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Hey guys, awhile ago I bought some Enkei EDR9 rims with a packaged deal including some Hankook evo 12 tires.  Since I ordered them as a package, the factory was going to mount the tires using some special wheel balancing machine that finds hard spots and such by putting weight on the tire and also fill the tires with nitrogen.  Well, as you guys know, our cars call for appox. 29 psi (can't remember exact numbers), but these tires came with 42 pounds. I didn't want to mess with them because I was thinking that maybe the pressure was higher because of the nitrogen vs 02 or because the rubber was softer than factory tires and that was to add more support to the sidewalls.  This is the second summer I've been running them like that and I've had a couple people mention that my tire pressure is too high.  Looking at the tires and their wear, it doesn't appear to be showing any signs of over inflation.  Should I drop the pressure down to factory or keep it where it was originally set?

By the way, I was avoiding messing with the tire pressure because of a lack of shops in my area with nitrogen so that's why I turn to you fine gentlemen.

Thanks

Essentially, when you're adding air, you're adding a mixture that is primarily nitrogen.  Purely nitrogen filled tires isn't really that advantageous.

This is also a good read, http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=191 (http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=191).

It looks like the specs for the Hankook Ventus V12 Evo calls for a maximum cold inflation pressure of 50 psi in most tire sizes.

As far as what its filled at 42 psi, they more than likely did that for shipping reasons.  You should really lower the psi to something more appropriate for the car.  Some cars call for higher psi, some cars call for lower psi.

If I recall correctly, the Accord asks for 32psi front and 29psi rear.  You should set your tires to somewhere closer to those figures.  You can experiment a little, but 42psi is fairly high for your setup.

Tire pressure is not set higher because it is filled with nitrogen.

^This. If it means anything, most of the guys that I've seen here run about 32 all around. I've been running ~34 for as long as I've owned the car (I'm accustomed to a stiff ride) and have normal wear. Like Mark said, bring your tire pressure closer to stock and you should be fine.

Alright, thanks guys for the quick responses.  And thanks Mark for the effort you obviously invested in looking that information up.  I'll be sure to drop those today before I head off to the mountains.

I usually run 32 psi all around for daily driving, but I air up to about 40 psi for long road trips on the freeway.

Well I did drop the tires down to 32 front and 29 rear and feel it made a suprising difference.  I feel stupid for never asking about that from the start.

In defence of the nitrogen vs air.  I have noticed that since I bought these tires, last april 2010, the tire pressure did not change one pound till today when I dropped the pressures.  All four tires held the exact same numbers as they did the day I picked them up. I can't say anything similar to any other set of tires I've had on cars or motorcycles.  So at the very least, they are good for the reliability aspect, especially for those who are too lazy to actively monitor such things.  That's the only aspect right now that I can vouch for.