Relative tire pressure?
 

Hi,

I'm curious as to what our relative tire air pressures are compared to the maximum sidewall pressure on the current tires. Be sure and use the maximum sidewall pressure, not the OEM numbers found in the owner's manual or door frame.

For example, I now have Sumitomo T4s rated at 51 psi and though I run slightly lower pressure in the rear, I'm running at the maximum sidewall pressure. So this is how I would calculate past pressures I've found in my tires:

• 32 psi OEM - difference is 32-51=-19 psi or -19/51=-37%
• 42 psi Prius community lore - earliest 'higher' pressure used, 51-42=-9 psi, -9/51=-17%
• 51 psi, current - 51-51=0 psi, 0%

Yes, I realize that a symmetrical scale of values is unlikely in this group. However, there needed to be a way for folks who may be running closer to OEM pressures. Also, the scale is semi-log to provide the wide ranges likely to be found. If you go to plot it, be sure to adjust appropriately. You'll also notice no metric to USA units is required.

Thanks,
Bob Wilson

I voted 20%+ because I run 42.86% higher than the sidewall max. 50psi - SWMax is 35psi. You do notice a significant increase in road noise, but it doesn't bother me. The increase in mileage I have seen is significant enough for me to continue with this much higher pressure. I have seen about a 3-5MPG increase since upping the pressure. Please take caution though, my tires are steel belted radials and you must make sure that your tires are of similar construction because if they aren't, the sidewalls won't be able to take that kind of abuse, and catastrophic failure could result (enormous bang followed by rim on bare ground :thumbup:).

How to use this data? :confused:

For the moment, I just slap 35psi in them... that's the max sidewall pressure on my crap tires... once I get another set of wheels, and some better tires, the sidewall max will significantly go up, and so will my tire pressure.

The only viable use I could see is for people to have a data set in front of them of people who overinflate, and the fact that enough people are doing it and not destroying their tires, that maybe the pointless argument will stop. Highly unlikely, but plausible explanation.