jacksyee

Hello,



I have Pilot Super Sport 235/35/ZR19 front and 305/30/ZR19 Rear Tires.

The diagram above (I think) means that cold true pressure should be 34/40 PSI. I live in Hong Kong and the winters are very mild.

Recently I got a "fill tire" light for the rear left tire (-4). Oddly the sensor showed the same pressure as the right Tire (I believe it was 34).

In any case I checked and reinflated all my tires to the above pressures (cold). I then went to TPM and set the tires to winter and went through the 'learning' process.

This cleared the fault, however the tire pressures read by the sensors and displayed on the screen were not 34/34/40/40, they were 29/29/35/35, or about 5 PSI less than measured by the pump and by my hand held pressure sensor (an ancient metal one that looks like a pen with a plastic stick that pops out)

I seem to remember there was a way to calibrate them but I can't figure it out. This is complicated by having never received a manual when I bought the car used. I had a PDF manual but can't locate it.

Can anyone help? (And does I look like my pressures are correct - should I use the plate on the car)?

Regards,

Jack

Dennis C

My TPM sensors usually read 4 PSI less than my tire gauge. I think this is normal. I also use the pressures recommended on the plate.

heliflyer

Perfectly normal - The TPMS sensors are not intended / calibrated to provide a guaranteed accurate readout of actual pressure - they are however sensitive to changes in pressure and this is what makes them good at the job they are there for.
They are only intended to highlight a reduction in pressure and thus indicate a puncture - the fact that they give you an approximate pressure readout is a bonus.

jacksyee

Oh great thanks. That's a relief.

Macster

Deleted.

Terry Adams

TPMS alerts me when the pressure drops at the beginning of every winter, by registering a pressure that is more than 4 psi below the door plate number. I use that because it is likely the best pressure compromise between handling, comfort and wheel protection against potholes.

That gauge you have with the pop out scale is cheap and inaccurate. For a nice German car, I use a

Reifendruckmessgerät

http://www.flaig-präzision.de/produk...ssgeraete.html

Got mine from Griot's Garage, but don't know if they still carry it or where in HK you would get a similar.

RJKflyer

Odd that people are reporting TPMS as inaccurate, as my TPMS is accurate to within the 0.1bar resolution of the display. As tested against a calibrated 1% meter.

Don't forget that the 'Info pressure' function - which displays variance against required pressure - is temperature compensated.

Required pressures per the panel on the door shut (or wherever) are indeed 34/40psi, but/and these at at a nominal 20 degC.

My 'Info pressure' shows 0 variance on all tyres against required, but as the ambient is about 12 degC, the actual pressure on the fronts, for example is 32.4psi.

(Sorry for the horrendous mixing of metric/imperial units!)

MadScience

I'll second that tpms has been pretty on for me, both in my '09 997tt and a '14 bmw f31.

FWIW, the cheap digital gauges seem pretty good. Amongst all the gauges I own, the stick ones are only inaccurate at altitude, and there's one (molton, so hardly cheap) filler gauge that was clearly never calibrated correctly.