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mwalsh
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Re: Put some air in those tires!

Sun Apr 10, 2011 9:17 am

DarkStar wrote:though if I lost a few pounds that would probably help a bit)... :D


Yeah, I need to loose 30-40lbs myself before I even consider spending 100s of $ on wheels that will shave 10lbs off each corner! :lol:
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TomT
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Re: Put some air in those tires!

Sun Apr 10, 2011 9:17 am

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 wrote: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.
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TomT
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Re: Put some air in those tires!

Sun Apr 10, 2011 9:18 am

Yeah, I'm currently on my unsprung mass diet myself!

mwalsh wrote:Yeah, I need to loose 30-40lbs myself before I even consider spending 100s of $ on wheels that will shave 10lbs off each corner! :lol:
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DarkStar
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Re: Put some air in those tires!

Sun Apr 10, 2011 9:25 am

DeaneG wrote: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.
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DarkStar
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Re: Put some air in those tires!

Sun Apr 10, 2011 9:31 am

mogur wrote: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.
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TomT
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Re: Put some air in those tires!

Sun Apr 10, 2011 9:50 am

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 wrote:
mogur wrote: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.
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DeaneG
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Re: Put some air in those tires!

Sun Apr 10, 2011 10:23 am

DarkStar wrote:... 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.
Last edited by DeaneG on Sun Apr 10, 2011 10:26 am, edited 1 time in total.
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garygid
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Re: Put some air in those tires!

Sun Apr 10, 2011 10:26 am

More pressure, less comfortable ride.
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Re: Put some air in those tires!

Sun Apr 10, 2011 10:30 am

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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TomT
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Re: Put some air in those tires!

Sun Apr 10, 2011 10:40 am

Really? And it says this where?

Herm wrote: Max pressure listed on the sidewall has a 100% or more safety factor built in.
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