No matter what the gauge reading says.

I suggested this idea before, but no discussion ensued. Comments, anyone?

 

[PMK]

20 psi, in all three tires.

 

[Peter Aawen]

You really CAN NOT tell if a tire has got the right pressure in it by looking at it!! And that applies even more so for radial tires!! The 'look' of the bulge in the sidewall can be very deceiving and completely at odds with the pressure in the tire. So PLEASE, don't ever rely on how your radial tires on ANY vehicle LOOK!! At best, it could cause wear &/or ride & handling problems; at worst, it could be deadly!! nojoke . :lecturef_smilie:

As to the 'correct' pressure, unless you & your load on the Spyder/Ryker is WAAAY outside the 'normal range' of users, then for most 'real' auto tires (ie, NOT Kendas) with speed & load ratings that meet or exceed those shown on your Spyder/Ryker's tire placard, then you are probably going to be fine running something like 16-18 psi up front, and say 16-20 psi in the rear - bearing in mind that a larger sized tire generally needs a little less air in it to carry the same given load. So if you run 18 psi in a 165/55R15 up front at 18 psi, then swap to a 175/60R15 tire without changing your usual load, 16 psi is probably going to be a better choice in that larger tire. On the other end of the Spyder/Ryker, swapping out a 225 wide tire for a 205 wide may require an extra 2psi or so; but if you go up in profile at the same time as going down in width, that need for 'extra air' may be negated. I've recently swapped from a 225/60R15 tire that ran & wore very well at 16psi to a 205/65R15 that I'd normally expect to need saaay 18 psi instead, except the higher profile & the differences in 'actual' tire sizes vs nominal sizes has shown the new tire is actually a tad larger than the old tire so the optimum pressure for the new tire is also 16psi! :thumbup:

But regardless, I very much doubt that there is anyone out there regularly riding a Spyder/Ryker that is loaded up enough to NEED more than saay 20 psi in a 'normal' auto tire mounted on the Spyder/Ryker (car) rims (tall &/or very large riders like Peteoz may be amongst the exceptions that prove that 'rule'! ) Most 'usual sized' riders & loads will generally get a better balance of tire compliance with the machine's suspension and better traction, ride, handling, and tire life at something a bit lower, altho they may not be used to the 'feel' that those pressures bring, probably because they've become used to running on over-inflated tires over time/thru tire fitter's apathy or lack of tire pressure knowledge! Of course, there may also be some who knowingly choose to run more than 20psi in their non-Kenda auto tires fitted to a Spyder/Ryker, maybe to optimise fuel economy over tire life & suspension compliance, puncture resistance, or traction; or possibly simply because the've grown to like the 'firmer feel' that the higher pressure gives them; or 'thinking' it gives them more 'direct steering' despite the lack of grip those pressures usually entail; but that's their choice & prerogative, rather than strictly being a necessity for optimal tire performance.

If you want to search my old posts here, or look for info on the 4psi rule elsewhere, you can use that repeatable & measurable method to determine fairly accurately what is the optimal pressure for YOUR tires on YOUR vehicle in the current conditions/ambient temps etc when used & loaded the way YOU do that, but it does take some initial effort on your behalf; there are also other methods that can get very close, too - chalking the tire & examining the tread imprint; wetting/painting the tire & checking how its track looks; or even weighing the loaded tires on each end & doing the load/pressure calculations using the tire manufacturers supplied load/pressure info.... but with all the many & varied methods available that I've tried, I've found that for the vast majority of Spyder/Ryker users, they all come back to ending up pretty close to the same pressures mentioned above - 16-18 psi up front and 16-20 psi in the rear, with a few exceptions for special needs &/or applications (eg, go higher if you really want to spin the rear tire & light it up at every set of lights.... ) Of course, you may choose to use pressures outside those ranges for any reason you like too, but in doing so, just be aware that it is very likely that you WILL be compromising some aspect of your tire's performance by doing so. :lecturef_smilie:



Or you could simply set your tires at whatever pressures you feel like, then Ryde More, and Worry Less, and maybe pay the bills later! hyea:


Over to you! :thumbup:

 

[BLUEKNIGHT911]

