Casualties of the snow

[Ares]

When it snows i tend to leave pug to enjoy at peace,i had a misfortune to slam it to that side road concrete thing,twice,i slamed it with wheels,spined than slammed again...
mechanic told me that if it was some other car my wheels would go like DeLorean in Back to the future 2...

[OdinEidolon]

Myth?

try it,
get your car in some snow, try setting off in 1st
and then try setting off in 2nd, and see the differnce,


set off in 1st the car will just spin,
obviously you will have better grip with the winter tyres so you may not see much improvement,
but on ordinary tyres it does make a differnce..


Theres no Myth in it what so ever,


plenty of info on the net,

from one source,


Driving in snow and ice
Gentle manoeuvres are the key to safe driving - stopping distances are 10 times longer in ice and snow.

Wear comfortable, dry shoes for driving. Cumbersome, snow-covered boots will slip on the pedals.
Pull away in second gear, easing your foot off the clutch gently to avoid wheel-spin.
Up hill - avoid having to stop part way up by waiting until it is clear of other cars or by leaving plenty of room to the car in front. Keep a constant speed, choosing the most suitable gear well in advance to avoid having to change down on the hill.
Down hill - reduce your speed before the hill, use a low gear and try to avoid using the brakes. Leave as much room as possible between you and the car in front.
If you have to use brakes then apply them gently. Release the brakes and de-clutch if the car skids.
Automatic transmission - under normal driving conditions (motorways, etc) it's best to select 'Drive' and let the gearbox do the work throughout the full gear range. In slippery, snowy conditions it's best to select '2', which limits the gear changes and also makes you less reliant on the brakes. Some autos have a 'Winter' mode which locks out first gear to reduce the risk of wheel spin. Check the handbook.

I live in the Belluno province, Italy. It's in the middle of the Dolomitis, near Cortina. We have loads of snow every year. Moreover, I enjoy hiking and climbing, so I have to drive up steep slopes and small snowy roads tens of times every year. I know how to drive on the snow pretty well. I've found myself stuck several times (especially with my mum's Clio with crappy winter tyres!), and I know hot to act in this case. I tried several times everything possible.
If you really want a good hint, here it is: if you canno get up a small, straight hill, go back, turn around and go up in reverse. This helps a lot. (only fwd vehicles of course.)

Why would setting off in 2nd help? Reading from what you posted:

Pull away in second gear, easing your foot off the clutch gently to avoid wheel-spin.

But in 2nd you have MORE wheelspin than in 1st. Let's say you let the car at idle and ease the clutch gently: in 1st at 800 rpms you are at ~5mph, in 2nd you are at ~9mph (approximate figures, you get the point).

So, more wheelspin. Makes no sense otherwise. The only diference is that by setting off in 1st you have more initial grip, but then you have to change gear earlier. And changing gear means interrupting the power to the wheels and risking to lose traction, but it's easy to correct, no big deal.

Why starting in 2nd? Why not in 3rd then! Or 4th! If 2nd is better then 1st, then 3rd is better than 2nd.

It's just a myth you have in UK, don't know why...

EDIT: also the "avoid wheelspin" stuff is madness... especially on summer tyres. Just the other day I helped a guy who was stuck on a steep hill, he had summer tyres and could not move. A friend of mine and myself started pushing from behind, he did not rev and the car was just stationary... we told him to rev it to 2000-2500 and keep it there, and off he went, no problems at all.

[V6Exec]

But in 2nd you have MORE wheelspin than in 1st. Let's say you let the car at idle and ease the clutch gently: in 1st at 800 rpms you are at ~5mph, in 2nd you are at ~9mph (approximate figures, you get the point).

So, more wheelspin. Makes no sense otherwise. The only diference is that by setting off in 1st you have more initial grip, but then you have to change gear earlier. And changing gear means interrupting the power to the wheels and risking to lose traction, but it's easy to correct, no big deal.

Why starting in 2nd? Why not in 3rd then! Or 4th! If 2nd is better then 1st, then 3rd is better than 2nd.

It's just a myth you have in UK, don't know why...

