Would an LSD help in the snow

[varsas]

SmoothRB said:

Downhill you would be braking. I'd rather have RWD 'cos you can engine brake with the rears and normal brake with the front.

Good point, I'd agree with that.

[NoelWatson]

varsas said:

SmoothRB said:

FesterNath said:

But neither does snow. So, how come RWD generally has better traction in the dry, but not the snow?

I'd say your problems with an SLK are more tyre related, and that generally FWD cars have narrower tyres.

As the car accelerates you get weight transfer towards the rear axle. This gives a RWD more grip and a FWD less grip. One reason FWD drag cars suck.

But that is a dynamic condition. Driving on ice is slow speeds/accelerations, moving off from stationary etc. So weights transfer is not a significant factor.

Except for going up hills, where you still get weight transfer, .

On a slippery hill, what would the weight transfer be? 1%?

[Blue Meanie]

Well, we get 10 feet of snow a year where I am, and I'd rather have the rwd thanks very much. When the fronts in a fwd are slipping, you have nothing. No steering, no brakes, feck all. At least with rwd if you do break traction with the driven wheels, you stil have some modicum of control as to direction, and breaking.

Still, all of this is a moot point if you have the wrong tyres, on any configuration.

[shirt]

i have a rwd auto with an lsd [e28 528i] and have had no grip issues other than when i've intentionally wanted to kick the back end out [low speed country lanes or turning the car round without reversing in works' car park].

my dad has an m sport 3 series auto with no lsd. he had one journey in the snow and has since resorted to using mum's fwd daihatsu stbox to get anywhere as he keeps kicking the back end out due to lack of throttle feel.

i reckon its horses fo rcourses. go easy and most cars are fine in the snow

[SmoothRB]

NoelWatson said:

On a slippery hill, what would the weight transfer be? 1%?

Cosine of the angle I think? So on an 80 deg incline (hade) would be ~17% extra to the rears.

[10 Pence Short]

My old DC2 was great in the snow. Relatively skinny tyres, a very tractable engine and an lsd on the front, weighed down by the engine kept things right.

[PhillipM]

varsas said:

Assuming the biggest problem you have is going up hills, you need a car which will work best in that situation. When you go up a hill the weight transfer is toward the back of the car, so to get the most weight over the driven wheels (more weight = more traction) you'll be wanting the engine at the back, and the rear wheels driven.

In practice cars with that arrangment have wider tyres/other things that make them unsuitible for snow but in theory, if you wanted to build some kind of snowey hill climbing 2WD special that's what you would do.

For hire, one snow-defeating beastie, rear engined, rear wheel drive, independent rear wheel braking, £500 per day....



Yes, I think you're right in your summation that a beetle would also work relatively well in the snow.


Important factors in the snow?

1. Driver
2. Driver
3. Driver
4. Tyres
5. Weight distribution
6. Transmission (LSD, 4wd, etc)
7. Nut behind the steering wheel.

Edited by PhillipM on Saturday 26th December 18:47

[Who me ?]

Zad said:

What you need is one of the older type progressively locking viscous diffs. They are rather good in the snow.

Or one of these.

Plus - about two one metre lengths of thin rope/string etc and something like doormats/old sacks.
Dig out front of rears ,tie rope to outer corner of doormat /sack etc,place as close as possible to just under front of rears, and other end to rear of car ( after rear axle obviously).get yourself moving -you can stop somewhere convenient to retrieve rope + sacks ( for future +use )

[Pcot]

urmm said:

Maybe a silly question. Both brother in law and i have fairly nippy RWD german cars without LSD which are both a bit useless in the snow - When they get stuck they both spin one wheel. Would an LSD help as I would assume they would prevent this and give more traction?

Yes, thats correct.

[PhillipM]

Pcot said:

urmm said:

Maybe a silly question. Both brother in law and i have fairly nippy RWD german cars without LSD which are both a bit useless in the snow - When they get stuck they both spin one wheel. Would an LSD help as I would assume they would prevent this and give more traction?

Yes, thats correct.

Did you have to go through such a long winded technical answer? You could have just said "Yes"...

[EvoBarry]

Blue Meanie said:

Well, we get 10 feet of snow a year where I am, and I'd rather have the rwd thanks very much. When the fronts in a fwd are slipping, you have nothing. No steering, no brakes, feck all. At least with rwd if you do break traction with the driven wheels, you stil have some modicum of control as to direction, and breaking.

