This is interesting and useful information but some comments might be in order:
Where I live, the ambient temperature when the sun is just coming up can be around 60 F and then 3 hours later it can be 90. And the temperature of the asphalt pavement can be much higher. So the conditions and time are rather important to get a good test.
A similar comment applies to letting air out.......which I think never should be done without going through a full 24 hour cycle.
Regardless of what the pressure IS after riding a while, if it goes back down to your "normal" cold value after sitting overnight, then it is NOT appropriate to be letting air OUT.
And this might be stating the obvious but these numbers won't apply to other types of vehicles.......although the theory is still valid.
Please ignore the comments I've quoted above, for the reasons I'll state below:
Regardless of the ambient & road temps when you check your tire pressures cold & what the ambient & road pressures may have reached when you check your tire pressures after ryding for an hour, if your tire pressure has risen by more than 4psi and you intend to continue ryding in the existing conditions, you need to add air to your tires as outlined in my post above. Now sure, if you KNOW you are ryding into a massive & freezing blizzard or any other significantly different conditions, then you might not want to add air pressure to inflate your tires to suit the conditions you've just been ryding in, but I'd hope that most would consider ryding into said blizzard might be a bit foolhardy & consider any forecast changes before they head on, and that they'd likewise consider expected changes if ryding on into any other significantly different conditions.
Re letting air out - if you've ridden for an hour and your tire pressures have not risen by 4psi, then your tire pressures are too high & you can safely let 'a touch' of air out now! Yes, I should have specified that by 'a touch' I'd normally mean saay 1psi, & generally never more than 2 psi - & for that I apologise, but I'd also expect that most could work out that if you started with 19psi & your tire pressures are now 26 psi then you'd not want to let more than a couple of psi out anyway - but please, if you know most people are running saaay 15 psi or so in their tires but the tire fitter who recently installed your new tires inflated those tires up to 40 or even 60 psi to seat the bead & then left that pressure in there (don't laugh, it happens!) even when the warning on the tire sidewall says something like Maximum pressure 35psi, and you've ridden for an hour on that 40 or 60psi (or whatever other stupidly high pressure might be in there) then please, let more than 1-2 psi out now. PLEASE! Only please do try to use the rough guide I provided & generally only let out 1/2 of the difference between what your tire pressure is now & what it should have been if your tire pressure only went up by 4psi - see my example in the earlier post. That will let you gradually step down closer to a safe pressure without leaving your tires under-inflated the next morning, and over time you should notice that your tires are gradually needing less & less changes up or down to achieve that 4psi increase from their cold start pressures, which means you are now running pressures that are much closer to the ideal pressure for YOU and for your tires & the way you ryde & load your Spyder on the roads and under the conditions you are generally ryding in!
Next comment, Please note that this 4psi figure & the 'rule of thumb' that I've outlined above can be used for any Passenger car 'P' type tire or any Light Truck 'LT' type tire that you might use on your Spyder, your passenger car or your light truck, van, or 4WD that's running 'J' or 'JJ' type safety rims just so long as it is running pneumatic tires made of a rubber &/or silica compound & they are inflated with compressed atmospheric air. There are some specific proviso's to make this 'rule' work for other types of tires, rims, vehicles, & gasses, but generally, pneumatic tires inflated with atmospheric air on Spyder, car, or light truck/4WD rims will all work pretty much the same way, and this method of determining what pressure to run in them is a handy way that almost anyone with a consistent air pressure gauge can use to fairly reliably get closer to their ideal pressure for their tires & ryding/driving. It's consistent, it's repeatable, and it considers any & all variables that might exist in the conditions or circumstances you ride/drive in/thru/under in the hour between checking your cold start pressures & reading the pressure an hour later, giving you a good guide about how those pressures can be used &/or adjusted to better suit the conditions & variables that you are now facing and expect to be ryding/driving into, thru, & under as you proceed.
And if you don't want to use this or any other method, I'm fine for you to make your own choices and do that, but I've posted this here in the hope that it might help some Spyder Ryders &/or vehicle drivers in their attempts to determine better tire pressures for the tires they've chosen to run on their ride or maybe even on their car, van, truck, or 4WD, rather than to draw nit picking comments from people who have little if any idea but just want to nit pick or argue......
hyea:
