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Recommended tire pressure too high
- Thread starter jamnmon66
- Start date
Decided to run 38 on the rear & 42 on the front. Its a nice balance of protecting the rears from center wear and keeping really good feel in the front. Seems to hover at around 300 kwh/MI at 75 on the highway with the wheel covers off (with an unscientific autopilot test). Not too bad on efficiency and I'm happy with the ride... firm but not harsh at all. Surprisingly, these tires don't seem any louder than stock. No mileage warranty on these Pirellis but we had the same tires on my wife's Infiniti before we sold it and they were still in good shape after 20k+ miles (didn't measure the tread depth but visually they had about half of the tread remaining).
Perfect timing for the tpms update in the new firmware.
Perfect timing for the tpms update in the new firmware.
TomB985
Member
Just lowered mine to 35 PSI front and rear, and my initial impressions are good. Seems to have a bit less of a frenetic ride, and the grip feels a bit more predictable. I'm interested in tire life and comfy ride over a tiny amount of efficiency, so we'll see how it goes.
TomB985
Member
After a couple days I can say I’m impressed with the change at 35 PSI. The car just drives better, and it’s not just a jittery ride. Traction seems a little better and more predictable, which I think is a result of the larger contact patch. If anybody’s on the fence with lower pressures, give it a shot and I think you’ll be impressed.
--1--
Member
Twenties recommend 43psi. I checked mine today on my one day old TM3, all four, rock solid at 43.
TomB985
Member
I just wanted to post a quick update after I rotated at 10,000 miles.
I lowered to 35 PSI with only 2000 miles on the odometer, and then rotated them at 5,000 and today at 10,000. I recorded a full 7/32 tread depth at 5,000 all around, in the exact same today at 10,000. The tread wear looks perfect, wear measurements are consistent across all four tires, and I’m extremely happy with how the car behaves at 35 PSI.
I highly recommend you guys give this a try.
I lowered to 35 PSI with only 2000 miles on the odometer, and then rotated them at 5,000 and today at 10,000. I recorded a full 7/32 tread depth at 5,000 all around, in the exact same today at 10,000. The tread wear looks perfect, wear measurements are consistent across all four tires, and I’m extremely happy with how the car behaves at 35 PSI.
I highly recommend you guys give this a try.
TomB985
Member
Unfortunately I couldn’t give you a good answer to that. My driving is varied enough that I don’t have any consistent data before or after. Subjectively I haven’t noticed a difference.
A totally other vehicle , a bicycle, they discovered that at a sertain point , higher pressure did not give lesser energy to use per mile.
Known in this field is Jan Heine, who did much reasearch on pressure for bicycles. There it has to do with the human body wich gives vibrations and so the lesser energy needed by lesser deflection of tire, is at a sertain point lost again by the vibrations, even on a flat road like highway also is.
This is my explanation of the story I read about it, did not understand the principle totally.
On a less flat road ( stones ) the balance even shifted to the lower pressures that gave less energy use then higher pressure , in sand ( but I dont think there are Tesla's that do offroad driving) verry low pressure is better for " fuel saving".
But research could show , that the 42 psi for Tesla, needs yust as much energy a mile as 35 psi , even if a machine drives the vehicle.
Known in this field is Jan Heine, who did much reasearch on pressure for bicycles. There it has to do with the human body wich gives vibrations and so the lesser energy needed by lesser deflection of tire, is at a sertain point lost again by the vibrations, even on a flat road like highway also is.
This is my explanation of the story I read about it, did not understand the principle totally.
On a less flat road ( stones ) the balance even shifted to the lower pressures that gave less energy use then higher pressure , in sand ( but I dont think there are Tesla's that do offroad driving) verry low pressure is better for " fuel saving".
But research could show , that the 42 psi for Tesla, needs yust as much energy a mile as 35 psi , even if a machine drives the vehicle.
