Optimal tire PSI for max range?

GerryAZ said:

Personally, I disagree with the general statement that stopping distance is increased with higher tire pressures. My experience with 3 different LEAFs (all heavy cars) is that wet stopping distance (at least with better quality tires) is improved with higher pressures than the 36 psi recommended by Nissan. I believe this is due to tire distortion (contact patch distortion and tread grooves closing) under braking loads. In my climate, with all of the tires I have used on the LEAFs except the OEM 17-inch Michelins, the stopping distance is significantly reduced on wet pavement with 44 psi compared to 36 psi. It is true that braking traction is generally reduced with higher tire pressures on a lighter weight car. Both wet and dry braking distance with the OEM Michelins were so bad that pressure changes did not help so I replaced them with much better tires.

Note, the door placard on my 2019 SL Plus recommends 36 psi which is the same as recommended for my 2015 SL. They both came from the factory with 215/50 R17 Michelin Energy Saver A/S tires and the 2019 is considerably heavier because it has a larger battery pack. This indicates to me that Nissan did not really consider the weight in determining the recommended inflation pressure.

Click to expand...

No question that tire design is a big factor in braking performance, and it seems that the stock Michelins are not optimized for braking distance. I think you can beat them with almost any tire on that spec... Pretty bad that way. They _are_ quiet. and they do seem to offer good range at a given pressure.

I took the discussion above to mean "excessive pressure relative to load" can lead to longer braking distances. I don't think there's any doubt about that at the end of the day.

Interesting point about Nissan not doing the work to raise the recommended tire pressures for the heavier car. Shame on them if that's the backstory. It seems to cast more doubt on the manufacturer recommended pressures, which already tend low as I've noted above. But that said, anything above 35 psi will meet the stock tire's load rating, as I've explained, so it's not about that. As long as the load rating is high enough to also support the heavier car's weight, it's technically OK. They should have switched to an XL tire and then set the pressures accordingly. I think the 40kwh models should have them too. Budget issue I bet. XL tires cost more.

I'm also not super keen on the stock tires maxing out at 44psi. In Colorado, where we routinely see 30 F swings in daily high to low, that's a 3 psi swing. You could exceed the max cold rating in the course of a day if you park in the sun on a warm day, having set your pressures as recommended by folks here on a chilly night. Not beyond the imagination. Another reason to dump these tires as soon as we've worn them out.

Note, the door placard on my 2019 SL Plus recommends 36 psi which is the same as recommended for my 2015 SL. They both came from the factory with 215/50 R17 Michelin Energy Saver A/S tires and the 2019 is considerably heavier because it has a larger battery pack. This indicates to me that Nissan did not really consider the weight in determining the recommended inflation pressure.

Click to expand...

I thought that the door sticker on my 2018 SL recommended 38psi. I'll have to recheck that. Anyway, when you factor in typical driver neglect (or the neglect related to physical infirmity, as with me), 36psi is dangerous when 34 is not really safe.

At 36 psi the tires are underinflated. This can be shown by the treadwear pattern on the tire. I.E. the tread wears out on the edges first. If they are properly inflated, the tread wears evenly across the face of the tread. Over-inflation would cause the center of the tread to wear first. Proper inflation also gives the best results on braking. 42 psi seems about right from my observations. If you prefer a softer ride, try 40 psi instead. Nissan's recommendations seem to be based on having a softer ride over tire wear. Since they don't warranty the tires for treadwear (or anything else for that matter), Nissan is free to modify tire pressure in favor of ride quality.

If you increase the tire pressure to 45-46 psi, your range will increase slightly at the cost of treadwear and ride harshness. Not worth it in my opinion. Above that pressure you are exceeding the tire's rating and could cause unexpected blowouts. Mind you that all pressures readings are cold pressures and that manufacturers take heating into account so as long as you set the cold pressure at or below the max recommendation you should be OK.

I agree, the correct pressure will give best overall traction and even tire wear. In my experience, that pressure is between 40 and 50 psi for Leafs (depending upon tire brand, size, and characteristics). I ran 44 in the OEM tires after seeing excessive inside/outside edge wear at 36 psi shortly after purchasing the 2011. The OEM tires on all 3 cars had even wear across the tread with 44 psi cold, but the Michelins were marginal in regard to traction regardless of pressure. I run 46 to 48 with the Bridgestone DriveGuard run flat tires I have now (maximum cold is 51) and have even wear after almost 15,000 miles (rotations every 5,000 miles). If I reduce the cold pressure, the DriveGuards heat up more while driving so the pressure gets up to the same level. I use 46 to 48 cold so they increase about 3 psi as they warm up. I was actually surprised to see how much more they heat up with lower inflation pressures since they are designed to drive at up to 50 mi/hr for up to 50 miles without any air pressure.

I ran 38psi for the first year, and had no issues. But as my physical abilities declined I went back to 40-42, just because I don't check it often enough. And that TPMS screen is just so darned hard to find!

