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Why 42 PSI ?
- Thread starter enemji
- Start date
The softer the suspension, the lower the tire pressure. In that regards the Model 3 is a performance suspension by default, compared to other cars on the road.
If you were to keep 34psi on the Model 3, the car would be bouncing on the rubber rather than the springs and dampers.
FYI - My BMW sports package has 39/46 PSI recommended on a stagger setup.
39/46 psi? You sure that's not the max load/high speed pressures? What kind of bmw is that?
Guess your door sticker only has the high load pressures. In the owner's manual, 2004 330i, for up to 4 passengers, recommended pressures for 18" staggered in your size is 32 psi front 38 psi rear. 5 passengers with luggage is 39/46 as stated in your door sticker.
I used to have a E46 M3 myself
I ran 255/40/18 rear tires at like 38 PSI and the middle of the tires were wearing out quicker than the edges.Semi trucks, heavy duty vehicles, or RV's, the pressure is determined by tire load chart and axle weight measured from a scale (this applies to all vehicles, but heavy duty vehicles have potential for much larger range of tire loading (moving van vs 80k lbs tractor trailer). So, one would drive to the scale, weigh the vehicle, look on the tire load chart (that is designed for the tire, not the vehicle), then set the minimum pressure on the chart. This provides a minimum safe running pressure (to low is dangerous for blow out, and too high pressure is a rough ride). You can always go higher up to the tire max cold inflation, but ride quality will be impacted.
Typically passenger tires do not publish the load chart of weight vs pressure (but if you called the manufacture they would have it). Also, how many people have actually weighed their car (minus race cars looking for 4 corner weights for balance / suspension). Folks have mentioned above, if you are loading your car to the max and full passengers, increase you pressure to max on tire sidewall. If you are commuting by yourself, you can reduce it down to recommended PSI on door sill that should be optimized for safety, milage, and comfort.
Bottom line, the tire manufacturer dictates the PSI vs load rating for each tire model. Car manufacturers specify recommended/max PSI for the OEM tire. But, you probably don't want to put a light truck tire on your car and increase the pressure to 75psi or more as your rim may not be designed for that.
If you change tires, you want to make sure the tire load rating is higher than your axle rating. As long as the load rating is close, than the door sticker is probably still accurate, but if you put a higher load rating tire on the car, you want to consult the tire manufacture chart for recommended pressures.
Typically passenger tires do not publish the load chart of weight vs pressure (but if you called the manufacture they would have it). Also, how many people have actually weighed their car (minus race cars looking for 4 corner weights for balance / suspension). Folks have mentioned above, if you are loading your car to the max and full passengers, increase you pressure to max on tire sidewall. If you are commuting by yourself, you can reduce it down to recommended PSI on door sill that should be optimized for safety, milage, and comfort.
Bottom line, the tire manufacturer dictates the PSI vs load rating for each tire model. Car manufacturers specify recommended/max PSI for the OEM tire. But, you probably don't want to put a light truck tire on your car and increase the pressure to 75psi or more as your rim may not be designed for that.
If you change tires, you want to make sure the tire load rating is higher than your axle rating. As long as the load rating is close, than the door sticker is probably still accurate, but if you put a higher load rating tire on the car, you want to consult the tire manufacture chart for recommended pressures.
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Current tire labels likely show what used to be called full load pressures, because higher pressures give greater margin of safety against underinflation.
Very interesting analysis. But this example is assuming all the pressure in the tire is due to it touching the ground, right? But if we jack the car up the tire will still probably have nearly the same pressure, well at least not zero psi.
I like that you related psi to inches on the ground though. Never thought of it before.It bounces on the tire rubber if I drive at lower pressures. The suspension is just that firm. Tire wear is superbly even. I do not even need to rotate the tires.Guess your door sticker only has the high load pressures. In the owner's manual, 2004 330i, for up to 4 passengers, recommended pressures for 18" staggered in your size is 32 psi front 38 psi rear. 5 passengers with luggage is 39/46 as stated in your door sticker.
I used to have a E46 M3 myself
Pressure = force/area. Since the cross sectional area is relatively constant (although lower pressures result in a larger contact patch), the higher the pressure the more force the tire can withstand without deformation. It's likely that Tesla tuned their suspension spring mass damper system with the assumption that the tire pressures are between 42-45psi. The more you deviate from it, the more likely you are to have an under damped or over damped behavior. This is also why heavy duty trucks run higher pressure, due to the weight of the vehicle, they need more pressure to deal with the force that is distributed over the small contact patch. It might be a good idea to compare the tire pressures of vehicles of similar weights to the Tesla with the same size tires and see what tire pressure they run. It's likely it will be in the same range
Additionally, Tesla is likely trying to avoid tire deformation which results increased rolling resistance which would reduce range.
Additionally, Tesla is likely trying to avoid tire deformation which results increased rolling resistance which would reduce range.
How's the ride and tire wear at 35psi? i recently switched to 275/40/20 106Y as well and its super bumpy at 38-40 psi. TIAI get it, not sure why your question was not answered but I have been struggling to understand this as well, for instance on the model Y there are 3 different load range tires for just the front axle.
Model Y performance front tire is 255/35/21 load range 98 or 1,653 max load
Model Y with 20" induction wheels are 255/40/20 load range 101 or 1,819 max load
Model Y with 19" gemini wheels are 255/45/19 load range 104 or 1,984 max load
using a tire pressure calculator
and going by the tire mounted on the front of the performance model Y 42 psi on the front tire would equate to 38 psi on the Induction wheel tire and 34 psi on the gemini wheel tire.
Tire Pressure Calculator
Easy to use tire pressure calculator. Use our tire pressure calculator to calculate the new tire pressure needed when changing tire sizes.tiresize.com
I just switched tire size from stock to a 275/40/20 with a load range of 106 which would equate to 32 psi, I have been running 35 psi and setting off the tpms tire pressure warning, wish we could reset them to a custom psi like maybe 35 or 36.
GreenCoffee
Member
Having the tpms warnings too often when running that low so bumped back up to 38psi, ride is much better now though after spending 5k on the redwoods motorsports ohlins gt spec dampers with swift springs, my preferred setting out of 32 clicks is 0 or full soft
I'll adjust to 36 and give it a try. LA roads are terrible so maybe thats the real culprit. Thanks for the info
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Think the cold/42 psi to summer heat, causing 50 psi and bumping up to the max of the tire pressure can be a problem.
Annoying but possibly the best guidance is 42 psi at most times, meaning stay away from 50 psi in rhe heat, letting air out and filling at certain times of the year
As for the reason for this number is due to many factors playing into max range with decent ride comfort/suspension abilities.
Whatās the complaint with maintaining 42psi?
Annoying but possibly the best guidance is 42 psi at most times, meaning stay away from 50 psi in rhe heat, letting air out and filling at certain times of the year
As for the reason for this number is due to many factors playing into max range with decent ride comfort/suspension abilities.
Whatās the complaint with maintaining 42psi?
UncleCreepy
Member
Someone on the internet said it's wrong. There's even a fancy calculator that undoubtedly proves that Tesla has no clue what the right tire pressure is.
stopcrazypp
Well-Known Member
To clarify, in case someone gets the wrong idea: the fancy calculator says the tire can be safely lowered to a lower pressure and still maintain the rated load capacity for the vehicle. However, that makes an assumption that the "correct" tire pressure should be the bare minimum for the load capacity, but the reality is there are multiple factors why that would be the "wrong" tire pressure (efficiency, noise, performance, extra margin for overloading, etc).
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