tire pressure and altitude changes

[Guest]

Hi Every Buddy. I live at 7000 ft, I ride between 9000 to 4000 ft what, if anything, should I do to cold tire pressure? I'm kinda thinking go down 10% when I go up, and go up 10% when I go down. And if I ride between both elavations in one day leave it alone

[bwringer]

I wouldn't worry about it. Set cold tire pressure as you wish at home and ride happy.

There's only a little more than 2psi difference in absolute pressure between 4,000 & 9,000 feet.

http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html

[jbs80106]

Agree. Now if you lived a 4000 and were going to do some riding up around 9000 for a longer duration you might want to adjust fuel mixture so you don't run too lean...but I may have that the wrong way around, might be richer at altitude (less air) if you were tuned fine for sea level.

I too live at 7kft, ride up over around and through the mountains and back without any issues.

[SqDancerLynn1]

Bike gets richer as the altitude goes up, less air, less compression. I was up around
9K ft on a early 70's 750K (Tioga Pass) Would not hardly run, had to work hard to keep up 20mph. If you plan on staying at that altitude ? A bump in compression wouldn't hurt

[duaneage]

I took a bicycle over Taiwan's Southern Island road and went from sea level to 8000 feet. I had to let air out of the tires half way up and put air back in half way down. A water bottle I drained at the summit was crushed by the change in air pressure.

Carry a small gauge and check the pressures going up, I carry a small electric pump for emergencies, it could be used to adjust pressures if need be.

[DanTheMan]

On my last trip to CA via Yellowstone, Tetons,Zion and back via the high country in Nevada, Utah, and Rocky Mtn Nat Park, I never screwed around with my tire pressures, even at 12k feet. I crawled around mountains above 6k feet all my life in all kinds of vehicles, including my touring bicycle with 130 psi 1" wide tires, and have never yet adjusted tire air pressure due to altitude. This includes going up to the top of Mt. Evans at 14k feet.
You inflate your tires to the proper pressure cold, don't bleed off pressure when they're hot, and so far in my experience, unless they appear to be running flat, don't adjust them for altitude. The only reason to adjust the pressure would be if they appear to be running flat.