Re: Tirerack: If BMW 50/50, why 4 more psi in rea (archive)

Manufacturers base their recommended pressures on several factors after lots of testing. To put it in simple terms, these are the most important criteria:

1. Load requirement
2. Handling
3. Ride comfort

First and foremost, the tires have to properly maintain the weight of the vehicle. The pressures listed would represent the MINIMUM amount of air required to safely carry the weight of the vehicle.

Second, BMW wants to take handling into consideration and by using lower pressures up front, it helps dial in some understeer, which is a very safe handling characteristic.

Lastly, manufacturers want the car to have a comfortable ride. Lower pressures mean comfortable ride, but again, they won't go lower than what is safe for the tire to maintain weight requirements. Even if the weight distribution is 50/50, they may stagger the pressure to get the ride/handling characteristics they want.

Why does BMW recommend 4 more psi for the rear tires? How does BMW determine the recommended psi? In other words, why 29/33 instead of 31/35 etc.? Thanks a lot, if you can answer this, because no one seems to have an answer.

Follow Ups:

[ Follow Ups ] [ Wheel/Tire Message Board ] [ Msg. Board FAQ ]

Questions, comments, or problems, please visit the Roadfly help desk.