2009 Prius in Florida 33 mpg

I owned a 2002 honda insight since 08...trust me psi in your tires at max is the way to gver at insightcentral forum there is a member named NathanC and he puts over 100psi in his tire and gets over 100mpg.Im not here to argue.

 

Yes, I have often stated in PC that 'best' pressure is an individual judgement call, depending on the driver's priorities.

But my point in this thread is that you can't make sweeping or blanket statements that 42 PSI is grossly over-inflated, at least for U.S. market tires. For our tires, that pressure is within the tire's rated operating range, as molded into the sidewall (usually 44, sometimes 51 psi). It doesn't cause excess center wear here, as proven by many hypermilers using that and even more pressure for the full life of their tires.

If you cannot use over 37 psi without experiencing premature center wear, then something is different about the products or road conditions in your market.

 

Not here to argue either.

But, it does sound like you are saying something different and unrelated to what I was saying. Perhaps if you could elaborate on your statement "is the way to go". What is it that you are trying to accomplish by the higher pressures? Better fuel economy?

If you are saying I made that sweeping statement? Because I didn't. I said it is the case for my tires. Maybe grossly (if that's what you're getting at) is too strong, but definitely over-inflated.

 

I am challenging this center wear claim, at least for U.S. market customers:

 

Yes, if you want great mpg you should run your tires with max psi.

 

I can't imagine that they make tires one way for the US that allow any tire pressure which wear evenly and then use a different process for tires to be sold in other countries that are sensitive to tire pressure. Obviously I can't comment on US tires or environment but there could be other factors at play.

I would agree with you had I not inspected my last set of tires when they were worn to minimum (1.5 mm here) to find that the outer treads were still about 3 mm. That was over a distance of about 70,000 km. (43,500 mi). I never measured the tread at all during the life time of those tires, only visually inspected, and never picked up through visual inspection that the centers were wearing faster than the outsides. I might not have even noticed had I not measured them. I was surprised to find what I found.

Just putting the data out there.

And for what it is worth, from my experimentation I found exponentially less benefit in MPG gained with tire pressure above 36/37 PSI. I personally think a lot of people's perceptions on this subject is the placebo effect. I certainly have never come across any posts here or from other sources were someone posted quantifiable data recording tire pressure and wear stats over the long term, so only have my own data to go by.

I certainly would be interested in any documented data rather than the occasional anecdote.

I get tanks of 4.2 - 4.4 L/100 km (sometimes the occasional tank at 4.6 L/100 km) running my Bridgestone Ecopia PZ-X at 36F/34R PSI. People can draw their own conclusions.

	L/100 km	MPG (US)	MPG (Imp)
1	4.2	56.0	67.3
2	4.4	53.5	64.2
3	4.6	51.1	61.4

 

1.5 mm is illegal in most of the U.S., except in a few very dry places with a 1 mm limit. 2 mm is the legal minimum elsewhere, and even 4 mm is very strongly recommended in wet areas such as where I live.

When I finally calibrated my seat-of-the-pants-minimum-wet-traction-requirement against an actual tread depth gauge, my old personal limit landed very close to that 4 mm rule. I now stick to 4 mm for replacement, unless it is reached in mid-June to mid-September. Then replaced with real rain again on the horizon.

That said, the 1.5 mm center-to-edge difference you found is de minimus. And not yet demonstrated to be any different than tires run at the door placard pressure. The worn out center issue under discussion refers to much greater differences that are plainly visible without gauging.

The very rapidly diminishing return function is agreed upon, and very frequently acknowledged in this forum. MPG and handling vs. ride harshness is a personal judgement decision.

 

I erred in this reply, conflating mm's with the common U.S. measure of tread depth, 32nds of an inch. All the numbers I introduced above, should have been 32nds, not mm's. Brain fart. Mea cupla.

For translation: 1.5 mm = 1.9 /32nds".
3.2 mm = 4 /32nds".

I'll stand by the claim that to compare this measured but not visually apparent center-to-edge difference, we need to make the same measure on the other tires. Past claims of center wearout were clearly made from visual appearance.

Sorry for throwing in this confusion. Another reason the U.S. should go metric. As we were actually doing, until election day 1980.