You really CAN NOT tell if a tire has got the right pressure in it by looking at it!! And that applies even more so for radial tires!! The 'look' of the bulge in the sidewall can be very deceiving and completely at odds with the pressure in the tire. So PLEASE, don't ever rely on how your radial tires on ANY vehicle LOOK!! At best, it could cause wear &/or ride & handling problems; at worst, it could be deadly!! nojoke . :lecturef_smilie:

As to the 'correct' pressure, unless you & your load on the Spyder/Ryker is WAAAY outside the 'normal range' of users, then for most 'real' auto tires (ie, NOT Kendas) with speed & load ratings that meet or exceed those shown on your Spyder/Ryker's tire placard, then you are probably going to be fine running something like 16-18 psi up front, and say 16-20 psi in the rear - bearing in mind that a larger sized tire generally needs a little less air in it to carry the same given load. So if you run 18 psi in a 165/55R15 up front at 18 psi, then swap to a 175/60R15 tire without changing your usual load, 16 psi is probably going to be a better choice in that larger tire. On the other end of the Spyder/Ryker, swapping out a 225 wide tire for a 205 wide may require an extra 2psi or so; but if you go up in profile at the same time as going down in width, that need for 'extra air' may be negated. I've recently swapped from a 225/60R15 tire that ran & wore very well at 16psi to a 205/65R15 that I'd normally expect to need saaay 18 psi instead, except the higher profile & the differences in 'actual' tire sizes vs nominal sizes has shown the new tire is actually a tad larger than the old tire so the optimum pressure for the new tire is also 16psi! :thumbup:

But regardless, I very much doubt that there is anyone out there regularly riding a Spyder/Ryker that is loaded up enough to NEED more than saay 20 psi in a 'normal' auto tire mounted on the Spyder/Ryker (car) rims (tall &/or very large riders like Peteoz may be amongst the exceptions that prove that 'rule'! ) Most 'usual sized' riders & loads will generally get a better balance of tire compliance with the machine's suspension and better traction, ride, handling, and tire life at something a bit lower, altho they may not be used to the 'feel' that those pressures bring, probably because they've become used to running on over-inflated tires over time/thru tire fitter's apathy or lack of tire pressure knowledge! Of course, there may also be some who knowingly choose to run more than 20psi in their non-Kenda auto tires fitted to a Spyder/Ryker, maybe to optimise fuel economy over tire life & suspension compliance, puncture resistance, or traction; or possibly simply because the've grown to like the 'firmer feel' that the higher pressure gives them; or 'thinking' it gives them more 'direct steering' despite the lack of grip those pressures usually entail; but that's their choice & prerogative, rather than strictly being a necessity for optimal tire performance.

If you want to search my old posts here, or look for info on the 4psi rule elsewhere, you can use that repeatable & measurable method to determine fairly accurately what is the optimal pressure for YOUR tires on YOUR vehicle in the current conditions/ambient temps etc when used & loaded the way YOU do that, but it does take some initial effort on your behalf; there are also other methods that can get very close, too - chalking the tire & examining the tread imprint; wetting/painting the tire & checking how its track looks; or even weighing the loaded tires on each end & doing the load/pressure calculations using the tire manufacturers supplied load/pressure info.... but with all the many & varied methods available that I've tried, I've found that for the vast majority of Spyder/Ryker users, they all come back to ending up pretty close to the same pressures mentioned above - 16-18 psi up front and 16-20 psi in the rear, with a few exceptions for special needs &/or applications (eg, go higher if you really want to spin the rear tire & light it up at every set of lights.... ) Of course, you may choose to use pressures outside those ranges for any reason you like too, but in doing so, just be aware that it is very likely that you WILL be compromising some aspect of your tire's performance by doing so. :lecturef_smilie:



Or you could simply set your tires at whatever pressures you feel like, then Ryde More, and Worry Less, and maybe pay the bills later! hyea:


Over to you! :thumbup:

Again " TIRE SCIENCE " is your correct answer ... :thumbup::thumbup::thumbup:.............thanks Peter .... Mike :thumbup:

 

[bigbadbrucie]

