Tire Pressure and Range - One Mans Test Results

Objective:
I wondered just how significant air pressure really is to EV range and decided to test it.


Background:
Car, (MYLR) left a 60f heated garage to 40f ambient and was driven 25 miles to warm up. Air pressures were validated between 2 digital gauges (which match to within ¼ psi, and tire TPMS. 11 mile interstate runs with speed matched, trip odo reset @ identical start and stop points, autopilot and self-driving managing the car, and all climate/HVAC off. Runs are back to back, at night, same direction, with traffic a non-factor. Tire pressures were checked via TPMS before and after each run. The 35 psi run did show a ½ PSI increase from start to, so there was some heat increase.

I used large gaps in speed and pressure so we’d get obvious results.

As the 50mph (lower wind resistance) was repeatable it suggested the process didn’t require two passes @ 35 psi. (I was also low on battery. Got home at 2%.)


Results:

Thoughts:

• The 45 psi runs showed no tire pressure changes. 35 psi run did show a ½ PSI increase from start to finish so there was some heat increase.
• I don’t get these lowish power demand number in real life. Climate control has a big impact!
• I expected tire rolling resistance to play a reduced role at higher speeds, but I wasn’t so sure we’d see it, nor that it would be this significant.
• I’m a little bummed the two 75mph runs don’t match more, but at higher speeds it doesn’t take much for even minor wind changes to affect things.
• Ride difference was significant and immediately noticeable.
• I was surprised at the how significant air pressure changes are at lower speeds
• Although that usually means I’m local and care not at all.
• On a real-life trip where I’m expecting something like 250 miles of range at most? I’m not likely to worry about what is likely to be less than 5 miles of range difference.
• Range/pressure is not linear. Delta drops as pressure increases. Meaning the increase in 35-40 is larger than the increase from 40-45.
• I don’t run 35 PSI either. I normally inflate to 37-38 and add when I hit the 35 PSI warning light.

YMMV.

Note: This will be added to the "Air Pressure" document I've shared/linked to elsewhere.

 

[Pianewman]

Thanks ... JACO has a few designs. Which is better for Tesla tires, especially the ease of measurement?

They're the same internal gauge, just different convenience features. Nothing special about "Tesla tires."

 

[dafish]

My Tesla TPMS and three home digital wallmart specials all agree to within 1/4 PSI. My very expensive in tire nozzle gauge is off by 5 PSI consistently. Hard to be certain which ones are "right", but I know which ones I believe.

 

[jcanoe]

They're the same internal gauge, just different convenience features. Nothing special about "Tesla tires."

Depending on the OE tires, i.e. 19" Gemini wheels and wheel covers, it can be difficult to get the chuck of an air hose or tire pressure gauge to make a good connection with the tire valve stem. One solution is to pull off the wheel cover.

 

[Ray_R]

Thanks ... JACO has a few designs. Which is better for Tesla tires, especially the ease of measurement?

View attachment 923763

I use the Elite Pro. I like the digital readout and the button that lets air out when I over inflate.
Tesla tires are no different than any other car tires as far as measuring air pressure goes.

 

[Pianewman]

Tesla tires are no different than any other car tires as far as measuring air pressure goes.

...or in any other way, except some have a foam liner...which is common in other vehicles, as well.

 

[jcanoe]

The TPMS in my 2020 LRMY are accurate. Three out of four TPMS sensors agree on the pressure reading with my Intercomp gauge (when the tires are cold). The fourth TPMS sensor usually read 1 PSI lower than the other three sensors.

Many portable tire inflator pumps have a built in pressure gauge. If you use the air hose at a service station then you can add 1 to 2 PSI extra when filling the tires with air. Later, when the tires are cold, you can slowly bleed off the excess air until the tire gauge reads the desired pressure.

 

[Nubo]

All Tesla Pros out there
Any recommendation for a digital tire pressure?
Thx and enjoy your ride

A digital display really isn't adding value. I prefer this analog unit Deluxe Tire Gauge (0 to 60 PSI)

 

[rlsd]

A digital display really isn't adding value. I prefer this analog unit Deluxe Tire Gauge (0 to 60 PSI)

I use a digital pump. I set it to the desired pressure then start pumping. When the target pressure is reached, it stops automatically. It works great. The pressure level on all four wheels on the car app is consistent with the level set by the pump.

 

[Nubo]

I use a digital pump. I set it to the desired pressure then start pumping. When the target pressure is reached, it stops automatically. It works great. The pressure level on all four wheels on the car app is consistent with the level set by the pump.

Now that does sound useful. Might consider that when my current pump packs it in.

 

[CMPT PAD]

I use a digital pump. I set it to the desired pressure then start pumping. When the target pressure is reached, it stops automatically. It works great. The pressure level on all four wheels on the car app is consistent with the level set by the pump.