After all is said and done on this subject; I have found on my 2017 sv ,
chalking the tires @ 75* are set best at 36 lbs front and 35 lbs rear. 20 lbs in rear Cargo area 1 driver.

Lamb, when you chalk, you want to extend an inch or so down the sidewall, then take it for a spirited (but safe!) drive. Ideally with some sweeping hard turns. Then take the temps at middle and both shoulders. Check the chalk to see how far the shoulder of the tire rolled over.

The front tires in particular on a FWD Leaf have to do a lot more work than most cars. They have to provide drive traction, endure turning forces..and have to endure differential braking forces as during regen, the rear brakes are (mostly) not engaged unless you're stopping hard. If you're using eDrive, this regen is also more aggressive when slowing on a turn, with 100% of "braking" force on the front tires. Fortunately for us in the snow belt, the stability management does engage the rear brakes as required during regen-driven deacceleration in slippery conditions so you don't end up swapping ends

If you drive "gentle", a few PSI obviously will help. But if you're aggressive, you're better off to dial down tire PSI a bit and purchase adjustable camber bolts for your Leaf ($25). Then have your alignment pals dial in .5 negative, perhaps -1 if you like taking turn ramps like Andretti. You might think that your inside shoulders will take a beating but that has not been my experience on the street with more aggressive negative camber. My street/autocross car also had rear shims to dial in a touch more negative there as well. Dialling in negative 1 up front may negatively affect range for highway commuters, so is worth an experiment for sure.

Btw, the Michelin A/S tires I just took off the OEM summer rims were worn out evenly, aside from one tire, which did show more shoulder wear than the others. The 2018 SL car was used by a driving school before I purchased it...the owner mentioned a ball joint was replaced under warranty. I'm going to predict camber on that side is slightly positive, and OEM, there is no adjustment, so the dealer likely left it.

johnlocke said:

At 36 psi the tires are underinflated. This can be shown by the treadwear pattern on the tire. I.E. the tread wears out on the edges first. ..

Click to expand...

Not underinflated. See my previous posts. If Nissan's engineers sent out the cars at 40 psi, someone would skid into an accident, then start a class action suit claiming braking distance was reduced as they exceeded the load/pressure rating for the tire. The stock tires though have a pretty soft sidewall and low tread wear rating

LeftieBiker said:

Note, the door placard on my 2019 SL Plus recommends 36 psi which is the same as recommended for my 2015 SL. They both came from the factory with 215/50 R17 Michelin Energy Saver A/S tires and the 2019 is considerably heavier because it has a larger battery pack. This indicates to me that Nissan did not really consider the weight in determining the recommended inflation pressure.

Click to expand...

I thought that the door sticker on my 2018 SL recommended 38psi. I'll have to recheck that. Anyway, when you factor in typical driver neglect (or the neglect related to physical infirmity, as with me), 36psi is dangerous when 34 is not really safe.

Click to expand...

I would be curious about that door sticker as well. I traded in my old 2013 SV (8 faithful years of service without a single issue, minus recalls I suppose?) for a gently used 2020 SL Plus last month. I noticed that even the much heavier car, the sticker still recommends 36 PSI. The weight difference between the two (2013 SV 3,291 lbs vs. 2020 SL Plus 3,946 lbs) about an extra 655 lbs before you even start putting people in it. So is the tire just made differently to support the additional weight at the same PSI or is the same tire just have that much wiggle room for weight that even adding an additional 164 lbs per tire still within the "legal" safe zone of the tire? I did try to drive them on 36 PSI for a while just to see if I could tell any difference. Mainly, greatly reduced driving efficiency (not used to seeing 3.x on miles per kilowatt hour no matter how easy I drove) and the tires were actually louder which I never noticed before in my previous Leaf. You know that "squeak" sound you can hear in parking lots sometimes when turning the wheels, moving slowly to turn/backup/etc. The car being so quiet, I could hear that and figured if my tires are making sound, must be some wasted energy going out to generate it. Anyway, since all the tire guys seem to be filling in this topic, I figured why not ask since I have all of your attention? :mrgreen:

It looks like the GVW max weight has dropped about 140lbs. On the older Leafs GVW was closer to 1000 lbs over curb weight. On your car, it's 860 lbs. Remember that 36 psi (again referring to that the load table) for a Load Index 90 tire (OEM Spec from your sticker) is the "correct" pressure to support 1323 lbs per tire. That's 5292 lbs, so still above your GVW. That's why Nissan has not changed the sticker pressure. Will you lose some stopping distance as you pressure up? 100% yes. Will you get a small increase in range as you air up? Yes, again based on what folks with experience here are reporting.

Rather than spec'ing an XL tire (which I think they should have), Nissan has left air pressure alone while reducing the max weight you are "allowed" to carry. It's always a balance between ride quality, traction and handling, and a 50 series tire does not have much of a sidewall to soak up road imperfections. Likely this is why they are not just sending the cars out with 44 psi.