You really CAN NOT tell if a tire has got the right pressure in it by looking at it!! And that applies even more so for radial tires!! The 'look' of the bulge in the sidewall can be very deceiving and completely at odds with the pressure in the tire. So PLEASE, don't ever rely on how your radial tires on ANY vehicle LOOK!! At best, it could cause wear &/or ride & handling problems; at worst, it could be deadly!! nojoke . :lecturef_smilie:

As to the 'correct' pressure, unless you & your load on the Spyder/Ryker is WAAAY outside the 'normal range' of users, then for most 'real' auto tires (ie, NOT Kendas) with speed & load ratings that meet or exceed those shown on your Spyder/Ryker's tire placard, then you are probably going to be fine running something like 16-18 psi up front, and say 16-20 psi in the rear - bearing in mind that a larger sized tire generally needs a little less air in it to carry the same given load. So if you run 18 psi in a 165/55R15 up front at 18 psi, then swap to a 175/60R15 tire without changing your usual load, 16 psi is probably going to be a better choice in that larger tire. On the other end of the Spyder/Ryker, swapping out a 225 wide tire for a 205 wide may require an extra 2psi or so; but if you go up in profile at the same time as going down in width, that need for 'extra air' may be negated. I've recently swapped from a 225/60R15 tire that ran & wore very well at 16psi to a 205/65R15 that I'd normally expect to need saaay 18 psi instead, except the higher profile & the differences in 'actual' tire sizes vs nominal sizes has shown the new tire is actually a tad larger than the old tire so the optimum pressure for the new tire is also 16psi! :thumbup:

But regardless, I very much doubt that there is anyone out there regularly riding a Spyder/Ryker that is loaded up enough to NEED more than saay 20 psi in a 'normal' auto tire mounted on the Spyder/Ryker (car) rims (tall &/or very large riders like Peteoz may be amongst the exceptions that prove that 'rule'! ) Most 'usual sized' riders & loads will generally get a better balance of tire compliance with the machine's suspension and better traction, ride, handling, and tire life at something a bit lower, altho they may not be used to the 'feel' that those pressures bring, probably because they've become used to running on over-inflated tires over time/thru tire fitter's apathy or lack of tire pressure knowledge! Of course, there may also be some who knowingly choose to run more than 20psi in their non-Kenda auto tires fitted to a Spyder/Ryker, maybe to optimise fuel economy over tire life & suspension compliance, puncture resistance, or traction; or possibly simply because the've grown to like the 'firmer feel' that the higher pressure gives them; or 'thinking' it gives them more 'direct steering' despite the lack of grip those pressures usually entail; but that's their choice & prerogative, rather than strictly being a necessity for optimal tire performance.

If you want to search my old posts here, or look for info on the 4psi rule elsewhere, you can use that repeatable & measurable method to determine fairly accurately what is the optimal pressure for YOUR tires on YOUR vehicle in the current conditions/ambient temps etc when used & loaded the way YOU do that, but it does take some initial effort on your behalf; there are also other methods that can get very close, too - chalking the tire & examining the tread imprint; wetting/painting the tire & checking how its track looks; or even weighing the loaded tires on each end & doing the load/pressure calculations using the tire manufacturers supplied load/pressure info.... but with all the many & varied methods available that I've tried, I've found that for the vast majority of Spyder/Ryker users, they all come back to ending up pretty close to the same pressures mentioned above - 16-18 psi up front and 16-20 psi in the rear, with a few exceptions for special needs &/or applications (eg, go higher if you really want to spin the rear tire & light it up at every set of lights.... ) Of course, you may choose to use pressures outside those ranges for any reason you like too, but in doing so, just be aware that it is very likely that you WILL be compromising some aspect of your tire's performance by doing so. :lecturef_smilie:



Or you could simply set your tires at whatever pressures you feel like, then Ryde More, and Worry Less, and maybe pay the bills later! hyea:


Over to you! :thumbup:

Well Peter is certainly long-winded with his answers, BUT, read his answers completely and you will learn a lot. Thank-you Peter, you’re a wealth of GOOD information!

 

[Peteoz]

Well Peter is certainly long-winded with his answers, BUT, read his answers completely and you will learn a lot. Thank-you Peter, you’re a wealth of GOOD information!

