Tire pressures
- Thread starter Drjcb198
- Start date
32 front 36 rear sounds correct - but the label on the driver door shut next to the lock will tell you as pinted out. THB, if you haven't put air in the tyres for three months 
then they were probably right when you got it, the air has just slowly leaked. I drive mine every day, and try to remember to check them once a week - I'd suggest every couple of weeks as a minimum would be best, if only because if you don't you'll go through tyres at a rate of knots, and your fuel consumption will drop 
then they were probably right when you got it, the air has just slowly leaked. I drive mine every day, and try to remember to check them once a week - I'd suggest every couple of weeks as a minimum would be best, if only because if you don't you'll go through tyres at a rate of knots, and your fuel consumption will drop I tend to have the tyre pressure the same front and back. 32psi
I have heard that BMW have slightly higher rear tyre pressure to encourage oversteer but I am uncertain what the benefits is. (Unless it is safer to go through hedges backwards!) Does anyone know if this is why they have decided a 50:50 weight distribution car should have a smaller contact patch at the rear?
I have heard that BMW have slightly higher rear tyre pressure to encourage oversteer but I am uncertain what the benefits is. (Unless it is safer to go through hedges backwards!) Does anyone know if this is why they have decided a 50:50 weight distribution car should have a smaller contact patch at the rear?
BMW and all manufacturers will tend to keep things on the side of understeer, it's much better to go through the hedge pointing forwards :?
I believe the higher pressure on the rear is partly because they're wider, there's more "unsupported" tyre tread.
I believe the higher pressure on the rear is partly because they're wider, there's more "unsupported" tyre tread.
In every car I have ever driven, the drive wheels are higher PSI than the non-drive wheels - irrespective of whether it's FWD or RWD, and the Z4 is the first car that I have had that has a staggered set-up. My car says 2.3 bar on the front, 2.6 bar on the back, which works out at 33 / 38 psi I think. I was surprised the rears are so high, but there's lots of power, the weight shifts as Sars says, and perhaps the wider rears also have something to do with it.
However, IMHO you should look at the door shut plaque showing the pressures and do what it says, because someone brainier than me has worked it out already. If you then want to adjust the pressures that's your preference - i've just never bothered playing around. As my winters are all the same size I've dropped the back by 2 psi to 36, but that's only for fear of them exploding. Irrational, I know, but it's my head and I have to live with it
EDIT - Just realised that my iPad auto-wrong function made me look like I had a fit toward the end of the first sentence in the second para. For amusement, used to say "becausthose one somewhermob rainier than me has worked it out for me."
However, IMHO you should look at the door shut plaque showing the pressures and do what it says, because someone brainier than me has worked it out already. If you then want to adjust the pressures that's your preference - i've just never bothered playing around. As my winters are all the same size I've dropped the back by 2 psi to 36, but that's only for fear of them exploding. Irrational, I know, but it's my head and I have to live with it
EDIT - Just realised that my iPad auto-wrong function made me look like I had a fit toward the end of the first sentence in the second para. For amusement, used to say "becausthose one somewhermob rainier than me has worked it out for me."
Herminator said:
I have 225/45/17's all round and the tyre pressures are different 2.4 Bar front and 2.9 Bar rear so I don't believe that to be the reason, also when you break you want the fronts to deform and get flatter to increase surface contact, this may be another reason for the difference :idunno:
I've played around with the pressures on my non-RFTs and settled on 32F/34R, much lower makes it feel 'baggy' on the turn in, much more starts to make it unsettled on bumpy bends.
Tyres generally lose a minimum of 1 ft/lb per month, and need seasonal adjustment to take account of ambient temperatures. You lose/gain roughly 1ft/lb of pressure for every 10 deg F so they will be a few pounds down in cold weather and need a top-up.
Tyres generally lose a minimum of 1 ft/lb per month, and need seasonal adjustment to take account of ambient temperatures. You lose/gain roughly 1ft/lb of pressure for every 10 deg F so they will be a few pounds down in cold weather and need a top-up.
Ewazix said:
Is that on 18's? I was disappointed in the handling and ride of my car when I had my RFTs on the manufacturer recommended pressures (33/39). I lowered to 32/35 which really made the car feel settled with less dramatic tramlining. Made a significant difference.
A quick whip around the internet was unilluminating. It seems some run them hard some soft, some the same and some staggered. It seems to be suck it and see. I shall examine our tyres and stick another few psi in the rears for the sheer hell of it. Sounds like fun.
