Put some air in those tires!

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DarkStar

Well-known member
Joined
Jul 17, 2010
Messages
2,066
Location
Hillsboro, Oregon, USA
Stopped by Harbor Freight today and picked up one of these:

image_3456.jpg

12 Volt, 100 PSI High Volume Air Compressor

I found it interesting that while the door label states a pressure of 36 PSI the factory installed tires have a maximum pressure rating (cold) of 44 PSI. Since we could technically put whatever tires on the vehicle we wanted to, I thought about the pressure situation and decided the tires probably know best on how many PSI they can handle, so I filled them up!

The efficiency difference between 36 PSI and 44 PSI should be very, very small, however using the portable 12 volt air compressor makes it really easy for me to now check my air pressure during my lunch break once a week.
 
Has anybody tried using the Air Compressor that comes with the LEAF?

Can it be used WITHOUT the can of "goo", just to inflate
slightly-soft tires?

I would expect there to be a noticable difference in "rolling
resistance" between 36 and 42 psi.
 
garygid said:
Has anybody tried using the Air Compressor that comes with the LEAF?

Can it be used WITHOUT the can of "goo", just to inflate
slightly-soft tires?.

Yes, I have used the air compressor that come with the LEAF. It works fine without using the "goo" that comes with it. By the way, it's the same air compressor that came with the smart car that I sold when I bought my LEAF.

I notice that http://www.tirerack.com has the OEM LEAF tires now.
 
LakeLeaf said:
garygid said:
I would expect there to be a noticable difference in "rolling
resistance" between 36 and 42 psi.

I would expect that too. There certainly is with other LRR cars.

I went to 40lbs last week and, yes, I do seem to be doing a bit better, particularly (for some reason I don't really understand) at higher speeds.
 
$92 + $18 ship for one tire.
$92 each + $53 ship for 4 tires
(shipping from Nevada to 92653 in Orange County, CA)

I think we are still working on getting a price from a Nissan dealer, right?

And, no price yet on a rim, either OEM or a much lighter but same-size rim, right?
 
Randy3 said:
Yes, I have used the air compressor that come with the LEAF. It works fine without using the "goo" that comes with it. By the way, it's the same air compressor that came with the smart car that I sold when I bought my LEAF.
That's very interesting! I didn't even bother trying to use the Continental air compressor because all the info I ever found on it seemed to indicate that it needed the tire sealant installed on it to function properly.
 
Sigh... Once more: The pressure on a tire's sidewall is the maximum allowed for that tire, not the recommended operating pressure. Rarely do you or should you run a tire at that pressure. Example: The tires on my BMW are very high performance tires and have a sidewall rating of 48 pounds. The recommended pressures for my car are 29 front/33 rear with normal load and 33 front/37 rear for maximum load. I run the latter. If I ran that car at 48 pounds not only would it ride like a truck, but the handling and braking would be significantly degraded. It would also be much harder on the suspension. But yeah, I might get a few extra tenths in mileage and a little better tire life... The tradeoff is not worth it in my opinion.

DarkStar said:
I found it interesting that while the door label states a pressure of 36 PSI the factory installed tires have a maximum pressure rating (cold) of 44 PSI. Since we could technically put whatever tires on the vehicle we wanted to, I thought about the pressure situation and decided the tires probably know best on how many PSI they can handle, so I filled them up!
 
mogur said:
Sigh... Once more: The pressure on a tire's sidewall is the maximum allowed for that tire, not the recommended operating pressure. Rarely do you or should you run a tire at that pressure. Example: The tires on my BMW are very high performance tires and have a sidewall rating of 48 pounds. The recommended pressures for my car are 29 front/33 rear with normal load and 33 front/37 rear for maximum load. I run the latter. If I ran that car at 48 pounds not only would it ride like a truck, but the handling and braking would be significantly degraded. It would also be much harder on the suspension. But yeah, I might get a few extra tenths in mileage and a little better tire life... The tradeoff is not worth it in my opinion.
So if you installed tires onto you Leaf that had a maximum sidewall pressure of 34 PSI you would still run them at 36 PSI per Nissan's sticker on the car? Probably not... If the tire is sized properly for the wheel it is mounted to, the tire manufacturer would know best what their tire should be inflated to, not the vehicle manufacturer. The information I've found also has stated running maximum sidewall pressure will decrease the possibility of hydroplaning and improve handling & braking.

Just a quick update on my experience though, we drove the car around a bit last night and I didn't notice any changes in the handling or "firmness" when hitting various bumps and potholes, definitely not "harder" on the suspension (though if I lost a few pounds that would probably help a bit)... :D
 
DarkStar said:
...If the tire is sized properly for the wheel it is mounted to, the tire manufacturer would know best what their tire should be inflated to, not the vehicle manufacturer...
Absolutely not. The correct pressure for the tire depends on the load (weight) which the car places on it and suspension setup and characteristics. The tire manufacturer does not control this. The tire manufacturer's (sidewall) pressure rating is the maximum pressure which could be used without risking blowing the tire sidewall or blowing it off the bead. It is by no means the "best" pressure for the tire, unless you value energy efficiency above your life.
 
