Question for tire pressure!

[keninpa]

Can anyone explain why the front tire to rear tire psi levels are 5 psi?

I have the stock 205/55/16 tires. BMW recommends 30 psi front and 35 psi rear.

Back in September when we got the car it had 38 psi in the front and 45 psi in the rear.
This made for an awfully bumpy ride. I immediately reduced it to 32 psi front and 36 psi rear.

How will this effect handling and tire wear? Anyone have any suggestions?

Thank you!

Ken

 

[bmwrocks]

Check the placard on the drivers side front door jamb. It shows the recommended tire pressures under various weight conditions. Mine shows 32 front and 38 rear.

As to why the front is lower than the rear, I think it is for putting more rubber on the road (less pressure) for the fronts as they are the steering wheels???

 

[MrElussive]

When dealerships prep the car, they often just inflate them to some random level...I don't think they take the time to care about filling the tires up with the proper air pressure. The rear tires require more air because the vehicle is RWD and the driving tires have the most stress put on them (acceleration of the car). It is not uncommon for a RWD car to require a higher air pressure in the back than in the front.
I believe BMW has two recommended levels of air pressure: Normal and Maximum Load (something along those lines). Max load is the one that has the higher pressure ratings. Filling up the tires to the "Normal" level will provide the smoothest ride. Filling up the tires to the "Maximum" level will provide the best handling and the best tire wear. When you are adjusting your tire pressures, make sure the tires are cold and that you do not overfill the tires. Significantly over-inflating the tires will result in a higher chance of a flat tire due to road irregularities and/or quicker tire wear.

 

[mscoins]

Significantly over-inflating the tires will result in a higher chance of a flat tire due to road irregularities and/or quicker tire wear.

Also there will less tread meeting the road surface which means less traction in adverse weather conditions. FWIW, my service tech recommends inflating 1 psi above max if you drive aggressively.

 

[MrElussive]

FWIW, my service tech recommends inflating 1 psi above max if you drive aggressively.

Good point, that is exactly what I do for my own car (I run at 36psi, one psi over). Really great if you are a flat-out "sprited" driver.