Since it’s ramping-up time for the new semester, a bit of recycling is in order. The Science of Speed is a video series the National Science Foundation made to explain some of the science of motorsports. One of the segments (which I wrote) is on Tire Pressures. Go take a look at it on the NSF site. (Note – you can’t play it through my site because of the licensing agreement for some of the video that was used. The picture is to make the blog more visually interested. Don’t try clicking on it… or do. Nothing will happen.)
So one thing I’ve wondered is, how big a deal is it that they use nitrogen? I mean, if they just used standard air would they get more pressure at top temperature?
Yeah, atmosphere air will be less consistent in regards to air pressure. They adjust to the 0.25 psi, so I bet they want it as consistent as possible. For the daily driver I think its a waste of money.
Y’know, this talk about changing tire pressure to the quarter pound would be more convincing if I didn’t see most of the tire specialists using meters that only read to 0.1 psi… Do you really think drivers can tell the difference between a quarter pound if no other adjustment is made?
@skip: “standard air” is not safe inside a racing tire, because it contains water vapor and as you can imagine, when the tire hits 212 F (100 C) that water starts to boil. that could lead to all sorts of unwanted problems.
I think the issue is that the humidity of the atmosphere varies. When the tire is filled with air and the tire heats up, the pressure added by the water vapor varies with the humidity. Since the tires are set up cold, the pressure will vary when the tire temperatures are up. Because the process of “making” nitrogen eliminates the water, that inconsistency goes away.
Thank you Diandra! I’ve always thought that “quarter pound adjustment” was NASCAR psychobabble. When Jimmie Johnson hit the wall crushing the right rear, Chad told him it was hardly damaged. Jimmie drove the wheels off and finished well. When he saw the actual damage he said, “Chad lied to me!” If Jimmie didn’t sense that amount of damage, can he really sense .25 lbs of air pressure?