confused about tire pressure

newyawka · 01-17-2006, 09:48 PM

ok old school prius chat peoples, the newbie here is confused. members of this site have recommended tire pressure of 40/somewhere near 40. yet the manual and inside the drivers side door list it at 35/33. anything over that is "unsafe" blah blah blah blah....and so forth...a little confusing.

can ya help this kid? puh-weez?

tripp · 01-17-2006, 10:08 PM

Quote:

Originally posted by newyawka@Jan 17 2006, 08:48 PM
ok old school prius chat peoples, the newbie here is confused. members of this site have recommended tire pressure of 40/somewhere near 40. yet the manual and inside the drivers side door list it at 35/33. anything over that is "unsafe" blah blah blah blah....and so forth...a little confusing. can ya help this kid? puh-weez?

[snapback]192185[/snapback]

It does depend upon which tyre you've got. I'm going to assume that you have the OEM Goodyear Integrity tyres. In that case, I believe that they are rated up to 44 psi. That's the highest safe pressure that you should maintain. There are quite a few folks out there that keep their tyres at 42/40 (front/rear). I keep mine at 40/38 but only because that's what TonyPSchaefer does. :P Seriously, though, the ride will be somewhat rougher the more you inflate the tyres, but road conditions will effect how that translates into the comfort of the ride. If you're blessed with pretty smooth roads then you probably won't notice much. Folks have reported that increasing the pressure does seem to translate into increased wear on the tyres.

newyawka · 01-17-2006, 10:21 PM

Quote:

Originally posted by tripp@Jan 17 2006, 10:08 PM
It does depend upon which tyre you've got. I'm going to assume that you have the OEM Goodyear Integrity tyres. In that case, I believe that they are rated up to 44 psi. That's the highest safe pressure that you should maintain. There are quite a few folks out there that keep their tyres at 42/40 (front/rear). I keep mine at 40/38 but only because that's what TonyPSchaefer does. :P Seriously, though, the ride will be somewhat rougher the more you inflate the tyres, but road conditions will effect how that translates into the comfort of the ride. If you're blessed with pretty smooth roads then you probably won't notice much. Folks have reported that increasing the pressure does seem to translate into increased wear on the tyres.

[snapback]192193[/snapback]

ahhh, sweet. thanks brotha.

roryjr · 01-17-2006, 10:28 PM

Isn't it supposed to increase fuel economy, too?

Jack 06 · 01-18-2006, 12:55 AM

The whole point of "overinflating" tires is to reduce the size of the "footprint" a tire has on the pavement at a given moment. (Compare racing bike tires and mountain bike tires.)

I disagree with what Tripp reports others' saying. In 45 years of inflating tires on 36 cars above what the door jamb/glove box sticker says, I don't think I've ever incurred more treadwear than the tires should have gotten. True, at some point in too much overinflation, you'll get disproportionate wear toward the center of the tread (as opposed to what most people get, which is premature wear on the edges caused by underinflation). But there's a pretty wide latitude where you'll get even wear.

Just remember, at least once a month, to turn your front wheels as far as you can when you park to give you a clear view of the entire width of the tread close-up. Look especially at the shallower grooves near the edges. Does the wear look uneven?

ex-NYer

benighted · 01-18-2006, 06:29 AM

Quote:

Originally posted by newyawka@Jan 17 2006, 06:48 PM
ok old school prius chat peoples, the newbie here is confused. members of this site have recommended tire pressure of 40/somewhere near 40. yet the manual and inside the drivers side door list it at 35/33. anything over that is "unsafe" blah blah blah blah....and so forth...a little confusing. can ya help this kid? puh-weez?

[snapback]192185[/snapback]

The manual says higher pressures are "unsafe" only because the chance of puncture is slightly greater. In actuality it is much more unsafe to run them underinflated. I run mine at 42/40, not only because of the increased economy but I like a firm ride. Also I find tires on my cars usually wear more on the outside than the middle tread because there are lots of curves and corners in my area, increasing the pressure helps slow this pattern.

Walker1 · 01-18-2006, 08:35 AM

[quote]
The manual says higher pressures are "unsafe" only because the chance of puncture is slightly greater. In actuality it is much more unsafe to run them underinflated. I run mine at 42/40, not only because of the increased economy but I like a firm ride. Also I find tires on my cars usually wear more on the outside than the middle tread because there are lots of curves and corners in my area, increasing the pressure helps slow this pattern.

On my 2006 tires it states on the tire that maximun pressure is 44 lbs. I am running 42/40. I think the "Book" is written by people that go by stats, math, etc. Reality is what works best without going over the maximum limit of the manufactuer.

Betelgeuse · 01-18-2006, 08:47 AM

Quote:

Originally posted by Jack 06@Jan 18 2006, 01:55 AM
The whole point of "overinflating" tires is to reduce the size of the "footprint" a tire has on the pavement at a given moment. (Compare racing bike tires and mountain bike tires.)

[snapback]192313[/snapback]

Exactly! Well put! I'll add that the largest "danger" in overinflating your tires is that you reduce the footprint so much that you don't have good traction on the road. Any amount of inflation (within a reasonable range, of course) is going to be a trade off between traction and mileage. If you inflate your tires more, you will have a smaller "footprint" (or, should it be "tireprint"?) on the road, so you'll have better mileage and less traction/control. If you inflate your tires less, you'll have worse mileage and more traction/control. The 42/40 level has been choosen by people here as a "safe" compromise between safety and fuel economy. I should point out that there's no real evidence that this is a "safe" pressure, aside from the fact that we're all still here to post on this board :P

As someone else pointed out, more inflation will also lead to a (somewhat) rougher ride. If you're in NYC, all of those potholes may make you wish that you hadn't inflated your tires so much. . .

darelldd · 01-18-2006, 11:25 AM

Pressure is good! Of course I'm coming from the world of EVs and high-pressure Low Rolling Resistance tires, so 50psi is the norm there.

