I like to keep the pressure in my tires at 42 cold and 44 warm. I often check the digital read out on the dash to make sure all are close to equal. Last night I wanted to take a couple psi out of one and noticed that the TPMS was 2-3 psi higher than what the tire gauge was reading , and I have noticed that discount tire is usually higher than what I have on the read out for the TPMS. If my dash read 43, the gauge will read 40 . With discount tire I notice when I ask them to top the pressures off I usually get 45 when I ask for 43 or 42 psi.

Not sure what the most accurate. Kind of strange. Anyone else notice the same thing? Is the TPMS the most sensitive or would it be discount tires system with the autofill. The gauge I think would be less sensitive for obvious reasons but still not sure why the discrepancy

Use your own old school gauge for best results on level surface..cold tires

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Frankly I think most of these tire gauges are just approximations, they're not precision instruments. Many years ago I bought what I think is a high quality dial type gauge from Brookstone. Who knows, it may be wrong but at least I'm consistent!

I too have noticed a couple lb discrepancy in what my gauge reads and what the TPMS system says. I rely on my gauge when filling.

Consumer Reports occasionally tests tire gauges, and there can be quite a difference in the accuracy of the gauges. Generally speaking your gauge will probably be fairly accurate, but some of the models tested were not. I would trust your gauge over the one at the tire shop, since the tire shop one likely gets beat up pretty good. If you are unsure about your gauge, the top rated gauge was the Accutire MS-4400B which you can get for around $10. It's a digital gauge and reads in .5 lb increments. The top rated analog dial gauge was the Intercomp 360060. It's around $56. I actually own the gauge that came in second, the Accutire MS-4021B, which you can get for around $7.50, and it works well. I wish it read in tenths, because I'm a little too **** about such things, but .5 is good enough that I've learned to live with it.

Cheers,
Charles

Dial type tire pressure gauges generally provide the most resolution - you can usually eyeball-resolve pressure to less than 0.1 PSI, and they are very useful for assuring that all of your tires are at the same pressure. Having a bleeder valve on your pressure gauge makes it easier to get the same pressure on all tires.

If you are into accuracy then the Moroso 89575 gauge is a good choice. Although list price is way up there it is possible to find them at a reasonable price. They are digital, have 0.1 PSI resolution, .5% accuracy and a bleeder valve. http://www.moroso.com/catalog/catego...?catcode=27107

Regarding the accuracy of the TPMS sensors: with just a little thought it is easy to conclude that the sensors are as accurate or more accurate than most tire gauges - I would guess the accuracy to be better than 1%. If you set all your tires to the same pressure using a high resolution gauge and then the TPMS displayed pressures are all the same as each other, but not necessarily the same as the handheld gauge - they could differ by +1 or by -1 because of the quantization uncertainty (that means that if the quantization thresholds are 1 PSI apart then tires with very small pressure differences, like .001 PSI, could display a difference of 1 PSI) - then you can take it to the bank that the sensors are accurate. The only way that they would read the same and replacements would read the same is a high degree of accuracy.

I have looked at this carefully with my fancy tire gauge and the sensors on my car are spot on.

The Accutire MS-4021B gauge cited above is certainly adequate to set your tires in a manner that will let you realize all the safety benefits of your TPMS and attain the specified tire performance.

I have no doubts that the OEM TPMS sensors are accurate and as long as they agree then you should trust them.

I have four tire gauges and they all read different, but are within 3 pounds of each other.
My analog Milton agrees with the TPMS so I use that as my standard.

;->

My vehicle TPMS was working accurate before. HOwever, after I replaced 4tires and they mess with TPMS sensor, it is few psi off. Yes, It was Discount Tires store.

I just had my tires rotated and pressure checked at discount tire. They have about 6k miles on them. Tire guy said he inflated to 38 lbs as winter was coming and they would be a little less at colder temp. They were machine filled and I guess with an automatic cutoff when pressure was reached.

TPMS is reading 38's and 39's.

I have a machine I use to fill the tires at home . Its like a mini compressor with a digital gauge on it. Got it from Walmart AND it fits perfectly into the little loop belt that hold the first aid kit in the trunk.