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I recently took a flight on a (Lufthansa) Bombardier CRJ900 aircraft. As I was about to embark, my eyes caught this image:

enter image description here

And the aircraft wasn't even loaded with the passengers yet. If I saw this in a car, I would assume a flat tire or other loss of air pressure...were these wheels under-inflated?

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    $\begingroup$ Hmmm, I don't see where this tires are flat... Those are no bike tires, which touch the ground with a coin-sized patch. Instead, they should touch the ground with the full width of their treads. $\endgroup$ – sweber Jun 2 '18 at 18:51
  • $\begingroup$ Not sure why you think this has anything to do with a car's tires... If the aircraft is fully loaded that's the way they're supposed to look. And there's no air in there, it's nitrogen. $\endgroup$ – Juan Jimenez Jul 15 '18 at 12:42
  • $\begingroup$ @Squareoot: Make this an answer, perhaps? $\endgroup$ – einpoklum Jul 15 '18 at 14:22
  • $\begingroup$ @JuanJimenez He says in the question, passengers weren't even loaded yet. $\endgroup$ – Cloud Jul 16 '18 at 6:27
  • $\begingroup$ Doesn't look abnormal to me $\endgroup$ – selectstriker2 Jul 16 '18 at 17:44
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enter image description here

It's absolutely normal. Above is how the manufacturer even depicts the nose tire in the airport planning manual (.pdf, page 42).

The pressures are checked by line engineers typically before leaving the hub, as well as an inspection by a flight crew member before every flight.


While not available on the CRJ900, there are many jetliners that have tire pressure sensors. See:

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High tire pressure means less rolling resistance at least on a good road. However it also reduces grip that makes braking less efficient (source). Hence high pressure may make sense for a bicycle but not for a plane where the power is more than abundant.

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    $\begingroup$ Another factor might be mileage. A plane usually travels only a short distance on its wheels, in contrast to road vehicles. So for a plane you could allow yourself a lower tire pressure to gain braking efficiency for the cost of a little bit more wear. For cars underinflation would be a bigger problem. $\endgroup$ – Dohn Joe Jul 20 '18 at 10:37
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Neither car nor aircraft tires are supposed to be inflated to the point where only a small percentage of the tire is in contact with the ground. If you can think of a scientific argument why they should be, post it. It's very common knowledge that inflating tires to maximum pressure reduces sidewall effectiveness and overall tire performance.

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  • $\begingroup$ What is "sidewall effectiveness"? Also, I didn't talk about maximum pressure, which is not good for cars either, but it seems strange to me that so much of the tire would be on the ground. $\endgroup$ – einpoklum Jul 17 '18 at 8:10
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    $\begingroup$ A tire is not a 100% rigid device. They are made of synthetic rubber because they need to give. When there are any sideloads on the tire, the surface that provides contact with the ground to give you control and traction is the tire's sidewall. In tire engineering parlance, it's called "lateral stability." As to max pressure, inflating the tire to the max rated pressure is the only way to get the visual effect you want, which in 99% of cases is the wrong situation you want in any tire. $\endgroup$ – Juan Jimenez Jul 17 '18 at 9:13

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