Tire Pressure vs TPMS

I just bought a used 2009 Nissan Altima, and the tires are not the original ones. The tire pressure warning light stays on. The tires on it are Champiro 328 245/45/zr18 100w mounted on nissan 18" wheels. I checked the tire pressure and it was just over 40 psi. So I tried lowering the pressure to 32 psi as indicated in the door jam for the original tires, then I drove the car around (over 16 mph.) hoping to reset the TPMS sensor, but the sensor light is still on. The dealer said make sure the tire sensors weren’t removed from the wheels; And that the valve stems should be metal, which they are. Since the tires are not the original, what tire pressure should I keep these tires at? Should I just let the TPMS warning light stay on? I would appreciate any information. Thank You, Arnold Martinez

The tire sensors may not be in these aftermarket rims. Metal valve stems are no guarantee. Or, the sensors may have bad batteries. I’m surprised the dealer didn’t just use his scanner to see if the sensors are sending a signal to the TPMS. This should be an easy thing to do. But, as long as your willing to keep an eye on the tire pressure, like we all should, this problem is simply a nuisance.

Also, since these are not the tire size the chart was designed for, I have no idea how to determine the proper tire pressure. Maybe someone else on this site can help.

On every vehicle sold in the US, there is a sticker ? commonly called the tire placard - that lists the original tire size and the proper pressure for that size. The placard is usually located on a doorpost or in the glove box ? but sometimes it is located in the trunk or on the fuel filler door.

BTW, it doesn’t matter who makes the tire or what pressure is listed on the tire’s sidewall, if the tire size is the same as the placard, then the pressure listed on placard is also appropriate.

According to Tire Guides, a 2009 Nissan Altima should have come from the factory with … well… a variety of tire sizes, depending on the exact model, but all of them were Standard Load (SL) tires with a 93 or a 94 Load Index. Please check your placard, because what follows will be incorrect if the placard shows something other than that.

Your 245/45R18’s are Extra Load (XL) tires with a load Index of 100. For what we are dealing with here, their load carrying capacity is the same as the original tires, so the placard pressure is still appropriate.

That leaves the problem of the TPMS, and I am afraid you’ll have to dismount the tires to be sure the sensor is still there.

One more suggestion. Have you read the owner’s manual? These systems, be they based on pressure sensors like yours or wheel speed sensors, need to have a “baseline” established for the system to monitor against and trip the warning light if the pressure strays too far. There may be a protcol in your owner’s manual to reset the baseline pressures. My manual calls it “reinitializing”. It’s different from just resetting the system, which does not change the refernce baselines.

Try reading the manual first. I can’t guarantee it’ll help, as you may actually have one of the problems that others have alluded to, but it just might.