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Lowering tire pressure on Gemini 19s

asaulo1

Member
Mar 2, 2021
64
26
California
After over 2k miles, I feel that the ride of the MY is quite firm especially over broken pavement. Currently running Gemini 19 wheels and was wondering what tire pressure I should lower it down to for a more compliant ride. Currently set to 44 psi which is what it came from the factory. Cheers!
 

Adirondack_D

Member
Mar 13, 2021
25
14
Upstate NY
My concern with softening the tire pressure would be uneven wear. These tires aren't cheap to replace, and I'd hate to wear them out quicker by going too far in one direction or the other with tire pressure.
 
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frankvb

Supporting Member
Supporting Member
Feb 29, 2020
927
572
San Diego, CA
Be aware of the fact that for XL tires the load rating is only valid at 42 psi. Having said that, I can't imagine you will run into problems e.g. at 40 psi.

BTW: car sticker says 42 psi is the correct pressure, 44 psi is on the high side.
 
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Robocheme

Member
Feb 3, 2017
218
214
Northern California
How's your review on the coilovers, I have a set on order. Do they quiet down the ride any?
Here's my review. I didn't notice any change in the noise level so I put on some door seals.

 

jcanoe

Active Member
Oct 2, 2020
3,440
3,500
Maryland
The recommended tire pressure (42 PSI) Front and Rear is noted on the label on the B pillar by the driver's door opening. I have been experimenting with tire pressure for almost a year and while my Model may not be fully broken in at 4000 miles I feel the ride is less harsh than when new. I have found that somewhere around 44 PSI is my preferred tire pressure setting. The tire pressure will fluctuate by 2 to 3, maybe 4 PSI as the tires heat up. The maximum tire pressure (51 PSI) is molded into the sidewall of the Continental ProContact RX tires. Even then there is a safety margin so its not like the tire will explode if you happen to inflate the tire to 52 PSI. I would not intentionally inflate the tires above the recommended maximum pressure. All tire pressures are specified cold before the vehicle is driven. (Severe under inflation generates more heat within a tire and is a leading cause of blowouts. Under inflation due to lack of tire maintenance by the owner/operator is why auto manufacturers are required to have tire pressure monitor systems in all new vehicles.)
 
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jcanoe

Active Member
Oct 2, 2020
3,440
3,500
Maryland
I have been running my Model Y at 38 lbs cold, and it definitely is a touch softer ride . Any opinions on how much I am harming the ultimate life on these tires welcome
The manufacturer's recommended tire pressure (front and rear) is always on a printed label on the B pillar next to the driver's door. For the Tesla Model Y that is 42 PSI (cold).

Under inflated tires will run hotter; under inflation is the leading cause of tire failure.

Tesla specifies Extra Load (XL) rated tires for the Model Y. XL tires require 41 to 42 PSI to meet their rated load.

When you lower (or raise) the cold measured tire pressure by 1 or 2 PSI from the recommended pressure then there should be no issue.

When tires are under inflated the tires can wear faster on the edges than in the center. When tires are over inflated the converse can happen, the center of the tread area can wear faster than the edges.

The reason that all new vehicles come with a tire pressure monitor system (TPMS) is that there were too many accidents where gross under inflation of one or more tires was a direct cause or a contributing cause in roll over collisions and other fatal accidents.

Tesla provides clear information on proper tire maintenance on page 166 of the Tesla Model Y Owner's Manual:
https://www.tesla.com/sites/default/files/model_y_owners_manual_north_america_en.pdf

WARNING!

Under-inflation is the most common cause of tire failures and can cause a tire to overheat, resulting in severe tire cracking, tread separation, or blowout, which causes unexpected loss of vehicle control and increased risk of injury.
Under-inflation also reduces the vehicle's range and tire tread life.

Check tire pressures using an accurate pressure gauge when tires are cold. It takes only about one mile (1.6 km) of driving to warm up the tires sufficiently to affect tire pressures. Parking the vehicle in direct sunlight or in hot weather can also affect tire pressures. If you must check warm tires, expect increased pressures. Do not let air out of warm tires in an attempt to match recommended cold tire pressures. A hot tire at or below the recommended cold tire inflation pressure is dangerously under-inflated.

As noted by anaconda, under inflation will reduce your driving efficiency and decrease your range. How much range? Perhaps ~ -1% per PSI below the recommended pressure; if you increase your tire pressure you can increase your range by ~+1% for every PSI above the recommended tire pressure.

The maximum tire pressure is printed on the sidewall of the tire. For the OE tires on the Tesla Model Y this is 51 PSI (cold). Tire pressure readings should always be taken when the tires are cold before the vehicle has been driven and not when the tires are outdoors and exposed to the sun. A quality tire pressure gauge should be used, rated for accuracy within +/- 1 PSI.

As we enter fall, keep in mind that tire pressure will drop approximately 1 to 2 PSI for every 10 degree drop in temperature. (I recently checked and inflated the tires on my Model Y to 45 PSI.) I know that in the coming weeks the tire pressure will drop with the temperature to between 42 and 44 PSI which is where I want it to be anyway.
 
Last edited:

Pianewman

Active Member
Oct 28, 2020
1,475
1,054
Fort Worth
Agree with the above. I've moved from 42psi to 40, 38, 45...I don't feel a significant difference. That said, I'll stay at 42psi or slightly above, to minimize wear, and maximize mileage.
XL rated tires (necessary because of the weight of the MY) have stiff sidewalls, and 45aspect ratio tires just don't have enough space to permit much flex, at any PSI.

The tires create the harsh "slap" over uneven concrete joints. The MMP coilovers I've installed reduce it some, but not enough to make my wife appreciate the $3500 cost. (sigh...) The harshness is still there. What the MPP coilovers DO improve is the overall clumsiness of the car over more dramatic road imperfections. (I'll be driving on I20 through Shreveport next week: I don't expect miracles, but hopefully the car won't be AS willing to go airborne!!!!)
 

jcanoe

Active Member
Oct 2, 2020
3,440
3,500
Maryland
I have owned my Long Range Model Y for 15 months and have tried driving with the tire pressure of the OE Continental Procontact RX tires set between 39 PSI and 46 PS, either intentionally or because I was too lazy to add air to the tires as the temperature dropped. I find that the most comfortable setting is 44 PSI. I have tried to further quantify whether it is best at 43 PSI or 45 PSI but I keep coming back to 44 PSI (measured cold.)
 

Pianewman

Active Member
Oct 28, 2020
1,475
1,054
Fort Worth
jcanoe: ...and you're "picking the fly *sugar* out of the pepper"! Don't you agree that while we're driving, these pressures change 3-4 psi? I don't see how you could possibly tell the difference between 43psi and 44psi. Between 38 and 42, or 42 and 46, but...

(...and I thought I was OCD!!!! HAHAHA!) 😭 😭 😭
 

jcanoe

Active Member
Oct 2, 2020
3,440
3,500
Maryland
jcanoe: ...and you're "picking the fly *sugar* out of the pepper"! Don't you agree that while we're driving, these pressures change 3-4 psi? I don't see how you could possibly tell the difference between 43psi and 44psi. Between 38 and 42, or 42 and 46, but...

(...and I thought I was OCD!!!! HAHAHA!) 😭 😭 😭
I drive same route every day so I am familiar with every bump and rut in the road. So after 500 round trips (between 25MPH and 45 MPH) I can tell the difference that outside temperature, speed and tire pressure can have on the ride of my Model Y. I understand that tire pressure will increase 2 or more PSI while driving. My reference point is always the cold tire pressure reading in the A.M. Over time the ride has improved although not by much and not until I had driven ~3,000 miles.
 

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