PDA

View Full Version : Handling issues? Check those tire pressures!


Emission
05-26-2003, 10:59 PM
Our X5 3.0 has the Michelin all-season tires 235/65-17 as standard equipment. Before my trip from LA to Phoenix, I decided to raise the air pressure in all four tires to 36 psi (BMW recommends 32 psi front and rear the way my car was loaded). The idea was the hot temps, and higher speeds, necessitated higher pressures.

On Friday, ambient temps in the desert were between 99-108 F. as we drove during the day. It was HOT! The physical tire temps (taken with an infrared thermometer) were in the low 130’s F. (front) to the low 140’s (rear) after cruising at speeds averaging about 80-85 mph for several hours.

Saturday, I drove on to Tucson – another 120 miles across the desert. Ambient temps remained in the low 100’s, but driving speeds were higher (averaging 85-95 mph). Under these conditions, a problem surfaced…

At speeds over 90 mph, the X5 was darty – almost hard to keep in a straight line. The car just didn’t seem stable. It was comfortable at 80 mph, but 90 mph required work to keep it straight.

In my head, I went through all of the possibilities. Nothing made sense, except tire pressure. I pulled off the desert highway into a rest stop, pulled out my gauge, and checked the pressures. Wow! All four tires were 42-43 psi! The heat had caused the tires to increase nearly 7 psi each. Considering BMW recommends 32 psi front a rear, 42 psi all-around was obviously excessive. I bled each tire down to 36 psi again.

The good news, back on the highway the X5 drove like a BMW again – stable at speed, and not darty.

Lesson learned.

The HACK
05-27-2003, 11:49 AM
Seems like this problem is a lot more of an issue on the SAV. On the way to Vegas I was running 38psi cold, and hot about 45psi and car tracked like an arrow.

By the way, you should take the X5 out to a track sometimes. :thumbup:

Emission
05-27-2003, 12:01 PM
Originally posted by The HACK
Seems like this problem is a lot more of an issue on the SAV.

I think the all-season design (with round shoulders), combined with high-profile (65-series) tires, makes the tire cross-section bulge at high pressures - really pushing the centers out. I've driven plenty of cars across the desert (like yourself) and never seen this issue.

My X5 won't go on the track. Too heavy, and the wrong tires.

Ronen18
12-02-2011, 08:38 AM
Hi what tire pressures for BMW X5 3.0i 2003?

rdorman
12-02-2011, 10:19 AM
If you bled them down hot then you will probably find that the cold temp is now low! I find that in most BMW's increasing the tire pressure on the fronts 2-3 lbs helps balance the handling. I generally just run the rears at what ever they recommend.

Emission
12-02-2011, 10:31 AM
Hi what tire pressures for BMW X5 3.0i 2003?

Welcome to Bimmerfest!

Check the driver's door jam for the proper inflation pressures. I usually run them a couple PSI harder, as OEMs tend to like their tires on the soft side.

- Mike

petriej
12-02-2011, 11:31 AM
Hi what tire pressures for BMW X5 3.0i 2003?

This is epic! You bring back an 8 year old thread to ask for tire pressures? :rofl:

Thank goodness Emission is still on the boards!

Emission
12-02-2011, 11:33 AM
This is epic! You bring back an 8 year old thread to ask for tire pressures? :rofl:

Thank goodness Emission is still on the boards!

Yeah, I was thinking... wow... 2003! :yikes:

I think my E53 (which I owned at the time) is in a junkyard by now. Last I heard, it had 120,000 miles on it and it was going to its third owner...

- Mike