EDIT: also the "avoid wheelspin" stuff is madness... especially on summer tyres. Just the other day I helped a guy who was stuck on a steep hill, he had summer tyres and could not move. A friend of mine and myself started pushing from behind, he did not rev and the car was just stationary... we told him to rev it to 2000-2500 and keep it there, and off he went, no problems at all.

The torque at the wheels is a increased in lower gears by the gear box - think in torque and not in terms of speed and it will become clear to you.

In my old V6 I would show friends the "one gear trick". On a flat road at a standstill I would put the car in 5th, and slip the clutch a bit on tickover to get moving, then take my foot off the clutch and put it hard down on the accelerator. As the revs increased and the available torque increased the rate of acceleration increased.

One year on a clear road I was climbing a hill in 5th doing a decent speed, there was drifting snow at the crest that I was not aware of. When I hit the snow the available torque from the V6 in 5th gear caused a wheelspin.

In snow starting in a higher gear means that the engine is running with less power - less torque at the wheels means the ratio of grip to torque is better. And if you want the real proof. On a moderate road put a car in first, revs the nuts off it and dump the clutch - wheel spin. Try is in second and you will generally not get that spin.

[OdinEidolon]

But in 2nd you have MORE wheelspin than in 1st. Let's say you let the car at idle and ease the clutch gently: in 1st at 800 rpms you are at ~5mph, in 2nd you are at ~9mph (approximate figures, you get the point).

So, more wheelspin. Makes no sense otherwise. The only diference is that by setting off in 1st you have more initial grip, but then you have to change gear earlier. And changing gear means interrupting the power to the wheels and risking to lose traction, but it's easy to correct, no big deal.

Why starting in 2nd? Why not in 3rd then! Or 4th! If 2nd is better then 1st, then 3rd is better than 2nd.

It's just a myth you have in UK, don't know why...

EDIT: also the "avoid wheelspin" stuff is madness... especially on summer tyres. Just the other day I helped a guy who was stuck on a steep hill, he had summer tyres and could not move. A friend of mine and myself started pushing from behind, he did not rev and the car was just stationary... we told him to rev it to 2000-2500 and keep it there, and off he went, no problems at all.

The torque at the wheels is a increased in lower gears by the gear box - think in torque and not in terms of speed and it will become clear to you.

In my old V6 I would show friends the "one gear trick". On a flat road at a standstill I would put the car in 5th, and slip the clutch a bit on tickover to get moving, then take my foot off the clutch and put it hard down on the accelerator. As the revs increased and the available torque increased the rate of acceleration increased.

One year on a clear road I was climbing a hill in 5th doing a decent speed, there was drifting snow at the crest that I was not aware of. When I hit the snow the available torque from the V6 in 5th gear caused a wheelspin.

In snow starting in a higher gear means that the engine is running with less power - less torque at the wheels means the ratio of grip to torque is better. And if you want the real proof. On a moderate road put a car in first, revs the nuts off it and dump the clutch - wheel spin. Try is in second and you will generally not get that spin.

You have no grip - torque is not that important. Yes the torque to the wheel is lower in 2nd (and then in 3rd, 4th etc...), but a sudden increase corresponding to 800 rpms (from stationary to moving at idle) in 1st means getting from 0 to 5mph, in 2nd from 0 to 8-9mph. And when the wheels are "doing" 9mph the car is probably still doing 4-5mph... wheelspin!
Yes- torque is more, but for the same torque you also get faster acceleration because for every engine rpm you have more wheel rpms.
The two things obviously compensate each other (otherwise energy would no be conserved).
Of course you can control the power with the clutch but:
- this wears the clutch a lot
- you can do that in 1st too! And you'll have more control over the throttle.

[lozz]

Why starting in 2nd? Why not in 3rd then! Or 4th! If 2nd is better then 1st, then 3rd is better than 2nd.

Any car thats got a decent clutch plate, normaly stalls if you try setting off in 4th,

if it was Myth why wouid 1st gear lock out on top notch auto cars be even thought of,


if you think its aload of bull, fare enough

[rapport25]

There is no wrong answers. If you have found something thst works you will keep doing it. I remember on Friday trying to overide my dsg box and manually shift to 2nd as I have always done in snow

[OdinEidolon]

Why starting in 2nd? Why not in 3rd then! Or 4th! If 2nd is better then 1st, then 3rd is better than 2nd.

