Optimal tire PSI for max range?

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be236

Well-known member
Joined
Jul 15, 2018
Messages
79
Location
Seattle, WA
I've seen this topic posted before, but figured it's time to start a new (fresh) thread.

So, I just picked up a used Nissan LEAF 2017. My tires PSI measured about 38 PSI with a pencil-like tire gauge.

The car's label on the door says it should be 36 PSI for all four tires.

The tires themselves says max PSI is 44.

Looking at the tires now at 38 PSI, they "look" underinflated/flat.

I'm looking to pump them up to 40 or 42 PSI to max my range.

What's the consensus about doing this?
 
More air pressure usually helps get a bit more range. I think 42PSI or so is often best. What tires are on your car? The stock Ecopia tires have 51PSI sidewall max.
 
NeilBlanchard said:
More air pressure usually helps get a bit more range. I think 42PSI or so is often best. What tires are on your car? The stock Ecopia tires have 51PSI sidewall max.

I have the original tires that came with the car.. I think it is 16" (whatever the standard tires are for the S model).
 
No need for a new topic as nothing has changed. 40-42psi is the best compromise between range and safety. I do notice that on my 2018 the ride and range are both fine at 38psi.
 
pressure for max range is probably just before the tire bursts. For safety, don't exceed the sidewall numbers. Keep in mind pressure affects handling as well as efficiency.
 
WetEV said:
be236 said:
I'm looking to pump them up to 40 or 42 PSI to max my range.

The car handles better with the tires at 40 to 42 PSI, and the tires last longer.

Great. I'll pump it to about 41 PSI then... currently at 38 PSI, when I drive, I just "feel" the tires are under-inflated, like the car sags as I drive...
 
be236 said:
WetEV said:
be236 said:
I'm looking to pump them up to 40 or 42 PSI to max my range.

The car handles better with the tires at 40 to 42 PSI, and the tires last longer.

Great. I'll pump it to about 41 PSI then... currently at 38 PSI, when I drive, I just "feel" the tires are under-inflated, like the car sags as I drive...

That's what I do with new cars; changing by 2 PSI and driving for a week or so; until I find the sweet spot for the handling I prefer.
 
Nowadays I pretty much always fill to the max, 44psi in the case of my Ecopia's. As said you get the best range the harder the tires your. I've also noted unless you run with near the max at least for the front tires, you get significant edge wear. My original Ecopia's lasted less than 20k miles and were basically bald on the sides and I was running probably 38psi, my replacement Ecopias(Ecopia+??) have the same mileage as my originals and still look like they have many miles left. Note the replacement Ecopias(at least the +?) are a much better wearing than the crap OEM Ecopias.
Another reason to fill to the max is a tire will never gain air pressure(well unless you fill cold, which you aren't supposed to) so even if you fill to the max, more than likely in a month or so it will be down a few PSI. It's easy to forget about the tires and you don't want to get them getting below say 38psi, or at least I don't.
 
Another reason to fill to the max is a tire will never gain air pressure(well unless you fill cold, which you aren't supposed to) so even if you fill to the max, more than likely in a month or so it will be down a few PSI.

Unless they snuck in a change while I wasn't paying attention, all listed tire pressures are always for cold fills.
 
LeftieBiker said:
Another reason to fill to the max is a tire will never gain air pressure(well unless you fill cold, which you aren't supposed to) so even if you fill to the max, more than likely in a month or so it will be down a few PSI.

Unless they snuck in a change while I wasn't paying attention, all listed tire pressures are always for cold fills.
Interesting, I always thought the PSI listing was a max, if you fill it cold it can easily gain 5psi hot so if you fill cold to the max......well you'll be over max :? Of course I know the max isn't really the max, I've heard of people going 10-20lbs over max without blowing up the tire......
 
I just went to Les Schwab Tires and I asked the guy to fill me to 42 PSI and he was almost adamant about leaving it at 38 PSI saying that's what it should be etc and pointing me to the recommended PSI of 36 shown inside my door jam...

... so I had to insist him to do it anyways to 42 PSI... which he did.

