max oem tire pressure

rookie101 · 03-18-2008, 09:21 PM

what is the most psi any1 has run in the oem tires. im using 42/40 now but i think a higher psi would work out better.

john1701a · 03-18-2008, 09:29 PM

I ran 44/42 with my Allegras on my Classic Prius. Then the same on the OEMs from the HSD Prius. And continued on with it when later switching to HydroEdges.

Max Cold PSI is no big deal. Tires nowadays hold there shape wonderfully at the highest stated pressure.

.

SpartanScott · 03-18-2008, 10:10 PM

I used 49/47psi for a 3000 mile roadtrip which resulted in 50MPG for 30 degree temps and 55MPG for 50+ degree temps. Total trip average was 52.7MPG. Speeds ranged from 65-80mph (71mph avg). After the trip I deflated to the usual 44/42. I am sure it helped with my fuel economy, but not by much. Most of the improvement comes from getting the psi out of the 30's.

bwilson4web · 03-19-2008, 05:17 AM

My Sumitomo are rated at 51 psi and I run that pressure all the time without a problem. I'm getting excellent mileage and it corners like it is on rails.

Bob Wilson

JimboK · 03-19-2008, 07:16 AM

I know of some that have run 60+.

eestlane · 03-19-2008, 10:53 AM

Ah! The cult of the high tire pressures to get a couple more mpg and a stiff ride.

Lets see now, the Toyota engineers were smart enough to design a very complicated and efficient car. Remember, the main goal for them was to design a fuel efficient car, and that includes the tire pressures. But from what I read on this forum, they were totally stupid when, after running hundreds of hours of tests of tires at various pressures, they decided to "arbitrarily" recommend 35 and 33 psi for the Prius. Come on now, folks, there is a lot of wrongheaded thinking going around. Sure, you want the best gas mileage, but there are other things to consider that the Toyota engineers probably figured in. For example, the extra wear and detuning effects on the suspension components and the rest of the car. As a fellow engineer, I resent the second-quessing by many untrained people in this matter. If the tire pressures are so totally wrong, the rest of the car must also be quite poorly designed and therefore you should not have bought it.

cyberprius · 03-19-2008, 11:15 AM

Quote:

Originally Posted by eestlane

Ah! The cult of the high tire pressures to get a couple more mpg and a stiff ride.

If the tire pressures are so totally wrong, the rest of the car must also be quite poorly designed and therefore you should not have bought it.

This is a question, I suppose, but I put the tire pressure at 42/40after reading comments on this board. Since then I have had two flats in two months, which according to my "tire guy" were caused by rocks (I drive on lots of marginal dirt roads).

However, two other cars "in the family" driving much the same roads with Kumho tires at 30/30 and 28/28 have had no flats in the past couple of years.

So, is it possible that higher pressures make the tire more likely to have flats on gravel. Or is the Goodyear Integrity just a "less better tire?"

David Beale · 03-19-2008, 11:15 AM

The tire pressures are usually specified by the tire manufacturer. The tires shipped with the car are usually chosen at "the last minute", to get the best price. So the pressure is usually specified from a table, tested quickly, and set in stone. Often incorrectly!

Do not run more than the max pressure on the sidewall. A tire engineer warned me (and anyone else who would listen) that with "too much" pressure in the tire, you could damage it internally if you hit at speed an abrupt road transition, such as a pothole. Being an engineer, he works on the safe side, so recommended pressures below the max rating on the sidewall.

If you go to a tire store and look at the max pressure ratings on the sidewalls of actual tires, you will note the better quality tires have higher numbers than the poor quality tires. The Goodyear Integrity is a low cost tire, so consider it a "poorer quality" one. For example, it is rated at 44 PSI max, while the same size Nokian WR is rated at 54 PSI max.

I run a nice conservative 40 PSI front, 38 PSI rear, with Nokian WR tires in the 15" stock size.

eestlane · 03-19-2008, 11:50 AM

[quote=David Beale;580774]The tire pressures are usually specified by the tire manufacturer. The tires shipped with the car are usually chosen at "the last minute", to get the best price. So the pressure is usually specified from a table, tested quickly, and set in stone. Often incorrectly!

I can agree with your statement above for the 2004 Prius, but for this "hastily recommended " tire pressure to continue through the 2008 model year without some sort of review and recommendation change does not seem credible. Especially if they increased the pressure, and could then advertise an even better mpg.

bbald123 · 03-19-2008, 11:59 AM

No, tire pressures are set by the auto manufacturer to achieve the desired sidewall spring rates and rebound rates.

This is the basis for the suits against Ford in the Bronco roll-overs of some years ago. They specified an unsafely low tire pressure to avoid re-engineering the suspension to gain desired ride qualities.

The tire manufacturer certifies maximum tire pressures and load ratings.

03-18-2008, 09:21 PM	#1
rookie101 average member Join Date: Jan 2008 Location: hatfield PA Posts: 22 My Car: 2008 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	max oem tire pressure what is the most psi any1 has run in the oem tires. im using 42/40 now but i think a higher psi would work out better.

