Tire pressure observation
02-26-2010, 03:47 PM
#16
The recommended pressures for your car are the baseline assumption Porsche used to calibrate its suspension. As part of the deal, those pressures will generally put the most tread on the ground for an OE width tire, though there is obviously some latitude there. You can riff on these pressures, to your taste. The results are pretty predictable.
AFAIK, lower pressures are used at the track to accommodate what happens when the tire gets hot. Nobody's tire gets that hot on the street.
The benefit of nitrogen is that it's more temperature stable. A tire filled with nitrogen will remain at its set inflation pressure over a wider range of temperatures. A tire filled with air will gain or lose about 1psi per ten degrees of ambient temperature, give or take. That's also been my experience. I don't personally find the rest of the nitrogen sales pitch persuasive, but I can't disprove it.
My .02, anyhoo...
AFAIK, lower pressures are used at the track to accommodate what happens when the tire gets hot. Nobody's tire gets that hot on the street.
The benefit of nitrogen is that it's more temperature stable. A tire filled with nitrogen will remain at its set inflation pressure over a wider range of temperatures. A tire filled with air will gain or lose about 1psi per ten degrees of ambient temperature, give or take. That's also been my experience. I don't personally find the rest of the nitrogen sales pitch persuasive, but I can't disprove it.
My .02, anyhoo...
02-26-2010, 09:55 PM
#17
Three Wheelin'
Experimenting is always interesting....however, if you search for previous posts, there is a history of people trying lower pressures, enjoying the softer ride, then wishing later that they hadn't when they bent a rim on a pot hole.
Finding optimal pressures at track events makes the most sense as the pavement is usually in decent condition and you're dealing with a limited temperature range & conditions.
My guess is that if the factory numbers were off, we would have seen a long history of reports of improperly worn tires. We haven't -- so I'm guessing that (assuming relatively stock suspension), the factory numbers are trustworthy for street conditions.
Finding optimal pressures at track events makes the most sense as the pavement is usually in decent condition and you're dealing with a limited temperature range & conditions.
My guess is that if the factory numbers were off, we would have seen a long history of reports of improperly worn tires. We haven't -- so I'm guessing that (assuming relatively stock suspension), the factory numbers are trustworthy for street conditions.
