How do you catch a slide in a 4WD car?
Discussion
Lost the back end on the Impreza this morning in the snow. 35mph round a right hand bend that I normally take at 50mph. Not braking or accelerating hard. Some how caught it even though it was completely sideways and not really sure how I didn't slide it into a drystone wall. I have now replaced the rear tyres that I have been putting off changing!
From what I remember, I lifted off completely and turned in to the slide and luckily managed to get it pointing in a straight line again. Now in a FWD car, you would be able to power out of it and in a RWD car, more power would probably be a bad idea. But how about 4WD? Did I do the right thing or should I have used some power to straighten it up? I have driven a Golf 4MOTION which only transfers power to the rear axle when the front loses traction and you can feel this working, so powering out would work but Subaru 4WD is a 50:50 split. Would all the power have been transferred to the front axle or would more power have gone to the rear axle causing it to spin. I've never had any moments like this in this car but would like to know what to do next time if it ever happens again!
From what I remember, I lifted off completely and turned in to the slide and luckily managed to get it pointing in a straight line again. Now in a FWD car, you would be able to power out of it and in a RWD car, more power would probably be a bad idea. But how about 4WD? Did I do the right thing or should I have used some power to straighten it up? I have driven a Golf 4MOTION which only transfers power to the rear axle when the front loses traction and you can feel this working, so powering out would work but Subaru 4WD is a 50:50 split. Would all the power have been transferred to the front axle or would more power have gone to the rear axle causing it to spin. I've never had any moments like this in this car but would like to know what to do next time if it ever happens again!
Sounds like you did what was right in the circumstances to avoid a crash. In a 4WD I have found you can generally squeeze a little power on once you're counter steering to drag the car straight. The type of drive train is all important though, as they react differently and so respond best to different manners of manipulation. As long as you get the front wheels pointing the right way you should be able to squeeze the power on and the drive through the front wheels should drag the car straight, whereas in RWD you may find this keeps the skid going in one direction or flicks the car in the other direction and carries on skidding!
wackojacko said:
Similar way you catch a FWD car, slight opposite lock and boot it. Apply to much oppo and boot it it'll eventually grip and fire you in the direction of the wheels.....
And if it happened because of ice you'd have either swapped ends or under-steered off the road.It really depends on why it happened and what the road conditions are.
OP go find an empty snow filled car park and learn what your car does beyond the limit because depending on steering angle you can either provoke massive under steer or massive oversteer.
Do not lift off, not completely anyway, this transfers weight off the rear and adds braking which can make the rear step out further.
Once you catch the slide apply moderate throttle and the car will straighten up, be ready to wind the lock off or you may fish tail and spin out in the opposite direction. Do not use too much throttle or you will spin up the rear wheels and the tail will stay out. This is fun if you have an airfield to play on, not so much when ditches/kerbs are present.
Sounds like you stayed pretty calm and did a reasonable job, the Impreza can be driven at ridiculous angles quite easily once you get a feel for the car. Some sessions at Carlimits or similar are really worthwhile.
Edit to correct some predictive text errors.
Once you catch the slide apply moderate throttle and the car will straighten up, be ready to wind the lock off or you may fish tail and spin out in the opposite direction. Do not use too much throttle or you will spin up the rear wheels and the tail will stay out. This is fun if you have an airfield to play on, not so much when ditches/kerbs are present.
Sounds like you stayed pretty calm and did a reasonable job, the Impreza can be driven at ridiculous angles quite easily once you get a feel for the car. Some sessions at Carlimits or similar are really worthwhile.
Edit to correct some predictive text errors.
Edited by Toltec on Friday 10th February 20:08
wackojacko said:
Understeer on opposite lock .............
Please tell me that you didn't just say suggest that.
In what world is deploying 220-300bhp, which will spin up all four wheels, in a slide with a novice driver a good idea?Please tell me that you didn't just say suggest that.
My point was that on ice it really doesn't matter which ways your front wheels are pointing because if they are spinning because you've 'booted it' you are a passenger.
rhinochopig said:
wackojacko said:
Understeer on opposite lock .............
Please tell me that you didn't just say suggest that.
In what world is deploying 220-300bhp, which will spin up all four wheels, in a slide with a novice driver a good idea?Please tell me that you didn't just say suggest that.
My point was that on ice it really doesn't matter which ways your front wheels are pointing because if they are spinning because you've 'booted it' you are a passenger.
To which for my age I've had alot of time sliding cars in the Dry, Wet and snow.
Referring to the back stepping out on a slippery surface. Anything slight (hopefully all you will experience on the road) and lifting off will likely get you back in shape, especially the back has stepped out due to too much throttle in the first place.
Anything more than slight and it is a matter of balancing the throttle and the opposite lock. To be honest, not something I've had to do on the road to any great degree.
My experience from the basalt tiles at the Prodrive Proving Ground is that you can be on the lock stops as sideways as possible and it is a boot full of throttle that will pull you out of the slide. All quite undramatic so long as you get the balance right taking the lock and throttle back off at the right point - before you find yourself in the same situation at the other end of the steering rack!
Anything more than slight and it is a matter of balancing the throttle and the opposite lock. To be honest, not something I've had to do on the road to any great degree.
My experience from the basalt tiles at the Prodrive Proving Ground is that you can be on the lock stops as sideways as possible and it is a boot full of throttle that will pull you out of the slide. All quite undramatic so long as you get the balance right taking the lock and throttle back off at the right point - before you find yourself in the same situation at the other end of the steering rack!
wackojacko said:
rhinochopig said:
wackojacko said:
Understeer on opposite lock .............
