Lowell_Greenberg Posted July 27, 2018 Share Posted July 27, 2018 Does the 2018 Legacy use direct or indirect TPMS sensors? If direct, what OEM part number is used. I am asking in connection with winter tires and the added cost of purchasing TPMS sensors for winter rims. Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
Lowell_Greenberg Posted July 27, 2018 Author Share Posted July 27, 2018 I should clarify- indirect systems use ABS and not direct TPMS sensors- so the question is better phrased- direct sensors versus an indirect method. Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
securityguy Posted July 28, 2018 Share Posted July 28, 2018 Subaru cars all use direct sensors...none use ABS. Link to comment Share on other sites More sharing options...
madmax988 Posted August 31, 2018 Share Posted August 31, 2018 Indirect tpms haven't been legal on new cars since I think 2007. While direct are more expensive, be happy you don't have indirect system. My mom's 05 Scion TC has them and it's horrible, the light comes on constantly sometimes because temperature changed 20 degrees outside, sometimes for no reason, sometimes because of a flat, so you are constantly checking tire pressure if you want to be sure. And other times you can be down 10+ psi and the light won't come on yet. Link to comment Share on other sites More sharing options...
ronemus Posted September 3, 2018 Share Posted September 3, 2018 There is a Schraeder sensor that folks have been using successfully, but I don't know the part number offhand; I drive a '17 and there were major changes on the '18. Searching for 2018 TPMS should bring up the relevant threads. The Schraeder sensor is much less expensive than the Subaru-branded part. Link to comment Share on other sites More sharing options...
BobbyR Posted September 3, 2018 Share Posted September 3, 2018 Bit off topic but how do check the status of the tires? I can't find any way to check the pressure using the TPMS. I've checked the manual and played with the vehicle settings looking for it. Maybe it's staring me in the face but I can't find anything. I've never had any warning about tire pressure so I'm not suspecting a problem but, at this point, the only way I can check my tire pressure is the old fashioned way with a tire gauge. Link to comment Share on other sites More sharing options...
DugsSin Posted September 5, 2018 Share Posted September 5, 2018 This video (near the end) shows how to use the steering wheel switches to find your tire pressures. https://www.bing.com/videos/search?q=2018+Legacy+tire+pressure+video&view=detail&mid=A8B09F991BF5D9AAAF80A8B09F991BF5D9AAAF80&FORM=VIRE Link to comment Share on other sites More sharing options...
BobbyR Posted September 5, 2018 Share Posted September 5, 2018 Thanks for that. No way I could find that. I'll give it a try next time I'm in the car. Link to comment Share on other sites More sharing options...
ncted Posted September 6, 2018 Share Posted September 6, 2018 I am glad my Legacy allows me to check my tire pressure from the driver's seat. The mediocre Goodyear Eagle LS2 OEM tires on my car like to randomly lose a few PSI over a short time, even with the stupid nitrogen the dealer insisted on using to inflate them. Link to comment Share on other sites More sharing options...
BobbyR Posted September 6, 2018 Share Posted September 6, 2018 Stupid nitrogen. LOL! I read somewhere that when tires lose pressure it is mostly the smaller O2 molecules that seep through the tire walls leaving the larger N2 molecules behind. This means that, over time, as you continue to lose O2 and top up with regular air, you end up with mostly Nitrogen in your tires. Sounds reasonable but I have no idea if it's true. Link to comment Share on other sites More sharing options...
ncted Posted September 7, 2018 Share Posted September 7, 2018 I get the theory of nitrogen being better in tires. The reality for me so far, and not just with the Legacy, is nitrogen-filled tires have less stable tire pressures than air-filled (78% Nitrogen to begin with) tires. Ironically, both tires I've had Nitrogen in from the dealer were Goodyears, so maybe it isn't the nitrogen's fault. Link to comment Share on other sites More sharing options...
DugsSin Posted September 7, 2018 Share Posted September 7, 2018 Nitrogen sure keeps our pressures stable when we are going from freezing Jersey to hot S. Florida and back. Link to comment Share on other sites More sharing options...
ammcinnis Posted September 7, 2018 Share Posted September 7, 2018 Nitrogen sure keeps our pressures stable when we are going from freezing Jersey to hot S. Florida and back. No. There is nothing special about nitrogen vs. plain air with respect to temperature ... about 1 psi increase per 10 degrees (F) temperature rise. At normal temperatures and pressures, both nitrogen and air conform to the Ideal Gas Law and can be described by the same classic equation: PV = nRT. In the case of tire inflation, V, n, and R are all constant, so the equation neatly reduces to P ~ T (where P is absolute pressure and T is absolute temperature). The only real benefit to nitrogen for tires is that it's guaranteed to be dry (i.e. free of water vapor), while poorly managed shop air can contain a significant amount of water. But dry air works just as well in your tires as nitrogen. I read somewhere that when tires lose pressure it is mostly the smaller O2 molecules that seep through the tire walls leaving the larger N2 molecules behind. Not true. Molecular diffusion would indeed be a factor if you were to inflate your tires with helium, but both nitrogen and oxygen molecules are so large that diffusion loss through tire rubber is unmeasurable. "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
tumbleweed 49 Posted September 9, 2018 Share Posted September 9, 2018 I always use 78% nitrogen in my tires. Link to comment Share on other sites More sharing options...
Brisvegas Posted September 9, 2018 Share Posted September 9, 2018 I always use 78% nitrogen in my tires. It would appear we all do if we use "air" Link to comment Share on other sites More sharing options...
madmax988 Posted September 9, 2018 Share Posted September 9, 2018 I believe from personal experience that 100% nitrogen definitely can be a big help if your tires aren't particularly great at sealng for instance on my old beat-up Jeep that had tires that were a slightly larger size than OEM with nitrogen I could go 4 to six months without losing for any pressure with regular compressed air I could only go about a month Link to comment Share on other sites More sharing options...
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