Jonny Z:
"Also I let the car sit for a while after inflation, compressed air is warm and I let it settle before adjusting the pressure."
Air that has gone from a compressor into your tires should be cold, not warm.
My question on tire pressure is more about gauge accuracy. I read an article years ago that stated the pencil-type guages are actually the most accurate. Dial type gauges can be notoriously inaccurate, even expensive ones. And then there are the newer digital type.
I've noticed that none of these types of gauges ever specifies a level of accuracy, or an error percentage, on the packaging or instructions. They always say "reads in 0.5psi increments," or something to that effect.
If you're gauge isn't very accurate then getting exacly the reading you want is meaningless.
- Glenn