Why 45 psi?

[Deans]

Why does Tesla recommend a tire pressure of 45 psi for my 60D MS?

The curb weight is roughly 4600 lbs. With full load, that brings the total weight to 5600 lbs, or 1400 lbs/tire.
The stock Goodyear tires having a load inflation chart as follows:

30 psi - 1411 lbs
31 psi - 1458 lbs
32 psi - 1492 lbs
33 psi - 1527 lbs
34 psi - 1561 lbs
35 psi - 1598 lbs
36 psi - 1653 lbs

This is as high as the chart goes! The maximum load for each tire is reached at 36 psi (1653 lbs).
The tires can accept pressures up to 51 psi. But what is the advantage? Inflating the tires to 45 psi will help fuel efficiency and range, slightly. But I would think that savings would be more than offset by the shortened tire life due to over inflation. Furthermore, ride quality suffers quite a bit at high PSI and so does handling.

What am I missing? I've been inflating to 45psi, per the door jam. But the ride is rough. I would like to know why I need 45psi? If it's only to maximize range, and not for safety, that I'd like to lower it!

It seems like the proper inflation would be in the same range as other cars (32 psi - 35 psi). And that's assuming the car is loaded up with 5 passengers and luggage.

I'm not an expert and I'm not recommending anyone lower their air pressure. I would just like to understand what I'm missing. Thanks.

 

[GSP]

Deans,

I would guess that Tesla recommends 45 psi to get better rated range.

Modern tires can be run at the max sidewall pressure without wearing faster in the center. I have been using 45-50 psi for both my Model S and my Chevy Volts. No problem with tire wear on either Volt. For the first 30,000 miles the wear has been even. I just got the S.

I like running high pressure with the sporty ride and handling. I like stretching my range also, espically in the Volt. Back in the day when I used to autocross everyone pumped up tire pressures for the event.

However, high pressure is not for everyone. If you like a softer ride I would try 35 psi. I think you are correct that there would be no problem other than slightly less range.

GSP

 

[GHammer]

Well I don't know why but tire rack makes it very clear that inflation must be higher than 45psi

 

[msnow]

Mine are Michelin Primacy's and I leave it at the engineering and manufacturer recommended setting of 45/46 psi.

 

[JRMW]

Discount Tire inflated my tires to 39psi when they installed my winter tires.

the left half of my display converted from my odometer (what I have set there) to a picture of my car and car tires with red exclamation points stating that the tires were underinflated. I also got tire underinflation chimes.

the tire under-inflation display wouldn't go away until I inflated my tires over 41psi if I remember correctly.

not sure if you can disable that somewhere...

 

[jerry33]

What am I missing?

All tire pressure recommendations are based on a set of assumptions. The basic four are:

1. The ambient temperature is 18C (65F). If it's higher than that you need to adjust the pressure upwards.

2. Speed. The GY chart (and all other charts from the tire manufacturers (as far as I know) are based on a 65 mph sustained speed. If you run faster than that, then you need to up the pressures.

3. Load. For cars the load that the pressure recommendations are set at are for what the engineer thinks is going to be normal for that car--not necessarily the GVW.

4. A daily pressure check at the start of each driving day. (Don't shoot the messenger.) If you don't check every day, then you need to adjust the pressures upwards so that you never go below.

In addition there are factors particular to each car, such as handling and weight transfer (to name a couple--there are more).

Another list:

1. Higher pressure reduces heat in the tire which causes tire failures and shortens tire life.

2. Higher pressure reduces the chances of having uneven wear.

3. Higher pressure provides better transient response in an emergency situation.

4. Higher pressure reduces the chance of hydroplaning.

5. Higher pressure is required when the temperature is above 65F (18C) or below 65F and inflated indoors.

6. Higher pressure is required so that the pressure does not fall below the minimum if you don't check pressures each day before you drive.

7. Higher pressure is required if you carry more load than the car was designed to normally carry (note that this might be less than the GVW--it could be only one or two passengers).

8. Higher pressure provides better traction in most, but not all, on-road winter conditions.

9. Lower pressure increase ride comfort, which is highly subjective and probably depends a lot on the amount of "natural padding" present

10. Lower pressure reduces vehicle damage during off pavement usage.

Note that track use--where you adjust the pressures to get the most contact area is a whole 'nuther subject, and basically not applicable to normal driving (unless you like buying tires frequently).

