Is it time BMW cars were banned from the roads during snow?

[Obelix]

It's actually not at all obvious. If you'e ever watched Ice Road truckers, you can see on many occassions they add a large concrete block to the tractor units to increase the weight to improve grip.

 

So why would adding weight in the passenger cabin not increase the weight in the front tyres, and why would it not increase the traction of the tyres?

[Eater Sundae]

It increases the weight that the front wheels are trying to pull without adding anything to the maximum grip available. Pretty obvious really. A bit like adding extra weight to an artic and wondering why the wheels spin.

 

I think you ought to have another go at explaining that, as what you've said so far doesn't help at all.

[L00b]

So why would adding weight in the passenger cabin not increase the weight in the front tyres, and why would it not increase the traction of the tyres?

It does of course...but depending on how much weight is loaded and where, and the road and circumstances, the centre of gravity is displaced backwards - that's the crux of the issue here, I believe.

 

If the load is particularly heavy and rearmost of the cabin (e.g. bits of cast iron in the boot), a same FWD car would lose traction sooner than at its standard kerb weight plus a single occupant-driver, for the simple reason that the weight bearing on the front axle is less than that bearing on the rear axle. This is as true of e.g. a standing start at the bottom of an uphill snowy/icy road, as e.g. a drive at high-ish speed through a long and deep puddle (with aquaplaning as the outcome).

 

Doesn't mean that the front axle is less loaded than at kerb weight, or that front traction is less (than at kerb weight) when the car is extra-/over- loaded in the cabin, but simply that uneven longitudinal weight distribution (say, from a nominal 50:50 to 40 front : 60 back) has an effect on front traction, given relevant circumstances.

 

Here is a useful reference for the unbelievers

Edited February 5, 2015 by L00b

[Obelix]

Which is why we've been talking about load in the passenger cabin - and why I gave the example of a caravan excessivly loading the rear towbar somewhere up the thread.

[RootsBooster]

It increases the weight that the front wheels are trying to pull without adding anything to the maximum grip available. Pretty obvious really. A bit like adding extra weight to an artic and wondering why the wheels spin.

You really don't seem to understand the physics.

Unless the extra passengers and luggage are located behind the rear axle (which would be very uncommon in most vehicles), weight would also be increased on the front wheels.

 

---------- Post added 05-02-2015 at 10:15 ----------

 

It does of course...but depending on how much weight is loaded and where, and the road and circumstances, the centre of gravity is displaced backwards - that's the crux of the issue here, I believe.

 

If the load is particularly heavy and rearmost of the cabin (e.g. bits of cast iron in the boot), a same FWD car would lose traction sooner than at its standard kerb weight plus a single occupant-driver, for the simple reason that the weight bearing on the front axle is less than that bearing on the rear axle. This is as true of e.g. a standing start at the bottom of an uphill snowy/icy road, as e.g. a drive at high-ish speed through a long and deep puddle (with aquaplaning as the outcome).

 

Doesn't mean that the front axle is less loaded than at kerb weight, or that front traction is less (than at kerb weight) when the car is extra-/over- loaded in the cabin, but simply that uneven longitudinal weight distribution (say, from a nominal 50:50 to 40 front : 60 back) has an effect on front traction, given relevant circumstances.

 

Here is a useful reference for the unbelievers

...none of which contradicts what myself or Obelix have been saying.

 

Roosterboost is saying that adding passengers and luggage reduces traction at the front wheels.

[monkey104]

Do they have the same problem in Germany? I think not. Maybe the real problem is the nut behind the wheel

 

Yes they do albeit not as bad as winter tyres are compulsory.I lived there for 9 years

[Harrystottle]

Many new BMW's also have run flat tyres. These have very stiff sidewalls and when they are low profile as well, don't provide much grip in the snow.

[L00b]

...none of which contradicts what myself or Obelix have been saying.

Why would it have to?

[RootsBooster]

Why would it have to?

 

It wouldn't

 

It clarifies things a little though, for roosterboost, who may think that the info in your post agrees with him.

[carosio]

Back around1968/9 a friend and myself (in a '62 Ford Zephyr) and loads of other cars were making fruitless attempts to ascend Hoyle St up to the roundabout as there had been a heavy snow fall. A council Landrover was towing each and every one up to the island then back down to Meadow St for the next. I think it was a SWB with typical heavy tread-pattern tyres, and using a tow chain.