Tire Pressure

pimpinteddy

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When i look at the manual for a car it tells me a range of pressures i could put on the car like 28-33 psi. but which would be more econamical being closer to the 28 or the 33?
 

Svempa

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33. Although I don't think it'll be much difference between the two consumtion wise.
 

KaJuN

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33. Although I don't think it'll be much difference between the two consumtion wise.
Yeah I don't see how it could really affect fuel consumption. But I've heard it's better to have lower pressure in winter to give better traction in snow.
 

the Interceptor

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A higher pressure makes the patch where the tire touches the ground a tad slimmer, therefor reducing rolling resistance, which reduces fuel consumption.
 
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Dino

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just keep in mind to change tire pressure when the tires are cold, so they are all even and not underinflated when cold.
 

Top Geek

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But I've heard it's better to have lower pressure in winter to give better traction in snow.
That will come normally as the air will contract as it gets colder, but do check to make sure they are even and don't become too low. I just checked my tires, which were at 25 psi in -15 celsius, and I normally keep them at 32 psi. It will only get colder here this time of year, so I filled them up to 31 psi.
 

prizrak

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It's a necro post but since there was already a related thread I figured I'll ask here :)

So I got new wheels (pix will be posted in my car thread soon) which are running 235/40/R18 tires, so now I'm trying to figure out what I should have for tire pressure. There is a chart on my door that tells me different pressures for different wheel/tire combinations that came with the car. The strange thing is that it tells me that I should have 30PSI all around for both 16" and 17" rims. I was always under the impression that lower profile tires would need to be inflated more than higher profile tires. 30PSI was too low even for my 16's, I found that the car drove best right around 33.

Any thoughts on what pressure I should use? I was thinking 35 for now.
 

LeVeL

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My dad's A4 has virtually no sidewall compared to my Accord and he runs higher tire pressures, so I think you're right about bigger wheels needing more PSI. I'd do something like 35f/33r on yours; I like to have a little more in the front tires because the car turns in a little better (although you could make the argument that it also increases understeer). I really don't think there is a significant different in gas mileage with +/- 2-3psi
 

_HighVoltage_

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Yeah, you can definitely go higher. Tires are normally rated for up to 50psi, so it won't blow up in your face.

30psi seems way too low even for a 16" wheels. I run my Volvo with 36psi up front (which elevates to 40, when the temperature gets above 80 degrees) and 34 in the rear (38 when hot).

Maybe I'm just exaggerating, but I really can tell a difference, compared to running just 32psi.
 

thevictor390

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I run ~33 PSI on my 225/45/18. I think that's just a little over what it tells me to do on the inside of my door. My tire pressure monitor warning goes off at about 28.
 

GRtak

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Check the tire sidewall, and the tire manufacturer's website. there should be some info on that tire's airpressure needs. After you have them inflated within specs, check them on occasion to see if there are any weird tire wear issues.
 

prizrak

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Thanks guys!

They were definetly over inflated, checked them today they were at 50psi. That explains why it was mostly struggling for traction.

30PSI is wayyyy too low for 16"s as well I had them at 33 all around.

Right now I'm sitting at 35, have yet to drive it so will see how it compares.

@LeVeL I can tell 1 psi as well :)
 
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Cobol74

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If my estate if loaded then 35psi is recommended by the manufacturer, if not 30psi recommended. I tend to have them higher for the reasons stated - I do not do performance driving in it so my goal is higher mpg hence I tend to stay at 35psi (or a little higher) mostly. Works for me.
 

prizrak

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Drove around with 35 all around, I like it, might experiment a little bit to see if I want it slightly higher/lower but its good so far.
 

_HighVoltage_

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Just remember what I said - 35 on cold tires is 40 on hot tires.

Kinda off topic but...I remember reading somewhere that the largest amount of punctures are caused by underinflation (apart from glass, nails, curbs etc...). Any truth to that? Which is worse - under or over inflation?
 

LeVeL

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I'd say under is worse because you don't want extremely soft sidewalls that the rim will just roll over under cornering... it wouldn't be pretty in an extreme situation. Unless you overinflate to the very maximum a tire will take... then that's probably worse.
 

prizrak

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Just remember what I said - 35 on cold tires is 40 on hot tires.

Kinda off topic but...I remember reading somewhere that the largest amount of punctures are caused by underinflation (apart from glass, nails, curbs etc...). Any truth to that? Which is worse - under or over inflation?
I'm aware :) Max PSI on this is 50 so I'm well within operating range.
I'd say under is worse because you don't want extremely soft sidewalls that the rim will just roll over under cornering... it wouldn't be pretty in an extreme situation. Unless you overinflate to the very maximum a tire will take... then that's probably worse.
Both are pretty bad,
Underinflation - increase in friction and temperature of the tire, this will lead to faster breakdown of the compound and tire separation.
Overinflation - unless going over maximum will decrease traction and also stiffen up the tire so a risk of rapture/tire coming off the wheel is greater.

Under/overinflation doesn't necessarily have a huge effect on the sidewall, sidewall stiffness is more the way the tire is designed then the air you put in it. The new tires I have for instance are almost perfectly round in the front and perfectly round in the back even at 35psi. My old tires would have a very noticeable contact spot at that PSI.

LeVeL,
Out of curiousity what is the PSI on your dad's car and the tires? I suspect I should have something pretty close.
 
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