Portuguese to English Tech/Engineering Mechanics / Mech Engineering Agricultural machinery

Em condições operacionais normais, verifique os valores de pressão de freio a ar entre 40 e 500 passos.

What is the translation of "passos" in this context? Air pressure would normally be measured in PSI - is this a Brazilian slang term for PSI, perhaps...?

The text is from a series of technical manuals for a tractor. It is in Brazilian Portuguese and the client has already told me that it was originally translated from English, so it is possible that "passos" is a very poor translation from the English... but I have no idea what it could be. (The original English texts are not available - presumably they have been lost.)