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Midlife

Finding proper tire pressure

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Guys, it is amazing what so-called professional tire stores tell customers about proper tire pressure.  I have a 80k 2010 car and the service manager immediately went to the door panel to see what the manufacturer recommended for tire pressure.  WRONG!  That's the pressure recommended for the tires provided with the car when sold new.  Every tire model has its own unique profile/design and the tire pressure changes whenever that tire model goes onto various different vehicles.  Tires recommend maximum tire pressure but that is NOT what the pressure should be.  So...how do you determine optimum tire pressure?

Start with the obvious: you want the tire to have maximum contact with the road and you do that by examining the tread contact with the pavement.  Here's how I do it: a run a line of water in front of the tire and drive the car over the water far enough that the water left by the tire track is completely dry.  Examine the water mark across the tread: when tire pressure is optimum, the water pattern when the track just reaches dry-ness should be equal across the entire tread.  If the water drys first in the center and last at the edges, then the tire is underinflated.  If the water pattern drys last in the center and first at the edge, then the tire is overinflated.  Adjust tire pressure so that you have a consistent, even pattern.  Do this for all four tires and the pressures should be fairly equal.  You can average the four if they are not too far off.  Some cars may have such a weight different from front to back that you may have to vary tire pressure front and back. 

I've been doing this for 20+ years after being told this by a former tire mechanic.  Most tire stores have never heard of this and refuse to believe it.  It works!

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I have never used this water method.  Sounds pretty cool. 

I typically use the door sill pressure as a guide, as it is tied to the load rating of the original equipment tires, especially in my truck when I am towing something.

I will have to check into the water method with my local tire guru, we can compare notes.....

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On 2/5/2020 at 7:59 PM, Midlife said:

Guys, it is amazing what so-called professional tire stores tell customers about proper tire pressure.  I have a 80k 2010 car and the service manager immediately went to the door panel to see what the manufacturer recommended for tire pressure.  WRONG!  That's the pressure recommended for the tires provided with the car when sold new.  Every tire model has its own unique profile/design and the tire pressure changes whenever that tire model goes onto various different vehicles.  Tires recommend maximum tire pressure but that is NOT what the pressure should be.  So...how do you determine optimum tire pressure?

Start with the obvious: you want the tire to have maximum contact with the road and you do that by examining the tread contact with the pavement.  Here's how I do it: a run a line of water in front of the tire and drive the car over the water far enough that the water left by the tire track is completely dry.  Examine the water mark across the tread: when tire pressure is optimum, the water pattern when the track just reaches dry-ness should be equal across the entire tread.  If the water drys first in the center and last at the edges, then the tire is underinflated.  If the water pattern drys last in the center and first at the edge, then the tire is overinflated.  Adjust tire pressure so that you have a consistent, even pattern.  Do this for all four tires and the pressures should be fairly equal.  You can average the four if they are not too far off.  Some cars may have such a weight different from front to back that you may have to vary tire pressure front and back. 

I've been doing this for 20+ years after being told this by a former tire mechanic.  Most tire stores have never heard of this and refuse to believe it.  It works!

Midlife, your method did not work for me, it has been 2 days and the black tracks are not drying up.

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