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Tire pressure is measured cold. After the tire warms up, the pressure should not increase more than 10%. If you start at 30 psi, then it should not go above 33 at full temp. If the pressure is too high, start with a lower pressure. If it does not go up 10%, add a little to the starting pressure.
On my RT-S, this translates to about 17.5 - 18.0 on the fronts, and 28 in the back......
Using a 'rule of thumb' like that one Bike-O-Din is a great way to make sure that YOU get your tire pressures right for YOU, the way you ride, your loading, the roads you ride on etc, and it's easy enough to be repeatable, readily understood, & applicable to pretty much any vehicle too! However, your guide is only ALMOST right - you got the add & minus pressures the wrong way around!! :yikes:
If the pressure goes up by more than 10%, your starting pressure needs to be
HIGHER, not lower as you mention in the bit I made bold in the quote above!! That's cos lower pressures will let the tire flex more & therefore make the pressure increase greater, which is the opposite of what you want if the increase is greater than what you want. There's some good explanations on the why's & wherefore's of that to be found if you want to google it.
Conversely, if the pressure does not go up by 10%, you need to
DROP your starting pressure rather than add as you mentioned in the bits I underlined in the quote above; same reason tho, just the other end of the measuring stick - lower starting pressure = more tire flex = greater pressure increase once warm... which in this case is what you do want to achieve. ;-)
The tire industry uses a variety of these 'rules' to work out the optimum tire pressure, altho the rules vary a little depending on the specifics of the particular vehicle use. The one I grew up with was known as 'the 4psi Rule' - instead of aiming for 10% increase in tire pressures, it aims for a 4psi increase (if you want to know more, google it!) But they are all basically aimed at achieving the same thing & they all produce very close to the same results anyway.... ie. the tire people looking after race cars & bikes might use anything between 3psi & 10psi increase or anywhere from 4-5% thru to 15% increase, or they might even look for a similar tread temperature % increase evenly across the tread face, but in reality they all aim to achieve a set pressure or temperature increase in the tire from cold start temps to operating temps (increases in tire tread temps mean increases in tire pressures)
But the critical thing to remember about all of these rules/methods is that if your pressures increase by TOO MUCH from cold, you must ADD PRESSURE to your cold starting pressure to make the resulting pressure/temperate increase LESS once the tire is warmed up; while if they increase by NOT ENOUGH from cold, you must SUBTRACT PRESSURE from your cold starting pressure to make the resulting pressure/temperature increase MORE once the tire is warmed up!
As for the pressures YOU arrived at for you, your bike, & your riding etc. - they won't necessarily apply to anyone else - what your guide or the 4psi Rule or any of the other techniques out there arrive at is really only applicable to the rider/driver & their vehicle, their general use etc. So no-one else should (or can really) rely on
your pressures being right for them, just like the 'compromise' recommendation on the vehicle placard isn't ever going to be right for each & every rider/driver out there - those recommendations are a good start point but just don't take into account all the variables that can impact on what the OPTIMUM pressure is for any specific tire on a vehicle ridden/driven by a specific rider/driver of any specific vehicle on whatever roads they ride/drive on - so each of us really should work out our own OPTIMUM tire pressure for each tire & vehicle we use, ideally using one of those repeatable 'rules' mentioned above or one of the others that can be found amongst all the tire industry documentation that abounds on this sort of thing! :thumbup:
