Brand: Will tire with low pressure place stress on drivetrain? - Minneapolis Star Tribune
Q: You’ve spent a lot of ink on tire diameter differences caused by unusual tire wear. How about describing the impact of one low-air-pressure tire on the AWD system. I run my tires at 35 psi except for one wheel with a leaky alloy rim. Sometimes it is down to around 25 psi before I get to it. How much is that changing the effective wheel diameter (and affecting my AWD mechanicals). I’d never really thought about this scenario before, so let’s explore it. Intuitively, it seems logical that a significant decrease in air pressure would reduce the rolling diameter of a tire. That’s confirmed by the fact that several tire pressure monitoring systems monitor the distance between the axle centerline and the pavement — a significant drop in pressure would give a shorter reading on the sensor, which is interpreted as low... I used a plumb line dropped from the top of the tire, through the wheel’s centerline to the garage floor. I marked the tire and the floor at the plumb bob’s point. With the tire inflated to its normal 35 psi, I rolled the vehicle backward exactly one tire revolution and marked the floor at that spot. I then dropped the tire pressure in that tire to 25 psi and rolled the vehicle forward exactly one tire revolution and marked that spot. Using the equation for diameter — circumference divided by pi — the 35 psi tire was 30. 97” in diameter while the same tire at 25 psi was 30. 90” in diameter. Source: www.startribune.com