Any car thats got a decent clutch plate, normaly stalls if you try setting off in 4th,

if it was Myth why wouid 1st gear lock out on top notch auto cars be even thought of,


if you think its aload of bull, fare enough

Why then don't you start in 3rd? If the car stalls if you try to set off in 4th or 5th depends hugely on the type of engine and on the mapping of the low revs injected quantity. If you release the clutch very carefully, even my 406 can start in 4th. On the 106 1.5D I could do that in 5th, on my dad's C3 1.1 it was not possible in 4th or 5th, but OK in 3rd.

[KozmoNaut]

Setting off in 2nd (or 3rd) brings the car further out of its powerband compared to the gearing. Less power from the engine means that it's easier to control how much power goes to the wheels by slipping the clutch. Yes, it puts marginally more wear on the clutch, but most clutches have over 200,000km in them anyway, so it's not like it's going to make a huge difference.

I've had to start in conditions where even just letting the clutch out slowly in 1st with no throttle at all would just spin the wheels. I had to start very very gently in 2nd to get going. And this was in a 1988 Corolla with all of 70hp, probably less by the time I owned it.

I've also "won" a couple wintertime stop light races in my old diesel Panda because I set off in 2nd with hardly any wheelspin while the guy next to spun and spun and spun his wheels through 1st, 2nd and 3rd gear. Every time I got going slowly and steadily while he was sitting in the other lane, barely moving in his car with 2-3 times the horsepower.

And as for the "I'll just drive carefully" argument, it's bunk. When there's ice and snow on the road, there is no way you can drive carefully enough that you're able to stop if someone runs out it front of you, even if you go 10mph and cause a traffic jam. Summer tyres are absolutely useless on snow and ice, even on dry roads in cold weather winter tyres fare better. Only if by "driving carefully" you mean "I'll stay home if there's any snow at all" can your decision to forego winter tyres be OK in any way.

[OdinEidolon]

And as for the "I'll just drive carefully" argument, it's bunk. When there's ice and snow on the road, there is no way you can drive carefully enough that you're able to stop if someone runs out it front of you, even if you go 10mph and cause a traffic jam. Summer tyres are absolutely useless on snow and ice, even on dry roads in cold weather winter tyres fare better. Only if by "driving carefully" you mean "I'll stay home if there's any snow at all" can your decision to forego winter tyres be OK in any way.

+1 on that. Every EU country has by now realized that winter tyres in winter are a must, exept UK to be honest.

I cn undestand not wanting to spend 300£ on winter tyres on a car that is worth 1000£, but at least on new cars that are worth 20000£ people should realize it's the best investment one can do.

[Busman]

I never understood the point of winter tyres untill my coach had a set fitted in Switzerland, and wow, what a difference. Not only would it go up hills better, it stopped better to.
I think this is one of those things that if you've never spent some conciderable time using them, you don't realise what a great saftey thing they are.
And I would be more inclined to listen to the people on this site from snowier climbs who understand this issue so much better than us brits.

[V6Exec]

You have no grip - torque is not that important. Yes the torque to the wheel is lower in 2nd (and then in 3rd, 4th etc...), but a sudden increase corresponding to 800 rpms (from stationary to moving at idle) in 1st means getting from 0 to 5mph, in 2nd from 0 to 8-9mph. And when the wheels are "doing" 9mph the car is probably still doing 4-5mph... wheelspin!

There is friction between the tyre and the snow, layers of snow, and the road. That friction gives you grip, but it is very limited.

Yes- torque is more, but for the same torque you also get faster acceleration because for every engine rpm you have more wheel rpms.
The two things obviously compensate each other (otherwise energy would no be conserved).

Not quite - acceleration (rate of change in velocity) is highest in the lower gears. The maximum speed will be lower, but the acceleration higher.

Of course you can control the power with the clutch but:
- this wears the clutch a lot
- you can do that in 1st too! And you'll have more control over the throttle.