03-18-2008, 09:29 PM	#2
john1701a Senior Member Join Date: Jan 2004 Location: Minnesota Posts: 2,548 My Car: 2004 Prius Package: Pioneer #3 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 3	Re: max oem tire pressure I ran 44/42 with my Allegras on my Classic Prius. Then the same on the OEMs from the HSD Prius. And continued on with it when later switching to HydroEdges. Max Cold PSI is no big deal. Tires nowadays hold there shape wonderfully at the highest stated pressure. .

03-18-2008, 10:10 PM	#3
SpartanScott Michigan Member Join Date: Mar 2007 Location: South Lyon, Michigan Posts: 52 My Car: 2007 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: max oem tire pressure I used 49/47psi for a 3000 mile roadtrip which resulted in 50MPG for 30 degree temps and 55MPG for 50+ degree temps. Total trip average was 52.7MPG. Speeds ranged from 65-80mph (71mph avg). After the trip I deflated to the usual 44/42. I am sure it helped with my fuel economy, but not by much. Most of the improvement comes from getting the psi out of the 30's.

03-19-2008, 05:17 AM	#4
bwilson4web Senior Member Join Date: Nov 2005 Location: North Alabama Posts: 1,357 My Car: 2003 Prius Package: #1 Nominated 2 Times in 2 Posts TOTM Awards: 0 Friends: 5	Re: max oem tire pressure My Sumitomo are rated at 51 psi and I run that pressure all the time without a problem. I'm getting excellent mileage and it corners like it is on rails. Bob Wilson

03-19-2008, 07:16 AM	#5
JimboK One owner, low mileage Join Date: May 2006 Location: Chesterfield, VA Posts: 1,901 My Car: 2005 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 2	Re: max oem tire pressure I know of some that have run 60+.

03-19-2008, 10:53 AM	#6
eestlane Member Join Date: Sep 2007 Location: Space Coast, FL Posts: 47 My Car: 2007 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: max oem tire pressure Ah! The cult of the high tire pressures to get a couple more mpg and a stiff ride. Lets see now, the Toyota engineers were smart enough to design a very complicated and efficient car. Remember, the main goal for them was to design a fuel efficient car, and that includes the tire pressures. But from what I read on this forum, they were totally stupid when, after running hundreds of hours of tests of tires at various pressures, they decided to "arbitrarily" recommend 35 and 33 psi for the Prius. Come on now, folks, there is a lot of wrongheaded thinking going around. Sure, you want the best gas mileage, but there are other things to consider that the Toyota engineers probably figured in. For example, the extra wear and detuning effects on the suspension components and the rest of the car. As a fellow engineer, I resent the second-quessing by many untrained people in this matter. If the tire pressures are so totally wrong, the rest of the car must also be quite poorly designed and therefore you should not have bought it.

03-19-2008, 11:15 AM	#8
David Beale Senior Member Join Date: Jul 2006 Location: Edmonton Alberta Posts: 1,343 My Car: 2007 Prius Package: B Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: max oem tire pressure The tire pressures are usually specified by the tire manufacturer. The tires shipped with the car are usually chosen at "the last minute", to get the best price. So the pressure is usually specified from a table, tested quickly, and set in stone. Often incorrectly! Do not run more than the max pressure on the sidewall. A tire engineer warned me (and anyone else who would listen) that with "too much" pressure in the tire, you could damage it internally if you hit at speed an abrupt road transition, such as a pothole. Being an engineer, he works on the safe side, so recommended pressures below the max rating on the sidewall. If you go to a tire store and look at the max pressure ratings on the sidewalls of actual tires, you will note the better quality tires have higher numbers than the poor quality tires. The Goodyear Integrity is a low cost tire, so consider it a "poorer quality" one. For example, it is rated at 44 PSI max, while the same size Nokian WR is rated at 54 PSI max. I run a nice conservative 40 PSI front, 38 PSI rear, with Nokian WR tires in the 15" stock size. __________________ Edmonton Alberta "Pearl" is a 2007 Driftwood Pearl Prius.

03-19-2008, 11:50 AM	#9
eestlane Member Join Date: Sep 2007 Location: Space Coast, FL Posts: 47 My Car: 2007 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: max oem tire pressure [quote=David Beale;580774]The tire pressures are usually specified by the tire manufacturer. The tires shipped with the car are usually chosen at "the last minute", to get the best price. So the pressure is usually specified from a table, tested quickly, and set in stone. Often incorrectly! I can agree with your statement above for the 2004 Prius, but for this "hastily recommended " tire pressure to continue through the 2008 model year without some sort of review and recommendation change does not seem credible. Especially if they increased the pressure, and could then advertise an even better mpg.

03-19-2008, 11:59 AM	#10
bbald123 Thermodynamics Law Enforcement Join Date: Nov 2007 Location: Harrisburg, PA Posts: 192 My Car: 2008 Prius Package: #6 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: max oem tire pressure No, tire pressures are set by the auto manufacturer to achieve the desired sidewall spring rates and rebound rates. This is the basis for the suits against Ford in the Bronco roll-overs of some years ago. They specified an unsafely low tire pressure to avoid re-engineering the suspension to gain desired ride qualities. The tire manufacturer certifies maximum tire pressures and load ratings.