X5 stuck on the beach

[Weasel]

Just think of a tractor with tall thin tires with a narrow/deep pattern vs a drag radial tire with wide narrow contact path... I get a mental image of a tubbed prostreet car stuck in the sand with a tall skinny tires truck pulling it out.

[JCL]

Originally Posted by Penguin

My assumption would be that the tire width and pressure that resulted in a "square" tire contact patch would likely be optimal.

I'm with Fraser and Weasel; I would go for a narrower tire based on my experience in soft sand (and deep snow).

I am trying to imagine the diameter of a tire with a 2" wide and 25" long contact patch. Would that be something like a 10' or 12' diameter wheel? Taken to such an extreme, the contact patch actually would be pretty much like a flat board.

[Mujahid]

Originally Posted by watrob

Well you see, I drive mine on the Beach every weekend to get to the beach house. Well I mean I did with the E53, then with my first E70 and then with my 2nd E70. That 2nd E70 did not quite make the beach one Friday night in Jan 09, as I hit the second cutting to get onto the beach a king high tide the night before had washed the cutting out and I buried it in 350mm of salt water and X5's don't float.

With the amount of electronics in that lower floor area I would not want to even spill a bucket of water over in the front, even the sensors on the adaptive drive suspension cannot handle exposure for a long period of time in water!

It took only minutes to fill the lower floor area with water and all you could feel was that the carpet was wet and then the iDrive started to light up light a Xmas tree and everthing started to fail & then the transmission goes into park. The only way to get pulled out is to get the red release key out of the trunk and release the transmission.

The X5 only has around 220mm clearence, so water over 300mm is a no no and never make a bow wave as the air intake in the front will kill your motor, you cannot compress water in your cylinder heads, bent conrods!

Anyway I picked the 3rd new X5 up last Friday night to use over the weekend just to test some new 6mm offset castor bushes I had install, two hours later I was rallying up the beach, oh and I did not use the second cutting, to much water in it, went out the first cutting instead!

Hi there Watrob, I just had a look at my owners manual (2005 X5 3.0i) and it states that water depth of 50cm should not be exceeded. Is this realistic? you seem to have more experience with driving on the sand - any advice. I am concerned about why the manufacturer would allow fording depths of 500mm (although they do say that one should not stop in the water. Many thanks.

[Weasel]

That's about a foot and a half (19 inches) which would be ok as long as you keep moving along slowly. You don't want to go too fast and push water into the air intake, and don't want to stop for more obvious reasons. But I wouldn't try doing this on sand like at the beach as the ground under the wheels will just wash out... like in the original post.

I just had to go through some deep water like this last weekend when we had flooding rains for a few days, but probably didn't go deeper than 14-16 inches.

[ard]

Nevermind....

[Mujahid]

Originally Posted by Weasel

That's about a foot and a half (19 inches) which would be ok as long as you keep moving along slowly. You don't want to go too fast and push water into the air intake, and don't want to stop for more obvious reasons. But I wouldn't try doing this on sand like at the beach as the ground under the wheels will just wash out... like in the original post.

I just had to go through some deep water like this last weekend when we had flooding rains for a few days, but probably didn't go deeper than 14-16 inches.

thank you for your reply - had a grea time on the beach!

[ard]

Originally Posted by JCL

I'm with Fraser and Weasel; I would go for a narrower tire based on my experience in soft sand (and deep snow).

I am trying to imagine the diameter of a tire with a 2" wide and 25" long contact patch. Would that be something like a 10' or 12' diameter wheel? Taken to such an extreme, the contact patch actually would be pretty much like a flat board.

Wide tires in snow and slush are a 'no no' since they tend to ride up on top, reducing control... paradoxically this is PRECISELY what you need in soft sand.

Reduced pressure in ANY tire will increase the contact patch- just physics. 30 psi with 900 lbs on that wheel = 30 sq in.... take that same 900 lbs but with 20 ps... 45 sq in. Not that simple, but illustrative. Releasing air will increase the patch in bothe length and width.


A

[JCL]

Originally Posted by ard

Wide tires in snow and slush are a 'no no' since they tend to ride up on top, reducing control... paradoxically this is PRECISELY what you need in soft sand.

Reduced pressure in ANY tire will increase the contact patch- just physics. 30 psi with 900 lbs on that wheel = 30 sq in.... take that same 900 lbs but with 20 ps... 45 sq in. Not that simple, but illustrative. Releasing air will increase the patch in both length and width.


A

Several of us who have driven in soft sand noted above that we will take the narrower tires (with reduced pressure). This refers to soft sand, not packed sand, when I at least would want the wider tires. Not sure about the other posters above who regularly use their X5s to get to beach houses.

While we discussed reducing pressure in the posts above, and I agree with your concept of internal pressure being equal to ground pressure, the vehicle in the video has RFT, so your illustrative example won't apply.

[ard]

I disagree that narrower tires in soft sand is a good idea. Just increases the propensity of the tire to dig down and not float. Ever ride a bicycle in the sand??? Would you rather be on a "road bike" with a 1" tire, or a cruiser with 2.5" tires??

A runflat will increase contact patch, but obviously not as much as a standard tire- once the tire begins to self support I am guessing no more spread.





OT, but my sole experience with driving on the beach was a rental AWD in Australia... above Brisbane, from Noosa up to Fraser Island

Did you know they set up Radar traps ON THE BEACH as well as Sobriety Check Points?!?! (The latter being distinctly un-australian.)

Oh, the rental policy includes NO COVERAGE if you put the car in ANY water. Just to reinforce the point, the rental shop had a wall of pictures showing all sorts of disasters...making the one in this video look like a normal drive!

[JCL]

Originally Posted by ard

I disagree that narrower tires in soft sand is a good idea. Just increases the propensity of the tire to dig down and not float. Ever ride a bicycle in the sand??? Would you rather be on a "road bike" with a 1" tire, or a cruiser with 2.5" tires??

A runflat will increase contact patch, but obviously not as much as a standard tire- once the tire begins to self support I am guessing no more spread.

My road bike tires run at 125 psi. You can't compare 25 psi cruiser tires with 125 psi performance bike tires. It isn't about the shape of the contact patch, but rather the pressure.

The RFT comment was not that it will increase the contact patch (at normal pressure, it will have no effect over a non-RFT tire), but rather that as you deflate it, it becomes self supporting and thus does not gain any increased contact patch, at least to the extent that a non-RFT does. As such, your illustrative example tends to not apply to a RFT.