Tire pressure fluctuation
08-08-2022, 07:01 AM
#1
Junior Member
Thread Starter
Tire pressure fluctuation
2022 GLC 300
When the outside temps were in the 70's 2 months ago the MB app would show that the tire pressure was around 36 after driving. Now that we are in consecutive days of temps in the mid to upper 90's, the MB app is showing me readings of 33-34. This is on all 4 tires. I know it's not an individual tire issue because both before and current PSI are on all 4 tires.
Any ideas?
Thanks
When the outside temps were in the 70's 2 months ago the MB app would show that the tire pressure was around 36 after driving. Now that we are in consecutive days of temps in the mid to upper 90's, the MB app is showing me readings of 33-34. This is on all 4 tires. I know it's not an individual tire issue because both before and current PSI are on all 4 tires.
Any ideas?
Thanks
08-08-2022, 01:18 PM
#2
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Join Date: Nov 2018
Location: San Francisco Bay Area
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2019 C63CS
Well, you need to regularly check the tire pressure when tires are cold and adjust them to the desired pressure. Tires lose air over time. It's not uncommon to lose 1 psi per month just from the air naturally escaping through the pores in the compound. I check mine every two weeks and they always need a bit of a top off. In addition tire pressure changes with ambient temperature. Every 10F in temperature change results in 1 psi of pressure change in both directions. So in your car if you are now two psi low at 90F compared to 70F that means your tires lost about 4 psi, because going from 70 to 90 should increase their pressure by 2 psi from the expanding air, but since you seem to be about 2 psi low now that means you actually lost 4 psi. On a new car or a set of new tires that's not unusual. It takes a bit of time for the tires to fully seal, so you can lose a bit more air initially, but it should stabilize.
