Better Tire Pressures - 2015 Kia K900 Long-Term Road Test

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Better Tire Pressures - 2015 Kia K900 Long-Term Road Test

We've been experimenting with different tire pressures in our long-term 2015 Kia K900 and think we've found a sweet spot.

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fordson1

Good work. I wonder how it would feel if they just put some better tires on it, for $66k.

kirkhilles1

I don't see how 31 psi is "comically low" for a sedan. My guess would've been 32 psi. My Miata has a REALLY low 26 psi from the factory and 28-30 psi seems about right. SUVs seem to have around 34 psi, so I'd agree it's a little on the low side, but I don't think that 35 psi cold is "normal", especially if you do it during winter and forget to adjust it in the summer and now could be running well into the 40s psi hot.

fordson1

This thing is 4600 lbs and a little under-tired...so that's pretty low.

s197gt

i wish car mags would/could interview some suspension and tire engineers and ask them what the heck they were thinking? we know they have to make compromises but what are the reasons they end up choosing the manufacturer recommended specs? why do they choose the tires they did?

i do remember one of the car mags interviewing Hau Thai-Tang, Chief Engineer for the 2005 Mustang, and he talked about taking product submissions from various tire manufacturers when trying to decide what tire to go with for the then all new mustang. he made it sound like a lot of R&D went into the selection; although the Pirelli Pzero Nero all-season seemed to be universally panned on the forums (like pretty much every OE tire). I didn't think they were that bad.

our e90 has an extremely low front tire pressure spec of 26 psi (36 rear). but those specs are with run flats; which it no longer had when we got it with 30k miles. i ended up putting 32 up front and 35 in the rear.

capriracer

Here's a write up on how tires are selected by the OEM's:

barrystiretech.com/oetires.html

misterfusion

My 500L has low-profile 225/45-17 tires, which is normally a recipe for a harsh ride (at least in L.A.). But my car was very comfortable in the first two weeks, and after the second week I took it on a round-trip to Phoenix. When I got back, I got a TPMS alert -- all four tires were low by 5-6 PSI. They're nitrogen-filled, which means they came from the dealer under-inflated. When I inflated them to spec, THEN I got the harsh ride I would normally expect.

I finally compromised by airing them down by 3 PSI -- not enough to trigger the TPMS, but enough to make the ride comfortable again. My long-term solution is to eventually trade the OEM Continentals for much better Pirellis, but really the spec pressure just seems unreasonable.

agentorange

kirkhilles1 said:

I don't see how 31 psi is "comically low" for a sedan. My guess would've been 32 psi. My Miata has a REALLY low 26 psi from the factory and 28-30 psi seems about right. SUVs seem to have around 34 psi, so I'd agree it's a little on the low side, but I don't think that 35 psi cold is "normal", especially if you do it during winter and forget to adjust it in the summer and now could be running well into the 40s psi hot.

I am someone else who gets irritated when told that 35 PSI is the minimum for tyre pressures. For lazy, ill-informed folks, maybe. I don't think this car is especially under tyred. The Dodge Charger weighs nearly as much and uses 245 section boots all round. It is VERY interesting that the front suspension design is so sensitive to input. It suggests to me that choosing replacement rubber for the front could be a problem if you go to another manufacturer.