DSTC - yes or no in snow?

[ianu]

Hi all,
You are right NCS XC90 - there is more than one factor that makes up the DSTC and some of it you cannot turn off - this only turns off the Spin Control (which means it doesn't try and brake a spinning wheel to help transfer drive to one that isn't).
I've had a couple of opportunities to test with it on and off recently and demonstrate the differences.
Bottom line - unless you're deliberately trying to tackle some fairly slippery conditions and getting nowhere - leave it on because it's definitely looking after your safety.
At the Total Off Road event last year I tried a slippery gravel slope with it on and got bogged down on the slope as it braked the spinning wheels (maybe I wasn't going fast enough to start with ??). I had to retreat to the bottom (see the video clip on my photo album link http://www.cig.canon-europe.com/p?p=GY23RkESdUB
- Password TOR 2009) and try again with it off - success .
Second opportunity was roughly a week ago with about 9 inches of snow in a deserted Retail Park car park - I took the chance to demonstrate to my neighbour how sure footed this 2 ton vehicle is when things get slippy.
Basically started the run round the car park trying to follow a figure of 8 slowly picking up speeed. With DSTC on if you accelerate in a straight line you get limited spin and start to take off as drive moves to the rear wheels as it brakes the front wheels (for those of us that have still got AWD :-( ) and the TCS light flickers. As you turn into a bend it is practically impossible to accelerate as the car starts to slide sidways - it cuts the power everywhere until the car straightens up. With your foot flat to the floor it doesn't make any difference - get ready to catch it as soon as you straighten up though as it will release the power back to your right foot.
With DSTC off - it will still intervene if you're going sideways - but will allow the wheels to spin much more readily as you try and straighten up or turn into a corner. A number of occassions I was able to control a slide with a degree of opposite lock - either whilst applying power whilst cornering - or controlling the power slide as you return to the straight ahead.
Unless you've already bust the laws of physics - it's practically impossible to induce a sideways slide with DSTC on (normal mode) - as it will have cut the power as the yaw control takes over.
I think the lesson here really is - if there is little or no grip when your trying to move in a forward direction - and little chance of grip on any wheel - consider turning it off so you can at least keep all the wheels moving to try and grab something from the surface - otherwise the DSTC will end up braking all the wheels until you've got nothing.
Turning it off should be a pre-meditated concious decision - that either things aren't working for you with it on - or you've already evaluated the condition ahead of you and reckon you'll need all the help you can get so you don't get stuck in the first place.
With all the snow we've had here this last week - not many huge hills here in Oxfordshire - but have had no reason to turn it off. Golden rule - remember the laws of physics - if there no grip - there's no grip, heavy objects naturally want to travel in a straight line .....
Before anyone lambasts me - the car park was deserted - and no living animals were harmed in the making of the spectacle.
My neighbour was serioulsy impressed though - his BMW hadn't moved all week..and he's considering either an XC60 or 90.

These were my observations in a fairly controlled environment and we were able to experience the difference between them quite easily - you don't often get the chance - but it never fails to impress me this car - fan blooming tastic..

Cheers
Ian.

[Beavis]

best i make a prayer to the heavens tonight and wish for a bit of snow and a deserted work car park tomorrow..... ;-)

found this too last week http://www.youtube.com/watch?v=ZtrtmEN0kjk

and just hope that non of those scallies that sit in their novas at the local shopping centre turn up tutting!

[npw]

Changing the subject slightly, I thought you might me interested in what happened to me on a 2004 XC90 a couple of years ago with the DSTC. I was travelling down the M5 in the middle lane at 70 MPH when the van that I was passing suddenly pulled over the white line and into my lane, for no reason, there was nothing in fromt of him. I swerved into the outside lane as a natual reaction and fortunately there was nothing there, and then immediately attempted to straighten up. Bearing in mind that this all happened in the blink of an eye, I was aware that I was now travelling at 70, but that the car was slightly sideways.

Before I had time to react there was a loud graunch from the rear of the car car, which was the DSTC working out that the car was facing in one direction and travelling in another and applying the appropriate wheel brake. The car instantant became arrow staright and I continued without incident. I quickly looked back to see the van drive wave an appology ( yes honestly) and carried on my way.

I do not suggest you carry out the same ***tional test of the system, but on that day I am certain that it saved me from a very nasty situation.

[rchiu13]

There are many different responses to this topic, I live in Mass and we just got a snow storm. From experience, when driving on packed snow or powder up to 6 inches the DSTC feature will simply brake your tires to prevent you from spinning or sliding. However, turning it off which in the vehicle will say something like "traction comntrol off" doesnt mean that at all, it simply means that the power will instantly be transferred to the rear wheels when the front tires loose grip. I have tested this so many times in my driveway and in parking lots with snow and ice. Turning off the DSTC is pretty much turning on 4x4 in a vehicle, some will probably disagree with me, but I tow a snowmobile trailer and drive through up to a foot of snow sometimes. Off road and mountain roads, I always drive with the DSTC off, on roads with hard packed snow and some ice, usually on. Really you have to try it out while driving with your driving style to see how it affects you, my 2008 xc90 has yokohama geolander all terrain tires and with the awd and the dstc off; when driving in snow, I feel in complete control.

[ally]

Can't say for Volvo and AWD, but other vehicle manufacturers with 2WD RWD etc, recommend it is switched off in snow and ice - presumably so that the car will then try to move

[chb]

Not seen snow this year yet, but in the past two UK winters I found it better to leave DTSC on all the time and just rev the balls off the car to get up anything slippy. The yaw control stops the car twisting, and the car will feed drive to any wheel that has grip.

[Blue693]

Sweden - 17" winter Hakka r tyres from Nokian - non studded. Have driven the car with the dtsc on through 12" of snow, wet slush and on compacted ice and not had a single problem. No slipping or wheel spin. Never had to use the winter setting.

Solution - buy some winter tyres. Nokian make them in all sizes and the non studded tyres can be used all year round.

[ally]

Entirely agree about the winter tyres, they make a huge difference, so much so that I'm not really bothered if the AWD doesn't work.
We've got Avon Ice Rangers on and they are very good, and we actually kept them on all year with no wear issues at all, however I sourced a second set of wheels so will revert to summer tyres later on as they do handle slightly better

I've also got Avon winters on my BMW which had absolutely no trouble getting around in the snow and ice we had 4 weeks ago

[Arianne]

XC90 owners, you've bought four wheel drive. But those wheels only make contact with the road through the tyres.

DSTC or no DSTC - it's the rubber that makes the difference in snow & ice. I would rather have a standard 2wd hatchback with winter tyres than an XC90 with 4wd and summer tyres.

The way it works across most of Northern Europe & The Alps is that almost everyone swaps their tyres between winter & summer.

And with more snow forecast for the UK this Friday, those of us with winters will be glad of the extra traction available from the XC90 AWD system.

Maximum embarrasment will be had if someone in their Vauxhall Vectra drives past a wheel spinning XC90 - just because the Vectra has winters fitted and the £30k+ XC90 is stuck with summer Conti rubber!

No brainer - Pirelli Scorpion Ice & Snow on all four wheels plus XC90 AWD. Nice

[paultyler1]

My MY13 XC90 doesn't have a switch to turn the DSTC off, it just comes up on the dashboard that it is on - how do I turn it off?

Also, what does the "winter" switch do?