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Old 04-04-2013, 01:54 AM   #17351
Dirt Bringer
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So I've been playing with tire pressures and I'm currently running 41/39.5 psi. I'm not sure if this is too high and whether there are any risks to running it this way. I am well aware that the recommended pressure is much lower, something like 32/30, but seriously, screw that, no one listens to that anyway. I feel like the steering is a lot more positive and the car handles much better with the more heavily inflated tires, but at the same time, I'm not sure if this is a good idea or not. Today I checked tire pressure and adjusted as I had been running closer to 44 (my previous gauge was a piece of crap), but overall I feel like the car handles better with more air. Maybe the problem is just the crap tires?
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Old 04-04-2013, 03:34 AM   #17352
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Quote:
Originally Posted by Dirt Bringer View Post
So I've been playing with tire pressures and I'm currently running 41/39.5 psi. I'm not sure if this is too high and whether there are any risks to running it this way. I am well aware that the recommended pressure is much lower, something like 32/30, but seriously, screw that, no one listens to that anyway. I feel like the steering is a lot more positive and the car handles much better with the more heavily inflated tires, but at the same time, I'm not sure if this is a good idea or not. Today I checked tire pressure and adjusted as I had been running closer to 44 (my previous gauge was a piece of crap), but overall I feel like the car handles better with more air. Maybe the problem is just the crap tires?
I was totally wondering this as well.
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Old 04-04-2013, 03:56 AM   #17353
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Originally Posted by danstheman7 View Post
Looks good! how much did it cost you?
It was pricey, came out to $400 shipped. Way better than a flimsy universal one though!
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Old 04-04-2013, 03:58 AM   #17354
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Quote:
Originally Posted by Dirt Bringer View Post
overall I feel like the car handles better with more air. Maybe the problem is just the crap tires?
The tires also act as a spring, and increased air pressure effectively raises the spring rate.
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Old 04-04-2013, 06:01 AM   #17355
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Quote:
Originally Posted by Dirt Bringer View Post
So I've been playing with tire pressures and I'm currently running 41/39.5 psi. I'm not sure if this is too high and whether there are any risks to running it this way. I am well aware that the recommended pressure is much lower, something like 32/30, but seriously, screw that, no one listens to that anyway. I feel like the steering is a lot more positive and the car handles much better with the more heavily inflated tires, but at the same time, I'm not sure if this is a good idea or not. Today I checked tire pressure and adjusted as I had been running closer to 44 (my previous gauge was a piece of crap), but overall I feel like the car handles better with more air. Maybe the problem is just the crap tires?
If you really wanted to maximize tire wear, you could spring for a pyrometer. (around 75 bucks at Advance Auto Parts) Recommended tire pressure varies because of the weight of the load the tire carries. If you shoot the tread in the center and edges with a pyro, the temp should be equal. If there is a variance, ie: center is warmer than the edges, that would indicate over inflation. Under inflation would show a higher temp near the sides of the tread than the middle. Either would result in uneven, (premature), tire wear because the contact patch does not have the weight distributed evenly across the width of the tread, which also means less then optimal traction. We're not talking huge differences here , just for clarification. So if you really wanted to be anal about proper inflation, that would be the way to do it.

Note that over inflation may help with mpg's due to reduced friction against the road though, but you're wearing out the middle before the edges.

John

edit: I might also add that an alignment issue would result in unequal readings. Simply stated, friction = heat.

Last edited by Guzzi 1; 04-04-2013 at 06:52 AM. Reason: added info
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Old 04-04-2013, 06:34 AM   #17356
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Quote:
Originally Posted by Dirt Bringer View Post
So I've been playing with tire pressures and I'm currently running 41/39.5 psi. I'm not sure if this is too high and whether there are any risks to running it this way. I am well aware that the recommended pressure is much lower, something like 32/30, but seriously, screw that, no one listens to that anyway. I feel like the steering is a lot more positive and the car handles much better with the more heavily inflated tires, but at the same time, I'm not sure if this is a good idea or not. Today I checked tire pressure and adjusted as I had been running closer to 44 (my previous gauge was a piece of crap), but overall I feel like the car handles better with more air. Maybe the problem is just the crap tires?
I found either 36/34 or 35/33 to be best. If I went to 38/36 it was too high and in an aggressive turn the rear tires would lose grip.

