P85D 19" tire pressure recommendation is now 50psi

[efusco]

50K service on my S85 last week, tire pressure adjusted to 45psi per my service bill.

 

[EarlyAdopter]

But the front motor probably only adds 50-75lbs or so....not enough to justify raising tire pressure so high. I mean honestly adding a passenger to the car adds more weight than the front motor does.

Curb weight of the P85: 4647 lbs
Curb weight of the P85D: 4936 lbs

They both have the same rear drive train, so the front motor + inverter + half shafts + beefed up front crash structure must weigh 289 lbs.

 

[BerTX]

Googling a bit came up with a few interesting hits. Particularly this older thread where these guys run 60-70psi in 44max psi rated tires to get better mpg. Tire pressure above 44 psi? - CleanMPG Forums There was a mention of someone running 120psi and a mention from an engineer that said tires wouldn't spontaneously blow up until well after 200psi. I may go out and pump up my tires to 50psi and see if it makes any difference. It's probably negligible.

Those are typical tire inflation numbers (60 psi in 44 psi rated tires) for the 1st gen Honda Insight. Extensive roll testing (setting tire pressure, starting car on a hill in neutral, seeing how far it rolls, then changing pressure and re-run) was done, and it was found that there was improvement up to 60 psi, then no significant change above that.

The reason for the roll testing is that there are too many factors to eliminate on a hybrid to get an accurate energy usage comparison. I would think that the Tesla, with much better energy usage measurements, would be fairly simple to do some testing to find the optimum inflation pressure.

It will be different for every tire make/wheel size combination -- that is the advantage with the Insight, as there is only one tire to test.

 

[JakeP]

50K service on my S85 last week, tire pressure adjusted to 45psi per my service bill.

Which tires are you running? Michelin Primacy MXM4, Goodyear RSA2, something else?

 

[efusco]

Which tires are you running? Michelin Primacy MXM4, Goodyear RSA2, something else?

Goodyear Eagle RS-A2, 19" of course

 

[dirkhh]

Goodyear Eagle RS-A2, 19" of course

So possibly the change to 50psi is only for the Michelin Primacy tires?

 

[efusco]

So possibly the change to 50psi is only for the Michelin Primacy tires?

Perhaps. But the Goodyear are rated to 51psi as well.

 

[Terra117]

So what about the TPMS?

Unless they raised the warning pressure, they just increased the delta between 3 tires and one that is low.

 

[commasign]

From the discussion in the Firmware 6.2 thread, if you look at my tire tread report, my tires were unevenly worn (inner/outer vs center) after just 5000 miles. This was with pressure set to 45psi. So definitely should be 50psi on the P85D. If pressure is too low, the tire sags and the inner/outer will wear faster than the center.

 

[AndreyATC]

I wonder if the spec went up for 21s as well

 

[RiverBrick]

My Model S has a TPMS warning for over inflation, as I found out in the descent going West from Truckee. The strange thing is, I tested the pressures at a rest stop and they weren't even 50 psi warm. So, they're either adjusting the TPMS as well, or my system is buggy.

 

[Lloyd]

My Model S has a TPMS warning for over inflation, as I found out in the descent going West from Truckee. The strange thing is, I tested the pressures at a rest stop and they weren't even 50 psi warm. So, they're either adjusting the TPMS as well, or my system is buggy.

Just do a TPMS reset at the new pressure and that should go away.

 

[RiverBrick]

View attachment 77114

I wonder if it has anything to do with the excess tire wear around the edges.

 

[jerry33]

So what about the TPMS?

Ignore it unless it says too low, but unless you have a large puncture, you will likely catch any slow leaks way before the silly TPMS alerts.

 

[thegruf]

incredulity alarm kicked in here.

If 245/45/19 is 50psi that means that 245/35/21 is going to be more like 56psi.

I dont know of any summer car tyres rated that high.

If an owner inflates to this pressure on a cool morning, then drives hard fully laden on a hot afternoon - that's way into the safety margin of the tyre and any tyre company will disclaim responsibility for failure.
It's not just structural failure here, but susceptability to failure instead of deflation from what would normally be minor damage too.

Somebody needs to get a statement from Tesla for the official position on this.

Also it makes it incredibly important that owners changing tires selects exactly an approved tire and there are a lot of subtle variations of apparently similar tires to the unwary. eg how many owners double check they have the correct load rating on replacment tires. i know I do now, but I have been caught out previously.

Furthermore as a safety concern Tesla S/Cs should be required to check the tires load rating and note it on the service sheet, and inform the owner the vehicle is unsafe where replacement tires are not to correct specification.

 

[CHG-ON]

I agree. I would like Tesla to issue an official statement on this. Correct pressure is important. Too little: too much heat, flex and wear. Too high and less contact patch. This stuff isn't all that complicated. Not to mention unintended over- or understeer, which could be disasterous. Auto mfrs have been rating correct pressures for years.

incredulity alarm kicked in here.

If 245/45/19 is 50psi that means that 245/35/21 is going to be more like 56psi.

I dont know of any summer car tyres rated that high.

If an owner inflates to this pressure on a cool morning, then drives hard fully laden on a hot afternoon - that's way into the safety margin of the tyre and any tyre company will disclaim responsibility for failure.
It's not just structural failure here, but susceptability to failure instead of deflation from what would normally be minor damage too.

Somebody needs to get a statement from Tesla for the official position on this.

Also it makes it incredibly important that owners changing tires selects exactly an approved tire and there are a lot of subtle variations of apparently similar tires to the unwary. eg how many owners double check they have the correct load rating on replacment tires. i know I do now, but I have been caught out previously.

Furthermore as a safety concern Tesla S/Cs should be required to check the tires load rating and note it on the service sheet, and inform the owner the vehicle is unsafe where replacement tires are not to correct specification.

 

[AndreyATC]

incredulity alarm kicked in here.

If 245/45/19 is 50psi that means that 245/35/21 is going to be more like 56psi.

21s always have been lower PSI per Tesla
Mine were 39 or something for staggered 21s
I wonder if they raised PSI for bigger wheels as well

P.S. I'm running 42PSI on my aftermarket 20s with PSS tires

 

[commasign]

Well, here's the final answer: If you have a P85D with 19" wheels and your door jam sticker says 45psi, you can call or email your local SC and ask for the updated 50psi sticker. Just did this.

 

[dhanson865]

Well, here's the final answer: If you have a P85D with 19" wheels and your door jam sticker says 45psi, you can call or email your local SC and ask for the updated 50psi sticker. Just did this.

Good to know. Thanks for the update.

 

[thegruf]

21s always have been lower PSI per Tesla
Mine were 39 or something for staggered 21s
I wonder if they raised PSI for bigger wheels as well

P.S. I'm running 42PSI on my aftermarket 20s with PSS tires

Smaller ratio 45 -> 35 always going to be higher PSI