Tyre pressure..

[Arfcollins]

Aha, I detect myths!

Tyre pressure remains constant, regardless of the weight on the bike, even if that weight changes. Attach a pressure gauge to a tyre and jump on the bike - the pressure will not change.

Aha, I detect a myth too! It will depend on the original pressure as to whether you can easily measure the increase in pressure caused by the weight on the bike. If the pressure is low enough that the tyre is significantly flattened this means the volume of the tyre has decreased. Smaller volume = higher pressure. If the tyre is at 140psi the change will be too small to be measurable.

Not this is in any way important, I'm just being pedantic.