I want 42/40!

benighted · 01-14-2006, 05:53 AM

On Wednesday I went to Les Schwab to have my tires rotated and asked the guy to make my tires "42 in the front and 40 in the back". But after I got the car home I found a dissapointing 36 PSi all around. Today(technically yesterday, its 2:45AM) I took it back and asked them to put the right amount of air in my tires and he looked at me like I was crazy and asked "Why so much air?" So I told him why(gas mileage, handling). He also told me that having that much air is a bit more dangerous because it can be penetrated by road hazards easier but the tire is rated for 44 so he went ahead and did it. So far everyone has been reluctant to add the right amount of air. How many of you have had this experience?

Tempus · 01-14-2006, 01:42 PM

I voted "Other" because I don't know or care what a service person does to my air pressure. The first thing I do when they hand me the fob is adjust it myself, just like I check the oil level before I drive off.

QED · 01-14-2006, 01:52 PM

I voted other. I adjust my own tire pressure. I currently use 37/35. Until I research it further, I am reluctant to increase the pressure 20% over the recommended 35/33, to 42/40 (but that's another tread).

Frank Hudon · 01-14-2006, 02:24 PM

well 36 was way better than the 28 all round when I bought the car. Drove to the nearest gas station pumped to 42F 40R and hit the hiway and 1830Km's later was home. Been 42 40 ever since. On last weeks check they were 41 39 and I pumped to 42 40.

mehrenst · 01-14-2006, 02:52 PM

I run 40/38. The dealer I use for service has cautioned me both times that it could contribute to tire wear at the center of the tread. However, they set it to what I specify and just make a note on my service order.

WHile I bought my Prius at Toyota 101 in Redwood Cit, CA I get it serviced at Putnam Toyota in Burlingame as a matter of convience (its near a train station). I've been very happy with them.

EricGo · 01-14-2006, 03:41 PM

Quote:

Originally posted by benighted@Jan 14 2006, 06:53 AM
So far everyone has been reluctant to add the right amount of air. How many of you have had this experience?

[snapback]189721[/snapback]

I keep an air guage in the car, and check tyre pressures when I fill up.
On the occasions I have brought the car in for an oil change, I have mentioned that I keep the tyres at 42/40 so that they do not release pressure.

GreenMachine · 01-14-2006, 03:52 PM

Quote:

Originally posted by EricGo@Jan 14 2006, 03:41 PM
I keep an air guage in the car, and check tyre pressures when I fill up.
On the occasions I have brought the car in for an oil change, I have mentioned that I keep the tyres at 42/40 so that they do not release pressure.

[snapback]189943[/snapback]

Eric, since you normally would be driving the car when you stop to fill up, the tires wouldn't necessarily be cold. How do you adjust for that to get the equivalent of 42/40 cold tire pressure? Is there some formula you use?

EricGo · 01-14-2006, 04:39 PM

Quote:

Originally posted by GreenMachine@Jan 14 2006, 04:52 PM
Eric, since you normally would be driving the car when you stop to fill up, the tires wouldn't necessarily be cold. How do you adjust for that to get the equivalent of 42/40 cold tire pressure? Is there some formula you use?

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Hi GreenMachine,

You are right -- I am probably off by a psi or two.
A fellow named Dan Kroushi in Pennsylvania showed that very minimal differences in fuel economy accrue in the 38 - 42 psi range on the Prius stock tyres, so I use 40/38 in the summer and 42/40 in the winter. I have checked tyre pressures at home a couple of times, and never found pressures under 38.

I have seen a calc that corrects for temperature, but cannot remember details -- only that in my local climate range of -10* -- 35 C, it was not a big deal.

If PV = nRT is a fair approximation, and Temp is in Kelvin, a change of 27C degrees would be about a 10% change in pressure.

*addendum -- fixed error

Vincent · 01-14-2006, 06:55 PM

My 06 is Staying at 35/33

Maybe it's just an 06 thing, but after driving an 05 TRAC rental for 4 months and 6,900 miles at 40/38 I'm keeping the Integritys at the factory 35/33 settings. The 06 ride is smoother and quieter (although I'm sure it's mostly the new noise/harshness improvements), and I'm at the same 47-48 MPG I was getting with the 40/38 hard riding 05.

