So just got new rubber about 3 weeks ago on my 06' new Dunlop American Elites.

Our summer has been much cooler this year. Mornings have been in the low 50's.

So my indy said to run the tires at 40PSI both front and back. I see below 60 degrees that the tires are at 36PSI or so. So if I fill in the AM to 40PSI at that cooler temp by afternoon it will be way over 40PSI...likely 44 or so. Especially if I'm on the highway for a spell.

I've seen on Saturday's when wife and I head out for the day I'm removing air from both since it's later in the day and temp is 70 degrees or higher vs. when I leave for work during the week with the bike.

Any suggestions? Seems like all I do is add or remove air...

THANKS!

 

Always check pressures on a cold tire. Tire pressure will build due to heat as a rule. What the pressure is when cold is all that matters.

2010 Limited with some stuff

 

if you can fill with nitrogen, 100% nitrogen is less subject to expansion ( rising PSI) due to temperature.

larger molecules less likely to migrate through the rubber

and drier

not worth paying alot, but if you can get cheap.

I will says that here in AZ, nitrogen fills ( all vehicles) have made my life easier with ambient temps often over 110º, and common elevation from 1000' to 7000'

costco now uses nitrogen, those guys like pizza

mike

 

Check it and set it cold. I have the tire pressure sensor on my Zumo 390 and the rear tire can get to mid to upper 50's on a hot day two up long ride...

 

Nitrogen is an inert gas in which there will be NO pressure change regardless of what the temperature is. That being said, the heat generated by the flexing of the tires will cause the pressure to raise slightly (a couple of pounds), but that is negligible. That pressure increase is only from the expansion of the rubber due to temperature, which makes the air space slightly smaller to cause that pressure "increase". However, the air in which we breathe and use from the air pump to inflate our tires is already78% nitrogen, so buying pure nitrogen is a waste of money. Only people who race or those who feel they need an "edge" in this regard are the ones who think it`s worth it to buy nitrogen. In the HVAC industry nitrogen is used extensively for leak checking and as a filler of a space which will have brazing done, to prevent oxygen to react at the spot being brazed.

 

You can do it either way. A tire on a chilly fall morning will be about 5 psi lower than a tire running down the highway on a blistering summer day. Cold is the listed pressure, but actually it's the running pressure that is critical. Your bike sitting there with zero pressure in the tires is just fine. Ride it that way and then it's not.

This isn't a bad read on the subject of tire pressure:
http://www.tirerack.com/tires/tirete....jsp?techid=73

Fwiw, on my racer I tune hot pressures, and keep records. I do not bother with this on any of my street machines.

PV=nRT. That's the old ideal gas law. Applies to pure nitrogen, or the 78% nitrogen blend known as air. However, tanked nitrogen is dry, air has humidity. Moisture can drop out as a liquid, or become a gas again. That can make pressures interesting, but still pretty much a non issue because there just isn't that much moisture in the tire. None the less, you will not cause problems by using nitrogen.

 

Interesting... I don't think I've ever had to remove air from my tires. But regardless, I think I would still stick to the cold psi number... that is, "cold" as far as the tire not being run yet.

Seems like quite a conundrum... Heat is a tire's worst enemy (well, aside from nails and such), so it would stand to reason that as the weather gets hotter, the "cold" psi should/would also increase to accommodate the higher temp.

Are you saying that, if you air up "cold" to 40 psi in the morning when it's 50 F, not move the bike, and then the temp rises later in the day, that cold 40 psi is now more like 44 (as an example), and thereby now over inflated? However, you also said, "Especially if I'm on the highway for a spell." The psi on a tire will increase on a running tire, and stay that way for a long while after it has stopped running, that is why psi is to be checked "cold" (before the tire has been run), and an increase in psi on a hot tire (one that has been run) is normal and made to be run that way. So checking your psi after the tire has been run is not a good measurement.

I'm no expert, so I can't give you a solid answer, sorry... What I do, is air up in the am before the ride to the proper cold psi, and call it a day. Even when/if I've had to air up in the afternoon before starting a ride, I don't recall ever having to remove air from my tires, or my wife's bike's tires. This has worked fine for me in short and long trips (400 miles or more) through all types of different weather and elevations in the same day.

Sometimes we can over-think things.

 

Check the cold tire pressure once a week and ride.

 

Your way over thinking this.
You don't constantly add/remove air from your car tires do you?

Air pressure will build as the tire heats up (just driving around the block a few times will put some heat into the tire).
Your car tires do this too.

As mentioned, just check (and adjust) air pressure when the tires are cold (as in first thing before riding).
No need to let any air back out an hour into a ride just because the pressure increased a little.

 

Always check tire pressure when cold. Cars or Bikes.
And, 40 psi is too much for the front. On virtually every HD, 36 front / 40 rear.