Not sure what I make of his comments...
 
be236 said:
I just went to Les Schwab Tires and I asked the guy to fill me to 42 PSI and he was almost adamant about leaving it at 38 PSI saying that's what it should be etc and pointing me to the recommended PSI of 36 shown inside my door jam...

... so I had to insist him to do it anyways to 42 PSI... which he did.

Not sure what I make of his comments...

Can't blame the tech; they're trained to go by the book. The first time I had the car into the dealer I forgot about this, and when the work order came back, they had written
Tire pressure 44psi
KEEP AT 36 PSI
!!!

Except it was bigger than that. It was scrawled across the entire page and the exclamation marks had ripped the paper a bit.

So after that when I took it in for the battery checks I set the pressure to 36 just to keep someone from having a stroke. :lol:
 
My ex-GF drove a Corolla with 32psi stamped on the door sticker: she rarely added air, so it was usually in the mid twenties. I inflated it to 36 once, to compensate a bit: she threw a fit, and called her mechanic, who of course parroted the above. She was afraid the tires would explode at 36 (or maybe it was 38, I don't recall) and my 45 year knowledge of cars was as nothing compared to the guy with official overalls and maybe 5 years' experience.
 
Set them to max sidewall pressure. There is no danger of bursting. they are not balloons. Higher pressure gives stiffer sidewalls which means more stability when cornering which also benefits EVs since their center of gravity is so low. You will also get a lot more mileage from your tires.

And one other point; Some will say your stopping distance is "greatly" affected by tire pressures and if it weren't so well believed it would be laughable but its really tragic. If you want better stopping distance, get better tires. Under inflating tires under the ridiculous pretense of better safety is just pathetically sad.
 
be236 said:
I just went to Les Schwab Tires and I asked the guy to fill me to 42 PSI and he was almost adamant about leaving it at 38 PSI saying that's what it should be etc and pointing me to the recommended PSI of 36 shown inside my door jam...

... so I had to insist him to do it anyways to 42 PSI... which he did.

Not sure what I make of his comments...

And you are surprised??? He makes a living selling tires.

What if I told you manufacturers purposefully recommended lower than optimum tire pressures in exchange for better prices from the tire manufacturers?

Do you know how much reducing tire life by 10% is worth??
 
Ok, got it..

well, my tires should be at about 42 PSI now... not sure if I'll notice any difference in terms of the ride feel or range... probably way too early to tell...
 
My first post here..go figure :)

The tire fellow at Schwab was doing his job exactly.

Tire inflation pressure is a function of the specific tire's load rating and max pressure, vs the GVW rated max load it will see. For my new Ecopia Plus tires (215/50R17 XL) we can see the max pressure is 50psi, at 1512 lbs (from the sidewall). It also has a higher load rating (1512lbs) than the Michelin Energy Savers. It's an XL (extra load) tire with a load index of 95.

The 2018 Leaf SL has a curb weight around 3500 lbs, and GVW of 4453lbs. We know weight distribution is pretty close to 50/50 so each tire needs to support a max of 1113 lbs or so (4453/4)

You can find the Bridgestone inflation pressure /load charts here: http://octopup.org/img/car/tires/Bridgestone-Firestone--2006--Replacement-Tire-Selection-Manual.pdf

On page B12 of the tables, you can look up the 215/50 17 XL spec: 215/50R17 (XL) Load Index 95. and read across to the 1134 lbs column. The pressure there is 29psi. So for this tire, and the Leaf's GVW, 29 psi is what the pressure "should" be, to maintain the correct contact patch across the tire. I'll likely run them at 36psi, which is the correct pressure for 1356 lbs of load per tire.

One of the ways we test tire pressures on the autocross track is to check temps across the tread area after each race. Too hot in the middle, you are overinflated. Higher temps at the shoulder means under inflation. You want consistent temps across the tread face.

If you run an OEM tire at max pressure, you'll likely find elevated temps mid tread, and your contact area will drop. You don't want this if you need to stop in a hurry...and it may have zero effect on range.
 
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