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bwilson4web · 03-15-2009, 09:35 AM

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

03-15-2009, 09:35 AM	#1 (permalink)
bwilson4web Engineering first Join Date: Mar 2009 Location: Huntsville, AL Posts: 843 17 i3-REx - '14 BMW i3-REx Last 3: 45.67 mpg (US) Blue Bob's - '19 Tesla Std Rng Plus Thanks: 94 Thanked 248 Times in 157 Posts	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 __________________ 2019 Tesla Model 3 Std. Range Plus - 215 mi EV 2017 BMW i3-REx - 106 mi EV, 88 mi mid-grade Retired engineer, Huntsville, AL Last edited by bwilson4web; 03-15-2009 at 09:45 AM..