We often get asked about offroad driving techniques, but not often by owners of a BMW X5 M-car!

Hi Practical Motoring,

I’ve just read your excellent review of the current X5 M50D – a model I am purchasing this Tuesday.

My partner and I also have a 2011 Land Rover Discovery 4 (5.0L V8) which we bought recently to handle any unsealed roads in our country district (Far North, New Zealand) and most especially for the Te Paki stream (pictured below) which is a popular 4WD trek that enables you to go from sealed road to Ninety Mile Beach. I’ve driven it once before (in a year 2000 Range Rover I used to own) and most of it is beside a wide, shallow stream (there is one place you cross it) and all of it is on sand. Most of the sand is medium to firm.

I’m thinking of selling the Discovery. But that’ll leave the X5, with its less off road orientated makeup, 20 in wheels and low profile, run-flat tyres (which, presumably, there is no point deflating) as the only car we can do Te Paki stream in. Do you think the X5 is suited to this special trip, or likely to embarrass itself?

Kind Regards,

B Kerikeri, New Zealand

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Hi B

You are quite right to be concerned. As sand is soft, tyres tend to sink into it. The solution is to reduce tyre pressure which creates a greater footprint of the tyre so you have more tyre touching the ground, and the vehicle doesn’t sink in as far and so you end up “floating” on the sand. The amount to reduce pressures varies – firm sand might be 25psi, soft 10. A good starting point is 20psi, compared to probably 35psi or so on road.

Unfortunately, low-profile tyres with 20-inch rims cannot be deflated very far because otherwise the rim touches the ground. And as you point out, runflats are a further problem because, as they’re designed to run without any air pressure they don’t increase their footprint much when aired down. So, I wouldn’t be taking the X5 offroad as it is, and you’re also very likely to scratch the rims.

However, there is a solution. You can buy another set of rims, preferably 19-inch or 18-inch, whatever the smallest will fit. You can find out by taking your car to a BMW dealer and having them test-fit wheels from other X5s. I’d love to be there when you rock up and ask, it’ll not be a question they get every day!

The reason a test fit is important – I suspect the brake discs on the X5 M50D are greater diameter compared to the slower X5s, so it may well be that wheels that fit the slower vehicles do not fit the M50D. And while the front brakes are generally bigger than the rear, don’t assume that to be the case either without checking. You may also consider aftermarket wheels for the X5, provided they fit and are appropriately load rated.

Once you have your wheels then, fit offroad tyres to those rims – there are quite a few to choose from now. I’m not familiar with the NZ road regulations (hard enough to understand the Aussie ones) but you may be able to go for a slightly taller diameter. Don’t go any wider, and in fact a bit narrower wouldn’t hurt as the X5 M50D has pretty wide tyres. You won’t get any flotation with wider tyres, the contact patch will just lengthen.

You should also buy a 5th wheel and tyre, as without it you’ll have big problem should you get a puncture on the beach. I suspect the spare wheel will need to go in the boot and that will be inconvinent, but nowhere near as inconvinent as a flat without a spare a long way from bitumen. Also, take a flat plate of around 300x300x20mm wood for the jack which otherwise will sink into the sand. And I’d take a set of four traction ramps (Maxtrax or Tred) as they are superb at sand recovery.

Once the BMW has decent tyres you should be fine. The X5 has lots of torque, and it has a very effective all wheel drive system which drives all four wheels, all the time, and it permits stability control to be disabled without killing brake traction control. So once it’s got decent tyres I think it’ll do well enough.

Best of luck, and as we don’t get many BMW M owners wanting to drive on sand, please let us know how you go!

Further reading

• For more on tyre/rim choices, and an explanation of high/low profile tyre choice read this Reader Help question
• Small seven seat SUVs on sand
• BMW snow drive experience
• Stability control and traction control explained