tyre pressures

[john348]

Does anyone adjust the tyre pressures for two up with luggage touring.  And if so does it muck up the tyre pressure light or is that only for low pressure.  I am off next week with pilion plus luggage for 2 week tour round France.

[Leak]

Hi John,

I run mine at 2.5 (36) front and 2.9 (42) rear whether I'm solo or two up with luggage. Other ppl on here might not, they might run a completely different set-up   

[loads of miles]

I am the same as roadrunner run them at 36 front  and 42 rear There isnt anything in the handbook to suggest otherwise .
loads of miles

[cropbiker]

Same here.

36 front, 42 rear whether one or two up

[waspanman]

Hi
Just toured around Europe in 28-31 degrees C and monitored tyre pressures because of a puncture
I found that in that temperature they mostly ran between 5-10 psi above cold pressure, I guess this is due to Charles Law, so I reckon you shouldn't need to compensate as your tyres will warm and the pressures will rise naturally

[w8d4it]

Originally Posted by waspanman

Hi
Just toured around Europe in 28-31 degrees C and monitored tyre pressures because of a puncture
I found that in that temperature they mostly ran between 5-10 psi above cold pressure, I guess this is due to Charles Law, so I reckon you shouldn't need to compensate as your tyres will warm and the pressures will rise naturally

Just recently finished taking my daughter through an arduous semester of chemistry so I can't resist commenting that  Charles Law doesn't really deal with pressure.  It only states that volume of gas expands as temperature increases.  Without citing that volume must remain constant you don't have the increase in pressure.  You must incorporate Boyle's law as well to deal with the pressure aspect. The particular law that incorporates both is Amontons' Law of Pressure-Temperature.   

Having just come off as a know it all I will say that I constantly monitor the pressure gauge and find a relatively constant 8 psi increase when full warmed up and riding in the 90-100 F heat of Texas.

[Bajagrngo]

 

[Trumpet]

Well lets say that you are in a dessert hotel, and when you get up in the early  morning, its 30 American Degrees outside (Fahrenheit for you foreigners). You check your tires and make sure you put them at 42 PSI before you take off...per manual specs.

 By the middle of the day, you and in the kingdom-come dessert road which is now at 90 degree ambiance; your tire probably much hotter than that. You check your pressure at the truck stop and its 54 PSI. You need to take some air out due to the expansion of the air inside the tire due to the heat.

All this can be done without a calculator, nor the theoretical applications of Boyles' Charles' nor Amonton's Principles...can't it? BTW, I just taught a Physics course at a Community College in my village, so I know it can be done.