netjazz

Thought ride on my 545ia Sport was a bit to firm.(Got Dunlop run-flats)
Just have it a couple of weeks. Dealer delivered car with 37 PSI in front and 40 PSI in rear. Plate in car on drivers side door and manual shows inflation should be 32 PSI front and 35 PSI rear. Knocked the pressure down to these levels and see quite a difference.
Ride is no longer to firm,but now ideal. Even handling seems better. Most dealers and repair tire supply shops tend to over inflate tires. I recently bought a new set of tires for my 528i and the guy that did the installation had 50 PSI i/o 38/41, and the ride was like a rock. Could also be dangerous in real hot weather.
If you think your ride is to firm, double check the PSI against what is indicated on your door plate. You might be suprised by what you see. (and feel) I always check pressure on my cars at least once per month to see if pressure is low, and after every trip for service to make sure they got it right.

bmw545

I put 34 for the fronts and 38 for the rears.
I think it handles pretty well and pretty comfortable too.

JDN

I had a similar experience. Car was delivered over pressure in all four tires.

Lomag

The pressure setting depends on the load you carry in the car. If you're the only passenger or perhaps with one passenger then the minimum pressure of 32/35 psi would be okay. If you're carrying a full load (4 people + trunk stuff) then the recommended pressure is 38/42 psi. The higher pressure also protects the rims from pothole damage at the sacrifice of ride quality as we've all noticed.

I personally run 38/42 and when I got the car the pressures were 42/45, even higher!! I've never tried to lower them and I don't think I want to as I don't see the ride quality all that bad, not perfect either but.. I'd like to protect my rims too.

DrT

Now here's an interesting one. In a car hailed by BMW as being a near perfect 50:50 weight distribution, why are the rear tyres inflated 20% more than the front ? Asked my service manager the same thing, he said the car was heavier in the rear. So who's right ?

browellm

It's probably something to do with sprung and unsprung mass

/blag mode off/

This is good advice to anyone - check your tyre pressures.

Handling, stopping distances, safety, fuel economy and more are all affected. I had a tyre pressure warning the other day so checked all 4 tyres. Because the steering and handling are so communicative, I noticed a big difference after altering the tyre pressures.

JDN

The rear likely has higher pressure because those are the drive wheels. Also, that is where we stow our gear that would cause the rear to be somewhat heavier. Further, the Sport package has bigger tires on the rear.