Hyper_545i

Hello All,


I know there are a ton of topics regarding the air pressure recommendation on the E60's. The recommendations seem to be all over the place. I am just curious what the members on this forum are running and what the recommendation is. I used to run 36/38. I am now running 38/38. It feels like ti handles better, but the ride is a little harsh. I would love to hear what other members are running on the 18" 124 Sport wheels with 245/40/18 and 275/35/18 non-rft tires.


Thanks in advance!

jtbgonesailing

Per BMW owners manual 04-05 545i tire pressures with 18" staggered.

Max 4 people. 32psi F. 35psi R.
4-5 people + luggage. 38psi F. 42psi R.

Hyper_545i

Thanks for the reply! I know what the manual recommends. I tried the 32/35 and it was way to soft. I am assuming this was the recommendation with rft's. I just wanted to hear what other members were running as far as tire pressure.

DanielFD

No deference in tire pressures between rtf and non rtf. In general a higher rear pressure means your car leans towards oversteer, more pressure in the front and more understeer. What adds more to all this is the way ARS works. under a set speed (i think 80 kph) the ARS system works so that the car has more understeer then oversteer, this is so the car is more comfortable to drive. Over a set speed the car becomes "neutral" where a balance is made between understeer and oversteer. Playing with air pressures is going to effect that feel. This is not say you shouldn't, what you should do in my opinion is try and see what makes you comfortable. I'm a bit OCD, and i like to think BMW is smarter then me so I stick to what they say, that makes me comfortable. 32 35 for me, also the roads here are terrible and my car is lowered on Eibach springs and i'm running on Msport shocks, the car is tight enough already!

LessIsMore

Different tires can vary greatly in the sidewall stiffness and construction.

Hyper, you are correct in thinking the RFT's at a given pressure will feel more accurate/responsive on turn-in - the sidewalls are incredibly stiff. This steering feel they provide in turn-in is the single advantage of RFT's in my book.

To get that same feel out of non-RFT's of the same size, you'd have to run more pressure in the tire. This could cause uneven wear if you go too high.

In my 535i with 18" 124's staggered, recommended pressure is 35/39. I find that 36/39 suits me. However the 545i is heavier on the front, and overall, so I'd expect you to need more pressure up front, and possibly in rear, than I would to get the same feel.

Everything a manufacturer builds or recommends is a compromise, to find a middle-ground average that will please the most people or reduce their liablity or make things last longer. Doesn't mean it pleases enthusiasts, performs the best, or provides the most comfort ... and certainly doesn't mean it's the best way.