D3 Snow Performance & 19" MTR's

**gghaggis** · 10th August 2010, 09:58 AM

Originally Posted by chuck

Neil,

Does anyone know if 265 x 70 x 17 Goodyear Wrangler MTR's fit in the spare wheel well.

Regards

Chuck

Yes, but they'll need to be aired down to around 15psi.

Cheers,

Gordon

**Forest** · 13th August 2010, 07:59 PM

So, what tyre pressure should one use in snow?? Sand kind of pressure?? or higher??

I have an AT if that makes any difference.

**rmp** · 13th August 2010, 08:17 PM

For deep snow like in the pics, low pressure. Flotation and reduction in rolling resistance, just like mud and sand. Go super-low and you can float on top in some circumstances and vehicles.

**trobbo** · 14th August 2010, 06:34 AM

Originally Posted by rmp

Your setup and technique sounds fine except that selecting snow mode is not the best for deep snow. In that mode the car is set for slippery surfaces, and deep snow requires more power, certainly uphill and even to the depth you had it to as seen in the shots. Normal mode is what I would use (and in fact did that same weekend in snow elsewhere), or maybe mud/ruts.

Snow mode is fine for a thin, loose, slippery covering. Not what you were wading through.

Does the centre diff still lock up in normal mode?

**rmp** · 14th August 2010, 07:17 AM

Originally Posted by trobbo

Does the centre diff still lock up in normal mode?

Yes. The D3's centre "diff" is not like a purely mechancial unit on older models that is entirely locked or unlocked. It is a computer-controlled torque splitter -- which means it varies torque front/rear and degree of lock. This operation is constant and permanent. Different TR modes bias the lock (and other factors) one or or the other. TR is always active even when it is notionally disengaged with "Normal" selected, not the same as off.

Grass/Gravel/Snow considerably reduces the sensivity of the throttle so you can't acclerate as quickly and get the power down; which is why I don't use it in deeper snow. This design is good, but it also really annoys me on dirt roads -- takes forever to gather speed -- so I never use the mode and opt for Normal or Mud/Ruts instead. If the car slips a bit I can handle that using standard slippery-surface driving techniques. I would use GGS when it was very, very slippery, eg icy, but not on a dirt road when slip is controllable by the driver. But that's personal preference, and I wouldn't want to suggest what I do is the best way for everyone. Less confident drivers would be better off with GGS on dirt for example.

In general, it is better to err on the side of using Normal than select a wrong mode, and the modes are also there not just for the named terrains but also for the type of terrain and personal preference.

Usually when a D3 can't make it somewhere it's the driver at fault. The advanced electronics can't yet compensate for the helmsman.

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