PR 5's

[mcinlb]

So the manufacturer does not tell you to adjust tyre pressures based on load, but you are advocating making adjustments to some random pressure as you see fit. I'm afraid that does not make sense....

[Djairouks]

Originally Posted by mcinlb

So the manufacturer does not tell you to adjust tyre pressures based on load, but you are advocating making adjustments to some random pressure as you see fit. I'm afraid that does not make sense....

You read a manual and stop thinking, just blindly follow what really is for liability reasons, because if they said adjust pressure and there's an accident, they would have problems, that's all it is.
With fixed pressures no problems for them, but your tire wear and grip will not be optimal really.

Not random, a few pounds difference mostly depending on weight and temperature, it's not so complicated just use logic.
The manual says which oil or cooling liquid is used also, so with your thinking it's not allowed to use any other brand than what Triumph say, just think a bit, it's guidelines.

You mean to tell me with all the older long time riders here, you have never seen the pressure/load stickers on motorcycles swingarms, I must say this is surprising all my Japanese bikes had one, Triumph doesn't curve the laws of physics, look in this link they talk about it if you believe I'm not making sense !

My Triumph didn't have the sticker, as it was the demonstrator, but the mechanic never puts the max 36/42, they all say adjust accordingly.

https://ultimatemotorcycling.com/2020/04/28/under-pressure-air-pressure-for-motorcycles-that-is/

[AvgBear]

Tire pressure and temperature (both ambient and the tire's) are related. It's well understood that on cold days tire pressures (at rest) will read lower than similar checks on hot days.
Temperature changes also apply whilst in-use: an over-pressured cold tire may not warm enough / soon enough; and, an under-pressured tire may overheat -- especially when loaded / over-loaded, or at higher speeds.
An overheated tire can be dangerous / fail.
Many racers and others use the "4 PSI rule" to find the optimum tire pressures: If your tire pressures increase more than 4 PSI from 1st (cold) check to a later (in-use) check they are probably under inflated. Conversely, if they increase less than 4 PSI they may be considered to be over inflated.
But, 'Djairouks' is correct -- one size doesn't fit all.
 

[Aussie Tiger]

Agree with all that but here’s a recent observation relating to specific tyres.
I recently fitted Dunlop Trailmax Mission to my 900 Rally Pro.
These tyres have a rather unique makeup in that the rear is a much harder compound than the front. I set the pressures to the recommended levels. After some pretty spirited riding and once warmed up, the front tyre pressure increased by 3psi, the rear by 6psi and at one point was reading 7psi up from cold. With less spirited riding the increase is less pronounced but still with a strong bias to the rear.
Not drawing any conclusions yet, just an observation.