Quote:
Originally Posted by HummerH2
As for a previous question, the car is supposed to have a tire pressure of 37psi. Would it be safe (if I keep these tires on) to go up to 50 psi? I know it will help with gas but it may be unsafe for road handling.
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I pay more attention to the rated psi on the tires, than the "official" psi listed by the car maker (as the pressure rating on the tires is a somewhat conservative estimate of what the tires can safely handle, whereas the car plaque is just what the auto-maker thought was a good compromise between fuel economy and smoothness of the ride).
So, what's the maximum pressure rating on the tires (i.e. are they 44psi tires, the more expensive 88psi tires, or something else)?
Personally I wouldn't put 50psi into tires only rated for 44psi (although some on this forum have). However, I do feel comfortable putting 42psi into 44psi tires. And if your tires are rated for 88psi, by all means go to whatever you are comfortable with in the 50psi to 80psi range!
NOTE: Any raising of tire pressure will effect road handling, in both positive (more responsiveness) and negative (more "rough ride", and possibly a little harder to control) ways. How safe that extra pressure is (assuming your tires are rated to handle that much pressure), depends a lot on the driver (with some drivers and some vehicles extra pressure may actually be safer, due to the extra responsiveness/control). However, if you find you can't control the car as easily (with the higher pressure), just lower the air pressure back down to where you are comfortable.
For example, on my wife's Civic (with 44psi tires), she starts to really dislike the handling when the air pressure is above 43psi. So our target for that car is in the 41psi - 43psi range. Since the driving behaviors vary with driver, vehicle, and tires used, you will have to find your personal psi target by trial and error (keep raising the pressure until you dislike the handling changes, than back off the psi until you are comfortable with the drive again). The idea is to use the maximum pressure that is still low enough for the tires themselves, as well as being low enough that you are comfortable with the driving behaviors (because the higher the tire pressure the better the fuel economy, but at some point the higher tire pressure can sufficiently affect handling or other factors to be a problem).
NOTE:
From personal experience, I can tell you that driving behaviors start changing more rapidly as you raise tire pressure. So, for example, you might not notice much (driving) difference between 35psi and 37psi, but you might notice a large driving difference between 43psi and 44psi. The idea being, the higher the pressure, the more difference you will notice (in your driving) by just going a little bit higher. So at some point (which varies with the driver, the vehicle, and the tires), you will get to a psi where you really don't want to go any higher (because the driving behavior starts getting worse rapidly, as you raise the tire pressure even more). When you get to that point, just back the pressure off slightly (maybe 2psi) and call it good (as you've now found your personal psi target for that vehicle).