Aftermarket Tire Pressure [what tire pressure for my aftermarket tires?]

[rivera151]

So I just got a 2019 Model 3 Performance and this is the most fun car I’ve owned, hands down.

The previous owner took the wheels down to 18 and settled for Toyo Proxes Sport 245/45 Z R18. So I said, well lets see if we can find out what tire pressure this car needs with these tires.

Well that was a rabbit hole I just wasn’t willing to go down, at least not then, so I called Toyo customer service and left a message that I needed help with setting the tire pressure.

Well, later in the day I got a call from an (female) egghead who was quite knowledgeable, took all my stats (Car, original wheels and tires, original tire pressure on the pillar sticker) and determined that for my car, with original tires at factory pressure, the equivalent pressure for my car with my rims and tires is 32 psi.

I talked to the previous owner and he was not impressed, and just told me to set the tire pressure at factory 40-42 psi and not listen to the very knowledgable person working for the tire manufacturer.

1. What do you guys think?

2. How would I set the TPMS set point to 32 psi, if I wanted to do that?

 

[Birdsfan]

I recently swapped out my 20" ubers for 19" aftermarket wheels and Conti's all season tires. I used the tire pressure off the door jamb and told the car I replaced with 19" wheels. I haven't had a problem since with the TPMS.

 

[BigNick]

32 PSI will be way too low for a car of the M3P's weight. I would check with anyone who has a P3D- aka "Stealth" M3P with 18-inch Aeros and see what their door jamb sticker says.

 

[dhrivnak]

So I just got a 2019 Model 3 Performance and this is the most fun car I’ve owned, hands down.

The previous owner took the wheels down to 18 and settled for Toyo Proxes Sport 245/45 Z R18. So I said, well lets see if we can find out what tire pressure this car needs with these tires.

Well that was a rabbit hole I just wasn’t willing to go down, at least not then, so I called Toyo customer service and left a message that I needed help with setting the tire pressure.

Well, later in the day I got a call from an (female) egghead who was quite knowledgeable, took all my stats (Car, original wheels and tires, original tire pressure on the pillar sticker) and determined that for my car, with original tires at factory pressure, the equivalent pressure for my car with my rims and tires is 32 psi.

I talked to the previous owner and he was not impressed, and just told me to set the tire pressure at factory 40-42 psi and not listen to the very knowledgable person working for the tire manufacturer.

1. What do you guys think?

2. How would I set the TPMS set point to 32 psi, if I wanted to do that?

It depends on your goals. If racing I can see the lower pressure being an advantage. But is going for range that is far too low.

 

[rivera151]

It depends on your goals. If racing I can see the lower pressure being an advantage. But is going for range that is far too low.

My goal is to replicate the conditions with the original tires. So I figure that the 32 psi figure has to do with the optimum pressure that will translate to appropriate wall tension and thus grip comparable or as close to identical to the conditions with the OEM tires, but thats all assumed, pretty liberally, because I really don’t know about the subject.
Really more looking at a rationale/engineering perspective if anyone is knowledgable on this subject.

 

[TexasTezla]

32 psi? Too low. Needs to be 44-45psi

 

[Big Dog]

42+

 

[TM3blu]

Call Tire Rack. They know aftermarket wheel setups. Any pressure UP TO maximum printed on tire sidewall is acceptable.
Depending on your priorities, ride, handling, traction, or range. Door sticker will usually cover most cases.

 

[LTN17]

There's a tire pressure calculator at Tire Pressure Calculator

What's written there talks a lot about maximizing load capacity and tire wear. When one plugs in the OP's scenario, the calculator returns 32 psi for the new tires, which, as others here have said, seems too low. But there is some interesting info at that link.

 

[rivera151]

There's a tire pressure calculator at Tire Pressure Calculator

What's written there talks a lot about maximizing load capacity and tire wear. When one plugs in the OP's scenario, the calculator returns 32 psi for the new tires, which, as others here have said, seems too low. But there is some interesting info at that link.

This was very useful and probably exactly what I was looking for. Thank you for this very informative link.

Now on to item 2: can I set the TPMS set point to 32, if I wanted to?

Any takers?

 

[rivera151]

Well, honestly I think I have all the info I need from that last link. The bottom line is:

1. Yes, the recommended tire pressure that will replicate the OEM load-bearing capacity for my specific tires is 32 psi.
2. Nonetheless, if the new tires are XL tires, load bearing capacity is decreased below 40 psi.
3. So I think that weighing in certain degradation in load-bearing capacity at lower pressures vs possible inefficiency and grip issues running at higher than recommended tire pressure, I think the former seems like the lesser of the two evils.

 

[Limit X]

I have a 2018 stealth with aftermarket wheels and tires, I run 40 psi for street driving and go down to 33-35 on track. When the tires came installed, it was at 35, and I will say it was definitely soaking up bumps a lot better. Higher PSI also means you get better efficiency out of the car too, so if range is a factor. Those tires also have a 45 aspect ratio side wall, so you have a lot of cushion for pot holes not damaging your wheels.

 

[rivera151]

Those tires also have a 45 aspect ratio side wall, so you have a lot of cushion for pot holes not damaging your wheels.

Yep, that’s exactly why they are there. I do have a 1 hour commute that can be either 35 miles, or 50 depending on the route, and I do a round trip at least once a week. So efficiency may be a factor to consider as well In my use case.

 

[TexasTezla]

Seems to be an awful lot of overthinking here. Just push air in them and see what you prefer as a ride...softer more cushion use less psi, better range but a harsher ride more psi...

 

[Limit X]

Yep, that’s exactly why they are there. I do have a 1 hour commute that can be either 35 miles, or 50 depending on the route, and I do a round trip at least once a week. So efficiency may be a factor to consider as well In my use case.

Wow that is quite a long commute, I forgot to mention that those tires are rather sticky tires meant for spirited driving or track use. When you do replace them, consider going like all seasons, it will last a lot longer too.

 

[rivera151]

Wow that is quite a long commute, I forgot to mention that those tires are rather sticky tires meant for spirited driving or track use. When you do replace them, consider going like all seasons, it will last a lot longer too.

Ha ha. Thanks for the tip. Knowing the previous owner, this makes perfect sense.

 

[Xambler]

My Stealth with 18” wheels, Michelin Mx4s on front (originals) and Bridgestone Potenza RE980AS on rear. At 40 deg F out I put 42 lbs in each. Sticks at around 48 lbs when temp is in 80s and tires warmed up. Handles great on mountain curves and boring FL roads.

 

[jackmott]

32 psi is probably fine for that slightly bigger tire, tesla factory psi is a bit high on purpose to improve range. If you wanted to replicate that you would probably run 38 or 40.