I believe Peter A is a “type by touch” typist, Bruce hyea: ..... he HAS to be, because he would have worn the letters and numbers off his keyboard long ago :roflblack:

Pete

 

[Peter Aawen]

I believe Peter A is a “type by touch” typist, Bruce hyea: ..... he HAS to be, because he would have worn the letters and numbers off his keyboard long ago :roflblack:

Pete

Well, there is that.... but sometimes the computer just listens to me & does all the typing itself! nojoke

Some of the 'Talk to text' software available out there is pretty good these days! :thumbup:


And despite the 'one size fits all' pressures printed on your vehicle tire placards, tires & tire pressures are NOT just as simple as that, nor are they a 'set & forget' thing either; plus, as Mike has mentioned previously, there is a lot of science behind the whole subject, and trying to explain the complexities of years worth of study & learning in a single paragraph simply isn't possible most of the time - but I believe it helps people to understand their tires and setting suitable pressures juuust a bit more if I do go into a little of the detail.... hopefully presented in a way that some people can understand. And of course, if you don't want to know or even read any of it, that's fine by me, but I still like to put out there some things that might help those who ARE interested.

 

[Peteoz]

Well, there is that.... but sometimes the computer just listens to me & does all the typing itself! nojoke

Some of the 'Talk to text' software available out there is pretty good these days! :thumbup:


And despite the 'one size fits all' pressures printed on your vehicle tire placards, tires & tire pressures are NOT just as simple as that, nor are they a 'set & forget' thing either; plus, as Mike has mentioned previously, there is a lot of science behind the whole subject, and trying to explain the complexities of years worth of study & learning in a single paragraph simply isn't possible most of the time - but I believe it helps people to understand their tires and setting suitable pressures juuust a bit more if I do go into a little of the detail.... hopefully presented in a way that some people can understand. And of course, if you don't want to know or even read any of it, that's fine by me, but I still like to put out there some things that might help those who ARE interested.

Peter, I hope you didn’t think that I was criticising your posts ... that wasn’t my intent..... there is such a wealth of practical knowledge and experience in them, that I read And enjoy every word..... I set aside a couple of hours a night for a few days for each post :roflblack:

Pete

 

[Peter Aawen]

No worries Pete, I was just agreeing that I do touch-type (@ about 80 wpm last time I checked - which was a looong time ago now, tho! ) but I also frequently use 'Talk to Text' software (Dragan V2 I think?) so it's not quite so hard as many 'non-touch typers' or 'less able to talk under water with a mouthfull of marbles' readers might think!! :shocked: :roflblack:


Oh, and I was also pointing out that the subject itself just isn't as simple as most think either; so often it really needs 'a little more' to explain even just the basics in a way that won't raise more & harder questions to answer simply! And while those who might've read my answers before (or repeatedly! ) may get a little bored by me presenting it all again, we are always getting new members & readers here, and there's all of those plus many others who possibly haven't even thought about their tire pressures or fitting different brands or sizes of tires, or any of the rest of it before, but now that they have, they might like to know. :dontknow:


Anyhow, 'tis all good. Some like it, some don't; but I've at least tried to help, & those who want to take it on board might benefit. hyea: . :thumbup:

 

[Mikey]

:bbq: Wow you guy's are making me tired, I think I need a nap!!:roflblack:

 

[PMK]

Seems this 4 psi rule quoted often here is becoming almost biblical. Myself, I tested different pressures, in the various ranges often quoted and found the softer tires were not a good feel when riding.

What has often had me curious though, this 4 psi rule was derived for cars. Cars are much heavier and tend to place more load into the tires themselves. How can a lightly loaded tire, such as on the Spyder be expected to generate that much heat, unless initially under inflated?

Then, we should also consider ambient temps and heat absorbed into the road surface. Seems a rider in Arizona with very well heated road surfaces vs a rider in Maine could have great differences on the temperatures and resulting air pressure within the tire from expansion, simply from induced heat from the road surface itself.

The 4 psi rule can be searched and read about for cars, simply not sure it is best for motorcycles, or Spyders. Certainly found it not to our liking on the Spyder.

Is there, or has anyone found motorcycle specific information regarding obtaining best tire pressures vs pressure increase?

