Hey guys...

I don't know if this is a stupid topic but i was wondering what recommendations you guys have on tire pressure for various types of wheels. I had the 17" stock oem wheels and recently upgraded to 18". Obviously the optimal tire pressure is going to change right??. for the OEM wheels all i had to do was look inside the door to find the optimal tire pressure but since i upgraded to 18"s. what is the "optimal" tire pressure for good gas mileage and optimal performance. I inflated to about 40 PSI and i felt every bump in the road. I released some air down to about 30 and now it feels like it's running a little flat.

I just wanted to get feedback from other who are running an 18x7.5 with 225 40 18. what is the pressure in your tires and how u feel about the ride.

sorry about the long post but I saw a post similar on the honda forums and couldn't find one here so i thought i'd bring it up.

Thanks!!

 

it tells you what pressure you should run them in the car...

open door.. nice label right there..

size doesn't really matter.

 

well i see the point. but for the most part it would only be within 1lb of the pressure of the stock tire size. If a change at all was needed.

32 Front and 29 rear is stock. so maybe play around with that pressure adding 1lb to the numbers or removing 1lb from those numbers.. Such as 33 front, 30 rear. or 31 front and 28 rear. If it feels too "mushy" then go with the original or the +1lb setting. But no need to increase it all the way to 40lbs, you're asking to blow the tire out! Way too much. Hope that helps, let us know what you settle on.

Also make sure you get yourself an accurate tire gauge. I got an accutire from target. Nice digital one.

 

actually no you wont blow the tire out. ive worked at discount tire for like half a year and alot of my family are vp in the company (uncle vp florida region great uncle retired vp of company yadda) and you can raise your tire pressure on aftermarket tires with a great build, aka sport tires, to around 45psi on a hot day and be safe. not on cold days. id recommend inflating to 35psi after driving around on the freeway for about 20mins.

 

thanks for all the replies so far.. i really do appreciate it!! =)

 

hey luxscion- I don't mean to argue with you. But to tell someone a blanket statement about raising beyond the maximum pressure allowed on the tire is a bit unsafe. If the tire says that "maximum pressure" is 40psi and you take it to 45psi, then you're asking for trouble. Regardless of "great build" quality.

The maximum number is there for a REASON! Because it's the maximum pressure allowed on that tire. It MIGHT be able to put up with more, but why take that chance?

Also, based on what I've seen with this car's weight and tires that are hot, temperature wise, 35psi hot corresponds to 32psi cold. that means there is a 3psi rise in pressure when comparing cold to hot tire pressure numbers. The rears at 35 would be not have the same balance (front to rear). When hot, the rears should be inflated to 32psi. That would correspond to 30psi cold. Then the balance the factory was looking for of a 3psi from front to rear would be acheived. Not to mention understeer and weight loading. Over inflating will also wear out the centers quicker since overinflating would crown the center of the tire, allowing it to wear out faster.

 

is it recommended to inflate my tires to my desired PSI when the tire is cold or after being driven for roughly 10-15 mins??

 

above are tire myths! In reality - max pressure is typically 44psi cold. radials don't crown - the steel belts keep the tread flat - the outsides WILL wear out faster if UNDER inflated. Different width tires require different pressures to maintain proper tire contact patch shape. Higher pressure will result in less temp rise thus less thermal pressure increase.

 

Not driven and not in the sun - sunshine can raise the sunny side a few to several psi. As long as they are cool to the touch and the same temp then inflate to the desired pressure . Tire near the muffler may get warmer so watch that one.

 

it's far from a myth, maybe when you can look at the materials science as I have. and see how that yes, the centers do crown and tread will wear unevenly.. Then you can come here and dispute my findings. Yes overinflating will wear the centers of the tires.

 

I mentioned hot because sometimes you want to add air after you've driven your car. That way you can roughly know what the pressure will be after it cools down.
35front and 30 rear for when it's hot (driven for more than a couple of miles) otherwise a tire that is cold is one that is in the shade, and not direct sunlight on it, because that will raise the pressure as well (sunlight=heat).

best thing to do is to fill air up when hot, then when it's cold the next morning check it with a good tire gauge.

 

Lets say I am talking higher pressure instead of OVERinflating where OVER implies TOO much pressure although I know guys running 60psi in 44max tires. I have the xB which have different tires and not as low a tire profile at your tC so that affects things differently but I am running 40psi front and 38 rear and once the tread wears in a little it sits flat on the road just like 32 psi would. The advantage is lower rolling resistance, better cornering since the sidewall does not get scuffed and the tread remains in beter contact with the road, better tread contact when braking hard since the tire doesn't flatten as much when the weight transferres to the front tires and less tire wear. Now you may say it wears more in the middle but the middle is not as important as the outside tread for traction and we are talking millimeter differences plus by the time I do a couple of turns the edges are worn even with the center again anyway. If the tire gets bald in the center then it is time for new tires and I don't think that will be happening before the side walls dry out from the sun and ageing.

Now with your tC you have a greater risk of rim damage if your tires are a few psi low and should you get a leak with higher initial pressure you have a few more PSI to work with giving the pressure sensors more leeway to respond to the pressure difference to warn you before you have tire failure or rim damage from underinflation.