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like you say, very different systems.
a higher pressure bicycle tires imparts more bounciness (for lack of better term) on the rider and impacts the pedaling motion. an electric (or combustion) motor is not affected by that.
a bicyclist does not exert too much load on its tires. a 1800kg car does much more on its tires. a 7 psi difference will result in measurably different temperatures on the car... thats appreciable energy loss. the same bicycle tire, dropping down 7 or 14 or even 21psi of from reference, you'll never even feel it warm to the touch. there, its less about energy efficiency than it is about comfort
But dont say its a subject of research for Tesla, in the end it might prove to be also go for machine driven vehicles.
maiby not in the same amount , but still a tihing to do research about.
After a few year mayby TomB985 notices not that much energy loss as would be expected.
I mean to be able to give a rough idea of enery loss by lower pressure.
here it goes.
42 against 35 psi
42gives 35/42=0,8333 times as much surface of tire on the ground.
This gives ( my determined conclusions) 0,8222^2= 0,6944 the deflection of 35psi.
This gives 0,6944 times as much heatproduction at same speed.
Assuming energy loss then also 0,6944 as muc as 35 psi.
Now at 35 psi and driving 50mph, Tireresistance consumes about 20% of total needed energy.
80% so is consumed mostly by aerodinamic.
So 0,6944 times 20% = 13,88 % + 80% ( stays the same) = 93.88 % ergy use of 42psi against 35 psi when driving 80 mph.
So energy saving at that low speed of 6.12% , and that if the bycicle principle dont count.
maiby not in the same amount , but still a tihing to do research about.
After a few year mayby TomB985 notices not that much energy loss as would be expected.
I mean to be able to give a rough idea of enery loss by lower pressure.
here it goes.
42 against 35 psi
42gives 35/42=0,8333 times as much surface of tire on the ground.
This gives ( my determined conclusions) 0,8222^2= 0,6944 the deflection of 35psi.
This gives 0,6944 times as much heatproduction at same speed.
Assuming energy loss then also 0,6944 as muc as 35 psi.
Now at 35 psi and driving 50mph, Tireresistance consumes about 20% of total needed energy.
80% so is consumed mostly by aerodinamic.
So 0,6944 times 20% = 13,88 % + 80% ( stays the same) = 93.88 % ergy use of 42psi against 35 psi when driving 80 mph.
So energy saving at that low speed of 6.12% , and that if the bycicle principle dont count.
TomB985
Member
It's kind of an interesting topic, but I can't find much information on it. There's a lot of information about underinflated tires, but it's mostly anecdotal and testimony from "experts" talking about proper inflation. I can't find any kind of technical analysis on the efficiency difference.
Further muddying the water is how Tesla's recommended pressure is substantially higher than industry-standard specs require for a car is heavy as the Model 3. The Lexus GS uses the exact same tire size, and recommends 33 psi for a car that weighs nearly the same.
But in the end, it's all academic for me. With the off-peak rate of 7.3 cents per kilowatt hour, I don't really care that much. I keep my Aero hubcaps on because there is no practical reason not to, but I really like the improved ride and handling at 35 psi. And so far comparing with anecdotes online, my tire life will be among the best. And I don't drive conservatively.
Further muddying the water is how Tesla's recommended pressure is substantially higher than industry-standard specs require for a car is heavy as the Model 3. The Lexus GS uses the exact same tire size, and recommends 33 psi for a car that weighs nearly the same.
But in the end, it's all academic for me. With the off-peak rate of 7.3 cents per kilowatt hour, I don't really care that much. I keep my Aero hubcaps on because there is no practical reason not to, but I really like the improved ride and handling at 35 psi. And so far comparing with anecdotes online, my tire life will be among the best. And I don't drive conservatively.
rtanov
Member
I have also been driving for the last year or so with 35 psi on the original 18 inch tires, and my wear pattern is also very even. I think people driving at ~45 psi should watch for more wear in the middle of the tire which would be an indication of overinflation.
