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NixonNero- I keep my tire pressures to the recommended 36PSI. I check them on the dash indicator. They do vary a bit, so if I notice two of them have dropped below 36, after the pressure registers, when still fairly cold, I check manually. I have had to add about 1-2 PSI once since new. In the owners manual it says "it is permissable to add 3PSI to standard pressure if colder temps are expected soon. Tire pressures typically lose 1PSI for every 12F temp drop." So I plan to add pressure in winter.
Manual also says: add'ly req'd tire pressure per km above sea level:1.5psi/km.
 

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Based on my 4 years hybrid experience, the more pressure you can run in your tires, the better your mileage will be. My Fusion was in its sweet spot at 44 psi. I haven't started to mess with my Niro tires yet. Some people run as much as 50 psi but that seems to be a bit high to me. They say it still drives OK, though.
 

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Based on my 4 years hybrid experience, the more pressure you can run in your tires, the better your mileage will be. My Fusion was in its sweet spot at 44 psi. I haven't started to mess with my Niro tires yet. Some people run as much as 50 psi but that seems to be a bit high to me. They say it still drives OK, though.
Griswald- I wouldn't run that much air, personally. That is harder on the suspension, the people that build the car figure those pressures, and of course they want to go as high as reasonanble for better gas mileage. IMO a couple psi over is OK, but running that much air is harder on the suspension, ride, and handling.
 

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Griswald- I wouldn't run that much air, personally. That is harder on the suspension, the people that build the car figure those pressures, and of course they want to go as high as reasonanble for better gas mileage. IMO a couple psi over is OK, but running that much air is harder on the suspension, ride, and handling.
Until you've tried it, how do you know how it affects the car? In the Fusion, I couldn't tell any difference until I hit 45 psi. It rode and drove exactly the same except for rising MPG numbers.

Set mine up to 42 psi yesterday and will report back after a few drives.
 

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I have an SX Touring. Here in Canada we have no tire monitoring so I do it myself. The car came with nitrogen in the tires set at 36 lbs I checked recently,still at 36lb.

My 1990 Miata runs at the recommended 26lb. 44 lbs when slaloming.

I don't intend to slalom the Niro. It does very well in the twistys at 36lb.

 

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Until you've tried it, how do you know how it affects the car? In the Fusion, I couldn't tell any difference until I hit 45 psi. It rode and drove exactly the same except for rising MPG numbers.

Set mine up to 42 psi yesterday and will report back after a few drives.
I don't need to try something to know of the effect. If you overinflate tires, you get a smaller tread contact area. Less tread on the road. That affects handling. It increases the wear of the center tread over outside tread- so tires wear out quicker. It makes for a harsher ride, the tire is harder- which transmits to suspension, and more road noise.
After 10 fuel fillups with the proper pressures, I am averaging 55MPG. I am very sastisfied with that. I think if I was zealous enough for a small MPG increase to consider overinflation, I would remove the roof rails first. Per EPA ratings, that would be a 1MPG increase.
 

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I don't need to try something to know of the effect. If you overinflate tires, you get a smaller tread contact area. Less tread on the road. That affects handling. It increases the wear of the center tread over outside tread- so tires wear out quicker. It makes for a harsher ride, the tire is harder- which transmits to suspension, and more road noise.
After 10 fuel fillups with the proper pressures, I am averaging 55MPG. I am very sastisfied with that. I think if I was zealous enough for a small MPG increase to consider overinflation, I would remove the roof rails first. Per EPA ratings, that would be a 1MPG increase.

Again, you have not tried it. I and 10's of thousands of other hybrid and electric vehicle owners have.

Its not so drastic as you make it sound, were not talking an extra 40 or 50 psi. As long as you do not exceed the maximum number on the tire you wont have any of those issues you suggest WILL happen.
 

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Discussion Starter #9
On most vehicles the PSI on the car door is different then what the tire says. Car manufacturers use tire inflation as part of their suspension to cushion the ride. Handling isn't affected until you go over the tire psi spec.

On my previous VW Passat it suggested 35psi. I ran 42psi, tire rating was 45psi, and it increased 4mpg.