 

[Peter Aawen]

I think that you're thinking too much into it juuust a little PMK While the subject of tire pressures definitely IS a more complex thing than many surmise, and there are some constraints & differences that might apply in some specific circumstances/different applications, but for the sake of simplicity, a pneumatic tire is still a pneumatic tire, whether it's running under a Mack Truck, a Cadillac Seville, or a Can-Am Spyder; and while there may be some (really relatively minor in the overall scheme of things) differences in the WAY the tires for each are constructed & even in the STRENGTH of the (slightly) differently constructed tires, the physics involved in how any tire flexes to increase its temperature (& therefore the pressure of the air inside it) in order to reach its optimal operational temp doesn't change much at all. The lighter the load imposed upon the tire, the lower the pressure inside it needs to be in order for that tire to warm up sufficiently to properly activate the compounds used in the tire and let them do their job of keeping your vehicle safely on the road without over-heating! Not enough air in the tire leads to it over-heating; too much air in the tire means they don't warm up properly & so can't work properly to keep you safe...... :lecturef_smilie:

And yeah, some people use 6 psi instead of 4 psi, while very few that I am aware of use much less than 4 psi, simply because anything much more than a 6psi increase can lead to catastrophic tire failure while anything much less than 3psi means the tire won't grip the road properly & is more prone to 'over-inflation failures! Any pnuematic tire is not at its ideal temp for its best operation & traction etc when it's at rest - all pnuematic tires NEED to flex some during their operation in order to reach their optimal operational temperature, and that's achieved by allowing a large enough pressure increase in the air inside it to achieve that, at the same time as not letting that temp & pressure increase become too much so that the compounds &/or construction of the tire becomes compromised &/or the tire fails; and regardless of how much BRP might try to convince us otherwise, the tires we run under our Spyders are actually CAR tires and the upper and lower limits of the range of pressures that allow for this '4psi increase' is really quite small as a result of that - so basically, it all boils down to this.... all those variables you think might mean you need to vary the pressure increase you aim for are actually being taken into account by you operating the vehicle on whatever temperature the road is, whatever the ambient temp might be, & whatever the load on the tire might be, so the 4 psi increase (or 6 if you prefer that) works pretty much anywhere, because the laws of physics (at least as we know them for now... ) don't change very much regardless of whether your pnuematic tire is running under a Mack Truck in Oz, a Caddy Seville in Arizona, or a Spyder in Ontario. :thumbup:

 

[Freddy]

I think that you're thinking too much into it juuust a little PMK roflmao The pot calling the kettle black. :roflblack:

 

[PinkRosePetal]

A question from England. Going to put a Toyo Proxes TR1 225/50/15 car tyre on the rear of my 2016 Spyder RT Limited.Usually ride 2 up, I weigh 80 kilos and my wife weighs 60 kilos. Reading others posts, people use anything from 18 psi to 28 psi pressure. Would appreciate replies stating what pressure you use so I can start off with the most popular. Thanks in advance.

I'd start at 26psi. See how you feel on the road.

 

[AdyB]

Thanks for your replies, I didn't expect such technical answers. I just thought people would just give me a figure and I would use that as a base point. It seems somewhere between 20 psi and 25 psi would be a good starting point. Many thanks again for your time and experience in answering my question.

 

[BLUEKNIGHT911]

Thanks for your replies, I didn't expect such technical answers. I just thought people would just give me a figure and I would use that as a base point. It seems somewhere between 20 psi and 25 psi would be a good starting point. Many thanks again for your time and experience in answering my question.

OK here's the short version ..... For Kenda tires ONLY, use BRP's recommended PSI ..... For ANY AUTO tire, 17-18 psi Front and 18-19 Rear .... you can do all the testing you want. But these psi's have already been figured out using Tire Science..... ride safe - ride happy .... Mike :thumbup:

 

[Peteoz]

Thanks for your replies, I didn't expect such technical answers. I just thought people would just give me a figure and I would use that as a base point. It seems somewhere between 20 psi and 25 psi would be a good starting point. Many thanks again for your time and experience in answering my question.