Higher isn't always better.
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Old 04-04-2013, 07:27 AM   #17357
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Quote:
Originally Posted by flyboy1100 View Post

I found either 36/34 or 35/33 to be best. If I went to 38/36 it was too high and in an aggressive turn the rear tires would lose grip.

Higher isn't always better.
Especially for wet traction, too.
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Old 04-04-2013, 10:00 AM   #17358
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Originally Posted by flyboy1100 View Post
I found either 36/34 or 35/33 to be best. If I went to 38/36 it was too high and in an aggressive turn the rear tires would lose grip.

Higher isn't always better.
Better than the front losing grip and understeering into oblivion. I rechecked my pressure after the tires had cooled and it was closer to 40/38.5. Are we supposed to test pressure when the tires are warm or cold?
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Old 04-04-2013, 10:07 AM   #17359
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I run the max psi rating (44 I think) quite regularly. I get better mpgs and the car feels less sloppy. The dealer always sets it to 36/35 and I just head to sheetz for the free air.

I also don't really drive like a madman. I try to baby my little scoob.
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Old 04-04-2013, 10:24 AM   #17360
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Understeer is safer than oversteer. You dont want to spin into oncoming traffic, its better to take collision head on for more cushion.

I keep mine a bit higher then spec around 36-39psi.
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Old 04-04-2013, 10:54 AM   #17361
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Originally Posted by myrt1987 View Post
Understeer is safer than oversteer. You dont want to spin into oncoming traffic, its better to take collision head on for more cushion.

I keep mine a bit higher then spec around 36-39psi.
It's also a lot more boring.
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Old 04-04-2013, 11:21 AM   #17362
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It's also a lot more boring.
There's something to be said for control. Not everyone has learned how to control an oversteering car.
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Old 04-04-2013, 11:29 AM   #17363
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Originally Posted by Dirt Bringer View Post

Better than the front losing grip and understeering into oblivion. I rechecked my pressure after the tires had cooled and it was closer to 40/38.5. Are we supposed to test pressure when the tires are warm or cold?
Stone cold.

Run what you want, but I tried the higher pressures last summer and was not impressed, the stock tires loose grip easily and even easier yet when you ramp up the pressure higher than 4psi over stock.

I also saw no mpg loss by running them anywhere from 40 down to 34/32.

I still think 35/33 or 36/34 is the sweet spot. I generally drive really hard
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Old 04-04-2013, 11:37 AM   #17364
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Originally Posted by Dirt Bringer View Post
It's also a lot more boring.
Totally bro. If you ain't out of control, you ain't in control.
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Old 04-04-2013, 12:21 PM   #17365
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Totally bro. If you ain't out of control, you ain't in control.
"If everything seems under control, you're not going fast enough"
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Old 04-04-2013, 12:30 PM   #17366
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Totally bro. If you ain't out of control, you ain't in control.
...said the guy who gets the best fuel economy on this forum.

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Old 04-04-2013, 12:49 PM   #17367
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...said the guy who gets the best fuel economy on this forum.

Hey man, Im just living life 1/4 mile at a time.
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Old 04-04-2013, 01:23 PM   #17368
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Now, let's just say you run better tires.. The stock Yoko's suck. Can you successfully run a little higher with better ones?
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Old 04-04-2013, 01:36 PM   #17369
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Question for the guys with auto climate control...when you turn on the auto setting, is it supposed to turn on to full blast? No matter what the temperature setting, whenever I turn on auto climate control it turns up to full blast and doesn't lower. Is that normal?
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Old 04-04-2013, 02:19 PM   #17370
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Originally Posted by averagewhiteboy View Post
Now, let's just say you run better tires.. The stock Yoko's suck. Can you successfully run a little higher with better ones?
The higher you run the less the tire will mold to the surface, so the less friction aka traction. Back with higher profile tires the more you ran the less the wear - so checking with an ir thermometer doesn't necessarily tell you that the insides are wearing faster, it could just be the shoulders are wearing more slowly than the centers are.

