can we please clear something up?

[boss]

i was at a platday a while back and a guy we know broke a halfshaft in his 110

"how you do that?" i asked

"i pressed the brake"

"why?"

"if you lose traction through a diff, press the brake and it stops that wheel spinning like a difflock"

"......well thats not true is it"

"yes"

"no becasue your breaking on the wheels in equal ammounts adding resistance to the "risisting" wheel"

"yes but your braking on the spinning wheel.........it does work. i pressed the throttle aswell which is what broke the shaft"

***confused and annoyed expresstion on my face***



i was going to continue the argument becasue i was convinced i was right, but the rest of the club qued in backing mr left foot braking. then thought ok must be something im missing here and left it alone. this totally slipped my mind untill i read the same thing in a magazine just now.....i dont follow the "its on tv....it must be true!" or "its in a magazine.... it must me true!" rule.so i am again convinced that this is a retarded idea! deployed the lego model.......still doesnt work.


am i missing something here? or can a large amount of people be collectively stupid?


your thoughts please

[Disco Matt]

My view would be much the same as yours - I understand that this is how traction control works off road (by selectively braking spinning wheels) but when you push the pedal down you apply more or less equal braking to all the wheels.

Given that it seems prone to snapping halfshafts I've never felt the urge to try it!  :lol:

[V8MoneyPit]

Thinking this through.....

If you have the vehicle sat on a hill and the brakes on, stopping it moving. By gradually reducing the brake force, at some point the vehicle will start moving with the brakes still partially applied. Now, if one wheel was off the ground and you did the same thing, the wheel still in contact with the ground would start moving while the dangling wheel remained stationary (differential in motion). I think this is where the theory comes from.

However, if you translate the gravity forces in the example above to throttle through the transmission, it doesn't work. In this instance, the torque will be transmitted through the path of least resistance. In this case, both wheels have equal brake forces (this cannot be changed since the hydraulic pressure is equal across the axle), but the dangling wheel has less resistive force from the ground, so it will spin before the grounded wheel moves.

Myth.

As far as breaking half shafts goes, this occurs when there is a torque applied at one end and a resistive force at the other. So, giving it some beans and stamping on the brakes makes it about as likely as you can get to break a shaft!

[boss]

exactly my thinking! HA! IM NOT GOING MAD!

[V8MoneyPit]

exactly my thinking! HA! IM NOT GOING MAD!

How can you go something when you already are?  :P :lol:

[boss]

noooo...im normal but not boring.  :P

[V8MoneyPit]

Thought you were going to say you were normal, it's everyone else who's nuts  :lol:

[john656]

You could have always come back with the line...... if its that effective howcome your still stuck except now u have a fubared half shaft....... It makes sense but in the same respects doesnt, and the more i go over it in my head it wouldnt work.

[boss]

well when i said to someone else it cant work the reply was "is he still stuck?" maby a fluke?



 but whatever i knew i was right  :D

[Xtremeteam]

however i have given a dab of left foot braking in the situation of spinning a wheel, it aint as good as a locker or welded diff but it can help

[Devon-Rover]

There is a fine line between feathering the brake on the left foot and gently tickling it through a cross axle. than booting it and hoofing the brake. It does work to a degree and is more of get outta jail move than a true technique. Bit like using the handbrake to turn tighter.

[mass199]

A dab on the brake with your left foot works in some cases.

[Disco Matt]

What about the one of blipping the throttle then lifting off if a wheel is spinning? That one does work and is especially good if you're dealing with compacted snow on smooth rock (or even your ice-covered driveway in a normal car). I can only assume that spinning the wheel cleans out the treads, which then dig in and find some grip when you back off the power.

Unfortunately I didn't manage to video it, but there's a good photo on a friend's FB of me scrabbling up some rock steps in the snow with that trick. It seems to have gone straight past my conscious mind and become instinct!

[V8MoneyPit]

For those who advocate the braking technique, could you explain the science please? I can't see how retarding a spinning wheel can enhance forward motion of the vehicle. Surely, the torque will always take the route of least resistance?

Edit:
In thinking this through a bit more..... 'cos I'm bored!

There may be something in gently dabbing the brakes, since this can create inertial forces that can rock the vehicle and maybe put more load briefly on one of the dangling wheels.

Also, in the case of gently 'feathering' the brakes, the differentials will load up creating more friction internally. This may give the effect of limiting the slip and providing a little more drive to the other wheel on the axle.

Food for thought?

[Manicminer]

Ask Landrover  :lol:
It's the only way to drive the TD5 Disco after they removed the linkage for the diff lock

[boss]

sounds like a very simmilar tecnique to rocking it on the clutch....

[V8MoneyPit]

What about the one of blipping the throttle then lifting off if a wheel is spinning? That one does work .............