1) You would never find a tire with a maximum pressure rating that low as it could not pass DOT tests, but being hypothetical for a moment and assuming that you could, yes, I would run the LOWER of the two numbers.
2) No, the tire manufacture does NOT know what tire pressure the tire should be inflated to as this is based on a number of variables that differ from vehicle to vehicle. All they know and tell you is the maximum pressure that the tire can be inflated to safely (in other words, the pressure above which it may fail).

All my information comes from the DOT and tire manufacturers websites and you can feel free to look it up. I'd like to see some similar supporting evidence for your position, please...


DarkStar said:
So if you installed tires onto you Leaf that had a maximum sidewall pressure of 34 PSI you would still run them at 36 PSI per Nissan's sticker on the car? Probably not... If the tire is sized properly for the wheel it is mounted to, the tire manufacturer would know best what their tire should be inflated to, not the vehicle manufacturer.
 
DeaneG said:
Absolutely not. The correct pressure for the tire depends on the load (weight) which the car places on it and suspension setup and characteristics. The tire manufacturer does not control this. The tire manufacturer's (sidewall) pressure rating is the maximum pressure which could be used without risking blowing the tire sidewall or blowing it off the bead. It is by no means the "best" pressure for the tire, unless you value energy efficiency above your life.
I'm not suggesting pressurizing the tire to 44 PSI without any "load" on the tire. I'm correctly including all loading on the tire and wheel assembly. No risk to my life (or anyone else) by utilizing the maximum ratings.
 
mogur said:
All my information comes from the DOT and tire manufacturers websites and you can feel free to look it up. I'd like to see some similar supporting evidence for your position, please...
No problem! The information can be found on most manufacturer's sites, however Bridgestone Tire has the following info:

From: http://www.tiresafety.com/

[...]for passenger tires, never exceed the maximum inflation pressure molded on the sidewall. The inflation pressure for light truck tires may exceed that molded on the tire by 10psi. Any recommended front to rear pressure differential should be maintained.
In another section:

For continuous high speed driving, tire pressures should be increased by 3 to 5psi above the normal cold inflation recommended [by the vehicle manufacturer].
While you may get more "comfort" by running your tires at the vehicle manufacturer PSI recommendations, the tires (when properly sized and mounted to wheels) are designed to function with 100% performance at their maximum sidewall pressure.
 
What you just quoted refutes your own comments.

First of all, Light Truck Tires are of different construction and use a different testing regime than passenger car tires, so none of that is applicable to our discussion of the Leaf.

Second, 3 to 5 pounds is a ways from 44 on the Leaf... (FYI, a 4 pound increase had been typical for many years in many car manufacturers recommendations but is no longer usually the case due to the type of construction of modern tires; it was mostly a hold over from bias ply and early radial tires without steel belts and current construction techniques.)

Third, their - or yours, it's unclear which it is - reference to 100% performance ONLY relates to maximum weight carrying ability, nothing else. No modern car comes even close to needing that maximum weight capability so that number is meaningless in our applications. It will, however, increase the insipid hydroplaning speed as that goes up by the square of the tire pressure...

Anyway, do what you want as it won't hurt anything and is not unsafe per se, but you are reading something in to the numbers that is not there, and I wouldn't personally recommend following suit to anyone...


DarkStar said:
mogur said:
All my information comes from the DOT and tire manufacturers websites and you can feel free to look it up. I'd like to see some similar supporting evidence for your position, please...
No problem! The information can be found on most manufacturer's sites, however Bridgestone Tire has the following info:

From: http://www.tiresafety.com/

[...]for passenger tires, never exceed the maximum inflation pressure molded on the sidewall. The inflation pressure for light truck tires may exceed that molded on the tire by 10psi. Any recommended front to rear pressure differential should be maintained.
In another section:

For continuous high speed driving, tire pressures should be increased by 3 to 5psi above the normal cold inflation recommended [by the vehicle manufacturer].
While you may get more "comfort" by running your tires at the vehicle manufacturer PSI recommendations, the tires (when properly sized and mounted to wheels) are designed to function with 100% performance at their maximum sidewall pressure.
 
DarkStar said:
... No risk to my life (or anyone else) by utilizing the maximum ratings.

To find out for sure, measure your 60-0 braking distance or lateral acceleration capability with the tires set at 36psi and then at 44psi. If your position were true, why wouldn't all car manufacturers just tell us to run the tires at the sidewall pressure? It would be easier for everybody.

The quickest way to adjust a car's understeer/oversteer characteristic is by changing tire pressure. Increasing pressure above nominal at the front or back of the car decreases grip and encourages that end to start sliding first. If you want both ends to start sliding first, just run 44psi.
 
More people have died because their tires pressure was too low than because it was too high. Max pressure listed on the sidewall has a 100% or more safety factor built in. Sidewall pressure has always been the pressure I run my cars at, measured cold of course.
 
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