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What do you trust more - Onboard tire pressure monitor OR a physical tire pressure gauge?

  • Onboard computer

    Votes: 2 12.5%
  • Physical device

    Votes: 11 68.8%
  • I eyeball it

    Votes: 3 18.8%
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2021 Road Glide Special
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Discussion Starter · #1 ·
On board tire monitor is about 2-4 PSI lower than what my physical gauge says. I added a little bit of air in both tires anyway.

So my question is do y’all trust your onboard monitor and adjust PSI based off that or a physical gauge?

In my cars I’ve always trusted the tire gauge on the air compressor.
 

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meh, it's just a point of reference. I trust the TMPS until I need to add air and then I use my digital gauge and just accept the updated reading on my dash. I mostly look at the TPMS to see if I have a leaking tire.

So which physical gauge are using? The pencil style, a digital, or an analog and which do you think is trustworthy?
 

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Discussion Starter · #3 ·
I have this one on the air compressor. I have the pencil style to. IDK that one is better than the other. I just saw that the TPMS was 3 or 4 PSI different from the air compressor so just got me thinking.

Clock Automotive lighting Analog watch Font Measuring instrument
 

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If we're really being honest here...then yeah, for the most part I'll just eyeball it, unless she starts to handle funny.

If I'm going on a run - where hi-jinx may ensue - then I get out the digital gauge and make sure they're set on target.

If the seasons are changing and the average temperature goes up/down 30-ish+ degrees, I'll get out the digital gauge and make sure they're set on target.

If I switch to one of the girls that's been sitting for a bit...I'll get out the digital gauge and make sure they're set on target.

Otherwise, if they got enough air in'em to look round from across the lot, and she's running straight ... I don't give a damn what the exact number is.
 

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On board tire monitor is about 2-4 PSI lower than what my physical gauge says. I added a little bit of air in both tires anyway.

So my question is do y’all trust your onboard monitor and adjust PSI based off that or a physical gauge?

In my cars I’ve always trusted the tire gauge on the air compressor.
My old Joe's Garage branded one routinely reads 3 psi optimistic when compared to the TPMS on all of my vehicles. However, my new Rhino gauge is dead on with the TPMS pressure. Best $20 I have spent. I gave my buddy one for his BD too, he loves it. Amazon.com: Rhino USA Heavy Duty Tire Pressure Gauge (0-75 PSI) - Certified ANSI B40.1 Accurate, Large 2" Easy Read Glow Dial, Premium Braided Hose, Solid Brass Hardware, Best for Any Car, Truck, Motorcycle, RV… : Automotive
 

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While back I took rear tire off and put a different wheel with tire mount on. The factory tire was a long ways away from the bike and in a building.
It took to days for the TPMS to stop showing the pressure that was in the tire that cam off.
 

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2012 big blue pearl r.g. custom,chris rivas 574 cams. Rinehart extreme 4" RSD air cleaner barrnett c
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I have spoke wheels. The rear wheel is a total pain in the ass to check air pressure (wheel is tubless and the valve stem is straight because of weird rim band/tube flap to make it tubless)
I use a digital gauge when i check um

Glenn
 

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I check with the TPMS but I trust my gauge on my air compressor. The TPMS has too many parts but it's really handy to watch for changes.
 
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On board tire monitor is about 2-4 PSI lower than what my physical gauge says. I added a little bit of air in both tires anyway.

So my question is do y’all trust your onboard monitor and adjust PSI based off that or a physical gauge?

In my cars I’ve always trusted the tire gauge on the air compressor.
Do you trust the TPMS on your cage? Fact of the matter is the TPMS is only talking to the BCM every 64 seconds when you're traveling above 8 mph and if its not going above 8 mph it only communicates every 7 minutes. So if you go out and look at your tire pressure first thing in the morning using the TPMS. It is not going to be accurate. Always set the tire pressure using the physical gauge. Simply use the TPMS to keep an eye on the tires when you're on the road.
 

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Discussion Starter · #14 ·
I pretty much follow the TPMS in the cars. Idk why I thought bikes would be any different. I might have added a little to much air then.
 

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Do you trust the TPMS on your cage? Fact of the matter is the TPMS is only talking to the BCM every 64 seconds when you're traveling above 8 mph and if its not going above 8 mph it only communicates every 7 minutes. So if you go out and look at your tire pressure first thing in the morning using the TPMS. It is not going to be accurate. Always set the tire pressure using the physical gauge. Simply use the TPMS to keep an eye on the tires when you're on the road.
I'll be damned. No wonder it takes forever to get the TPMS to change on the screen. I'll be using my trusted gauge from now on. Thanks for the info!
 

