I tried searching about this and didn't really find anything so I thought I'd see if there's a chance I could get the answer here. Is it possible to lose a couple lbs of air over a couple weeks with aftermarket wheels and the OEM tpms? The reason I ask is because I went back home to Detroit about a month ago, with my new tire/wheel set up and checked my mileage. I got 38.5 mpg going there (an improvement of .5 mpg) but on the way home the mileage went waaaay down, like 6-7 mpg and I got 36 mpg (compared to 42-43mpg) I checked the air the next morning and the tires were at 29 psi and one tire was at 28. I didn't check them before the trip, yeah, I know its a good idea to do so.


So, what do you guys think?

 

its probably because your aftermarket rims are heavier than your originals. But then again, the forwards should be the same weight if not lighter than the OEMs. If the tire is mounting properly and there is no leak, you shouldn't lose air at all unless over a cold winter.

 

The wheel and tire combo is about 2lbs heavier but I thought I read somewhere that the tpms doesn't mount flush there and it cause a little air to leak over time. In my case, I've lost about 3-4 psi over the past 2 weeks.

Like I said earlier, my mileage changed alot. Even the additional 2lbs of wheel/tire weight didn't affect my mileage going home, but coming back I lost 6-7 mpg's and the psi was down to about 28-29. Now the tpms light DID NOT come on though

Thanks for any input here guys, I really don't wanna rip the tpms' out and have that annoying light on all the time, stupid government rules My 07' Mini used the VSS to check the air pressure, why couldn't they just stick with that, it worked!

 

I went to the dealer the other day to have a tire checked out that I can't keep air in, of which I had checked by a tire place and supposedly fixed. I was wondering if there was something in the stem, or tpms part that could be causing it. This is relatively new tech, and I don't know jack about the assembly.

The parts guy said it could be the "core" that if faulty, but more likely, the nut that holds it all together may not be tight enough. I have sort of noticed these before, but not paid them much attention. This is my second car with tpms. If you look at the valve stem, sure enough, there they are on the outside. Don't know what they need to be torqued to, but check it out and report back. They couldn't find anything wrong when they dunked it - so it's gotta be due to pressure squeezing it out of somewhere. The parts guy seemed to be quick with an answer as to what could be causing it, which leads me to believe it's a common thing. The core, if I needed to replace one, was quoted at $1 - that's like half the price of a stem cap! Wondering what it is exactly, but anyways, try tightening that assembly.

 

I haven't had any loss problems? I dunno

 

Whenever you had your wheel and tire combo installed, do you remember the tech rebuilding (putting new grommets really) the TPMS sensor? If the grommets in the sensor aren't replaced, then that sensor could leak air. Please look at the link below, to the an example of the grommet. Its the first item placed on the valve steam.

TPMS Rebuild Kits

I haven't had an issue with my TPMS sensors on an aftermarket wheel after they were installed to the aftermarket rim and whenever I had gotten new tires. Both times, the sensors were rebuilt by the tire techs.

To be sure that the senor or tire is leaking air, either wet the tire and sensor with soapy water and watch for air bubbles or place the suspected leaking wheel/tire in a large tub of water and watch for air bubbles.

 

Thanks everyone, especially Hootie and yeah, the manager said they rebuilt the tpms but I'm taking it back to him for everything to be checked out, I'm going back home next weekend and don't wanna have any issues with leaking air, although its leaking very slowly and I could just check and top off the air right before I go home and again when I come back. I'll have it checked out and chime back in here to possibly help out the next guy