Yeah, the aim of my original post was to say that you can start around 25psi, and work your way down to 12psi with no safety issues, until you find the psi that is right for you, Ady (although I wouldn’t recommend lower than 16)
That’s why you are seeing so many variables. I have found that Mike and Peter’s experience based advice works best for me, and have my fronts at 18 and rear at 20, with a weight of 140kg (about the same as you and your wife), and I started at 24 all round and gradually lowered pressure by a couple of psi a time until I felt most comfortable with handling and ride.

Pete

 

[PMK]

I think that you're thinking too much into it juuust a little PMK While the subject of tire pressures definitely IS a more complex thing than many surmise, and there are some constraints & differences that might apply in some specific circumstances/different applications, but for the sake of simplicity, a pneumatic tire is still a pneumatic tire, whether it's running under a Mack Truck, a Cadillac Seville, or a Can-Am Spyder; and while there may be some (really relatively minor in the overall scheme of things) differences in the WAY the tires for each are constructed & even in the STRENGTH of the (slightly) differently constructed tires, the physics involved in how any tire flexes to increase its temperature (& therefore the pressure of the air inside it) in order to reach its optimal operational temp doesn't change much at all. The lighter the load imposed upon the tire, the lower the pressure inside it needs to be in order for that tire to warm up sufficiently to properly activate the compounds used in the tire and let them do their job of keeping your vehicle safely on the road without over-heating! Not enough air in the tire leads to it over-heating; too much air in the tire means they don't warm up properly & so can't work properly to keep you safe...... :lecturef_smilie:

And yeah, some people use 6 psi instead of 4 psi, while very few that I am aware of use much less than 4 psi, simply because anything much more than a 6psi increase can lead to catastrophic tire failure while anything much less than 3psi means the tire won't grip the road properly & is more prone to 'over-inflation failures! Any pnuematic tire is not at its ideal temp for its best operation & traction etc when it's at rest - all pnuematic tires NEED to flex some during their operation in order to reach their optimal operational temperature, and that's achieved by allowing a large enough pressure increase in the air inside it to achieve that, at the same time as not letting that temp & pressure increase become too much so that the compounds &/or construction of the tire becomes compromised &/or the tire fails; and regardless of how much BRP might try to convince us otherwise, the tires we run under our Spyders are actually CAR tires and the upper and lower limits of the range of pressures that allow for this '4psi increase' is really quite small as a result of that - so basically, it all boils down to this.... all those variables you think might mean you need to vary the pressure increase you aim for are actually being taken into account by you operating the vehicle on whatever temperature the road is, whatever the ambient temp might be, & whatever the load on the tire might be, so the 4 psi increase (or 6 if you prefer that) works pretty much anywhere, because the laws of physics (at least as we know them for now... ) don't change very much regardless of whether your pnuematic tire is running under a Mack Truck in Oz, a Caddy Seville in Arizona, or a Spyder in Ontario. :thumbup:

Seeing as you brought the example of Mack truck, Cadillac, or Spyder, we pretty much accept the Mack does not run car tires, but you believe 4 psi increase at temp is correct. Then shall we attempt to group the opposite end of the spectrum, should a skinny bicycle tire see only a 4 psi increase?

I do find it odd though, that your method is willing to ignore ambient road temps as a variable in obtaining this 4 psi spec. It seems difficult to consider that a Spyder driven year round would retain the same initial tire pressure for all seasons. Locally, the road surface can range from acceptably cool where you could walk or stand on it in bare feet, to temps so hot that burns could occur.

Based on what you posted, in order to generate heat, a tire pressure is typically less, and tires that are deemed over inflated can run cooler. The road surface temp must have the capability to heat the tire, and with that, increase pressure. Therefore, that lower pressure tire determined by this 4 psi rule, and determined on a cool day with a cool road, might be a higher pressure on a hot day? Granted your base pressure would fluctuate depending upon ambient temps, but road surface temps will increase noticeably more.

FWIW, regarding the bicycle tire, those are checked and adjusted prior to each ride. Seems odd though, same initial pressure regardless of whether it is hot or cool, on the hot road temps, we have blown the tire off the rim as it got heat in it.

Glad this 4 psi rule works for some, based on post on the FB group, it seems many have tested it only to find it less than worthy for them.