bruceholmes

My background is in go kart racing, a quarter pound or half a pound of air pressure can make a significant difference in track performance but for my cars I am wanting to conduct a poll so as to get an idea of what people found to be useful tire pressures for a relatively aggressive driving style where performance is preferred over comfort. I have an 03 M5 and 04 530i. Both have the factory wheels with Michelin PS/2's on the M5 and Goodyear eagle F1 GSD3 on the 04 530i. I found on the M5 that the PS/2's are dramatically superior to the runflat's that came with the car. I've only had one flat which was fixed with the aerosol can of goo until I could get to the tire dealer but otherwise that's the only drawback. The Goodyear eagle Formula One GSD3's are awesome, make the Dunlop runflat's feel like they had been taken off a coal cart from the last century, maybe make that two centuries ago!!!!

So what have you found to be good tire pressures? My personal opinion is that the factory recommendations are too soft and give a mushy feeling from handling/performance standpoint. My dealer states that the lower air pressures enhance tire longevity but the statement immediately made me realize that he is seriously out of touch with the physics of tire dynamics.

The roads in southern California where I live are generally reasonably well-maintained but the concrete freeway is are often times pretty broken up and uneven. Currently in the M5 I am running 44 pounds in the back and 40 pounds in the front tires. Any suggestions, comments and/or perspectives would be appreciated.

cobradav

Over the past few years, since about '95, I have always run at the highest of the recommended tire/car numbers. If they gave a range I went to the highest. If they gave a pressure for max load then I used that. My tire life seemed to be at high end for tire. For instance a 30k tire I might get 40K miles. A 50k I might get 60K miles, etc. My ride was or is maybe a little more stiff but worth it to me. I will say that when tracking/autocrossing, etc most experts would say let out a 1/2 PSI for safety (not wanting the heated up tires to over-expand). Not running your configuration my actual pressures are not relevant to your set up so I won't give my PSI, but just agree high (not over tire or car mfr max recommendation) is best IMO.

Rudy

The key is to follow the car's recommendations, not the tire's. Many people look at the tire's sidewall to determine what pressures to run but you really need to be looking at the placard on the driver's door jamb to make a determination...

Ray Hull

Read your doorpost carefully. You must follow the symbols (circles, triangles, squares) for your TP, based on load.

Except, in my 545 sport's case, there is no setting for fully loaded, so I guess you are supposed to follow the standard pressure setting.

FWIW, I instructed my dealer to set my Dunlop Thumpflats at MINIMUM RECOMMENDED pressure when he changed my snow tires off. This has decreased ride harshness dramatically, but I think I am getting more tramlining than I recall last fall (all of 3 weeks before snows went on). But my commute route roads are well worn from truck traffic, so I can't be sure.

Bottomline is much less pounding (same crappy roads), but unfortunately, I can't tell you ##PSI that they used, as I don't have a real accurate gauge.

Don't be afraid to experiment, just be consistent.

Ray Hull

juan2mini

bruceholmes:
You would think our tire pressure was a state secret. I run PS-2's at 36 psi in the front and 40 psi in the rear. Hope this helps.

znod

I run the seemingly backwards and soft 34 front and 32 rear. I found that my 19's/PS2's give the best ride at those settings. And, of course, being a straight-line guy, more in the front and less in the rear is best for me. I don't worry much about tire milage and attack no twisties where my pressures will get me into trouble. After all, I always have DTC and DSC off anyway unless on the road or in the rain.

jsal

Back from my automotive days, the tire pressure recommendations usually are set by the ride/tuning engineers based on the selected spring rates and shock valving. I would assume that BMW is setting the tire pressures for the best combination of ride and handling - at least for the US. It would be interesting to see if there are any differences for european recommendations, as they may have selected higher tire pressures for higher speed driving.

I have been going by the recommended pressures on the door jam plate.

bruceholmes

I'm amazed by the paucity of information pertaining to tire pressures that anybody uses!!!!!!!!!!!!!! doesn't anybody do auto crossing in these cars????? I can hardly believe that anybody is going to own a car like this and not have a good tire pressure gauge!!!!!!!!! tires and the pressure at which they are run can transform the ride, handling and braking characteristics of your car. Why buy a performance oriented car not care about one of the most significant factors affecting its performance?

Come on somebody must have more info!!!!!!!!!!

sam530

After 73K miles and several Dunlop RFT's, 40 psi all the way around. The insides of these rear tires definitely wear faster than the fronts. I might go a little less on the fronts but I get a lot more tire with higher psi. I mainly drive LA freeways and I've noticed a little less control/stability at higher speeds (with higher psi) but probably a good thing with my driving record.

DD694

I use 35 PSI front and 39 PSI rear on my PS2 tires. The ride is superior to that of 18" RFTs and the handling is superb. I use a digital tire pressure gauge and check/adjust tire pressure every two weeks.