[digital pump] Pump with a digital readout?

 

[rlsd]

Yes, pump with digital readout.

https://www.amazon.com/Slime-40057-Cordless-Inflator/dp/B07CN89G6H

I like this model because it's cordless. You can use the USB ports in the car or a cell phone charger to charge the lithium battery but it probably takes longer. I bought this one in AutoZone for urgent use when my car had a flat tire and the pressure dropped down to 25 PSI. You can shop for a better model.

 

[SteelClouds]

There is a difference between pressures that needs to be considered. And that is impact resistance. A tire with less air pressure with be compliant but allow the tire to deform under impact than a tire with higher pressure. On 18 inch tires, this is not such a big deal but with 20s and 21s and a very small sidewall, that soft pressure will let the rim take a hit and rims are costly to replace. The higher pressure will be rougher riding but allow the tire to take the hit vs the wheel. Of course, you can take a hit that will pop the tire then all bets are off. But I just had a case where my 19s were run at 45 psi and took a very hard hit where it left black rubber marks on the side of the rim, bubbled the tire but the rim was intact. At 35 or even 40, I'm pretty sure it would have cost me a rim and a tire. It's not always about comfort and being efficient .

 

[legendsk]

For those of us who can't afford a compressor with a good digital gauge on it, (because we spent all our money buying Tesla stock), think how handy it would be if the Tesla App displayed tire pressure, real time. {Hint, hint, Tesla}

 

[SteelClouds]

Wont happen. They do it this way to preserve battery life of the sensor. I would really hate to have remove my tire from the car, bust a bead and maybe rebalance just to change a 5 dollar battery.

 

[andaconda]

Three out of four TPMS sensors agree on the pressure reading . The fourth TPMS sensor usually read 1 PSI lower than the other three sensors.

Same here. Three of four is 2 psi lower and forth is 3 psi lower. Confirmed by 3 separate gauges.

 

[Brian-MS90D]

I appreciate the OP's post. Thanks!

There really is only one impactful thing within our control regarding range, and that's speed. If you need to maximize range between charges, stay around 55 - 60 mph. The impact on range at faster speeds worsens significantly and is - unfortunately - not linear.

 

[TomB985]

There's only so far you can push PSI consistency.

These sensors monitor temperature as well as pressure, and we all know there's a direct relationship between the two of them. Sunshine on one side of the car while you're going down the road can elevate temps a few degrees, and pressure on that side rises accordingly. Accelerate hard and the rear tires get warmer than the front as they struggle to keep up with your right foot.

Pressure can change 3-4 PSI just with ambient temperature changes in a given day. I get that car enthusiasts are an obsessive group, but...

 

[CMPT PAD]

Same here. Three of four is 2 psi lower and forth is 3 psi lower. Confirmed by 3 separate gauges.

From the scientific standpoint -IMO- $50+/- gauges are not accurate enough .They will give approx readings. I bet I could use the same gauge and measure 3 times I would not not get same results

 

[tivoboy]

While digital is probably best, a solid compressor with a quality gauge is going to be very close. As some have noted, buying a tire pressure gauge alone and or compressor might be $$ (not too much, but understandably) maybe consider the INVESTMENT in one of the Tesla or third party tire repair kits, which include compressor and tire PST gauge. I haven’t done an A to B compare between this and my ’digital’ PSI gauge, its going to give the same readings across all tested samples.

The benefit being, that if one DOESN’T already have one of these in the car for either road trips or just in case, it does double duty as a tire repair kit.

There is a Tesla official version and I’m fairly certain that is OEM’d from ResQ which is a bit cheaper

Tire Repair Kit

The Tire Repair Kit contains an air compressor to regularly top off your tire pressure and a one-piece sealant canister to patch punctures. Simply attach the transparent hose to the tire valve and connect the plug to your vehicle's 12V outlet to begin repairing the hole and filling the tire. The...

shop.tesla.com

https://www.amazon.com/ResQ-71-063-021-Tire-Repair-Compressor/dp/B00BJ2TBL2/ref=sr_1_7?crid=URBI08XXAF6J&keywords=Tire+repair+kit+tesla+model+3&qid=1680791778&sprefix=tire+repair+kit+tesla+model+3%2Caps%2C164&sr=8-7&ufe=app_do%3Aamzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840

 

[SteelClouds]

I got battery powered inflator and so far it’s rocking. Gauge is accurate and the battery can add 4psi to all four tires for 35 psi and still have 3/4 charge
Fanttik X8 APEX Tire Inflator Portable Air Compressor, 2X Faster Inflation, 150PSI Cordless Tire Inflator with LCD Dual Screen, Suitable for Cars, E-Bikes, Motorcycles, For Up to 26.3 Inch Tires https://a.co/d/2vyH7Gw