Hey everyone-

Picked up a pair of the OEM 19's rims w/ stock Goodyear tires. They were brand new with less than 100 miles--great deal and I love 'em.

Question is, when I went for the oil change, the dealship aired the tires to 42 PSI all the way around.

I have a '10 SV Premium (bought the premium package for the Skyview and climate driver's seat, knowing I would eventually throw on some OEM 19's) and am wondering what PSI some of you guys run.

It drives great with 42, but the door placard indicates 33 or 34 (can't remember). But, that probably applies to the stock 18's that come with the car since mine is a Premium.

Thoughts?

As always, I really enjoy that info that I get from this forum...very useful!

 

thats way too high. the correct pressure for 18s and 19s is 33

 

I usally run 34-36, no more than that.

 

42 is a nice round number for a fullback or defensive back, but not for tires. if you took a curve at speed, and there turned out to be a few rills in the pavement, the smaller footprint of a tire with 42 psi combined with the tendency of an overinflated tire to 'bounce' might not leave you with the grip needed to hold the road.

Additionally, running these tires at 42 psi with normal driving is almost guaranteeing the center portion of the tread will wear out much quicker than the shoulder area, shortening tire life.

The recommended psi is 33.

I would not go much below 33, as normal driving at a psi below that pressure will tend to wear out the shoulder of the tread before the center portion. A psi lower than 33 will tend to lessen the ability to turn curves at speed, as well as leave the handling feeling a little mushy. Also, a psi lower than 33 means that you are running close to the trigger point (between 27 and 29) that turns on the TPMS system alert.

Running with a psi above 33 is usually fine. Many here on the org run 34 or 35 psi, and I run with 36 rear and 37 front. This tends to give a little firmer ride, enables taking curves better at speed, seems to give better handling, and, for my style of driving, results in even wear across the face of the tread. If I lived in area where I did less sharp turning, I would drop to 34 or 35 psi.

At times in the past, I have tried running at pressures higher than 37, but that did not seem to work very well for my style of driving. The ride was very firm, the tires wore too fast in the middle of the tread, and the tires tended to bounce on irregular pavement.

 

I recently started filling the fronts to 36 psi.

My bridgestones say on the tire DO NOT INFLATE OVER 40 PSI.

I'd say the person who inflated them wasn't that smart and I'd let some air out.

 

Great advice, guys. I took them down to 35 all the way around. 33 and 34 both felt a bit too mushy. Honestly, I'm kind of looking forward to these wearing out so I can put on a nice pair of Pilot Sports --the BEST tire ever made, in my opinion.

 

However, I just remembered....when I picked up my 370Z, they had inflated them to 42, as well. Apparently, someone must be obsessed with that number! ARGH

 

Could be the accuracy of the gauge you/they are using to check the pressures. At my place of employment, Penske Truck Rental, our master air gauge we used to check all our other gauges against was off by a whopping 6 PSI. This means that anyone who thought their tire pressure readings were correct, because their gauge matched the 100 PSI on the master gauge, were off by 6 PSI. 6 PSI isn't as big a deal when you're talking about 120 and 105 PSI 11R22.5s on semi-trucks, but, obviously, becomes a much larger issue when working with our company cars and the like.

I run my 245/45/17s at 40 all 'round because the response is so much greater than it is at 34. Sure, the footprint may be a bit narrower, but the sidewalls resist deformation, providing great, snappy handling on the sharp curves I commute through. Plus, anything I can do to boost gas mileage is welcome.

Most tires I've seen state the maximum, cold, inflation pressure to be 44, but I'm learning of more and more companies that don't want them even that high, curiously enough. (Passenger) Tires don't burst from overinflation until they are somewhere in the high 100 PSI range, so I'd never fear running the tires to a point where they become overinflated to an extreme and pop. Now, hitting a vicious pothole at speed... That's a different matter. =/

 

I read that dealers are supposed to set higher psi when storing the car before it's sold to prevent flat spots so maybe they got confused.

 

36 front/35 rear will give you a good balance and feel! I run that in the Max and run 36/36 in the Z.

 

All very true. Just be aware that at 40 psi, unless you are taking lots of sharp turns at a very good clip, the middle of the tread will probably wear out before the shoulder does, shortening the life of the tires.

 

If you're cornering hard enough to need 40 psi in any of the tires, you're cornering hard enough to where staggering the tire pressures front to rear by more than a psi or two would very likely be beneficial. Once you move away from the recommended 33 (or whatever), there is nothing sacred about keeping front and rear pressures the same. Probably all the more reason for staggering them.

For street use, you'd normally run the front tires at slightly higher pressure than the rears. At autocross where the behavior up around the limits of tire grip may need to be tweaked to compensate for things like nose-heavy weight distribution without sacrificing front tire mechanical grip, you might want the rear tire pressure to be higher. Either way can reduce understeer, but since the 'mechanism' involved is different your "choice" of which way to go on this becomes use-specific.

Every car I've had that I can remember this about handled better in street driving with somewhere between 3 and 5 psi more in the front tires than in the rears, and that includes some very hard driving. At autocross, which is harder driving still, the FWD Mazda (struts front and rear) has proved to be better with the rear tires set 7 - 10 psi higher than the fronts.


Norm

 

Where did you go for an oil change, Dealers and most well know shops play by certain rules, but if you go to chain retail places, even ones that have a good reputation, they have a different set of rules cause of the wide variety of cars that come through the doors, so they are just trying to limit the percentage of error and keep lawsuits to a minimum

 

Do you all use analog or digital tire pressure checker? What's more accurate?

 

Most of the time I use either of two round analog gauges, partly because I find them easier to read under a wider variety of lighting conditions and partly because it's easier to get a reading without letting much air out from not getting a good gauge to valve stem seal.

I do have a little pencil-type digital that lives somewhere in the Legacy that gets occasional use.

No two of the above read exactly the same - there's about a 2 psi difference between the highest and lowest reading gauges in the 34-ish range. It's probably best to establish your pressures using only one gauge (going by driving "feel" and handling behavior and not particularly focusing on the exact numbers), and then baseline any other gauges to that one.


At least two of my cars have a pencil-type mechanical gauge with the little calibrated stem that gets pushed out as backup, as they're still better than having nothing at all.


Norm

 

I use digital, primarily because I can see the numbers!! As far as accuracy, that is all about the manufacturer. Both Analog and Digital guages can be accurate (although IMO if I'm sweating more than one PSI I need to up my meds) but I've rarely seen two of any gauge read the exact same. I think Norm Peterson said it best by stating you should use a single gauge all the time and establish your baseline.