2001 Prism tire inflation

A few days ago Ray O recommended increasing tire inflation by 4 pounds. The car instructions specify 30 pounds. Wouldn't increasing this to 34
pounds affect the handling? How much of an improvement in gas mileage would this result in?
---MIKE---

>> (44 15' N - Elevation 1580')
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A few days ago Ray O recommended increasing tire inflation by 4 pounds. The car instructions specify 30 pounds. Wouldn't increasing this to 34 pounds affect the handling? How much of an improvement in gas mileage would this result in?
Why not keep gas mileage records and find out for yourself. In your case it will be minimal, probably less than 0.5 mpg. The handling will be affected, but this might not be a negative. Be sure to maintain the front to rear differential (if there is one). I had a 2003 Saturn Vue. The original pressure recommendation was 30 psi. GM upped the recommendation to 35 psi after they had problems with the suspension failing during rollover tests. I have always kept gas mileage records, so I got a good reading on the change. For a similar period (7200 miles at 30 psi and 35 psi) the mileage increased from 22.2 to 22.9 when I increased the pressure. The Vue is a heavier vehicle than yours, so the change is probably greater than in your case. But try it, just be sure to measure the mileage for both tire pressures over similar conditions and at least four tank fulls of gas for each pressure.
Ed
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---MIKE--- wrote:

Ray O is passing along some good advice. Most manufacturers suggest a tire inflation designed to provide a comfortable ride at the expense of handling, mpg and tread life.
Give this a try. It is not dangerous.
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A few days ago Ray O recommended increasing tire inflation by 4 pounds. The car instructions specify 30 pounds. Wouldn't increasing this to 34 pounds affect the handling? How much of an improvement in gas mileage would this result in?
---MIKE---

>> (44 15' N - Elevation 1580')
---------- Up to a point, higher tire inflation pressures will provide:
1) Reduced tread squirm, which prolongs tread life;
2) Reduced rolling resistance, which reduces fuel consumption;
3) Improved handling because the movement of the wheel is transmitted to the tread more quickly with less sidewall flex;
4) More tread wear in the center of the tread than on the shoulders, but I've noticed that at the manufacturer's recommended tire inflation pressure, the shoulders tend to wear more quickly than the center of the tread so the additional 4 psi evens wear.
5) Reduced heat buildup in the tire because there is less tread squirm and less sidewall flex
6) A harsher ride because there is less cushioning effect.
Manufacturers specify tire inflation pressures that give the best compromise between ride comfort, tread life, and handling, with the emphasis on ride comfort.
The main reason I recommend increasing tire pressure is reason #4 above - to even out the tread wear. To be honest, I suspect that the increase in fuel mileage will be negligible, but you will appreciate a longer tire life.
If you were going to enter the car in showroom stock races, then I would recommend increasing tire pressure up to the maximum listed on the tire.
--

Ray O
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Ray O wrote:

I run higher than normal by 2psi and find all of the above holds true. Also higher pressure gives higher aquaplane resistance. However it does reduce the contact patch and in dry and wet weather I find that affects grip fairly noticably. By 4psi im noticing a distinct lack of grip. But then i drive 'enthusiastically' most of the time. I never notice a difference in gas, but i have 25% drivetrain losses through full-time 4wd so i guess as a % of overall losses tyre loss is less on mine.
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Maybe a good idea is to run a few pounds higher in summer but lower in winter?
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wrote:

No. The lowest you should set tire pressure at any time of the year is the factory recommended tire pressure. Lowering tire pressure will result in even faster tread wear, and the weight of the vehicle tends to rest on the tire's shoulders instead of the center of the tread. Also, I've noticed that tire pressure tends to drop in the winter.
--

Ray O
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Ray O wrote:

Tire pressure will vary with air temperature. Lower temperatures will cause a decrease in tire pressure. So monitoring tire pressure during the fall is very important. In the spring as temperatures rise so will tire pressure. (PV=RT)
Winter tire pressure: lower pressure means a wider footprint. For snow that is NOT what you want. The wider footprint allows the tire to act like a ski and slid on top of the snow rather than dig down into the snow for greater traction.
Tread wear: if you are not convinced that Ray O is correct go out and buy a $2 tire tread depth gauge at any auto parts store. Measure the tread depth in the middle and both outside and inside edges of each tire. Keep track of tire tread depth for 10,000 miles at Ray O's +4 psi then drop tire pressures and run another 10,000 miles. You should be able to measure the difference in tire wear rate. (I ran my Corolla at +7 psi front and +4 psi rear to get maximum wear from a particular set of tires.)
YMMV
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On 14/6/06 2:56 AM, in article snipped-for-privacy@f6g2000cwb.googlegroups.com,

Nearly. You missed the "n" i.e. PV=nRT and that that is for an ideal gas. Also consider the diffusion of air through valves, sidewalls etc.
Hammo
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"Ray O" <rokigawaATtristarassociatesDOTcom> wrote:

oops..yes sorry
That is what I meant.... to run pressure at recommended level in winter but a bit more in summer
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I have run tire pressure at least 4 PSI over the manufacturer's recommended tire pressure year-round on the 9 Toyotas/Lexus I have owned as well as on the 50 or 60 demos I was assigned when I worked for a fairly successful automaker and drove around 50 K miles per year.
You are free to run your tire pressure at whatever you think is appropriate for you.
--

Ray O
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wrote:

reduce contact patch ? Usually it actually increases it because the middle of the tire now wears evenly with the outsides. The manufacturer's suggested psi is too low, period. It only benefits the comfort of the car.

so you claim to loose grip with 4wd full time. What do you drive on ? Black Ice ???? Give me a break.
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Interesting
I didn't now the above
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