Please tell me that you didn't just say suggest that.
In what world is deploying 220-300bhp, which will spin up all four wheels, in a slide with a novice driver a good idea?Please tell me that you didn't just say suggest that.
My point was that on ice it really doesn't matter which ways your front wheels are pointing because if they are spinning because you've 'booted it' you are a passenger.
To which for my age I've had alot of time sliding cars in the Dry, Wet and snow.
And they're not 'exactly the same as a FWD' when sliding. I had an Impreza before my Evo (plus a Landy and an X-Trail) and driving them like a front wheel drive will have you backwards through a hedge in no time. Just because an AWD is 50:50 it doesn't mean it won't over-steer.
Of course the simple answer here is:
It depends upon how much road is availible to "catch" the slide.
Any attempt to add power (and hence increase tyre slip) will increase the minimum radius around which the car can turn. Especially on a low friction surface (ice/snow) where the total magnitude of the cornering force is low. So, if the idea to to "get around a corner" then puttting the clutch down (which ensures the tyres are only dealing with lateral loads rather than longitudonal loads) will help.
However, this may leave you with insufficient yaw authority to get the car straight again (as the inertia of the car rotates it around the centre of mass, you run out of steering lock to "Put the front of the car back in front of the back" so to speak!
When you see a rally driver using a lot of power and a small amount of lock to power a car around a corner they will have already attained the correct entry speed, and yaw.
On the road, when the back steps out without warning it is usually becuase the driver has failed to estimate the surface friction (or that friction has changed (ice, oil, bumpy road etc). At this point you do not have the luxury of "setting the car up" and must now choose between making it around the corner (but maybe spinning) or getting the car "straight" but not making it around the corner.
Ultimately the final path of the vehicles mass will be determined by the total lateral acceleration availible to the car, and this is only reduced by using power. You see a lot of novice rally drivers making this mistake, and simply running out of road whilst trying to maintain yaw authority.
Of ocurse a "clutch down" save which is perfect for low friction slides, could be exactly the wrong thing to do when the car slides at high loadings / speed (fast on dry tarmac for example) where suddenly enabling a massive incease in tyre lateral loading, in combination with a large change in longitudinal load (and the associated mass transfer and ultimate reduction in normal loading at the rear of the car) can unbalance things even more.
So it short, there is no "correct" simple answer. It depends too much on the exact dynamics of the particular situation.
It depends upon how much road is availible to "catch" the slide.
Any attempt to add power (and hence increase tyre slip) will increase the minimum radius around which the car can turn. Especially on a low friction surface (ice/snow) where the total magnitude of the cornering force is low. So, if the idea to to "get around a corner" then puttting the clutch down (which ensures the tyres are only dealing with lateral loads rather than longitudonal loads) will help.
However, this may leave you with insufficient yaw authority to get the car straight again (as the inertia of the car rotates it around the centre of mass, you run out of steering lock to "Put the front of the car back in front of the back" so to speak!
When you see a rally driver using a lot of power and a small amount of lock to power a car around a corner they will have already attained the correct entry speed, and yaw.
On the road, when the back steps out without warning it is usually becuase the driver has failed to estimate the surface friction (or that friction has changed (ice, oil, bumpy road etc). At this point you do not have the luxury of "setting the car up" and must now choose between making it around the corner (but maybe spinning) or getting the car "straight" but not making it around the corner.
Ultimately the final path of the vehicles mass will be determined by the total lateral acceleration availible to the car, and this is only reduced by using power. You see a lot of novice rally drivers making this mistake, and simply running out of road whilst trying to maintain yaw authority.
Of ocurse a "clutch down" save which is perfect for low friction slides, could be exactly the wrong thing to do when the car slides at high loadings / speed (fast on dry tarmac for example) where suddenly enabling a massive incease in tyre lateral loading, in combination with a large change in longitudinal load (and the associated mass transfer and ultimate reduction in normal loading at the rear of the car) can unbalance things even more.
So it short, there is no "correct" simple answer. It depends too much on the exact dynamics of the particular situation.
rhinochopig said:
wackojacko said:
rhinochopig said:
wackojacko said:
Understeer on opposite lock .............
Please tell me that you didn't just say suggest that.
In what world is deploying 220-300bhp, which will spin up all four wheels, in a slide with a novice driver a good idea?Please tell me that you didn't just say suggest that.
My point was that on ice it really doesn't matter which ways your front wheels are pointing because if they are spinning because you've 'booted it' you are a passenger.
To which for my age I've had alot of time sliding cars in the Dry, Wet and snow.
And they're not 'exactly the same as a FWD' when sliding. I had an Impreza before my Evo (plus a Landy and an X-Trail) and driving them like a front wheel drive will have you backwards through a hedge in no time. Just because an AWD is 50:50 it doesn't mean it won't over-steer.
you need to read my posts properly before you start opposing them with things I either outline or you seem to mix up with what you think is wrong. Driving an AWD car the same as a FWd car is clearly not what I said in this sense but it seems you think I did. In terms of slides : FWD over steer to get out of a slide safely and quickly you apply slight opposite lock to the slide and a dab of power pulls the front into line with the rear, same story when correcting an AWD slide.... exactly the same...
You seem to forget I have been there done it got the t shirt blah blah
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