Driving style comes into this - depends if you use the throttle to control the speed whilst also using the clutch. Having driven a collection of vehicles of different types and sizes, I use one or the other not both (except on a steep hill start)

[OdinEidolon]

Yes- torque is more, but for the same torque you also get faster acceleration because for every engine rpm you have more wheel rpms.
The two things obviously compensate each other (otherwise energy would no be conserved).

Not quite - acceleration (rate of change in velocity) is highest in the lower gears. The maximum speed will be lower, but the acceleration higher.

Tbh I don't think I need to have someone tell me what acceleration is... What you say is wrong. When you depress the clutch the wheels go all of a sudden from 0 to 5mph (1st) or to ~double that (2nd gear). Of course you can modulate this by depressing the clutch very slowly, but not too much.

You just want road speed to match wheel speed (well, I don't agree: in certain situations wheelspin helps you going), since road speed is 0, you want to start the lowest possible. Torque is not a factor here. Of course in lower gear there is more torque: torque is just how much energy is transmitted to the wheel per engine rotation. Nm = Joules not by chance! This energy at stationary speeds is of course dissipated. Since total torque is constant (provided by the engine) lower wheel speed means more torque.

Have you ever seen F1 racers start in 2nd gear? Or racecars? Those also have so much power that they spin wheels at the slightest blimp of the throttle, even on the tarmac. What's the difference?

[jonsowman]

Reducing torque is indeed the key.

[OdinEidolon]

Reducing torque is indeed the key.

There is no facepalm smiley
I appreciate the fact that someone knos physics but this is not about the torque only:
First of all, the whole thing that you don't want wheelspin at all is wrong on most kinds of snow.
Second, you can control the torque as much as you would do in 2nd even in 1st
Third, why don't you start in 3rd?
Fourth, following this reasoning you say the wheel must turn very slowly. Initially, at zero speed, then gradually increasing. You cannot do that in 2nd, the 2nd gear is geared too high to have enough low speed rotation to minimize the starting wheelspin, even if you play with the clutch a lot. Let's say the slowest speed you are able to make the wheel rotate is 1Hz, that'll probably be 0.5Hz in first. There must be some wheelspin, I hope this is clear. Of course you cannot start gradually from 0Hz and continuously increase the speed of the rotation because the surface you are on has very low grip, the \mu is something like 0.05 in the best conditions (with summer tyres). Your feet / clutch cannot be as precise to make the wheel spin that low. So, agreed you must have some wheelspin, then it's better to have it at for the shortest time possible, and that is in 1st.

Please note I perfectly understand and agree with your diagram, but it is missing the whole matter of how much you are able to control the low-speed spinning. In 1st you can do so much better.

[jonsowman]

It gets a bit handwavey, but as well the torque T which causes Fd, there is the additional torque T' = I*d(omega)/dt (moment of inertia - fixed, multiplied by angular acceleration). This additional torque is the reason that, as you say, dumping the clutch in first would cause wheelspin but gently releasing the clutch is less likely to do so.

Now, there is more torque available in first than second (at a given engine power output): P = Tw. This is obvious - it is the reason you pull away in 1st, then move up to 2nd, 3rd, etc. The increased available torque means that rate of change of torque with transmission input speed (dT/dn) is greater, and so small movements of the throttle are likely to cause larger angular accelerations in 1st compared to 2nd. If this exceeds the frictional force Fr, the wheel will slip. The increase in transmission input speed can come either from further engaging the clutch (reducing clutch slippage) or increasing engine speed - they are one and the same as far as this is concerned.

Therefore for less experienced drivers, using 2nd means that their not-so-good clutch/accelerator control has less effect on angular acceleration and is therefore less likely to cause wheel slip. For experienced drivers, 1st gives you more control at the expense of requiring greater skill.

I believe that 3rd and above are not generally recommended since:
1) The output torque is so low that it begins to require good clutch control again in order not to stall the engine.
2) Due to the gear ratios the clutch slip duration would be longer in order that the vehicle can accelerate to above stall speed before the clutch is fully engaged, and that final speed would be too high for the conditions.

You are entirely correct in that some slipping is required, in fact the coefficient of friction of rubber increases slightly as it begins to slip (weird material).

As a side note, I notice you used "\mu". Are you a TeX user by any chance?