Honestly though, in ALL cars I've owned, I air up to near the max of what it says on the sidewall. With increased pressure (to a point, mind you!), you get better handling, longer wear (they get less hot) and better mileage. I can't come up with a logical reason why a tire at 40psi would be more prone to puncture than a tire at 35psi. Yes, it is harder to puncture a deflated balloon, but in these cases, the tire is *almost* equally hard relative to something that would puncture it.

richard schumacher · 01-18-2006, 11:33 AM

Modern tires bulge hardly at all with higher pressures, so uneven wear is not a problem. Anything up to the max on the sidewall is safe *for the tire*, but the car's suspension and handling were designed assuming the pressures given on the door pillar; using a different pressure will change the handling noticeably and perhaps the car's stability. I use 40/38 and am still pondering the value of slightly better MPGs versus pounding the chassis a little harder. It makes me drive a little slower and more careful of avoiding road defects.

01-18-2006, 08:35 AM	#7
Walker1 Senior Member Join Date: Jan 2006 Location: FL Posts: 897 My Car: 2008 Prius Model: Package: #2 Thanks: 1 Thanked 2 Times in 1 Post Friends: 0	[quote] The manual says higher pressures are "unsafe" only because the chance of puncture is slightly greater. In actuality it is much more unsafe to run them underinflated. I run mine at 42/40, not only because of the increased economy but I like a firm ride. Also I find tires on my cars usually wear more on the outside than the middle tread because there are lots of curves and corners in my area, increasing the pressure helps slow this pattern. On my 2006 tires it states on the tire that maximun pressure is 44 lbs. I am running 42/40. I think the "Book" is written by people that go by stats, math, etc. Reality is what works best without going over the maximum limit of the manufactuer. __________________ 2008 Red Barcelona Prius, Pkg. 2 And dealer installed leather seats. Current milege is 13,000. 2006, Black, Pkg. 1, Tinted windows, Leather wrap wheel cover, leather arm rest cover. 41,000 Miles, Bought on 1/7/06. Lifetime fuel average: 52.4 MPG. As of 7/8/08 NO defects or any other problems. This car has NEVER been to the dealer for any reason. I run the A/C on 68-70 degrees almost all year long. Note: Both Prius's have NEVER been to a dlr. for any defects or repairs to date.

01-18-2006, 11:25 AM	#9
darelldd Prius is our Gas Guzzler Join Date: Jan 2006 Location: Northern CA Posts: 5,336 My Car: 2006 Prius Model: Package: #6 Thanks: 18 Thanked 44 Times in 32 Posts Friends: 12	Pressure is good! Of course I'm coming from the world of EVs and high-pressure Low Rolling Resistance tires, so 50psi is the norm there. Honestly though, in ALL cars I've owned, I air up to near the max of what it says on the sidewall. With increased pressure (to a point, mind you!), you get better handling, longer wear (they get less hot) and better mileage. I can't come up with a logical reason why a tire at 40psi would be more prone to puncture than a tire at 35psi. Yes, it is harder to puncture a deflated balloon, but in these cases, the tire is almost equally hard relative to something that would puncture it. __________________ -= Darell the EV Nut =- * EV Pages * Prius pages * PLEASE avoid sending me PMs!

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01-17-2006, 09:48 PM	#1
newyawka Join Date: Jan 2006 Location: long island Posts: 11 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	ok old school prius chat peoples, the newbie here is confused. members of this site have recommended tire pressure of 40/somewhere near 40. yet the manual and inside the drivers side door list it at 35/33. anything over that is "unsafe" blah blah blah blah....and so forth...a little confusing. can ya help this kid? puh-weez?

01-17-2006, 10:28 PM	#4
roryjr Senior Member Join Date: Sep 2005 Location: Warrenton, NC Posts: 221 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Isn't it supposed to increase fuel economy, too?

01-18-2006, 12:55 AM	#5
Jack 06 Join Date: Oct 2005 Location: Winters, CA: Prius capital of US. 30 miles W of Sacramento Posts: 2,567 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	The whole point of "overinflating" tires is to reduce the size of the "footprint" a tire has on the pavement at a given moment. (Compare racing bike tires and mountain bike tires.) I disagree with what Tripp reports others' saying. In 45 years of inflating tires on 36 cars above what the door jamb/glove box sticker says, I don't think I've ever incurred more treadwear than the tires should have gotten. True, at some point in too much overinflation, you'll get disproportionate wear toward the center of the tread (as opposed to what most people get, which is premature wear on the edges caused by underinflation). But there's a pretty wide latitude where you'll get even wear. Just remember, at least once a month, to turn your front wheels as far as you can when you park to give you a clear view of the entire width of the tread close-up. Look especially at the shallower grooves near the edges. Does the wear look uneven? ex-NYer

01-18-2006, 11:33 AM	#10
richard schumacher Destination: Eschaton Join Date: Mar 2004 Location: United States Posts: 5,515 My Car: 2004 Prius Model: N/A Package: #6 Thanks: 100 Thanked 93 Times in 66 Posts Friends: 0	Modern tires bulge hardly at all with higher pressures, so uneven wear is not a problem. Anything up to the max on the sidewall is safe for the tire, but the car's suspension and handling were designed assuming the pressures given on the door pillar; using a different pressure will change the handling noticeably and perhaps the car's stability. I use 40/38 and am still pondering the value of slightly better MPGs versus pounding the chassis a little harder. It makes me drive a little slower and more careful of avoiding road defects.