 

[kort677]

Discount Tire inflated my tires to 39psi when they installed my winter tires.

as noted by others and the sticker in the door the correct pressure for your 19" tires is 45psi, discount tire didn't do a proper installation.

 

[jerry33]

as noted by others and the sticker in the door the correct pressure for your 19" tires is 45psi, discount tire didn't do a proper installation.

There is a lot of misinformation out there. Much of it is a hold-over from 40-50 years ago when most North American cars had bias-ply tires.

 

[kort677]

There is a lot of misinformation out there. Much of it is a hold-over from 40-50 years ago when most North American cars had bias-ply tires.

the door sticker is misinformation? could it be the russians hacking?

 

[BerTX]

The Eagle Touring tires may need to run at a higher pressure to reduce flexing, increasing the adhesion and life of the foam insert in each tire. I wouldn't recommend running much under the recommended pressure.

The OP just says "Goodyear", and may not have these tires. I think the recommended pressure was raised when the foam lined tires were being phased in. It didn't hurt the other tires, and the Eagle Touring tires needed the higher pressure.

Just observing and speculating, here.

 

[NikeWings]

I have ContiSilenys and my door jamb says 42 psi as does my SvC paperwork when they auto check my tire pressure upon any visit. Should I be boosting them to 45psi?

 

[msnow]

I have ContiSilenys and my door jamb says 42 psi as does my SvC paperwork when they auto check my tire pressure upon any visit. Should I be boosting them to 45psi?

No whatever the door jamb says. Are yours 19" or 21"?

 

[NikeWings]

No whatever the door jamb says. Are yours 19" or 21"?

21s so why 42 when you guys are talking 45? If I have a sticker of 42, does that apply for any tire?
Never thought much about tire pressure before but I guess I should start now. Thx.

 

[msnow]

21s so why 42 when you guys are talking 45? If I have a sticker of 42, does that apply for any tire?
Never thought much about tire pressure before but I guess I should start now. Thx.

Yours are a "thinner" lower profile tire so basically less air is required. No, the sticker is for your own rim/tire setup. Periodically I switch the right scroll wheel to display "Car Status" which is the PSI pressure of all four of the tires. When they lose a pound or so I use a nice digital pressure guage that I found on Amazon.com and this to fine tune it.
Tesla — Tire Repair Kit

 

[NikeWings]

Yours are a "thinner" lower profile tire so basically less air is required. No, the sticker is for your own rim/tire setup. Periodically I switch the right scroll wheel to display "Car Status" which is the PSI pressure of all four of the tires. When they lose a pound or so I use a nice digital pressure guage that I found on Amazon.com and this to fine tune it.
Tesla — Tire Repair Kit

OK, I'll monitor. Could you check that Amazon link please when you get a chance. Nothing popped up for me.
I got the tire repair kit as swag...they said I'd need it being a Boston driver. But my blowouts so far have been out the sides and I didn't even try the kit. Used roadside and they've been outstanding. Thank you.

 

[pers1]

from Tesla

In Norway I use +10% tire pressure for my winter tires as recommende by Nokian tires.

 

[jerry33]

the door sticker is misinformation? could it be the russians hacking?

No. The vehicle placard pressure is not misinformation. I was referring to the 39 psi that the tire store set the pressures to. I consider that pressure to be the minimum that I never want to go below except in unusual (for me) circumstances. The vehicle placard pressure is a starting point only and should be adjusted to reflect actual driving conditions (almost always this means and upward adjustment for on-road driving).

 

[GSP]

For what it's worth, the door jamb placard on my March 2015 build Model S with 19" Michelins calls for 50 psi. It looks like Tesla recommended 50 for a while, then went back to 45 psi. When Tesla did the annual service on my car, they went to the trouble to reduce my tire pressure from 50 to 45. I will set them back to 50.

GSP

 

[JRMW]

as noted by others and the sticker in the door the correct pressure for your 19" tires is 45psi, discount tire didn't do a proper installation.

I know. My point was that the car had a constant low pressure warning that I could not shut off.

My goal was to inform anybody who was thinking about lowering their tire pressure that alarms would go off.

 

[kort677]

I know. My point was that the car had a constant low pressure warning that I could not shut off.

My goal was to inform anybody who was thinking about lowering their tire pressure that alarms would go off.

isn't the point of the alarms to alert you to low pressure in the tires?
AFAIK the easiest way to shut those alarms off is to inflate your tires to the correct psi.