This, I believe, is to do with the fact that maximum torque transfer to the road is attained at the point just before the loss of traction. By lifting off and then blipping the throttle repeatedly, you are applying moments of traction. Effectively, it's the reverse of cadence braking.

You may well be right about clearing the treads too, of course.

[carbore]

Im in the Myth camp on this one and I think V8Moneypits explanations are spot on. That said There is usually a source of the myth and something that perpetuates it.

Id suggest that when people TRY this and 'it works" its simply becuase they have put the brake on and dropped the speed of wheel rotation to the point at which grip can be achieved, nothing to do with more throttle as they would be better off simply lifting off.

[MuddyDiscoveryJay]

Has anybody got or seen the "rugged guide" dvd? there is a full explanation in there and the demonstrator uses wheel rollers in  what would be a crossed axle situation. Science? no idea, theory? looked like it worked on the dvd. No excessive accelerator or braking was used. just gentle persuasion.

Jay

[boss]

black magic and witchcraft!

[lurch_917]

quick dabs on the breaks IE like cadence breaking does work in some situations as you have stoped the spin and for a moment you have drive to both sides till the diff catches up . its only a few seconds mind you but loads of dabs means loads of drive used this technique in deep snow in a car loads of times in Scotland's hills

[Disco Matt]

What about the one of blipping the throttle then lifting off if a wheel is spinning? That one does work .............

This, I believe, is to do with the fact that maximum torque transfer to the road is attained at the point just before the loss of traction. By lifting off and then blipping the throttle repeatedly, you are applying moments of traction. Effectively, it's the reverse of cadence braking.

You may well be right about clearing the treads too, of course.

I suppose it's similar to traction control again - you're detecting slip and backing off, then trying to give it more welly, then backing off, and so on.

I just know that I was told about the technique, tried it, found it to work and have attempted to refine it since!  :lol:

[Range Rover Blues]

Actually, the science is contradictory.  Limiting friction, maximum friction if you like is experienced between surfaces that are in statonary contact.  Friction is overcome with speed.
So in practice, the wheel with grip is stationary and the brakes (Equal calliper pressure) will have more grip than the spinning wheel on the other side, as the braking effort is lessened dues to the relative speed of the disk/pads.

I would guess the technique has something to do with stroring energy in the spinning wheel ect that can somehow be harnessed by appliying the brake.

Off couse if you have an ATB diff that is a different matter, the stationary wheel has 3 or 5 times the torque of the spinning one, so a little brake on the spinning wheel results in a lot more power to the wheel with grip.

Now how they work, that makes me head spin.

[90Mike]

I can see a bomb hole challenge coming on at this years Birthday Bash  :D

[Chris Putt]

Not entirely sure what the reasoning is but I too am an advocate...... Im thinking along the lines of a more crude version of fiddle braking?! I currently motor around in an old BMW 3 series (E30- 1990) no traction control and a standard open diff....

Now, in the snow it is 'lively' to say the least but I have found using a gentle application of the handbrake (acts on rear wheels only as per) if one back wheel is spinning tends to a) slow the spinning and b) get the other wheel doing something and helps gain grip and movement!

Chris

[stretchy]

I have used the left foot fidle breking many time and it works. when I was told about this techniqe I also dident see how it works as I understand its 4 wheel breaking. my personal opinion is that if you have an axle and one wheel is off the ground or litle or no traction it will take very litle presure for the brakes to stop this wheel momentarily sending the drive to the other wheel. the other wheel is being braked aswell but also the engine is working against this as you are still reving with right foot.

its fine aslong as you tap the pedal for a split second and dont rev the b****ks of it

stretchy
 

[Tommo]

As someone has written its a do or die 'get out of jail card'. I do it all the time when I'm cross axled or slightly beached and cross axled, but it has only ever pulled me out 4 or 5 times. Every time I do it it involves heavy throttle spinning the wheels (which are usually off the ground) pretty fast, then short very sharp repeated jabs on the brake pedal. For the first split second you hit the brakes some force is directed to the grounded wheels, hence on and off repeatedly starts a sort of rocking motion.

As soon as you do it you will feel whats going on, I think RRB is right about inertia from the spinning wheel being transfered to the other wheel through the diff as the brake is applied.

If anyone doubts the technique then I dare you to jack a wheel off the floor and try it.

[littlepow]

I know on rear wheel drive cars, applying the hand brake (as long as it's not a transmision version) will help to get off slippery surfaces. (This does seem to work with 3 series BMW's on wet grass).

[Tommo]

Yeah come to think about it I have jabbed the transit handbrake to get me unstuck in the snow before and its worked. It didnt work when I cross axled it leaving my steep drive on an angle though haha, that was an embarrasing day.

[dxmedia]

Effective method if done gently.