TPMS Question
Thread Starter
Instructor
Joined: Dec 2007
Posts: 147
Likes: 1
From: Bergen County New Jersey
TPMS Question
I have Brand New 2008 AO 200 miles, the question is: My Left rear tire pressure is lagging (30 as opposed to 31 psi) when you first fire up the beast, after driving, the pressure comes up equal or sometimes 1lb short. Normal..., Slow leak... or add the 1lb.??? This is probably a mute point to the Senior members but alas I'm a newbie with TPMS.
Input appreciated
Input appreciated
Melting Slicks
Joined: Nov 2004
Posts: 2,144
Likes: 0
From: Roselle Park NJ
St. Jude Donor '07 thru '25
The first thing you should do is check your tire pressures cold with a good quality tire gauge. Get them all to the correct pressure and then check the pressures in the DIC.
The DIC pressure is supposed to be an indicator and not a precise measurement.
Pressure will increase as the tires heat up.
If there is a sizable difference between the cold pressure on the gauge and the cold pressure on the DIC, a trip to the dealer might be in order.
The DIC pressure is supposed to be an indicator and not a precise measurement.
Pressure will increase as the tires heat up.
If there is a sizable difference between the cold pressure on the gauge and the cold pressure on the DIC, a trip to the dealer might be in order.
Race Director
Joined: Jan 2005
Posts: 10,924
Likes: 854
From: Daytona Beach FL
When the car sits still for more than 15 minutes the sensors go into a sleep mode to save their internal battery life. In the sleep mode they only transmit once per hour.
When you start driving more than 20 mph the sensors wake up and start transmitting once per minute (sooner if they detect a loss of pressure).
Additionally, your DIC only displays pressure to the nearest 1 psi, and your tire pressure gauge probably displays to 1/2 psi or greater accuracy.
So.....if your car has been sitting for awhile when you check and adjust your tire pressures with your gauge, the DIC won't update until you drive faster than 20 mph, probably for a few minutes, before the sensors wake up and all transmit the current pressures to the DIC.
Forum members that live at high altitudes report that the DIC display is always less than their pressure gauge. Those at 4,000 feet or higher report the DIC displays as much as a 4 psi difference from their gauge.
I think your 1 psi difference is just sorta normal.
Bob
When you start driving more than 20 mph the sensors wake up and start transmitting once per minute (sooner if they detect a loss of pressure).
Additionally, your DIC only displays pressure to the nearest 1 psi, and your tire pressure gauge probably displays to 1/2 psi or greater accuracy.
So.....if your car has been sitting for awhile when you check and adjust your tire pressures with your gauge, the DIC won't update until you drive faster than 20 mph, probably for a few minutes, before the sensors wake up and all transmit the current pressures to the DIC.
Forum members that live at high altitudes report that the DIC display is always less than their pressure gauge. Those at 4,000 feet or higher report the DIC displays as much as a 4 psi difference from their gauge.
I think your 1 psi difference is just sorta normal.
Bob
CF Senior Member
Joined: Feb 2006
Posts: 23,313
Likes: 25
From: Tucson Arizona
I believe the recommendation is to start with 30lbs cold in all 4 tires (albeit I put an extra lb or two in my front tires to help compensate for the cars 51/49 weight distribution ratio).
Tire pressures should increase in all tires as you drive and heat them up. The pressure increases aren't always uniform in all of the tires. Even having the sun shining on one side of the car can make a difference.
As was mentioned, buy a quality tire gauge and take your readings when the tires are cold. As temperatures change with the seasons, check and adjust your tire pressures frequently.
Tire pressures should increase in all tires as you drive and heat them up. The pressure increases aren't always uniform in all of the tires. Even having the sun shining on one side of the car can make a difference.
As was mentioned, buy a quality tire gauge and take your readings when the tires are cold. As temperatures change with the seasons, check and adjust your tire pressures frequently.
