Originally Posted by jonathanb715

Some pressure loss is normal. If it's more than 5 psi or so overnight, I'll check the tire very carefully to be sure there's not a thorn or piece of debris piking through the tire and causing a slow leak. If I can't find it, though, I will still go for a ride on it.

If it's down 20 or more PSI overnight I know something is definitely wrong and will pull the tire off and check both tire and tube very carefully before riding on it.

BTW, if the tire was filled from a CO2 cannister it will lose a whole bunch of pressure overnight - that's normal, just pump it up each day - once the CO@ has leaked out and is replaced by air it will act normally again.

JB