turning japanese

When I picked up my 2012 Sportwagon, the tire pressures were all over the place (I guess the dealer never check them.) I've since filled them all at 36 psi evenly. Although the label on the doorjamb says 33 psi all around.

My question is are people with this car (and stock tires/wheels: Michelin Pilot HX MXM4 225/50R17) running on the recommended pressure? I realize that mfgs like to err on the side of understeer and also for better wear. The car already understeers enough as it is and I'm not super concerned with wear although road noise and comfort is a big priority for me.

What's the consensus on best pressure for handling, comfort, and noise? Should I stick with the 33 psi?

Also any suggestions on 'better' tires? I want to stay with same size/same wheel. But I wouldn't mind some extra stickiness. But again my priority is noise and comfort. I have no real objections with these tires, it's primarily that I've never run AS tires and only summer performance tires (no bad weather here.) Is it best to just stick with the MXM4? A good performance summer tire might get me better mpg (less rolling resistance) and less noise (less aggressive tread.)

My service advisor did say that Acura has their own tire designation. Like Porsche does with their 'N' tire ratings. Is this true? They said it's better to get replacements thru Acura since they are designated for the chassis. With Porsche the 'N' just means that the tire has been tested and approved for the Porsche chassis (otherwise it's basically the same tire.) Is there such a thing as an Acura spec tire from Michelin or the other makers?

Thanks!

ceb

The Porsche/Audi/MB designation on tires is primarily load rating and an attempt to get customers to buy from the dealership but the basic tire is identical - esp for a car like Acura that has no sporting pretenses.

The dealer gave me my car with 40 psi all around - a bit high for the Conti DSW tires I'm running now. The slightly lower sidewall, combined with the more sporting nature of the tire and the higher pressure makes for crisper turn-in but has the downside of a markedly stiffer ride.

Dropping the pressure to 33 improved the ride quality and doesn't seem to have noticeable negative impacts on daily handling.

The manufacturer needs to find a fine line between comfort, handling and mileage so consider the 33 as a starting point to get your perfect pressure.

Better roads will allow you to run higher pressures and still be comfortable. Higher pressures increase handling and gas mileage.

I'm pretty comfy with 35 all around, raising it to 38 for longer road trips.

turning japanese

Thanks. So far, the 36 psi seems okay for me. I was curious if anybody was actually running at 33. I think I'll stick with 36 for now and see what happens (roads are pretty good overall here.)

An interesting note about the N designation. I run the N tires on my Porsches. You can get them at Tire Rack and so at least one isn't forced to get them from the dealer. But the big issue is insurance. I had a long talk with my insurance agent who is a car enthusiast and he said that there have been instances where insurance companies have tried to decline coverage on Porsches that had accidents and were running on non-N tires. When push comes to shove, I'm sure a lawyer would force them to pony up but it's still something one might want to consider.

kball

When I picked my wagon up last week the cold psi was 36, but the freeway ride away from the dealer the car was floating more than a hooker on meth. So i lowered about 2-3 psi. But there is a ton of road noise now with better tracking though.

I'm gonna switch out to michelin pilot sport a/s plus in a few thousand more miles. I run them on my lexus sc430 and really like them. 35k on them now with 6mm left. Still riding great but about 5k ago tire noise became more noticeable on them. Aggressive tread but comfortable ride. And i keep them at 37 cold psi

PyroDave

when i first had the car, the dealer filled it to 36, as it got a little warmer, that rose to 38, and driving raises PSI by about 3 for me, so i would get up to 41-42 PSI while driving, and this REALLY fucked with my traction and tire wear. in the rain, even with light gas, my tires would slip before starting, so be careful how high you go. the middle of the tire actually bulges out when your PSI rises. instad of being a flattish U type shape, they become more like a nipple(best way i could describe it, sorry) in the sense that you still have the U, but another smaller U shape is in the middle of that

ceb

Uh-oh, he said nipple.

With a cold fill of 36, it is unlikely that you'd get up to 41/42 while driving, but severe overpressure will increase the tire wear in the center.

I'd like to give a quick primer for those of you unfamiliar with psi and a modern car tire.

The proper psi is dependent on the car, the speeds you drive and the load you carry. It has nothing to do with the tire brand. The "max psi" printed on the side of the tire has nothing to do with how much air should be in the tire. It is merely a "not to exceed" pressure.

A perfect, properly mounted tire loses about 1 psi per month.

A ten degree change in temp causes a 1 psi difference in pressure.

Let's look at an example. You buy a car in June in Washington DC. The pressure is adjusted on a day when the temps are 90 and the tire pressure is adjusted to 33psi. Your tire will be subject to increased wear at about 28/29psi and your TPMS will alert of dangerously low pressure at around 25psi.

In July, your actual psi will have dropped to 32, but because the temps reached 100, your sensors will still show 33.

In August, your actual psi is at 31 and, because it is still 100, your sensors show 32

September gives you a "June adjusted" actual of 30 but because the temps are now 80, you sensors show (and the "new" actual psi is) 29.

October loses another psi so you're at 28, but since the temps now hover in the high 60's, you're really at 26 and you'll be getting TPMS warnings.

November starts getting cold and 50 is starting to sound warm in the morning, so you've lost that time adjusted psi (at 25 now) and a couple more because of the temps so your readings would be in the 23/24 range - dangerously low pressure - all in the timeframe of 6 months with nothing to actually give you a real loss of pressure.

TJ - sorry to have hijacked your thread but most folks don't understand the effect of time and temps on tire pressure.

gonzo08452

at what psi is the TPMS set to go off? I had the car at the dealer today to have the rear bumper aplique installed and the MPI states they set my pressure at 32psi. I'm confused since the pdi sheet set it at 35psi w/ nitrogen and the pdi was done on 5/22/12. I purchased the car the next day.

PyroDave

i said due to warmer temps, it went up 2 PSI or so. temps probably rose 30 degrees you poopie head. highway driving raises my PSI by 3 from the tires warming up. 38+3=41. beside that, i agree with what you said

kball

DIdn't i read somewhere around 25 or 26psi? coulda been the lexus manual though

ceb

Uh-oh, he said poopie head.

ceb

By law, the sensors must alert at 25% below the correct pressure, so about 25psi for our cars since the correct psi is 33.

You'll get increased tire wear at around 10% low so anything under 30 is bad for your tires. Below 25% is tire popping bad.

That's why you need to check your pressures at least monthly

robpp

iTrader: (2)

33 on the label inside the door on my 12 wagon/


mine cwas delivered with over 40 in each tire.

33 at sea level is 40 at 1 mile up LOL

i dinged the dealer on my survey for it too.

got a phone call. they said I should have brought it right back ....... told them they had their chance/

anyway its 33

dsc888

Terrific thread! I believe car makers put excessive air into the tire for the sole purpose of preventing flatspotting since they have no idea how long a car will sit on the lot. But it makes sense since the lower profile tires the TSX comes with might develop permanent spots. My 2011 Mazda CX-9 also has 50 series tires on 20 inch rims and it took 5000 miles for the flatspots to work themselves out as the car sat in the lot for 6 months before being sold.