I checked my pressure and all four had 40 PSI car felt like a basket ball.
Sticker on the side states 34psi all round but manual give 38psi for 20" tires. What are you folks using? 34 psi on my car triggers the TPSM...
Can I reset the tire pressure or what can I do?

 

Lower profile with larger rims will require higher pressure as load deformation of the tire is proportional to total air volume. The bigger the rim the smaller the air volume and so higher pressure is needed for correct shape of the contact patch. What does the owners handbook say?

 

I have 20's and run 34psi all round and no issues with TPMS.

 

Strange, I put 38 psi and then slowly lowered to 36. I will lower slowly again. My tire is 255/35/20 97Y and 34psi should be used.

 

35psi,no issues

 

Is your tire pressure gauge accurate? Are you allowing for ambient temperature effects ? The measured pressure at 10C will drop by 3psi at minus 5C, for example. About 1psi change for each 5C or 10F, approximately. The change is actually less than that but the exact number is harder to remember.

 

Yes I have two very accurate gauges. What I did is up the pressure to 38psi. TPMS dissapeared. I then lowered the pressure slowly and reached 34psi no probs so far. It seems a drastic pressure drop like 40 to 34 will trigger the TPMS.

 

The TPMS is set to recognize a 25% drop in pressure.

 

Well there you have it.

 

From the factory specified pressure, not from whatever it is set at. In my locale it can get cold enough to produce that effect without any air leaking from the tire. 10C down to -27C will do it. That would be over 6 psi loss in relative pressure due to temperature drop only. I suspect the TPMS system in the car has to be programmed for the tire size the car is equipped with.

 

So with car/ignition off if I was to let all air out of one tire, then pump it back up to the same pressure and then turn the car on would the tpms not know any difference? How about if with the car running and I let all air out of one tire then pumped it back up to the same pressure? Would a warning come up? Would I just drive until the warning/message goes away?

There musr be a way to do a factory reset of TPMS without having to go to a dealer.

 

No and yes then no. Unless the ignition is on the TPMS sensor will not cause a fault to display. It does not remember data so if the tire pressure is corrected while the ignition is off no fault will display. If the ignition is on the TPMS sensor will signal a fault as the pressure drops and the fault will display until the pressure goes up again then the fault will go out. No memory function exists.

If TPMS low pressure displays due to low ambient temperature effects and driving rises the pressure back above the minimum due to tire heating then the TPMS fault will go out.

The TPMS does not have to be reset. It automatically does so by receiving TPMS sensor radio frequency transmissions at fixed receivers in front of each front wheel and somewhere near each rear wheel. These receivers inform the ECU which wheel is transmitting which data.

I think it's possible that the ECU may need resetting if different sized wheels or tires re fitted but perhaps th TPMS sensors are specific to a given specified tire pressure range. Ie perhaps you need TPMS sensors for 34 psi specified pressure and different sensors if specified pressure is say 36 psi. Over inflation should not trigger a TPMS fault, only lw pressure should do that. It us also wheel specific. No comparison between wheels occurs. If one sensor is in a tire that is over pressure that has no effect on the others which may fault if under low pressure.

 

Thanks Jagular

 

This section is for the Jaguar XF. The X-Type has its own area

 

I am curious if anyone knows if the Torque app can read the tpms and individual tires.

 

I've got Torque Pro and I haven't seen that option in the list.