Mazda3 Forums banner

What's you're tire pressure (stock tires)

1 - 20 of 31 Posts

·
Registered
Joined
·
76 Posts
Discussion Starter #1
Hello,

Just picked up my speed3 2 weeks ago. During the test drive I did a couple quick lane changes on the freeway and noticed a little wallowing but just assumed that the car was under sprung to maintain ride quality or something. So a couple days ago I decided to check the tire pressure and found them to be 32-33 psi on average. Looked at the door jamb sticker and sure enough that's about whats called out. Then looked at the tire, max psi is 50 :shock: I decided to split the difference (+ a little) and went to 45psi all arround. Man, the handling of this car is now razor sharp, a completely different animal. Awesome. I did notice a little more torque steer as a result though, and of course it lowers the ride quality a little (rougher ride, as to be expected.)

Thought I'd share and see what others are running.

Later,
-Chris
 

·
Registered
Joined
·
388 Posts
I'm not really sure what others are doing (interested in seeing the outcome of this post)
but I'm putting 38-39 in front and 34 in the rear.


when I had 40 in the front I was loosing a little too much traction,
38 ish seems just about right; the lower pressure for the rear reflects
the weight distribution of the car.


45 seems a little high to me.
 

·
Registered
Joined
·
1,207 Posts
I second dbuenger... it will be interesting to see where this thread leads. I keep mine stock for now.
Correct me if I'm wrong, don't you try to increase pressure when you autocross?

Autocross = more tire pressure = better handling.
 

·
Registered
Joined
·
5,875 Posts
just be aware that higher pressure than recommended=higher risk of a blowout

I personally run 38 psi in my tires (regular 3, not MS) and find its a good middle of the road pressure. I up them to 40F/42R for autocross
 

·
Registered
Joined
·
267 Posts
39 in the fronts.........35 in the rears. The fronts need more since most of the weight i
s up there (and take most of the punishment of braking, turning, accelerating), the backs are mostly along for the ride. Also, a bit more may help gas mileage.
 

·
Registered
Joined
·
612 Posts
[quote author=wuespeed3 link=topic=70892.msg1244198#msg1244198 date=1172853352]


During the test drive I did a couple quick lane changes on the freeway and noticed a little wallowing but just assumed that the car was under sprung to maintain ride quality or something.
Later,
-Chris
[/quote]
That is just the suspensions initial lean in, pushed beyond that initial 'bob' it holds tight. I don't think ride quality was ever a true concern for the engineers. It is suprisingly good though considering.

[quote author=wuespeed3 link=topic=70892.msg1244198#msg1244198 date=1172853352]

Then looked at the tire, max psi is 50 :shock: I decided to split the difference (+ a little) and went to 45psi all arround.
I did notice a little more torque steer as a result though, and of course it lowers the ride quality a little (rougher ride, as to be expected.)

Thought I'd share and see what others are running.

Later,
-Chris
[/quote]

I was in the tire business for quite a few years. First off, that 50 psi is the max capacity, no where near safe operating pressure. Lower that. The higher you run your inflation, the sooner you will wear out the center of the tires, likewise the lower you run it, the sooner you wear out the outsides. I personally run 35 up front 36 in the rear. Anymore than that you risk premature wear of the tires, and you actually will degrade the amount of grip you have, hence your torque steer. You have less of a contact patch so it is easier for the torque to manhandle your tires, if you had a wider patch, the tires would grip better and you would have less torque steer. The illusion of better handling is probably faster steering, do to the thinner contact patches. That being said, a car at stock pressures versus a car severely overinflated on the skidpad... stock will win. In the slalom, it is actually better to be a bit over inflated on a lot of cars, but no where near as high as you have it. Not to mention those tires are not long for this world if you continue to run them that high. Just some stuff to think about.

:dhl:
There are a lot of resources out there for tire info. I think everyone should read some of it. They are the only safety/performance equipment that actually touches the ground. Be educated before you decide to make drastic changes. Enjoy.
 

·
Registered
Joined
·
408 Posts
so changing the tire pressure how does that effect the tire pressure monitoring with our cars?? does the car just adjust to whatever you put in there or do you have to do something to update it???
 

·
Registered
Joined
·
5,875 Posts
well, it depends a lot on the tire as to what optimal pressures for grip are, but its usually somewhere between 33-40 psi for street tires (it can be significantly higher for R-comps or slicks though). In our car, you want the fronts air to optimum grip. Then you want to air the rears for balance, meaning slightly above or slightly below the optimal pressure for grip. Ideally, your suspension would spread grip between the two so optimum grip pressure would=optimum balance, but thats an awfully hard setup to find on a FWD.

