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Discussion Starter #1
When I look at the tire pressure display, all 4 tires are around 45psi. But when I look at the label in the driver’s side door sill, it says 36psi. Should I keep them at the higher pressure or do I need to let some air out?
 

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Mine came from dealer with 40 PSI in the tires. That might be good for fuel economy but I suspect it might be less than optimal for braking.
 

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Tires mine came with say 44psi max. I have them in the high 30s. BTW the system started notifying me when the pressure dropped below 30psi.
 

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Discussion Starter #5
My tires were actually showing 47 psi when I first got it. Was the dealer supposed to reduce them to the proper pressure during their “prep” of the car? Over 10 lbs pressure seems a bit excessive.
 

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Cars are shipped with 50 psi to avoid flat spots. Dealer prep (often missed) is supposed to bring tires back to 36 psi spec.
 

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Kias recommended pressures are on the label on the driver door jamb, for my 16 in wheeled PHEV its 36psi. What is moulded on your tires is the MAXIMUM cold pressure the tire manufacture says you should ever have them at. Unless you want to do a Ford Explorer/Firestone tire special!
 

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When I look at the tire pressure display, all 4 tires are around 45psi. But when I look at the label in the driver’s side door sill, it says 36psi. Should I keep them at the higher pressure or do I need to let some air out?
I Used to run 44 psi, now I run 40 psi all the way around, for the gas mileage and tire wear, never had an issue in years of doing this.
 

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I Used to run 44 psi, now I run 40 psi all the way around, for the gas mileage and tire wear, never had an issue in years of doing this.
Ditto. I've run higher pressures on my VW TDIs and now my Niro. No issues with excessive tire wear or noticeably harsher ride. Definite increase in mpgs though so it's kind of a freebie.
 

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Ditto. I've run higher pressures on my VW TDIs and now my Niro. No issues with excessive tire wear or noticeably harsher ride. Definite increase in mpgs though so it's kind of a freebie.
This seems to be contrary to published studies that show only a slight gain to increasing pressure, and faster wear (not sure what "excessive" tire wear means). How do you know you get better mpg? Have you done long term tests at both pressures in the same season? I'd guess you would need to do over 5,000 miles before a trend would appear in your numbers. One tank doesn't do it.
 

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This seems to be contrary to published studies that show only a slight gain to increasing pressure, and faster wear (not sure what "excessive" tire wear means). How do you know you get better mpg? Have you done long term tests at both pressures in the same season? I'd guess you would need to do over 5,000 miles before a trend would appear in your numbers. One tank doesn't do it.
Yep, in my TDIs I tracked mileage pretty religiously for years, kept a spreadsheet and everything. I saw ~2mpg increase in mostly highway driving after increasing pressure from 32 to 45. In a vehicle that returned right around 55mpg that's ~3%. Tire life was basically unaffected and I got ~80k miles from a set over ~500,000 miles between two vehicles. Now, for sure there is a point of diminishing returns

In the Niro it's tough to say since it's a PHEV and measuring mpg (mpe?) is basically impossible but I expect that the improvement is similar.
 
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I saw ~2mpg increase in mostly highway driving after increasing pressure from 32 to 45.
Yes, going from underinflated should always result in a relatively large mpg increase. Recommended pressure wasn't 32 was it? A quick Google found 36 psi is the recommended pressure for several VW models. I'm surprised you didn't see an even bigger increase.
 

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Yes, going from underinflated should always result in a relatively large mpg increase. Recommended pressure wasn't 32 was it? A quick Google found 36 psi is the recommended pressure for several VW models. I'm surprised you didn't see an even bigger increase.
Recommended was 33psi for my '05 Jetta (32 was from memory, not bad for an old guy). Heck, the door tag on my '01 Golf says 26psi. The '05 was my first TDI and the one I spent the most time trying to get the best mileage out of. At stock pressures it got ~48mpg average. After bumping it up to 45psi I regularly saw 50+ (max for those tires was 48psi). Granted this is an extreme case where the pressure difference is very large since the recommended was fairly low to start.
 

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Those are bizarrely low recommended pressures. The VW ones I googled were also Jetta models. Do you happen to know the tire size from your prior cars? Perhaps they had an extreme high profile tire spec. Still, not getting it. It is possible that your manual had a higher recommended pressure for high speeds or load - that used to be fairly standard and I always used the higher one in the old days (for high speeds on cross country trips). For the cars I owned, that recommendation appeared in the manual, but not the door sticker. Can only assume tire design has changed significantly in the last 20 or 30 years.
 

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Those are bizarrely low recommended pressures. The VW ones I googled were also Jetta models. Do you happen to know the tire size from your prior cars? Perhaps they had an extreme high profile tire spec. Still, not getting it. It is possible that your manual had a higher recommended pressure for high speeds or load - that used to be fairly standard and I always used the higher one in the old days (for high speeds on cross country trips). For the cars I owned, that recommendation appeared in the manual, but not the door sticker. Can only assume tire design has changed significantly in the last 20 or 30 years.
The recommended pressure was definitely load dependent. 1/2 load = 26psi for the '01, up to 30psi front 35 rear fully loaded. Still pretty low. Both VWs run 195/65-15's. The recommended unloaded pressure went up from 26 on the '01 to 33 on the '05 with the same size tire. Part of it is the curb weights. The '01 checks in at svelte 2800lbs while the '05 is a slightly stouter 3200lbs. Part of it is tire design and part of it is likely perceived customer preference. Who knows. In a way your earlier comment was spot on. The factory pressures probably left the tires a bit underinflated compared to the optimum setting so when I pumped them up I saw a more dramatic difference than if I had started at a more "reasonable" level. As ever, YMMV.
 
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