What is the correct tire pressures?????
#21
Senior Members
Join Date: Aug 2004
Location: Lancashire (UK)
Posts: 442
Likes: 0
Received 0 Likes
on
0 Posts
![Default](https://5series.net/forums/images/icons/icon1.gif)
i think the actual reason for different pressures at the rear is a very complicated one involving that old school favourite of mine physics (pressure/volume/mass etc).
i remember a few yrs ago a motorsport guy i knew told me one reason was that if you ran at equal pressure all round, you would most likely encounter a lot of understeer in a rwd drive car. His "for idots" way of describing it to me without going into technical things was that raising the rear pressure will make the rear contact patch slightly smaller, thus decreasing overall grip. This means the car will have less understeer and will neither be faster or slower than with the equal
pressures.
I am sure there is also a lot more involved in making the calculation but that simple reason was all I cared to know about
i remember a few yrs ago a motorsport guy i knew told me one reason was that if you ran at equal pressure all round, you would most likely encounter a lot of understeer in a rwd drive car. His "for idots" way of describing it to me without going into technical things was that raising the rear pressure will make the rear contact patch slightly smaller, thus decreasing overall grip. This means the car will have less understeer and will neither be faster or slower than with the equal
pressures.
I am sure there is also a lot more involved in making the calculation but that simple reason was all I cared to know about
![Smile](https://5series.net/forums/images/smilies/imported/smile.gif)
#22
Contributors
Join Date: Jun 2004
Location: Netherlands
Posts: 3,374
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: [i][b][u]Since 19 august 2004[/u][/b][/i]: [color=red][b]530i[/b] High Executive[/color], Silvergray with beige interior, Popular wood, Servotronic, Sportssuspension, electric foldable and dimmed mirrors, dimmed interior mirror, pappelmaser braun wood, cupholders, styling 123 18" wheels, Logic 7, Steptronic, alarm class 3, electric sunscreen in the rear and suncreens for sidewindows, Comfort seats, heated seats, Xenon with headlightwashers, Adaptive corner lights ALC, Advanced airconditioning, lightpackage, Nav Pro, 6 cd changer, side airbags rearseats, bluetooth siemens S55, chrome kidneys, gearlever with wood, voice recognition retrofit, front windshield with green band.
Waiting for trunkopener button from Hobi :)
![Default](https://5series.net/forums/images/icons/icon1.gif)
So a higher pressure in the back makes the car oversteer more than understeer.. I like that more then understeer so I will keep the higher pressure for now.
#23
Senior Members
Join Date: Aug 2004
Location: Lancashire (UK)
Posts: 442
Likes: 0
Received 0 Likes
on
0 Posts
![Default](https://5series.net/forums/images/icons/icon1.gif)
mine was a simplistic view of things....I'm sure bmw take a lof of other calculations into account, like differences between springs fr/rear, diffs between shocks, tyre widths etc etc, even maybe rotational speed differences between front/rear......
I think it is fairly common on car likes these (bmw,merc,audi,saab) etc to see higher pressures recommended for the rear tyres.
I think it is fairly common on car likes these (bmw,merc,audi,saab) etc to see higher pressures recommended for the rear tyres.
#24
![Default](https://5series.net/forums/images/icons/icon1.gif)
Great discussion! I now realize I am running the wrong pressures. I have 245/40R18s all around and was running 29/35 (front/rear). Obviously, I miss-read the chart. Now I realize I should run 32/38. (or 36 all around because I am usually the only one in the car)
ANy know what the lug torque should be?
ANy know what the lug torque should be?
#26
Contributors
Join Date: Jun 2004
Location: Netherlands
Posts: 3,374
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: [i][b][u]Since 19 august 2004[/u][/b][/i]: [color=red][b]530i[/b] High Executive[/color], Silvergray with beige interior, Popular wood, Servotronic, Sportssuspension, electric foldable and dimmed mirrors, dimmed interior mirror, pappelmaser braun wood, cupholders, styling 123 18" wheels, Logic 7, Steptronic, alarm class 3, electric sunscreen in the rear and suncreens for sidewindows, Comfort seats, heated seats, Xenon with headlightwashers, Adaptive corner lights ALC, Advanced airconditioning, lightpackage, Nav Pro, 6 cd changer, side airbags rearseats, bluetooth siemens S55, chrome kidneys, gearlever with wood, voice recognition retrofit, front windshield with green band.
Waiting for trunkopener button from Hobi :)
![Default](https://5series.net/forums/images/icons/icon1.gif)
Anybody have such a wrench?? Since I am changing my winterwheels and summerwheels myself this could be handy I think. I used to do it by hand and feel.. So tight is tight but not too tight was my idea about it.
What does such an wrench cost??
What does such an wrench cost??
#27
Senior Members
Join Date: Aug 2004
Location: Lancashire (UK)
Posts: 442
Likes: 0
Received 0 Likes
on
0 Posts
![Default](https://5series.net/forums/images/icons/icon1.gif)
here's one on uk site...i'm sure they can be bought cheaper, just need to check the ony you buy has the right range (nm's) for what you want to use it for.
#28
Contributors
Join Date: Jun 2004
Location: Netherlands
Posts: 3,374
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: [i][b][u]Since 19 august 2004[/u][/b][/i]: [color=red][b]530i[/b] High Executive[/color], Silvergray with beige interior, Popular wood, Servotronic, Sportssuspension, electric foldable and dimmed mirrors, dimmed interior mirror, pappelmaser braun wood, cupholders, styling 123 18" wheels, Logic 7, Steptronic, alarm class 3, electric sunscreen in the rear and suncreens for sidewindows, Comfort seats, heated seats, Xenon with headlightwashers, Adaptive corner lights ALC, Advanced airconditioning, lightpackage, Nav Pro, 6 cd changer, side airbags rearseats, bluetooth siemens S55, chrome kidneys, gearlever with wood, voice recognition retrofit, front windshield with green band.
Waiting for trunkopener button from Hobi :)
![Default](https://5series.net/forums/images/icons/icon1.gif)
Thanks northernmonkey.. Checked out the torque wrenches over here and alread e-mailed a guy about one he is selling on internet!
#29
Contributors
Join Date: Jun 2004
Location: Netherlands
Posts: 3,374
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: [i][b][u]Since 19 august 2004[/u][/b][/i]: [color=red][b]530i[/b] High Executive[/color], Silvergray with beige interior, Popular wood, Servotronic, Sportssuspension, electric foldable and dimmed mirrors, dimmed interior mirror, pappelmaser braun wood, cupholders, styling 123 18" wheels, Logic 7, Steptronic, alarm class 3, electric sunscreen in the rear and suncreens for sidewindows, Comfort seats, heated seats, Xenon with headlightwashers, Adaptive corner lights ALC, Advanced airconditioning, lightpackage, Nav Pro, 6 cd changer, side airbags rearseats, bluetooth siemens S55, chrome kidneys, gearlever with wood, voice recognition retrofit, front windshield with green band.
Waiting for trunkopener button from Hobi :)
![Default](https://5series.net/forums/images/icons/icon1.gif)
Talking about tirepressure.. I want to buy a tirepressuregauge.. I've found a digital one that is only 19 euros! My only concern is the accuracy. I don't want to buy a gauge that isn't accurate because I can go to the gasstation to get innacurate pressures on my tires.
edit: Found this one at the halfords site for 13.95 euros. What do you think???
edit: Found this one at the halfords site for 13.95 euros. What do you think???