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30 vs 35 PSI - Tire Pressure

jacktesterson

Diamond Member
Sep 28, 2001
5,494
3
81
I have a 2005 Buick Century with about 65,000 Miles on it.

The car looks and operates like new. It's a very quiet and smooth ride.

Question

I just put 4 new tires on the car. The Specs on the door recommend 30 PSI which seems kinda low to me.

I know this car is meant for older people who want comfy, smooth and basic rides.

Is the 30 PSI meant to make it smoother on the road?

Would upping it to 35 PSI help with Gas Mileage, which is my main focus?

Discuss.

Tire size is 205/70/15. Just installed 4 new Michelins.
 

xBiffx

Diamond Member
Aug 22, 2011
8,232
2
0
I don't see why it would hurt gas mileage so why not give it a try.

Not an expert on tires but I doubt over inflating by 5 PSI is going to cause much concern. Seems like there is nothing to lose in trying it and seeing.
 

jacktesterson

Diamond Member
Sep 28, 2001
5,494
3
81
Last edited:

nerp

Diamond Member
Dec 31, 2005
9,816
71
91
35 would be fine. Expect to feel a slight difference in how the road/pavement feels the higher in PSI you go. And yes, it should help with mileage a little bit.
 

RedRooster

Diamond Member
Sep 14, 2000
6,600
0
71
I prefer higher PSI as it makes turning faster and the car just feels like its rolling more freely. Cracks in the road are way more noticeable though, and you might pick up a couple extra squeaks.
 

dawp

Diamond Member
Jul 2, 2005
9,645
1,066
126
as one former member used to say, inflate to sidewall :D

my car call for 29psi and I generally inflate to 35 and as others have said there isn't much difference, maybe a slightly harsher ride but that's it.
 

cmdrdredd

Lifer
Dec 12, 2001
26,433
209
106
We used to have the same vehicle and always did 35. It rolled smoother, gave slightly better mileage, and handling felt sharper.
 

Jimzz

Diamond Member
Oct 23, 2012
4,323
119
106
The 30psi on the door is COLD rating. By the time you drive to add air it may be closer to 35 than you think.

I prefer 36 in the front and 32 in the rear for tires myself.
 

C1

Platinum Member
Feb 21, 2008
2,253
54
91
I get longer/better tread wear at the higher pressures among other things.

Another issue is that tires leak down over time so that if you check a tire a few months later, dont be surprised to find its pressure has fallen by at least 2-3 psi or more. So really what is experienced in the time interval is sort of an average pressure. If you start off at 30 psi, in three months unchecked you could be easily riding on 27 psi.

An exception to all this is snow/ice environments. When that happens, I lower the pressure for better traction/road grip. Remember also that tires tend to leak down more/faster in cold weather.
 

smackababy

Lifer
Oct 30, 2008
27,028
75
86
I read somewhere that higher tire pressure does give slightly improved fuel economy, but can change the wear pattern leading to faster tire wear. That was a while ago though, so I'm not sure if it still stands or has been debunked by real science.
 

ThatsABigOne

Diamond Member
Nov 8, 2010
4,406
13
81
For best ride/mpg compromise, inflate 2PSI above on each tire above what is on the door frame. It works for me.
 

desy

Diamond Member
Jan 13, 2000
5,215
26
91
35 is fine
You don't want to overinflate as the centre will wear out premature like if you were closer to 40.Yes the ride will be rougher and yes you should see 5% better fuel economy
 

T2urtle

Diamond Member
Oct 18, 2004
3,426
3
81
My Sticker says 30PSI as well.

For my summer tires, 235/45/18 and 265/40/18, i orginally started them at 40psi and then recently for no reason i just dropped them down to 30PSI. The ride was nicer and NO MPG +/-, i did notice contact patch for the rear was wider/better. No traction issues found but i dont have much power at 300HP and AWD.

I normallly go 35 cold PSI on all cars, mainly cause in the winter some TPMS get triggered at 28 PSI and when you set them at 30PSI, its just happens too often.
 

phucheneh

Diamond Member
Jun 30, 2012
7,308
4
0
My car rolled off the dealer lot with the tires at like 40psi, maybe even slightly more, and I never noticed. The factory sets them at 40-50 for shipping/storage purposes and the mechanic is supposed to put them to spec when he does the PDI (pre delivery inspection, which is actually a pre-'put it on the lot' inspection).

Anyway, I set them down to about 35-36 and it seemed about the same. I think the door says 32 or 33. When the temps start dropping outside and I haven't serviced the car in a while, though, I will honest-to-god feel that something is not right once the pressures start dipping below 30. I've actually gotten out to inspect the car because it felt 'weird' and found nothing but 28psi of tire pressure. Even around spec, it starts feeling 'off.' And I've noticed over time that most cars are like this...35 really does seem to be like the magic number where the car is the most responsive, and as much as I would have previously disagreed with 'I can feel when my tires are 5psi low'...damn, I think I actually can.

On wear, I think 35 is still optimal for most cars with a standard spec in the 29-32 range. Setting to spec every few months means that there will be time between services (I'm just assuming most people top off the tires at oil changes) where the tires are below spec, so your 'average' pressure kind of comes down. Probably going to cause more wear on the edges of the tires.

