Tire pressure sweet spot

[StanF18]

I know the X5 tire pressure topic has been discussed many times, and I am not looking to start any heated arguments.
Justed wanted to share my personal experience after playing around with different inflation pressures. Quite a while back, I had found the "recommended" 33 psi cold to be inadequate (subjectively), both in terms of handling and in terms of too much rolling resistance. So I've always run at higher settings, but it was a bit difficult to determine what was "optimal". Luckily, the tactile steering feedback you get from a BMW is so excellent (compared to say a Toyota), that you get a pretty good feel for when the vehicle is gripping well on a hairpin turn, versus sub-optimal gripping, versus very poor gripping.

What I have found is that the old adage holds true: if a little bit of something is good, it does NOT mean that more is even better. Just for the hell of it, I experimented as high as 38psi front/40psi rear. Not a good place to be. While the rolling resistance was noticably low, the X just did not handle well on rapid lane changes or on sharp curves. There was a dramatic decrease in gripping power, and the smaller contact patches became even more obvious on wet pavement. I ran at this setting for a good 3 weeks just to convince myself, and it was obvious that handling was compromised in terms of grip and maneuverability.

I scaled back to 36psi front/37psi rear. This seems to be a "sweet spot" in terms of all-around handling. The steering feedback is fantastic and the tires grip with a lot of bite on both dry and wet pavement. The sense of "floating" and imminent loss of grip that I saw at 38/40 was gone. At the same time there was none of the sluggishness that was obvious at the textbook low 33psi.

Just for the record, I am running a 19" 255/285 staggered setup.

Just wanted to share. YMMV.

[chilliwilli]

I wonder if it differs pending on the wheel size. I run staggered 20's 295/315. I've experimented also and discovered my sweet spot has been 33psi front/34psi rear in summer and a bit lower in winter months with 295's all around. Also seems to wear out the tires less.

[cmyX6go]

I've never experimented. I've run 32psi all around on all three of my X5s, whether I was running staggered 19s, square 19s or square 18s for winter.

[roadfrog]

According to the door sill: 32 front 39 rear - thats for the staggered 19" setup on an '03.

IMHO, there's not a lot of difference +/- in a vehicle that has exceptional handling out of the chute. Especially 2-3 lbs and especially when fluctuation is so vast depending on ambient temps when pressure is checked.

[JCL]

Originally Posted by roadfrog

According to the door sill: 32 front 39 rear - thats for the staggered 19" setup on an '03.

Yes, but that is for 4/5 passengers and a full load of luggage (max load capacity). For up to four passengers, or an equivalent amount of luggage, the door sill says 32 front and 32 rear. (well, at least my 2003 model did, and that is what 2003 manual states)

[BMWLOVER]

I also have the same wheels as you and run around 35 all around. I have found it to be the best out of all the different combination's I've tried so far too.

[bigfish]

I have had an 01 4.4 and now have an 03 4.6 and have experimented with this issue for many moons with many different tire combinations. My current set up seems to be they way to go(for me at least).

Pirelli PZero Roso 315x20 front 33 psi rear 30 psi. Once the cold tires warm up after few miles (CA) they feel tightens quite nicely. I have also removed as much rear camber as possible as this effects wear and handling as well. Running the same wheel/tire width front and rear has allowed me to rotate front to rear and back. This has added 25%-35% more life to my tires depending on how and where I drive.


tb

PS. The pic's I attached show the old set up with Michelin Diamaris.....

[admranger]

Also depends on the gauge. I've seen up to a 3 psi difference between gauges (decent gauges too...).

Experimenting like you did is the only way to find the "sweet spot" for your vehicle.

[sethro]

For me it's 32PSI - 32PSI

The ride is smooth and firm lol

[X Foomph]

Again, another interesting topic with subjective comments.
I'm running the same set up as Stan and even ventured down the track of 40psi f & r for the first couple of months, mainly 'cause that's what the boss dude at the tyre shop said to inflate to.
After running with door frame sticker recommendations of 32 f & r, I've settled on a middle ground 35f & 37r. Seems to handle just that much better than at higher inflation.
Happy with wear to date.

Interesting and valid comment/observation by admranger on gauges.