My diesel truck Chevy recommends 36psi. Tires say 75psi. I run 68 psi. Ride is rougher but wear and handling doesn't change. I put the psi that high for towing trailers and hauling.
 

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I run 42 front, 40 rear, no off roading, so ride is not that much rougher on SoCal freeways. Handles fine, no worries. If I could just flatten SR-2 freeway run uphill, which just sucks the life outta the MPG numbers, I would have 50's also! Although the last fill was 46.1, a personal best! C'est La Vie!!
 

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On most vehicles the PSI on the car door is different then what the tire says. Car manufacturers use tire inflation as part of their suspension to cushion the ride. Handling isn't affected until you go over the tire psi spec.
Sorry, that is crap. The max pressure on the tire is the maximum safe pressure. Above that and you are at higher risk of blow offs and tire damage. The car maker determines what pressure is appropriate for the load placed on the car. That recommended pressure is always in a sweet spot between best efficiency, safety, and tire longevity. You can tinker with it a bit for your road condition and actual load. If you disagree with this, please cite a reputable source and link it.

Unless you do coast down tests, you will have no way of knowing if you have helped or hurt efficiency with your high pressures. Possibly an HP testing, but those are not really optimized for rolling resistance testing.
 

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Interesting chat...FWIW my I discovered my Niro Touring was inflated to 50 psi off the lot. I deflated to 36 psi. I actually liked it at 50...super firm. It's OK at 36 but I may try to up it to 40 and see if I like it better. There are plenty of discussions that claim a little overinflation isn't a really bad thing...not there yet but WTF was my KIA dealer thinking ?!
 

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Is the maximum inflation pressure for cold tires or the absolute you shouldn't exceed even when the tires are warmed up?
The KIA factory reco of 36 psi (in the book and on the door tag) is based on cold tires and this is also the common spec on all tires. However in Auto racing they play with tire pressures a lot and use different psi for different corners depending on the track layout. I'm huge F1 fan and tires/pressure/composition are huge factors in any given race. BTW, in case you didn't know, they race Hybrids these days !!!
 

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In fact they usually don't last a full race. Just a comment on inflation and performance at the high level. Of course it doesn't really apply to a street car that much except that there is a trickle down effect of tweaking air pressure. My 2nd car is a quasi-race-prepped ... 2006 Mini Cooper John Cooper Works GP....and it's very picky about air pressure with the 17" Hankook tires I run on OZ Racing rims. Better than the horrible stock 18" stock rims with Dunlop run flats....like driving on cement tires. The 17" combo performs better and is more "comfortable" and forgiving on the street, but still rides like a little buckboard. I actually don't race the car, but it came as a Factory Hot Rod from BMW at the end of live for that R53 model, just an itch I had to scratch and a bit of a rare bird.
 

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The Max tire pressure rating on the side of the tire on my EX with the 16in are 44psi. I set mine at Hot psi by tire monitor while after driving 30 miles on highway to 42psi. They cool down to 38psi cold settings. Im getting 50-51 mpg on mostly highway driving. My combined commute, of 36 miles im getting 56mpg avg.
 

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Our average so far is 58MPG (4 L/100km) on a 2018 Niro EX and I check the tires cold every month with a digital tire pressure gauge and keep them at the recommended 36 PSI.
 

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I run 42 front, 40 rear, no off roading, so ride is not that much rougher on SoCal freeways. Handles fine, no worries. If I could just flatten SR-2 freeway run uphill, which just sucks the life outta the MPG numbers, I would have 50's also! Although the last fill was 46.1, a personal best! C'est La Vie!!
Over the weekend, I drove from Silver Lake to Montrose up the Glendale Freeway portion of the SR-2. At 65mph and with 2 passengers, dash showed 36mpg for that predominantly uphill 11 mile trip. Going back downhill, I decided to take it easy at 60-65mph and the dash showed 87mpg for that 11 miles, haha.

Anway, when I bought the car from the dealer, the left front was 38psi cold and the other three tires were at 35psi. So I pumped those three tires to match the left front. Now their all at 37-38psi cold, and they reach up to 41psi hot.
 
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