My experience has been that even if you check your tires a lot and consistently keep them a few pounds above spec, center wear will be somewhere between nonexistant and 'not enough to worry about.' If you're going to take your tires as far as possible, waiting until the tread is just annihilated before replacing them (i.e. most people)...I'd much rather see bald centers than bald edges. I've never seen a tire come apart at the middle. And I've seen cars that made sparks when they drove (steel belt completely exposed). Separation at the edge of the tread, though, is definitely a concern.
 

fstime

Diamond Member
Jan 18, 2004
4,385
5
81
If it calls for 30 and you want to add a little more pressure, I would say try 33 PSI.

Over-inflating too much can lead to uneven tire wear in the middle of the tire.

The most important thing is you check and fill the pressure in the early morning when its still cool out and the car has not been driven. If you don't, your pressure reading will be much higher as the air inside the tires will warm up from the sun/temperature/driving around.
 

thescreensavers

Diamond Member
Aug 3, 2005
9,930
1
81
Remember Door Jam PSI is for the stock tires. For Ex: Pressure inside the tires affects load rating and its speed rating. So it can be different vs stock.

You should be able to run 35psi without issue imo.
 

Pacfanweb

Lifer
Jan 2, 2000
13,079
33
91
The 30psi on the door is COLD rating. By the time you drive to add air it may be closer to 35 than you think.
Yes, but that holds true if your cold pressure is 35, too. The heat increase is already figured in.

I'd run maybe 32. I think 30 is a bit low. If you're going to run it that low, check it often.

You're correct, the low pressure is so it'll ride better for the old people that buy them.

You WILL feel a lot of difference at 35 psi, so get ready for it. Ride will be a good bit harsher.
 

cheez

Golden Member
Nov 19, 2010
1,589
15
81
I have a 2005 Buick Century with about 65,000 Miles on it.

The car looks and operates like new. It's a very quiet and smooth ride.

Question

I just put 4 new tires on the car. The Specs on the door recommend 30 PSI which seems kinda low to me.

I know this car is meant for older people who want comfy, smooth and basic rides.

Is the 30 PSI meant to make it smoother on the road?

Would upping it to 35 PSI help with Gas Mileage, which is my main focus?

Discuss.

Tire size is 205/70/15. Just installed 4 new Michelins.
Yes 30 PSI is too low. It's for grandpa's and grandma's. Jack it up to 42 PSI both front and back. Your tires should be rated at upto 44 PSI if I'm not mistaken. So check the max allowed PSI on the tires first. Most are 44 PSI.

Yes it will help fuel economy as the rolling resistance on the tires have reduced tremendously.


I don't see why it would hurt gas mileage so why not give it a try.

Not an expert on tires but I doubt over inflating by 5 PSI is going to cause much concern. Seems like there is nothing to lose in trying it and seeing.
He's got plenty rooms. Jack it up 10 PSI or so.


cheez
 

cheez

Golden Member
Nov 19, 2010
1,589
15
81
The 30psi on the door is COLD rating. By the time you drive to add air it may be closer to 35 than you think.

I prefer 36 in the front and 32 in the rear for tires myself.
And depending on what side the car is facing the sun the tire pressure will go up as well temporarily. Temperature has a huge effect on tire pressure :D

I set mine at 40 PSI front and back for the Integra and IS350 F-Sport.




Guys, if you have lower profile tires (45R or less) and have a lot of pot holes on the road / freeways you will be better off with HIGHER PSI on the tires. I once had a sporty hatch with low profile tires with 33 PSI and went over the pot holes. The impact was strong enough to hit the rims and bent it. If the tire pressure was at 42~ 44 PSI it would have prevented from hitting the rims. The difference may not be huge, but it helps with higher pressure. Don't worry about damaging the suspension system. You have shocks and springs that absorb shocks. That's what the shocks are for lol.


cheez
 

Vetterin

Senior member
Aug 31, 2004
973
0
71
35 psi is not even a concern. I run my LRR tires at 42 psi but if you check out the hypermilers forums you will see that 50 psi is not uncommon.
 

monkeydelmagico

Diamond Member
Nov 16, 2011
3,961
142
106
And depending on what side the car is facing the sun the tire pressure will go up as well temporarily. Temperature has a huge effect on tire pressure :D

I set mine at 40 PSI front and back for the Integra and IS350 F-Sport.




Guys, if you have lower profile tires (45R or less) and have a lot of pot holes on the road / freeways you will be better off with HIGHER PSI on the tires. I once had a sporty hatch with low profile tires with 33 PSI and went over the pot holes. The impact was strong enough to hit the rims and bent it. If the tire pressure was at 42~ 44 PSI it would have prevented from hitting the rims. The difference may not be huge, but it helps with higher pressure. Don't worry about damaging the suspension system. You have shocks and springs that absorb shocks. That's what the shocks are for lol.


cheez
OP is rocking a buick. If the sidewall is any less than a 70 I'd be suprised. 40+ PSI is silly. Advice is best when it comes from a solid base of knowledge ........http://forums.anandtech.com/showthread.php?t=2343409 :whiste:
 

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