Pressure ratings on tires are for sea level and very cold so there is a safety margin - if you pump them up to 44 psi in the cold at low elevation then climb to a high elevation and when warm they could be over 50 psi. E.g. If you go from sea level to 9,000 feet that 44 psi turns to 48 psi. Of course you people on the east coast would have to either drive a long way or take the car up in an airplane...

Further then, if you had filled the tires at 30 deg f at sea level then climbed to 9,000 feet and the temperature was 80 deg, you would have 53 psi in them.
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Old 04-04-2013, 03:45 PM   #17371
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Originally Posted by averagewhiteboy View Post
Now, let's just say you run better tires.. The stock Yoko's suck. Can you successfully run a little higher with better ones?
why does everyone think more pressure = better?

it depends on the tire, load rating, size, etc etc etc. there are too many factors to just say "yes". generally speaking more pressure = less rolling resistance AKA traction. hence if you purely are going for more MPG you increase pressure, but if you are going for traction you drop the pressure.

here is a good article i just read and kinda want to try out in a few months when it is warmer
http://www.autocross.us/forums/lofiv...x.php?t46.html

Last edited by flyboy1100; 04-04-2013 at 03:50 PM.
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Old 04-04-2013, 03:48 PM   #17372
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Quote:
Originally Posted by flyboy1100 View Post
why does everyone think more pressure = better?

it depends on the tire, load rating, size, etc etc etc. there are too many factors to just say "yes"
I agree, the engineers who designated the tire pressure for the Impreza have access to much more sophisticated measuring devices than I do. Until I build my very own multi-million dollar test track, I will just use the designated pressure and not pretend my seat of the pants observations are as good as their calculated measurements.

I am such a lemming.
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Old 04-04-2013, 03:58 PM   #17373
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I agree, the engineers who designated the tire pressure for the Impreza have access to much more sophisticated measuring devices than I do.
True, but I'm guessing (like in all large manufacturing companies) that the engineers need to strike a compromise with the marketing folks. So engineering might want higher tire pressure to stiffen the sidewalls which will improve handling, and marketing might want softer tire pressures because their research shows that customers (in the USA) want a softer ride. Then marketing finds themselves painted into a corner because they also want the best MPGs they can get, so on the one hand they want tire pressure to go down, and on the other hand they want tire pressure to go up. "I don't know what to do!"

Marketing Guy =>

So the 32/30 PSI we see on the door jam sticker might be the result of that compromise. I generally prefer a firmer ride, so my practice is to inflate 3 lbs higher than the door sticker (35/33 PSI, in the case of our Imprezas with the 17" Yoko tires).
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Old 04-04-2013, 04:10 PM   #17374
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Originally Posted by gregorz4 View Post
Question for the guys with auto climate control...when you turn on the auto setting, is it supposed to turn on to full blast? No matter what the temperature setting, whenever I turn on auto climate control it turns up to full blast and doesn't lower. Is that normal?
When you start the car and it is cold, the fan will essentially be off. The when the car warms up, the fan will be at "full blast" and will lower over time. This is normal. Now if it is hot inside the car, the opposite may happen.
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Old 04-04-2013, 04:28 PM   #17375
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Quote:
Originally Posted by sgoldste01 View Post
True, but I'm guessing (like in all large manufacturing companies) that the engineers need to strike a compromise with the marketing folks. So engineering might want higher tire pressure to stiffen the sidewalls which will improve handling, and marketing might want softer tire pressures because their research shows that customers (in the USA) want a softer ride. Then marketing finds themselves painted into a corner because they also want the best MPGs they can get, so on the one hand they want tire pressure to go down, and on the other hand they want tire pressure to go up. "I don't know what to do!"

Marketing Guy =>
You have a very active imagination.

Whatever the process is that they use to derive the numbers printed on the door jamb, those are the recommended pressures and what the tires have in them when they test the vehicle for things such as fuel economy, cornering, braking, and stability.

You can alter from it one way or the other, but it is you second guessing the tested pressures.

Go for it, it is your car, but don't think that making up stories about what you think happened when the tire pressure was determined means anything but that you like to make up stories about it, in the absence of any evidence whatsoever, so you can rationalize your decision to use a different pressure.
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