**Tideland Prius** · 01-15-2006, 12:40 AM

Mine's bumped to 37/35. Yeah, it's much stiffer than 30/32 when I checked after x months. Funny how the front lost more air than the rear.

View Poll Results: Is your shop/dealer/tire supplier reluctant to put the amount of air you want?
Yes.	34	52.31%
No.	20	30.77%
Other (post)	11	16.92%
Voters: 65. You may not vote on this poll

01-14-2006, 05:53 AM	#1
benighted Chief thread hijacker Join Date: Sep 2005 Location: Westport, WA Posts: 530 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	On Wednesday I went to Les Schwab to have my tires rotated and asked the guy to make my tires "42 in the front and 40 in the back". But after I got the car home I found a dissapointing 36 PSi all around. Today(technically yesterday, its 2:45AM) I took it back and asked them to put the right amount of air in my tires and he looked at me like I was crazy and asked "Why so much air?" So I told him why(gas mileage, handling). He also told me that having that much air is a bit more dangerous because it can be penetrated by road hazards easier but the tire is rated for 44 so he went ahead and did it. So far everyone has been reluctant to add the right amount of air. How many of you have had this experience?

01-14-2006, 01:42 PM	#2
Tempus Senior Member Join Date: Feb 2004 Location: Washington DC Posts: 1,693 My Car: 2004 Prius Model: Package: #9 Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I voted "Other" because I don't know or care what a service person does to my air pressure. The first thing I do when they hand me the fob is adjust it myself, just like I check the oil level before I drive off.

01-14-2006, 01:52 PM	#3
QED Join Date: Nov 2005 Location: Sunny Hawaii Posts: 267 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I voted other. I adjust my own tire pressure. I currently use 37/35. Until I research it further, I am reluctant to increase the pressure 20% over the recommended 35/33, to 42/40 (but that's another tread).

01-14-2006, 02:24 PM	#4
Frank Hudon Senior Member Join Date: Jan 2004 Posts: 4,144 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	well 36 was way better than the 28 all round when I bought the car. Drove to the nearest gas station pumped to 42F 40R and hit the hiway and 1830Km's later was home. Been 42 40 ever since. On last weeks check they were 41 39 and I pumped to 42 40.

01-14-2006, 02:52 PM	#5
mehrenst Senior Member Join Date: May 2005 Location: San Jose, CA Posts: 411 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I run 40/38. The dealer I use for service has cautioned me both times that it could contribute to tire wear at the center of the tread. However, they set it to what I specify and just make a note on my service order. WHile I bought my Prius at Toyota 101 in Redwood Cit, CA I get it serviced at Putnam Toyota in Burlingame as a matter of convience (its near a train station). I've been very happy with them.

01-14-2006, 06:55 PM	#9
Vincent Don't Wait Until Tomorrow Join Date: Sep 2005 Location: South Florida Posts: 635 My Car: 2010 Prius Model: V Package: Navigation Thanks: 0 Thanked 21 Times in 13 Posts Friends: 0	My 06 is Staying at 35/33 Maybe it's just an 06 thing, but after driving an 05 TRAC rental for 4 months and 6,900 miles at 40/38 I'm keeping the Integritys at the factory 35/33 settings. The 06 ride is smoother and quieter (although I'm sure it's mostly the new noise/harshness improvements), and I'm at the same 47-48 MPG I was getting with the 40/38 hard riding 05.

01-15-2006, 12:40 AM	#10
Tideland Prius Moderator of the North Join Date: Oct 2004 Location: Canada Posts: 19,633 My Car: 2010 Prius Model: N/A Package: Technology Package (Canada) Thanks: 229 Thanked 346 Times in 245 Posts Friends: 23	Mine's bumped to 37/35. Yeah, it's much stiffer than 30/32 when I checked after x months. Funny how the front lost more air than the rear.