Running 45 psi all around is a bit dangerous, as if temperatures heat up 30-40 degrees, and then you warm the tires up from some heated driving, you could easily exceed the 50 psi max, and bad things can happen then. . .
 

·
Registered
Joined
·
5,875 Posts
TPMS will only go off if your pressures are dangerously high or low, they aren't all that sensitive actually. . .
 

·
Registered
Joined
·
822 Posts
I noticed that most of the respondants were a lot further south than I. I've played with the pressure a lot when I got the car and found the 35 front/33 rear give the best compromise of handling and ride up here in pot hole hell. I'm running my snows at 36/36, I tried 38 up front but it was just too harsh.
 

·
Registered
Joined
·
388 Posts
location definitely has a lot to do with it.

for some strange reason we have the most beautiful road
surfaces down here. I'm sure it's
a combination of mild weather and absorbent transportation
taxes.


hence the 38 (ish) front pressures I've been running.
 

·
Registered
Joined
·
1,960 Posts
[quote author=wuespeed3 link=topic=70892.msg1244198#msg1244198 date=1172853352]
Hello,

Just picked up my speed3 2 weeks ago. During the test drive I did a couple quick lane changes on the freeway and noticed a little wallowing but just assumed that the car was under sprung to maintain ride quality or something. So a couple days ago I decided to check the tire pressure and found them to be 32-33 psi on average. Looked at the door jamb sticker and sure enough that's about whats called out. Then looked at the tire, max psi is 50 :shock: I decided to split the difference (+ a little) and went to 45psi all arround. Man, the handling of this car is now razor sharp, a completely different animal. Awesome. I did notice a little more torque steer as a result though, and of course it lowers the ride quality a little (rougher ride, as to be expected.)

Thought I'd share and see what others are running.

Later,
-Chris
[/quote]
45 is way too high. The turn-in response will be good but you are severely compromising the grip because of the smaller contact patch. As it was pointed out, you will undoubtedly wear out the center of the tires first.

FWIW, I like to run at about 2 PSI over the recommended F/R tires pressures.
 

·
Registered
Joined
·
76 Posts
Discussion Starter #14
Good points guys, thanks for the feedback!

I did a search on "tire pressure" and found nothing relavent, hence this post; but then it was only in the mazdaspeed section, so that may be why I struck out...

I have always run my cars on the high side. My last car was a 03 Mach1 mustang. Running it on the high limit of tire pressure always resulted in even tire wear. I was a little worried that keeping them at stock levels on this car might result in outer edge wear, hence the bump up. I'll try 40 and see how the car handles; a little less torque steer would be a good compromise along with sharper turn in response, which I like a lot...

I added another option to the poll too, there was a big gap...


Regarding blowouts, remember that too low a pressure is equally bad and results in lots of blowouts also. Here in AZ I see many vehicles on the side of the road due to this every summer. The reason is overheated treads due to too much flexing, i believe.

Thanks!
-C
 

·
Registered
Joined
·
2,117 Posts
I think everyone is "nicely" telling you to...

LOWER YOUR PRESSURE!!

Run it 35-38 if you want it on the high side.. :D
 

·
Registered
Joined
·
612 Posts
40 is still to high, think about it. Mazda put that sticker on the car to let you know what they believed was the optimal pressure levels for the car performance and safety wise. You have to consider that. Especially the SAFETY factor. Now maybe you find you like it a little more firm, as I said I in fact run a bit over stock inflation. That being said, anything over the mid thirties for everyday driving will be detrimental to the over all health and longevity of the tire. As said before, it also will only give the impression of increased performance. To each his own. Drive safe.
 

·
Registered
Joined
·
1,842 Posts
40 psi in the front/49 in the back....for autocross use.... :klavergreg:
 

·
Registered
Joined
·
5,875 Posts
[quote author=proclam link=topic=70892.msg1245056#msg1245056 date=1172874158]
40 is still to high, think about it. Mazda put that sticker on the car to let you know what they believed was the optimal pressure levels for the car performance and safety wise.
[/quote]

No, mazda recommended a good handling/ride/safety balance, if you have a different balance (prefer more performance, and are willing to put up with a stiffer ride and higher risk of blowout), higher pressures are fine. 40 psi is a bit overkill, and unneccesary (doesn't increase performance much over 36-38, but still stiffens ride, and increases blowout risk further). Also, mazda doesn't want you to set your pressures that high b/c most people only check their tire pressures like once or twice a year, and 40 psi in winter=45-46 psi in summer, run those tires hard to heat them up a bit more, and you are exceeding the max tire pressure.

32 psi is NOT optimal for performance, despite the fact that this is mazda's recommended pressure. . .
 

