Hi

I have a very nice and very accurate air compressor. it is the best, so if you set it at like 35PSI, it is 35PSI on the money and does an auto-off . I have check it as well with 2 other garages.

Anyway, i set the tires on my car, cold in the garage to all exactly 35PSI.

When i reset the TPMS, it shows different PSI reading on the display per tire, all the tires are off by .5 to 1.3 off.

Anyone? can these be calibrated to be accurate.

 

Their accuracy may be +-1 psi. What's your reference again? A garage?

 

Every measurement tool has a tolerance. Without knowing the tolerances of whatever you're using, saying something being 0.5 PSI (or 1.4%) as "way off" seems like an overreaction. For all we know, the TPMS are measuring in KPa and the dashboard readout is simply a rough conversion and display of that in PSI.


Take your car through some clover-leaf 270° on-ramps at the limit of adhesion and then see the before and after pressure delta. Your driving habits have a bigger impact on the tire pressure than the relatively minor tolerances of the gauges in question.

 

Hey, Benny! Great timing on your post as I was JUST experiencing similar issues. 2015 F56 and in the garage prior to driving used my compressor to inflate and check with a digital gauge, the fronts at 38 psi and the rears at 35 psi.
Started the car, went in to the menu to reset TPMS (at which point it tells you to drive) and watched the bar fill up to 100%. End result? Readings all over the place!
Not like it was 5 lbs low or high but def not the exact amount just registered...understood that driving impacts the numbers. I was just on level road without any slalom like turning.

 

if the in-tire devices were precision sensors there would be no need for a reset procedure

 

Guys you're giving these tmps too much credit here. Yes they give us a value for the pressure, but it's just a guide which we should all check regularly of course.... Their real useful function is to look for large drops in pressure from the original reset value which we might not have noticed, that's when they raise an alarm for you.

When I fitted my winters last year, bought directly from MINI, I ran with them for about a week before I verified the pressures at my garage. They were all way too high, so I deflated them as necessary then set off, forgetting the reset. Mile down the road the system pooped itself, all 4 tyres.

Interestingly I've found mine all to be very close to what the garage airline says.

 

Slightly off-topic, but I had my first tire pressure warning today. Cold weather this morning so it dropped to like 26 psi. After driving around for 30 minutes it went back up to 30.

1) What psi level sets off the warning?

2) if the pressures go back up again does the warning go way or will I have add air and perform a reset?

 

My warning goes off at 30 psi. I fill it to 38 and the warning is gone, I don't reset anything. To eliminate pressure variations with temperature try nitrogen. It eliminates the water vapor in the tire which is what makes the pressure change. If it said 26 you probably have a leak in the tire.

 

30 is too low anyway. set it per door sticker which is at least 35 im sure.

 

I agree, I set mine to 35 at outside temps at about 70

I was told to try Nitrogen for winter use, I think I will try that

 

I was told by the dealer to let the air out 100%, start the car but do not drive it yet, Let the sensors react to low tire pressure. shut off the car, re-inflate to exactly 35PSI to all tires. Starts, do a tpms reset and drive conservative until its 100%, now they all read the same and exactly...go figure, but the dude was right.

 

Interesting, will give this a try, mine has recently been giving me fits