[Roman G]

I've noticed the idrive screen always shows a higher psi than my tire pressure gauge.

I be been doing some research and found it conflicting, somesay measure and fill when cold, others, after driving and warming up the tires.

So the questions is, how do you properly fill the tires. Do you under fill them a few bars when cold and let them warm up? Do you warm up the tires and then get them to correct pressure?

This is for street use not track, but regardless, I'm suppose to be at 32 front and 38 rear on MPSS.

Right now I've been driving until they warm up and then check and fill to 32 and 38.

Also, any one else have an issue with I drive showing higher numbers than tire gauge even after performing tpms reset from idrive.

[overcoil]

First, winter tire temp and summer tire temp so check seasonally the psi.

Always check the tire pressure when cold - when the car hadn’t been driven - whether 1-hour or 2-hour - or first thing in morning.

Hand held pressure gauges are notoriously inaccurate. So a combo of iDrive tire temp and hand held psi gauge is perfect.

As important as the psi gauge are tread depth gauge and observing shoulder wear particularly on front wheels will help extend tire life.

[Maynard]

Manual suggestions (or door jamb) are always going to be cold pressures. Track info will often list hot pressures, but unless listed that way, assume e/t is for cold. These are just suggestions, so you do not need to be exacting, modifying them will change subtle aspects of handling feel - I prefer my fronts higher, closer to the rears (about 35/38). The only absolute is the max pressure listed on the sidewall, but you should not be anywhere near that in regular use, or even at the track. Nitrogen is supposed to be more stable, but a PITA if you aren't close to a refill station.

Your air gauge needs to be reliable, more than accurate (i.e. should get the same reading from a tire 5 times in a row, even if the 'wrong' amount). If it isn't reliable, then just pitch it. If you want to get really compulsive about accuracy, find s/b with a really good air gauge and check your handhelds against that - you can mentally adjust if it reads a few # off. My gauges and dash are all w/i a pound of the same reading, but I haven't cross-validated on a/b else's gauge. It is more important to balance the tires around the car, rather than to get them at a specific perfect pressure.

Tires change by about 1psi for every 10degrees Fahrenheit, so pressures will be going up a little with the hot weather.

[dradernh]

As others are saying, tire pressures are set when the tires are cold. If you can't do that, drive as short a distance as possible to where you can fill them and check their psi.

This may seem like overkill, but I use this tire gauge for my street vehicles:

http://www.longacreracing.com/produc...BD%E2%80%9D-lb

Why? Because I spend a lot of money on tires, tire pressures make a difference in how the car feels to me, as well as in how much life I get out of a set of tires, ½ of one-percent accuracy ensures I'm getting accurate readings, and the gauge is made to last. Also, I prefer the display of an analog gauge, although I use both. Note that an analog tire gauge is most accurate in the middle of its range, so a 0-60 psi gauge will be more accurate than will a 0-100 psi gauge.

The wife prefers a digital readout. She uses one that costs half as much, displays in 0.1 psi increments, and is just as accurate:

http://www.longacreracing.com/produc...Gauge-0-60-psi

[biz4two]

Agree with other comments that tires should always be checked when cold. However, if a tire is low while driving (or hot), then you can estimate a correct PSI at plus 4.

IE: rear tire shows 34 psi after a 30 minute drive. To get it to proper psi level, you would add 8 psi. Because tire would read about 30 psi when cold.

In other words, as an estimate, tires read +4 psi higher when hot.

Don't forget to do a tpms reset each time you adjust your tire psi.


biz