·
Registered
Joined
·
76 Posts
Discussion Starter #19
Guys, seriously, look at the rating on the tire and read the Bridgestone safety pamphlet that came with them in your owner’s manual pouch (I did). These tires are rated to 50psi max COLD (ambient) installed on a vehicle weighing 5732Lbs (1433 per tire) max vehicle weight. This car, with me in it, full of fuel, soaking wet is no more than 3600lbs, only 63% of the rated vehicle weight listed on these tires. So, even if you figure about 60/40 weight balance then the fronts are only loaded to 2160Lbs, or 1080 per tire, which is still only 75% of the tires' rating. I'm running at 45psi cold, or ~90% of full pressure, on a vehicle whose front tires are loaded to only 75% of the rated weight.

IMHO (and I'm no expert, so take it for what it's worth) there is absolutely -no- safety issue here, -unless- I'm stupid enough to take 4 200+Lb friends on a joy ride over pot-hole riddled roads, which are few and far between here in Phoenix (potholes, not my friends, thank you very much :) ).

Also rest assured that the tire manufacturer took heating under normal driving conditions, as well as the tires ability to shed heat (the Temperature A rating), and potholes, into account when they put that load rating on the tire. Also also they MUST have included an engineering safety factor on top of that; usually 50-100% (IE they reduced the actual max pressure and weight). And also take into account that these are W rated tires which can withstand the huge inertial loads of driving at 168MPH, so they are constructed "hella friggin' strong" to begin with. So no way am I anywhere even close to driving on dangerously over inflated tires. Over stock inflation, sure.

But I appreciate your guys' concern, really. Just don't be so alarmist, sheesh. If you're not comfortable running yours that high, don't. I only described what I found; I didn't tell -you- to do what I did. Well, ok, I maybe did insinuate it is better this way, but that's not the same thing...

Mazda's recommendations are strictly driven by their lawyers protecting them from idiots who have poor judgment, then second based on their need to protect the suspension from damage for the warranty period (higher pressure = more stress on the shocks for instance). Handling, ride quality, etc. are a very distant third to those considerations IMHO.

Anyway the comments regarding contact patch are the only thing that might drive me to consider playing with this more. But I took a spirited drive up Yarnell hill to Prescot and 89A to Jerome this afternoon and the car handled magnificently, for what it is. What a blast to drive.

This is looking like a good discussion so far I think. I'm glad to see so much interest and the varied opinions.

Please let me know if I'm missing something here; and let's try and avoid "group think".

-Chris
 

·
Registered
Joined
·
335 Posts
Although I hesitate to throw in another opinion, I will. From a maximum performance viewpoint, what is important is the tire pressure at operating temperature under the conditions that you are interested in. Cold tire pressure is just a consistent reference point, and becomes unimportant once the tires warm up (unless your favorite curve is the end of your driveway). Now, what's really important is that you are loading your tires evenly across the tread section. If you aren't doing that, you aren't getting the maximum possible grip, and you'll also wear your tires unevenly. The right way to tell is to use a probe-style tire thermometer to check the tread temps across the face of the tire. The temperatures will depend on your alignment settings, tire pressure, and how you drive. Alignment settings aren't that easy to change on the side of the road, and I don't want to get into how you drive, so that leaves us with tire pressure. Assuming that you have an appropriate alignment, too little pressure will make the edges of the tire hot, and too much will make the center hot.

Most people don't have the ability to check their tire temps, so I'll share my experience and you can take it or leave it. At the track (high speed driver's ed at Texas World Speedway), with my stock MS3 and stock RE050As, I found that I was able to get a very even 170F across the front tires at a hot pressure of 42psi. The rears were a pretty even 140F or so at 38psi. So, under my conditions, the alignment, tire pressure and driving (which is much harder than anyone should drive on the street) were working quite well together. When my tires cooled down, guess what the pressures were? 34 front and 32 rear. Yup, that's stock. Surprised? Some people start at lower than stock pressures at the track because of so much pressure gain.

So I had an 8psi gain in the fronts. Where does that leave you? Well, that's up to you, but I doubt that pressures higher than 42psi hot are useful on the street. If you want 42psi hot, and your driving increases your tire pressure 6psi over cold, then you'd want your cold pressures at 36psi. If you are just tooling around on the freeway most of the time but want to be ready for the occassional off-ramp, maybe you want your cold temps to be at 38psi in the front, except that you may find that your tires wear too quickly in the center, so you may want to compromise and back off the pressure just a bit.

If you are running a very high cold pressure, you'll have quicker steering response because of the longitudinally narrower contact patches, but you are giving up max grip.

If you autocross, you have a difficult situation because you have to work with both cold and hot tires in the same run.
 
1 - 20 of 31 Posts
Top