Still, all of this is a moot point if you have the wrong tyres, on any configuration.

Or you could be a bit more gentle with the throttle and use the fronts to pull the car in whatever direction you want. Try that with a rwd. If the back end swings out on a fwd car you can keep the power on and use it to pull the car out of the skid. As 10p said earlier, my ITR is fine in this weather, the diff pulls it out of junctions nicely while others are at a standstill

[choading]

Would a LSD help in the snow

Edited by choading on Monday 28th December 07:09

[Blue Meanie]

EvoBarry said:

Blue Meanie said:

Well, we get 10 feet of snow a year where I am, and I'd rather have the rwd thanks very much. When the fronts in a fwd are slipping, you have nothing. No steering, no brakes, feck all. At least with rwd if you do break traction with the driven wheels, you stil have some modicum of control as to direction, and breaking.

Still, all of this is a moot point if you have the wrong tyres, on any configuration.

Or you could be a bit more gentle with the throttle and use the fronts to pull the car in whatever direction you want. Try that with a rwd. If the back end swings out on a fwd car you can keep the power on and use it to pull the car out of the skid. As 10p said earlier, my ITR is fine in this weather, the diff pulls it out of junctions nicely while others are at a standstill

That is all very well on slushy roads, but not on really snowed in roads. If you are being 'gentle' then pretty much anything will be fine. The issue is when traction is zero, and you have zero control through the only 2 contact patches that affect your movement. On a rwd car, you may well lose traction with the rears, but you will still have control through the fronts, as well as braking ability. This is from experience in Upstate NY winters, not from 'ooh, it's a bit snowy' in the UK.

[DickyC]

Driving the car is the easy bit. First you have to get in.

[Mannginger]

I like the tip for the handbrake usage above. Could have done with reading that a couple of days ago as had some "interesting" moments up in the Lake District!

[groomi]

varsas said:

DickyC said:

The most impotant thing governing a two wheel drive car's ability in the snow, before any form of traction control, to my mind, is having the weight of the engine over the driving wheels.

Front engined, front wheel drive is best. Rear engined, rear wheel drive is a poor second. Front engined, rear wheel drive is bad. My step daughter's MGF is poor in the snow but so much better than my wife's SLK. The SLK has traction control and gizmos aplenty but I'd go so far as to say it's the worst car I have ever experienced in slippery conditions.

I disagree.

Assuming the biggest problem you have is going up hills, you need a car which will work best in that situation. When you go up a hill the weight transfer is toward the back of the car, so to get the most weight over the driven wheels (more weight = more traction) you'll be wanting the engine at the back, and the rear wheels driven.

In practice cars with that arrangment have wider tyres/other things that make them unsuitible for snow but in theory, if you wanted to build some kind of snowey hill climbing 2WD special that's what you would do. That or reverse a FWD car up. FWD cars also need to steer, which means the driven wheels aren't always pointing straight up the hill, which is another disadvantage for them.

I agree that front engined RWD is the worst, not sure where rear engined RWD comes in, but I imagine it would be very good indeed, probably better then front engine FWD, I imagine a beetle would be great fun (and quite capable) in the snow?

Edited by varsas on Saturday 26th December 13:18

Hillman Imps (and their variants) are great in these conditions. All the benefits of rear engine, rear wheel drive, without any silly wide tyres Porsche style.

[DrTre]

choading said:

Would a LSD help in the snow

Edited by choading on Monday 28th December 07:09

No, you're wrong

[NoelWatson]

snotrag said:

But there's an obvious trick which I thought all phers would know - in a rwd car with one wildly spinning wheel, you use the handbrake. One hand on the wheel, one on the handbrake. As you pull away and feel one wheel light up and spin the power away, you feather the handbrake to work as a diff lock, which speads the torque more evenly between the wheels and often is enough to drive you forward.

Do brakes work non linearly dependent on wheel speed? Otherwise, I can't see how this works.

[mitch78]

choading said:

Would a LSD help in the snow

Edited by choading on Monday 28th December 07:09

If we're playing at Grammar Police today, it's either:

Would a Limited Slip Differential help in the snow?

OR

Would an LSD help in the snow?



Now, back to the topic:

As people have already stated, it probably wouldn't make much difference without winter tyres.

[choading]

I want to buy a MX5 or a M3