BB11

Hello all, finally got out of a sick bed and took the car out for a shot 80 mile drive, smooth and quiet, still have to tinker to get the right position but that is to be expected.

After posting some pictures I was asked about the tire pressure and using the pressure given to me from the dash I was informed it was probably too high. WhenI went to check it with my tire pressure gauge it was right a 33 but not on the dash display. So this has me very confused.. I would think the digital readout would be most accurate but on my ride it kept changing (I assume as the tires got warmer. So how do I gauge how much air to put in, use the dash numbers or my tire pressure gauge and maybe I need to buy a better than the $1 gauge..

Also, how accurate do you find the mileage shown on the dash display? Just curious.

The last thing is a bit different, I am sure I will find more but I found one nick on the car, seems to maybe have been touch up or just did not go through to primer, not a big deal although I keep my cars immaculate so it would be nice to to have it. Question I have to wrestle with is seeing if the dealer will do something and if that may not be a good idea, not sure how well their body shop will do on something like this or if it is even worth it. Thanks much
BB

bclexus

All four of my TPMS readings are accurate to within a fraction psi. How do I know? I have three different digital psi gauges, two register in 1/2 psi amounts and one registers in 1/10 psi amounts, and all register the exact same readings. I also have two gauges that are calibrated with certification...and the digital gauges match the certified gauges exactly. I even take into account the fractional psi that is lost whenever the valve is depressed while taking a reading...

I am very picky about my tires' air pressure being the same - to the point of being a fanatic about it. When the time of year dictates (going into cooler weather or going into warmer weather) I'll adjust my tires' air pressure. What I do is - I'll add a couple more psi than I need and then tweak the tire pressure down to what I really want after the car sits overnight in a dark garage. I take the garage's temperature into account, and also whether (based on the time of year) the outside driving temperatures will be increasing or decreasing from what the garage temperature is. I like to have the psi of all four tires change within a minute of one another (typically driving 1/4-1/2 mile at most) on a cloudy day or night time when the sun's radiant heat affects are not a factor. I even go as far as releasing the tiniest (minuscule) puff of air in order to match the air pressure in all four tires. It's almost like a game to me. Call me strange, but...

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Here is a common scenario - the vehicle owner has their tire pressure checked mid-day and adjusted to the recommended pressure during summer (e.g. 90+ degrees) after driving the vehicle for a period of time on hot pavement and with the radiant effects of the sun hitting the tires. Driving the vehicle for a period of time will increase the tire pressure 2-3 psi, the 90 degree ambient temperature will increase the tire pressure 1 psi for every 10 degrees or say 2 psi higher than at 70 degrees, and the sun's radiant effects can increase the tire pressure by 2-3 psi. That total could easily add up to 8 psi - or 8 psi higher than a vehicle's tire pressure that has been sitting in a dark 70 degree garage overnight. So, in the case of tires that are recommended to be inflated to 33 psi - if those tires are inflated to [only] 33 psi when the ambient temperature is 90 degrees and after driving the vehicle for a period of time on hot pavement and with the radiant effects of the sun hitting the tires, those same tires will likely only have 25-27 psi after the vehicle has sat overnight, which is referred to as 'cold'. 'Cold' is when the tires should be inflated to the recommended air pressure. And, people wonder why their TPMS warning light comes On when they just had the tire pressure adjusted recently...

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During the Summer I will set my tire pressure at 33.0 psi cold (cold = car parked overnight in an enclosed garage) at 73 degrees garage temperature. (Note: I'll adjust the set tire pressure by .5 psi for every 5 degrees above or below 73 degrees the garage temperature actually is.) This is based on the outside (ambient) temperature being (getting up to) ~27 degrees higher (or about 100 degrees) than the garage temperature. The tire pressure will increase as much as ~3 psi on daytime high temperature alone reaching as high as 100 degrees, another 1-3 psi increase for traveling on warm/hot pavement and cement vs. asphalt, and another 1-2 psi if the sun is out with a typical Summer UV rating. So, I start out with 33.0 psi on cold tires and my tires will naturally increase (based on above noted factors) by a minimum of 3 psi during morning or evening hours, or if the day is cooler than normal, or if the day is cloudy. I'll have a maximum increase of ~7-8 psi if all factors are at absolute peak, which is rather unlikely. I will usually only see a 5-6 psi maximum increase (to 38-39 psi) in the Summer.

During the Winter I will set my tire pressure at 33.5 psi cold (cold = car parked overnight in an enclosed garage) at 60 degrees garage temperature. (Note: I'll adjust the set tire pressure by .5 psi for every 5 degrees above or below 60 degrees the garage temperature actually is.) This is based on the outside (ambient) temperature being (getting down to) ~27 degrees colder (or about 33 degrees) than the garage temperature. The tire pressure will decrease as much as ~3 psi on outside temperature alone reaching as low as 33 degrees. However, the tires will increase 1-2 psi for traveling on pavement, and possibly increase another 1 psi if the sun is out even though the UV/radiant quality of the sun is much lower during colder months of the year. So, I start out 33.5 psi on cold tires and my tires will drop 0-3 psi based on outside temperature, yet the tires will increase 1-3 psi based on traveling on pavement and maybe increase another 1 psi based on the sun being out, thus all these factors offset one another for a minimal (~0 psi) change in psi compared to when I started out. I'll have a maximum increase of ~1-2 psi if all these factors are at peak (warm Winter day with full sun), which is very common and gives me around 35.5 psi maximum tire pressure. I will usually see a 0 psi drop to a maximum of ~1-2 psi increase (33.5-35.5 psi) in the Winter.



See the 'Tire Pressure Inflation Compensation and Adjustment' attachment file directly below.

BB11

Wow, thank you. So what tire pressure gauge do you recommend, I am certain the my car parts supply cheap one is not doing the job properly. I appreciate your long and detailed reply.

bclexus

You are welcome.

I would recommend the Accutire MS-4400B Pistol Grip Digital Tire Gauge. You can probably find them in one of your local auto parts stores; e.g. O'Reilly's, AutoZone, Pep Boys, Walmart, etc. If not, you can order one online from Amazon or find them on eBay, etc. They are only $10-$12 or so. They read in 0.5 psi increments and mine happens to be very accurate when compared to a very expensive calibrated gauge that reads in 0.1 psi increments.

BB11

Thanks again, will order one immediatly. Maybe i can find one locally. Also, thanks for the info on when to measure. Can i trust the car temperature guagecas correct in garage morning temperature? I hope so.

bclexus

The GS 350 outside temperature sensor is very accurate when moving (traveling), and it will be also very accurate in a garage as long as the engine and exhaust has had time to completely cool off and not give a false reading due to engine/exhaust heat.

A lot of people don't realize it, but the the sun's radiant effect can increase tire pressure by 2-3 psi just sitting parked with the sun shining on one portion of the car, and it doesn't take long.

ironcondor

Wow, that post should be a sticky! Awesome.