Tyre Pressure Changes During a Ride

[StinkyPete]

I've recently fitted a set of Garmin Tyre Pressure Monitors, which give me an actual pressure readout on my GPS while on the move, and a low pressure warning at a preset pressure that I input.

Riding solo, with 42 psi front and rear, and in this mild spring weather we are experiencing, tyre pressure on the move goes up to 46-47 psi in both front and rear.    On our recent "two-up" ride to the Melrose RTE, cold pressures at the start of the ride were 42 in the front and 44 in the rear.    The front went up to 46-47 and the rear rose to 50 psi.

I knew that pressures changed when the tyres heat up, but it's interesting to see some actual numbers.  I'm keen to see what the pressures go up to in some seriously hot weather.

[Brock]

Its all because of a guy called Boyle, and the law he wrote. All to do with volume and temp affecting pressure.

Here is a spreadsheet that might be interesting

https://www.dropbox.com/s/rf6eb77gf3je4b9/Tyre%20Pressure%20for%20temp.xls?dl=0

[StinkyPete]

Its all because of a guy called Boyle, and the law he wrote. All to do with volume and temp affecting pressure.

PV=nRT      as I recall

[Biggles]

Its all because of a guy called Boyle, and the law he wrote. All to do with volume and temp affecting pressure.

I'm glad he invented that because it could come in handy with this idea I have for an engine that doesn't need spark plugs to ignite the fuel/air mix.

[Brock]

Diesel might have some ideas on that.

[ST.George]

G'day  Pete,
I would b interested in those Garmin thingamajimmies - have u got a site address handy, otherwise I'll just look up mr Google.
 

[atoyot]

My TPMS does temps as well, and that can be scary in summer! Interestingly, I see similar rises in pressure, with the rear tyre increasing much more than the front as well. Same goes for temp.

[StinkyPete]

G'day  Pete,
I would b interested in those Garmin thingamajimmies - have u got a site address handy, otherwise I'll just look up mr Google.
 

The Pressure Monitors pair with the Garmin 590 GPS.    Here you go.....     http://www.ja-gps.com.au/Garmin/zumo-590lm-motorcycle-gps/

[tj189]

My TPMS does temps as well, and that can be scary in summer! Interestingly, I see similar rises in pressure, with the rear tyre increasing much more than the front as well. Same goes for temp.

which TPMS are you using Andrew?

[curious1]

The culprit for the pressure rise when tires warm up is the moisture in the tire. Use N2= Nitrogen and you have verrry little pressure rise. You can also use air from a diving cylinder which is extremly dry but connecting to tires is a problem.
Cheers
Alf

[atoyot]

My TPMS does temps as well, and that can be scary in summer! Interestingly, I see similar rises in pressure, with the rear tyre increasing much more than the front as well. Same goes for temp.

which TPMS are you using Andrew?

http://www.tirewatch.com.au/wordpress/

Pretty happy with them, but another small screen required. I like the idea of the sensor inside the tyre, but it would be perfect if they paired with my Garmin for one less gadget to mount and look at.

[tj189]

Thanks Andrew, yep had one of those in the ST1100 but never took it out before selling the bike. looks like I will just have to buy another one. Just wish the screen could be externally powered.

[Nigel]

Very Interesting topic. I was always told to check/adjust Tyre pressures when cold. Assuming that this is the start point. I thought the idea of monitoring pressures on the "move" was to find out as early as possible that the system had detected an air leak and there fore a problem IE Puncture? I understand that pressures varies  with changes in temperature, but I am not sure we need to concern ourselves with them! As long as we have set them correctly cold it should all be ok?????????????? What do you think?????????????

[Brock]

The major concern is to detect loss of pressure, as that is a dangerous condition, A higher temp/pressure, is off set by a grippyer tyre when hot.

Have a look at some ones tyre after a track day, melted rubber balls every where.

[StinkyPete]

The major concern is to detect loss of pressure, as that is a dangerous condition.

Correct, and my principal reason of getting the TPMS was for the low pressure warning.   I've set them both at 2psi below my normal cold pressures, and posted the pressures that I have seen while on the move, purely out of interest for the curious.