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how much does elevation affect tire pressure?

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I always wondered how much elevation affects tire air pressure since i usually air up at home which is at almost sea level , then drive up to the mountains to go ride. So i just looked into it and turns out it only raises it 2 or 3 pounds at the 5,000 foot level. However, if you were to check the tire pressure on your bike early in the morning while it was cold, drive a few hours and ride once its warmer, the warmer temps can also raise it another 2 or 3 pounds. So it is very possible for your tires to be 5-6 pounds over inflated by the time you get to your destination and ride.

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Yup

It takes roughly 30F change to change tire pressure 10%.

Altitude is pretty easy:

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

So if you put in 14 psi at sea level and 50F, then drive to 5K and 75F, your pressure could end up around 17.2 psi.

Never matter much for me, I always set tire pressure at the trail head. Really matters even less now, as I might see a few hundred feet in elevation change, not the 4K or so I'd see when living out west!

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I'm just on my first cup of coffee here, but I'm pretty sure that elevation won't affect the pressure in your tire, except in relation to ambient pressure. I'm also pretty sure that I'm not gonna put that little bit of pressure change on my list of things to worry about.

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I can tell you that it does. When I leave my house at 450 feet ASL, I have 20 psi in both tires. When I arrive at my ride spot at 3500 feet, it's always higher. The thing is that when you are reading a tire pressure gauge, you are reading the pressure differential between the tire and ambient atmospheric pressure. When you then move the tire to an area where ambient pressure is lower, the differential that will show on the gauge is higher.

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This is why I always adjust my pressures when I get to where I am riding. I will blow the tires up to about 20psi at home and then let them down to where I want them right before I go ride. I keep a bicycle pump with me just in case I need to go up a pound or two after I let them down.

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This is why I always adjust my pressures when I get to where I am riding. I will blow the tires up to about 20psi at home and then let them down to where I want them right before I go ride. I keep a bicycle pump with me just in case I need to go up a pound or two after I let them down.

thats a good idea. i always checked them at home cause i have an air compressor to use. wouldnt hurt to throw a bicycle pump in the truck.

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