Keep in mind that new tires have a lot (20% ??) more rolling resistance when new, something to consider if you're testing like crazy

Not surprisingly, the sticker on my car reads 36psi. Now I don't know if I somehow misread it, or if the dealership casually mentioned it and I believed them. At any rate, Nissan did indeed drop that ball as well as the dual voltage EVSE current limit ball.

I had a thought, earlier today. (It's much too late in the evening for thinking now.) What if Nissan was trying for the shortest possible stopping distance, rather than the softest ride for the Leaf?

denwood said:

Will you lose some stopping distance as you pressure up? 100% yes. Will you get a small increase in range as you air up? Yes, again based on what folks with experience here are reporting.

Click to expand...

Certainly it does, though that small increase in efficiency can add up to quite a bit more than one would think. For example, when running my tires at 36 PSI, I run about 3.8 miles/kwh average on routes. If I air them up to say 40 PSI, the same routes I run increase to 4.2 miles/kwh. So at first, one looks at that and thinks, geez only a 0.4 increase in efficiency, why bother? On my vehicle though, that small increase nets me +24 miles of extra range for every 60 kw/h of energy that I use. For the Gen 1 Leaf, that is an extra +8 miles for every 20 kw/h of energy used. On a Gen 1 Leaf, that extra 8 miles might make the difference between getting to your destination at a comfortable speed or creeping in at turtle mode with no AC/Heat running or just plain getting stuck only a few miles away from a charger.
Even though that might seem moot if your EV has a larger capacity and those few miles out of the hundreds per charge don't seem like much, a lot of us (myself included) are accustomed to trying to squeeze every last mile out of our Gen 1 Leaf. :lol:

To be fair, my Gen 1 Leaf would actually get closer to 5.0 miles/kwh on said routes, as I suppose the lighter vehicle, maybe better aero helps.

No doubt the closer you are to driving at the car's range limit, the more important a few miles here or there get.

We sprang for the big battery mostly to take range anxiety off the table, given that with all the incentives available at the time, the cost penalty was relatively minor.

knightmb said:

..., when running my tires at 36 PSI, I run about 3.8 miles/kwh average on routes. If I air them up to say 40 PSI, the same routes I run increase to 4.2 miles/kwh....

Click to expand...

That's a 10% increase, and pretty consistent with an older Mythbuster's test: https://ecomodder.com/forum/showthread.php/mythbusters-tests-tyre-tire-pressure-17151.html

This will of course vary widely with the tire type, load rating etc, however it's a good point as to the benefit of airing up a bit. It sounds like 40-42 is a good spot for the 215/50 17" to sit at, and likely a decent compromise on the stopping distance hit.

This thread perhaps highlights the issue of what the collective fleet efficiency loss is due to under inflation. It's almost certainly a surprisingly large number, indeed low hanging fruit on the quest to reduce our carbon footprint. I'll try a few rolling tests on my winters vs the new Ecopia 422 plus at different pressures and post back here. They are brand new so may not perform so well on the rolling test. Curious minds...

The psi difference make s a big difference around town, especially if you roll the car up to lights. On the highway, the difference is less noticeable as wind resistance is your biggest loss. Lower the car 2" to help there.

New Leaf owner here. I bought my 2019 Nissan Leaf this past March 2022, and only just recently, the tire pressure console told me the tire pressure was low. Yet I'm confused. Why are there two PSI numbers? The PSI number on the tire say 50 PSI, yet the sticker on the side of the front door say 36 PSI. Which one is the correct number to use? I read here that most people are putting 42 PSI or so. Would it hurt my Leaf if the PSI was 46? I currently have my tires on 46, for I tried to inflate the tires to 50 yet stopped at 46.

Welcome. The 50psi on the tire is the maximum allowed inflation pressure, which is too high for anything but carrying a big load in the car. The 36psi on the sticker in the car is Nissan's recommended inflation pressure for a comfortable ride. It is too low, and can actually cause extra wear on the tires, as well as lower range. 40-42psi seems to work best for most people, although if you like a softer ride you might want to try 38psi.

If all your tires are really at 46 PSI and you got a low pressure warning on the dash there is a problem with the TPMS system or one or more of the sensors are bad. If the car is still under warranty I'd take it back to the dealer to have them look at it. Otherwise, any decent tire shop should be able to diagnose the problem.

I think the 46psi is what they put in after the low pressure warning.

I got the low pressure warning for one tire which was at 28 psi. The others were at 30 psi. I inflated the tires to 46 and wonder if it is okay. I'll leave it for now to see how it performs. It's not 50 but it's not the low 36 that most here do not approve.

Tires always get lower pressure when they spend overnight in colder temperatures for the first time after months of summer warm temperatures. I live in northwest NJ, and the temperature this past early Friday morning (2 AM) was at 40 F, thus why I gotten the low pressure warning that morning.