Happy 2017 to you all.
A couple of days ago I was disappointed to need a push out of a shallow pair of ruts made by a Skoda Yeti 4x4 on a wet bit of grass. 3 or us had trooped off to get some logs to feed the hungry wood-burner in b-i-l's recently-refurbished French farmhouse. I went independently so I could open gates and things. The 2 s-i-ls arrived in the Yeti. As soon as the front wheels left the road and touched the grass the visible wheels spun and gripped alternately. S-i-l drove gently to the wood pile and we filled the back with logs up to headrest level.
The Yeti then went a few metres and, finding a convenient molehill, the front wheels started digging a pair of trenches whereupon s-i-l stopped driving it and asked me to take over. She said she had the 'off-road' system engaged, whatever that does.
I offered a push but I was invited to drive so, cursing the gearbox layout that put first and revese next to one another, I rocked while the girls pushed until it came unstuck and finally made it to the road. All this took place on a wet, grassy paddock with the slightest of downhill inclines. We were going downhill with the car loaded.
The handbook offered no means of locking anything, just the 'off road' button.
So, the question is; is the Yeti a poor excuse for an off-roader or was it operator error? Has anyone else needed a push in their Yeti?
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It all depends upon the tyres.
If you have standard road tyres fitted and not a tread suitable for off road work, you will have little more traction than a normal saloon.
You need chunky tyres to grip in mud and snow..
Just look at a tractor and see what they use.. or an original LandRover..
Of course they will not handle well at speed and be a lot noisier but that's the laws of physics for you.
Last edited by: madf on Thu 5 Jan 17 at 13:27
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>>You need chunky tyres to grip in mud and snow.
A lower 1st gear or even better a crawler set of gears as in many Subaru manual 4wd cars/SUVs - great in crawling traffic as well..
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If s-i-l had been in an AWD Subaru, this thread wouldn't have happened.
Just saying ;)
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+1 on the tyres.
Have seen plenty of amusing videos of 4wd 911s unable to get off a wet lawn.
High-profile narrow tyres have more off-road grip than low-pro wide boots.
Haven't really had a chance to use the Kizashi's 4wd on anything other than greasy tarmac yet but I'm not brimming with confidence that the mahoosive 235/45 tyres will be anything like the Subaru was in the badass winters of 2010/2011 , although I expect the Uniroyal Rainsports have a tread pattern better suited for mud/snow than the OE Dunlops.
Dog's non-turbo Forester should be on 215/60 tyres (the original Yokohama Geolanders are fairly crap on road but not bad on mud/snow) - my Turbo has the same size tyres but Goodyear EfficientGrips which are fantastic on the road and mediocre on crud.
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Wet grass is one of the slippier surfaces; it regularly defeats X?/Q? 4X4s, and I've even seen it defeat proper Range Rovers and Defenders with the wrong tyres on. So I wouldn't feel too bad. It might have been one of those situations she traction control off and judicious use of the right foot (brute force over brains...) got you out though?
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Wet grass can be extremely slippery - look how far celebrating footballers can slide on their knees.
As for tractors, even these can get stuck in the wet. I occasionally drive an old 2 wheel drive tractor on a sports field and it doesn't take much to bog it down if you lose momentum pulling the spiked roller even up a gentle slope.
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Subaru Forester can cope with anything: www.youtube.com/watch?v=mDmAJuFJJUE
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Was it actually in four-wheel drive? You mention only the front wheels spinning - in 4WD at least one wheel on each axles would spin. At least that's how a conventional 4WD works.
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Good point. There are 2wd versions. 4wd vehicles aren't, unless fitted with diff locks. The rut digging seems to indicate 2wd only. Or a very common mistaken technique of trying to move off with max power, demonstrated every winter on snow here in the High Peak.
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The usual problem with wet grass is that every wheel is on a similar slippery patch. I expect every wheel would have been alternately spinning and locking.
The best chance of getting it moving with ordinary summer tyres would be with gentle application of power. For many people, this is unnatural - if they anticipate being stuck, they give it more power.
The Yeti uses a Haldex clutch to feed the back axle. Normal torque distribution is >=90% to the front, so in normal use the Yeti will have the characterics of a front wheel drive car. Wheel slip at the front will cause the Haldex clutch to engage, transmitting pushing more torque to the rear. There are no mechanical diff locks on the axles, this is handled by braking spinning wheels individually.
As it has an off road mode, it's possible that in that mode the default torque split is more even in the absence of wheelspin since the Haldex is electronically controlled; and that the behaviour of the ESP/EDL is changed too.
The bigger, longtitudinal-engined Audis use a Torsen system for permanent AWD with the front/rear bias determined by gearing. I don't think the Torsen system is necessarily better off-road, but if you want an all-wheel-drive rally car then it's obviously the one to go for.
Last edited by: Manatee on Fri 6 Jan 17 at 12:14
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>> Was it actually in four-wheel drive? You mention only the front wheels spinning - in
>> 4WD at least one wheel on each axles would spin. At least that's how a
>> conventional 4WD works.
>>
I don't think the 4-wheel drive can be disengaged. I've read that it's a Haldex system that gives 90% to the fronts and 10% to the rears under normal conditions. Thereafter it's up to some dodgy software.
Only the left side of the car was visible to me as it started to struggle. The front and rear wheels would spin alternately as the car slowed to a halt. Neither driver used more than a whiff of throttle.
Last edited by: hawkeye on Fri 6 Jan 17 at 14:23
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One trick with a conventional drive car whose handbrake operates on the driving wheels is to very gently apply the handbrake as the clutch is engaged, almost stalling the engine, so that neither wheel can spin excessively at the expense of the other.
I've no idea whether this works with modern fancy drives.
You can use it its extreme form on a tractor with individual left and right brakes. If the nearside wheel for example is bogged in a ditch, locking it puts all the torque on the one wheel that can still get a good grip on the road, and can be used to drag the locked wheel out by brute force.
Contrary to what is sometimes advised about using a higher gear, a very low ratio at idling speed is often better for crawling on wet grass or sheet ice - The "Ice Cold in Alex" sand dune starting handle effect.
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The "Ice Cold in Alex" sand dune starting handle effect.
Indeed - great film in many ways. (even better book)
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Always thought it was a bit of a bummer that they only had lager available though. Might have pushed me over the edge that.
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"Luke warm bitter and a bag of crisps please" in Alex "wouldn't have the same box office appeal though would it?
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Contrary to what is sometimes advised about using a higher gear, a very low ratio at idling speed is often better for crawling on wet grass or sheet ice
If there was a clapping hands smiley - that post would get it. More often than not - a higher gear is exactly what one one doesn't want.
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>>One trick with a conventional drive car whose handbrake operates on the driving wheels is to very gently apply the handbrake as the clutch is engaged, almost stalling the engine, so that neither wheel can spin excessively at the expense of the other.
That's exactly what I used to do in a Citroen GS. FWD and the handbrake worked on the front wheels. That combined with a very torquey boxer engine, adjustable ride height, narrow tyres and a low overall weight, that car was almost unstoppable in snow as we had in 1981. I remember driving up the A4 out of Box to Corsham, passing many abandoned vehicles on the way. In those days only farmers tended to have 4x4s.
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Fantastic cars, those GSs. Dad had a 1220 Club in Bleu Delta, a lovely metallic blue with tan targa (plastic) seats.
But, yes, wrong tyres for wet slippy grass on the Yeti.
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Skoda Yeti SUV - needed a push on wet grass - madf
