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Discussion Starter · #1 ·
I have been playing with tyre pressures and I have found that my car, with the 17 inch alloys fitted, feels best when I pump my tyres to 38psi cold.
What have been other peoples experience or what are you all running?
 

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2013 Rio SX Hatchback
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I have been playing with tyre pressures and I have found that my car, with the 17 inch alloys fitted, feels best when I pump my tyres to 38psi cold.
What have been other peoples experience or what are you all running?
Which tires do you have?
 

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1998 Chevy Lumina, 2013 Kia Rio, 2002 Triumph Daytona 955i, 2005 Yamaha YZF-R6
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34 Posts
So far the factory recommended 32 psi all around has worked best for me. I'm on the 15" steelies with the stock 195/60/15 all-season Kuhmos.
 

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Cerato S Hatch Auto
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Most people find the usual placard recommendation of 32 PSI a bit "soggy", and you don't need to be an expert to notice this. I've always used 36 PSI with most tyre sizes, and many tyre shops will suggest a few extra PSI to reduce wear, improve fuel consumption and tighten up the handling.

It's possible to measure the effect of inflation on effective tyre diameter by calibrating the odometer at different pressures. I have a standard "test lap" of about 5 km, and tyre pressure will alter the odometer reading by about 20 metres over that distance when tyres vary between 32 and 36 PSI.

BTW, increased pressure effect on odometer will have a slight negative effect on calculated fuel consumption unless it is allowed for.
 

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2013 Soul+ Shadow, 1970 Opel GT 1.9 CIH 4M
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Pee Ess Eye

I have been playing with tyre pressures and I have found that my car, with the 17 inch alloys fitted, feels best when I pump my tyres to 38psi cold.
What have been other peoples experience or what are you all running?
At 38PSI I can hear the rattles now :eek:
 

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2020 Kia Sorento EX+
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409 Posts
my car was delivered at 38, i found it harsh, i prefer 34 as a nice compromise between performance and comfort.
 

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Discussion Starter · #7 ·
The factory 17 inch alloys with the factory Continental fitted.
Tried different pressures on a per day trial. Settled on 38psi as a good compromise for me. Firm ride but I don't think that it was harsh, and no rattles..............
The 32psi as listed on the plagard is way too soft and the car felt sloppy....
At 40psi, the car felt too harsh but 38psi feels really good.

Might also be the pressure gauge that I am using but 38psi on my tyre pressure gauge, the car feels really ncie on the road.
 

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13 Rio 5 EX Auto & 05 Crysler T&C & 52 Ford 8N
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LOL - Mine came from the dealer (clockwise from driver front) as 28, 32, 45, 34. The salesman said not to worry, the pressure warning lamp would go out "soon".

He was correct - after I checked the pressures and standardized on 32 the light went out.

I think I'll try 35.

Have I got this right - the xtra pressure gives increased wheel diameter and thus more distance travel per axle revolution - so the speedo & odometer & MPG (which are based on axle revs) will be reading lower than actual - but by probably less than 0.5% ?
 

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Cerato S Hatch Auto
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I think I'll try 35.

Have I got this right - the xtra pressure gives increased wheel diameter and thus more distance travel per axle revolution - so the speedo & odometer & MPG (which are based on axle revs) will be reading lower than actual - but by probably less than 0.5% ?
Yes, that's what I found when going from 32 to 36 PSI; it was only 20 metres in 5.31 km (0.4%). This is a trivial difference; the main economy effect is the decreased rolling resistance at higher pressures.

In case you're wondering, my "Home Lap" around the block is 5.31 km as close as I can determine by checking the odometer against accurate road markers. Naturally, the odometer only reads to 0.1 km, but finer readings can be derived from the house frontages which are exactly 20m. Saves going 30 km out to the highway markers to test new tyre/cars. OK, it is a bit OCD. :)
 

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Kia Rio S 2012 (3-door hatchback)
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My 2012 Rio, which came with 15" tyres, came from the dealer with around 36 Psi. I changed it to 32 Psi after seeing the recommended pressure on the car door. Took the car in for a service at the dealer and they told me to adjust it to 34 to 36 Psi. I feel the handling is slightly better at 36 Psi, but haven't noticed any difference so far.

Also I have recently inflated the tyres with Nitrogen after hearing about so many of its benefits. However, I haven't noticed any difference in fuel economy yet...
 

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Cerato
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No benefit from Nitrogen except for slightly longer between checking pressures. Oxygen component of air roughly 30% faster to leak out. Air is already 78% Nitrogen, so don't pay too much for the Nitrofill.
 

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former owner of a 2016 Soul SX 2.0L - Caribbean Blue
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Nitrogen in tires another one of those automotive myths. (unless you get it for free)

from KIA - TSB 058: Services and Products Not Recommended by Kia

Nitrogen Tire Fill:
This service appears to add little, if any, appreciable value to Kia customers. Tires should be filled with dry compressed air using the specifications listed on the driver’s door jamb plate or in the Kia Owner’s Manual. Dry compressed air already contains approximately 80% nitrogen. Keeping tires properly inflated with dry compressed air is sufficient to keep the tires in good condition throughout their useful wear life.
 

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Cerato S Hatch Auto
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Oh well it seems I paid AUD$30 for little benefits!
It might be worse than that. How can you be sure that they actually filled your tyres with Nitrogen? Even if the tyres are inflated and flushed 3 times, you'll only end up with 95% Nitrogen at best. I suspect that some places just do a sham fill and send you on your way with plain old air.

Filling tyres with Nitrogen might give a lower rate of deflation, but other alleged effects are imaginary. I used to work at a place where all sorts of gases were "on tap", but it never occurred to me to stick any of them in my tyres. Maybe Argon (inert gas) would have been better than air? Hey, how about Krypton?
 

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2012 Kia Rio 5-Door LX
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Filling tyres with Nitrogen might give a lower rate of deflation, but other alleged effects are imaginary. I used to work at a place where all sorts of gases were "on tap", but it never occurred to me to stick any of them in my tyres. Maybe Argon (inert gas) would have been better than air? Hey, how about Krypton?
LOL, I agree, the only benefit is for the shop selling you the stuff.
 

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Kia Rio 2013 S 1.4
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In my opinion , even in the best case scenario, where you got full nitrogen in your tires
(very hard to prove) the normal day to day condition don't require the use of a special air.
Unless you are a serious racer and your tires get hot because the friction, there is no point to spend money for a very very marginal performance.
But then again, that is my opinion
 

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Cerato S Hatch Auto
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Unless you are a serious racer and your tires get hot because the friction, there is no point to spend money for a very very marginal performance.
But then again, that is my opinion
No thermal difference between air and nitrogen. I think racers use nitrogen because it "seems like a good idea" and a cylinder of ntrogen is more convenient than compressed air and doesn't contain water.
 
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