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I'll be damned. No wonder it takes forever to get the TPMS to change on the screen. I'll be using my trusted gauge from now on. Thanks for the info!
The times that were posted are for many cars. THE HD system in different it can take much longer for it to reset.
The more often it checks pressure the shorter the battery life so they extend it .
 

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The HD sensors actually send data every 64 seconds after they are "woke up" from "Park Mode", by going 25mph for 20 seconds they are in "Drive Mode". They stay in "Drive Mode" after that until the bike has been parked or stationary for 7 minutes, then they go back into Park Mode. In Park Mode the update interval is only once every 4 hours, until it goes back in to Drive Mode again when the bike is driven 25mph for 20 seconds. The system is set up this way to extend battery life in the sensors.
Here's a Doc Harley video, FWIW, that gives his explanation on the system

Sooooo, when you go out to your bike in the morning, and turn the ignition on, the pressure information showing could be as much as 4 hours old (depends on when in the last 4 hours it updated). For me, thats not an issue because the tire has had plenty of time to"cool" completely to ambient temperature and what it is showing will be within a pound once it "wakes up" (unless I'd gotten a nail in it on the way home the previous day maybe). In the last year, that I have had HD's TPMS, this has been actually what I have seen happen too.

Unless the sensors are defective, they should be consistently accurate... or have the same "variance" consistently when compared to "your accurate gauge". TPMS will tell you that you may need to add air, by what it is reading, but you do not use them for adding air, because they only update every 64 seconds... unless they have slipped into park mode. In 64 seconds you will add way too much air :p so you use a gauge when adding air because it's reading is instant. The "Variance"between your "known accurate gauge" and the TPMS system is what's important to make a mental note of too.

For example, I have a manual gauge that I have deemed "accurate", and it is the gauge I use when adding air to my cars, truck, or motorcycle. On my truck, the factory TPMS sensors (Chevy) were spot on with my gauge, that was easy... but the replacements sensors I put in, after the 10yr old factory ones died, vary consistently 1 to 2 psi (depending on which of the 4 tires I'm checking) from what the gauge says when I'm checking the tires "cold" (not driven yet). On my bike, the TPMS is consistently within 1psi of what my gauge shows (once the sensors have updated).

So knowing this, if its 80F in my garage and before I ride the bike, if I'm checking my tires because I think my tires might be low, or they are low, I add air to the bike using my gauge and in the front I air it up to 38psi on the gauge and the bike's TPMS is going to show 37psi (because it shows 1 PSI lower than what my gauge shows). The back sensor is the opposite, it consistently show 1psi more than the gauge shows, so when I air it up to 41psi in the 80F garage, when the tires are cold, the TPMS is going to show 42psi. I have checked the tires a hundred times, cold-hot-whatever, and the variance between my sensors and that gauge is always within 1psi. If you experience the same thing, consistency in the variance, just remember that variance and take it into account when checking your TPMS... but when seeing if you need air or adding air use a gauge (because it gives an instant reading) and just know what the "proper" pressure (from an accurate gauge) is going to read on your TPMS... It is a great "reference tool" once you understand it and get used to it.

Also, If a tire has gotten really low on you while you are out, or if thats just when you happened to notice it, air it up to a safe level for riding... and continue on. But the next morning, or after the bike has sat long enough for the tire to cool completely to ambient temperature (inside and out), then check it with a gauge and get it to the proper PSI before the bike is ridden. Motorcycle tires warm up quite a bit when riding. Back tires regularly get to 145-165F in the summer... PSI in a tire increase/decrease approximately 1psi for every 10 degrees F of temperature change of the air in a tire. That's why when you see a manufacturer's recommend PSI's it says "Cold", and "cold" means not ridden/driven yet and at 68F ambient temperature as a reference point... If you are out riding the bike already, you have no way of knowing what its temperature is other than to guess... so get it spot on after its cooled completely... because the temperature of the air in the tire effects the PSI... whether you're using a gauge or TPMS.

Just food for thought...
 

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My TPMS reads spot on with the two gauges that I use on the reg. I also have a gauge on my fill valve and it reads 2 pounds low compared to everything else. So no matter what is said or what someone else tells you, you’re pretty much going to have to make the decision for yourself to what is reading right and what is reading wrong.
 
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