However, my tires have been squeaky with spirited driving around corners (I have several 90 degree turns and chicanes on my way to work which I use as a benchmark) and initial take-off. I inflated my tires to prepare for the lower temperatures coming and was surprised to find out that the squeaks were gone at 38-39 psi. This makes me think that 38 psi might be a better pressure than 35, and I will keep it like that for some time and continue observing wear and feel. I don't much care about efficiency so have no observations on that.
However, my tires have been squeaky with spirited driving around corners (I have several 90 degree turns and chicanes on my way to work which I use as a benchmark) and initial take-off. I inflated my tires to prepare for the lower temperatures coming and was surprised to find out that the squeaks were gone at 38-39 psi. This makes me think that 38 psi might be a better pressure than 35, and I will keep it like that for some time and continue observing wear and feel. I don't much care about efficiency so have no observations on that.
MacGreiner
5YJ
Lexus might have different weight distribution, and power distribution, and suspension geometry, all of which affects the wear on the tires differently. On top of that, as a brand they are geared more towards comfort than performance or economy.
So they can make any recommends as long as they dont exceed the bounds of safety.
It's quite clear with lower pressures there is more flex and thus more heat, and also a smaller effective diameter, both of which reduces rolling efficiency.
As to how much? I completely agree with you, it's all marginal whether youre powered by combustion or electric. I'd tailor the pressures first to driving feel and second to wear rate
To my conclusions the 42 psi is only done for the actiradius of the battery, and 35 psi is more then enaugh for the larger weight on the tires with more maxload then average, so completely save up to high speed, and even wear of treath.
But have to calculate it , for that I need those weights and tire data.
Also read a bout centrewear with the extreme 42 or even 47 psi , and you can go verry high above minimum needed pressure , before centrewear is happening.
And that Lexus Holmgang gives , is most likely the same weights as the Tesla, and weight and speed is the only thing that counts for the needed pressure.
When I calculate pressure with my made spreadsheet for motorhomes, I add first 10% to the given load a tire, and then calculate the pressure for that. With some weightdifference R/L then if one tire goes low as 85% of the pressure I calculate it for, then still dont give bad comfort and gripp. 10% adding is the same as making 91% of the load you calculate the pressure for.
I think that only if Load% goes down to 65% , centrewear will happen.
But have to calculate it , for that I need those weights and tire data.
Also read a bout centrewear with the extreme 42 or even 47 psi , and you can go verry high above minimum needed pressure , before centrewear is happening.
And that Lexus Holmgang gives , is most likely the same weights as the Tesla, and weight and speed is the only thing that counts for the needed pressure.
When I calculate pressure with my made spreadsheet for motorhomes, I add first 10% to the given load a tire, and then calculate the pressure for that. With some weightdifference R/L then if one tire goes low as 85% of the pressure I calculate it for, then still dont give bad comfort and gripp. 10% adding is the same as making 91% of the load you calculate the pressure for.
I think that only if Load% goes down to 65% , centrewear will happen.
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SammichLover
Banned
The very high PSI on bicycles is very much for lower rolling resistance, to minimize contact as your weight presses down on a very tiny tire patch.
However I’ve found 35 PSI to -hurt- handling for the stock tires. They start going dead, noticeable turn-in delay around 37 PSI. So should keep 39-40. Wear evenness also about as good as it gets at 40-ish.
However I’ve found 35 PSI to -hurt- handling for the stock tires. They start going dead, noticeable turn-in delay around 37 PSI. So should keep 39-40. Wear evenness also about as good as it gets at 40-ish.
TomB985
Member
interesting, but I suppose it makes sense. Your car is about 400 pounds heavier than mine, so I can see more pressure being helpful.
Mine actually bled down to 32–33 before I aired them up yesterday, and I noticed no negative handling characteristics at all. Definitely less jittery than when they were at 45.
what about 40 as a compromise b/t range and handling/wear? Nice even # too.
