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I like the tire pressure monitors on the Ascent. I was wondering if the units in the wheels are direct or indirect.

Direct takes a constant measurement of the actual tire pressure. Indirect compares relative tire rotation of the 4 wheels and extrapolates the tire pressure.
 

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I like the tire pressure monitors on the Ascent. I was wondering if the units in the wheels are direct or indirect.

Direct takes a constant measurement of the actual tire pressure. Indirect compares relative tire rotation of the 4 wheels and extrapolates the tire pressure.
They are direct. Each wheel contains an internal sensor which transmits the tire pressure to the ECU at set intervals when the car is in motion.
 

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Subies require direct TPMS because even 2/10th of a difference in diameter (such as by differences in tire inflation) can cause issues, and indirect monitors are not nearly accurate enough for that.
 

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Does anyone know if the US and Canadian Ascent is different? I emailed my sales rep yesterday with a few questions, including if the Limited has TPMS (trying to price out winter wheels and tires) and his reply was:

"Hey Scott. Subaru has never had the tire pressure monitor system."

So now I'm really confused. I'm fine without them, prefer that actually, given the cost to add them to additional wheels.
 

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TPMS (not) for Canada - alternative...

Does anyone know if the US and Canadian Ascent is different? I emailed my sales rep yesterday with a few questions, including if the Limited has TPMS (trying to price out winter wheels and tires) and his reply was:

"Hey Scott. Subaru has never had the tire pressure monitor system."

So now I'm really confused. I'm fine without them, prefer that actually, given the cost to add them to additional wheels.
Hi Scott, Subaru Ascents made for the Canadian market do not have TPMS.

If you want decent TPMS, you can use this kit (though, I'd prefer it with metal valve stems installed on the rims, but I used it with the rubber ones on my former 2010 Outback) - I found them highly accurate:

Since you don't have TPMS, you can swap the rubber valve stems with steel ones.

The key to using them is proper and careful installation so that:
  • You don't tear the valve stem.
  • You don't leak air out from not tightening the caps properly.
  • You tighten them down enough that they can register tire pressure.



I'd posted this info in another of our TPMS threads (still trying to figure out if we can cleanly merge them all)...

TPMS are mandated in the United States, thanks to Ford, and sadly to the people who got hurt or died. The TREAD Act was enacted by Congress in 2000, effective for 2008 and newer model years, after rollover incidents involving the Ford Explorer and Firestone tires.

There's a lot more to the TREAD Act (the name isn't really about tires) for those who are bored and like reading up on such things.

Here's the text of it for those really bored:
https://www.govtrack.us/congress/bills/106/hr5164/text

Wikipedia detailed summary:
https://en.wikipedia.org/wiki/Trans...ncement,_Accountability_and_Documentation_Act

Here's a good short summary:
https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/weinstein.pdf

Bonus doc:
https://one.nhtsa.gov/nhtsa/announce/testimony/tread.html

SHORT VERSION:
TPMS is mandated in the United States, but not Canada. Vehicles made for sale in Canada may or may not have TPMS depending on whether or not the manufacturer decided to do a slightly different spec vehicle for Canada.

My understanding is that theoretically, if you get an Ascent that was slated for the US market, but delivered to Canada, it would have the TPMS, unless they took the time to swap wheels. If you got an Ascent that was slated for the Canadian market but got it in the US, then they definitely swapped to wheels with TPMS as required by law when the vehicle is re-assigned as a US vehicle.
 

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Robert, you sir are a treasure of useful knowledge, many thanks for taking the time that you do to post such in depth stuff!

I used to work in the tire industry but manage a fleet of work trucks in my current job, and while I like the idea of TPMS i find that the systems in general have more issues than benefits. I am more than happy not to have to deal with them, as many vehicles will flash an error if running wheels that don't have sensors when the vehicle comes with it.
 

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Subies require direct TPMS because even 2/10th of a difference in diameter (such as by differences in tire inflation) can cause issues, and indirect monitors are not nearly accurate enough for that.
My tpms were always accurate and consistent on all four tires until I had the tires rotated. I am now seeing pressures that vary 3-4 lbs from each other. That never occurred before. In addition, I drive away after just filling the tires at discount tires (the staff stated there were already correct at 33) and the tpms indicated various readings different from 33. Everything stayed the same on the vehicle up to that point and this is an entirely new phenomenon, so I am wondering if the rotation had anything to do with what I am experiencing. Any suggestions?
 

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My tpms were always accurate and consistent on all four tires until I had the tires rotated. I am now seeing pressures that vary 3-4 lbs from each other. That never occurred before. In addition, I drive away after just filling the tires at discount tires (the staff sated there were already correct at 33) and the tpms indicated various readings different from 33. Everything stayed the same on the vehicle up to that point and this is an entirely new phenomenon, so I am wondering if the rotation had anything to do with what I am experiencing. Any suggestions?
I think it could be temperature related.
 

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I think it could be temperature related.
This is Denver, so the temperature since March when I took possession has spanned the spectrum without this TPMS varying this much. It appeared to be a sudden shift from entering the store to leaving Discount Tire with rotated tires. Not much of a temperature shift in one hour's time. I'm perplexed.
 

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Odd. I've not cross checked mine recently.

Did they add air? Or reinflate the tires? I'm baffled on this one, but you're the second person I've seen say something similar recently.
 

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The day of the rotation I assume they checked the tire pressure and added air to 33 as necessary per my instructions. That would be DT sop.
I would definitely check the air pressure and not assume that they got it right. Yes it probably is SOP but people are involved. Also they could have used different tire gauges which could be reading off from each other.
 

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I was there on Monday morning for an air check and watched them set the machine for 33 (right in front of the vehicle). The entire day the TPMS for each tire was off from each other and off from 33 by as much as three lbs. which based on the last 8000 miles had never occurred. I did not watch them fill the tires with air after the rotation but this symptom of differing tire pressure remains.
 

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I do not believe it has the receiver or harnesses. That's the answer someone else got from Subaru Canada, but not living there, I have not been able to verify. Regardless, enabling the feature in software would still be necessary.
 

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I do not believe it has the receiver or harnesses. That's the answer someone else got from Subaru Canada, but not living there, I have not been able to verify. Regardless, enabling the feature in software would still be necessary.
just checked the online manual and yep... not there..

"Tire pressure monitoring system (TPMS) (U.S.-spec. models)"
 
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