Physics Question
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Le Mans Master
Joined: Oct 2004
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From: Toronto Ontario Canada
Physics Question
My Mechanical Engineer friend says that since I rarely have a passenger in my car that I really should overinflate the drivers side tires a few pounds. His rationale is that the drivers weight would be unevenly distributed to the left front and rear tires and if they are overinflated a bit the tire wear would be equalized on both sides. Is he right ?
Melting Slicks
Joined: Mar 2005
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From: Phoenix Arizona
No need to worry about that because the torque of the engine under acceleration tends to pull the engine to the right or passenger side so it causes the car to lean that direction offsetting the weight of the driver. You can also add a 150 lbs. of weight to the passenger seat. I know, I'm a real racer! 
Melting Slicks
Joined: Dec 2000
Posts: 2,076
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From: San Jose CA
I usually put one pound more on the left side vs. the right, and one pound more on the front vs. the rear, when there's no passenger or luggage. Probably not significant, but I think it's logical.
Melting Slicks
Joined: Mar 2005
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From: Las Vegas Nevada
2020 C8 of the Year Finalist - Unmodified
Originally Posted by b4i4getit
My Mechanical Engineer friend says that since I rarely have a passenger in my car that I really should overinflate the drivers side tires a few pounds. His rationale is that the drivers weight would be unevenly distributed to the left front and rear tires and if they are overinflated a bit the tire wear would be equalized on both sides. Is he right ?
Racer
Joined: Oct 1999
Posts: 286
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From: Southampton PA
Several things here.
1. If you look at the percentage weight difference that we're talking about it's not a few pounds, it's only about a pound or so (unless you weight 300 lbs). And who's to say that the left-right balance of the car is perfect to begin with?
2. Now, let's assume one side is slightly heavier. Does that necessarily mean more psi in the tire? What about front-rear differences in weight? Given the same tire size and construction, if a car is 60/40 split front to rear do you always put more air in the front to compensate?
1. If you look at the percentage weight difference that we're talking about it's not a few pounds, it's only about a pound or so (unless you weight 300 lbs). And who's to say that the left-right balance of the car is perfect to begin with?
2. Now, let's assume one side is slightly heavier. Does that necessarily mean more psi in the tire? What about front-rear differences in weight? Given the same tire size and construction, if a car is 60/40 split front to rear do you always put more air in the front to compensate?
Race Director
Joined: Oct 2004
Posts: 10,089
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Originally Posted by b4i4getit
My Mechanical Engineer friend says that since I rarely have a passenger in my car that I really should overinflate the drivers side tires a few pounds. His rationale is that the drivers weight would be unevenly distributed to the left front and rear tires and if they are overinflated a bit the tire wear would be equalized on both sides. Is he right ?
My car came from the factory with the ride height staggered, unfortunately the wrong way, ie it was lower on the passenger side than the driver's side with driver on board. So I adjusted the ride height screws so the car was level side to side with the driver on board. NASCAR mechanics call this wedge, and what I did was set the car up so that with the driver on board there was zero wedge.
A more sophisticated way to do this is to set the car up on scales so that the weight is the same side to side on the wheels. But setting the ride height level when the car is loaded the way it will be driven is almost as good, because the car's springs act like a spring scale, and only requires a ruler.
Advanced
Joined: May 2005
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Originally Posted by flyzlow
No need to worry about that because the torque of the engine under acceleration tends to pull the engine to the right or passenger side so it causes the car to lean that direction offsetting the weight of the driver. You can also add a 150 lbs. of weight to the passenger seat. I know, I'm a real racer!
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Le Mans Master
Joined: Aug 2000
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From: Austin Texas
Originally Posted by b4i4getit
My Mechanical Engineer friend says that since I rarely have a passenger in my car that I really should overinflate the drivers side tires a few pounds. His rationale is that the drivers weight would be unevenly distributed to the left front and rear tires and if they are overinflated a bit the tire wear would be equalized on both sides. Is he right ?
The statics of the issue is that the center of gravity of the driver is fairly close to the centerline of the car and the tires are close to the outside of the car. Thereby even if you weighted in at 300 pounds, you wuld only have about a 100 pound disadvantage on the drivers side compared to the passenger side.
