Cornering in low gear
Discussion
Would someone please be kind enough to explain why my car (FWD if it makes a difference) and presumably most other cars, seems to hold the road better when cornering in a lower gear?
What I mean is - for the same corner, in the same conditions, at the same speed, in 3rd gear with plenty of revs the car behaves nicely and sticks to the road, whereas in 4th or 5th gear, with low(er) revs the car feels as though it wants to drift outwards.
TIA
What I mean is - for the same corner, in the same conditions, at the same speed, in 3rd gear with plenty of revs the car behaves nicely and sticks to the road, whereas in 4th or 5th gear, with low(er) revs the car feels as though it wants to drift outwards.
TIA
In a nutshell ...
1. The car is better "balanced", under constant power either maintaining, or slightly accelerating, it basically pulls itself out of the corner.
2. If slightly accelerating (or hard depending on corner/grip etc" then you are being pushed back into your seat, thus the seat is doing it's job and supporting you, so you feel less "thrown about".
Martin
Edited to add a article I wrote for a newsletter ...
One of the reasons often given for road positioning on bends is to increase the radius and therefore reduce the cornering forces on the car. This method is acceptable and typical for the IAM test, but is it the only, or best way?
At some point in a bend, you have to start to straighten the car, so that you are in a straight line as you exit. However, the point at which I do this is perhaps different to the "typical" IAM style.
My approach into a bend starts off the same, and for safety I go for “slow in, fast out”. To do this, I need to get the car pointing straight out of the bend, at the earliest opportunity. Let us take the example of a left hand bend.
Providing there is no approaching traffic I will be positioned towards the center of the road, if I have the visibility, I may well be over the center line, providing the road markings allow this.
Before I get to the bend I will access the speed required using a number of factors, not only the limit point but other visual clues such as the cross views, the angle of the center line, tree line or lampposts. Once completed I will balance the car on the throttle, maintaining my speed but not accelerating. I will also “hint” at the steering, that is put on a tiny amount of lock, a split second before I actually enter the bend, why, I hear you ask.
For a tyre to corner, something called a “slip angle” must be set up, this is a very complex subject that I will not attempt to explain fully (feel free to check the internet). In a nutshell, when turning the steering wheel, maximum cornering from the tyres, for the given amount of steering is not immediate, it can actually take up to half a second, dependent on many factors. By turning the wheel very slightly, I 'wake the tyres up' and set up the slip angle. Once set up, any increase in steering will have a more immediate maximum effect, and produce smoother turn in.
Once in the bend, I'll keep an eye on the limit point to ensure it doesn't start to move towards me (ie. a double apex bend). Providing this doesn't happen, at some point it will start to move away from me, signaling the start of the exit of the bend. At this point my vision is increasing and I'll start to accelerate and begin to “shave the bend”, that is actually tighten my line (and therefore increase the cornering forces on the car). As the limit point “sprints” away, I'll bring the car back towards the nearside. I can now begin to straighten the car, and as the steering comes off I can increase my acceleration even harder (dependent of course on the speed limit and if it is safe to do so).
So what have I achieved. By tightening my line I have got the car pointing straight at the earliest possibility and have not driven “all the way around the bend”. This allows my simply to get maximum acceleration sooner, and therefore increase my progress. By using acceleration in the bend (a big gasp I hear ...) I gently press myself, and any passengers back into the seats, giving them more support and preventing them from moving sideways, so I have additionally improved the quality of the ride and passenger comfort'.
Accelerating mid-bend, I better justify this ...
“For the given road conditions, you have an amount of grip available which you can 'spend' on either acceleration (+ve or –ve (braking)) or steering, or a combination of both. However, you have only a certain amount, say £10. So if you spend £5 on steering, you can only spend £5 on accelerating”. Personally I will drive so that I always keep some grip in reserve, in case the unexpected happens. However, especially in the dry, I have plenty of grip for my driving style and can safely use some of this reserve to accelerate mid bend, and then as the steering is straightened (I am now spending less on steering, so have more available for acceleration) I can accelerate harder.
One interesting feature of front wheel drive vehicles is the ability to steer the vehicle on the throttle. If I have a nice flowing bend (eg. 40 - 50-mph) that tightens slightly, by an amount that would require say an 1/8ish increase in turn of the wheel, I can actually leave the wheel completely still and just accelerate. Contrary to what you may think, the car will actually tighten its line, as if you had turned the wheel.
Why is this, back to the slip angle. Within limitations, an increase in the slip angle causes more cornering force. If you apply power to a cornering wheel, the slip angle increases, this provides more cornering force and so the car turns in. Of course there are limits, if the slip angle increases too much, the tyre breaks traction and understeer develops.
1. The car is better "balanced", under constant power either maintaining, or slightly accelerating, it basically pulls itself out of the corner.
2. If slightly accelerating (or hard depending on corner/grip etc" then you are being pushed back into your seat, thus the seat is doing it's job and supporting you, so you feel less "thrown about".
Martin
Edited to add a article I wrote for a newsletter ...
One of the reasons often given for road positioning on bends is to increase the radius and therefore reduce the cornering forces on the car. This method is acceptable and typical for the IAM test, but is it the only, or best way?
At some point in a bend, you have to start to straighten the car, so that you are in a straight line as you exit. However, the point at which I do this is perhaps different to the "typical" IAM style.
My approach into a bend starts off the same, and for safety I go for “slow in, fast out”. To do this, I need to get the car pointing straight out of the bend, at the earliest opportunity. Let us take the example of a left hand bend.
Providing there is no approaching traffic I will be positioned towards the center of the road, if I have the visibility, I may well be over the center line, providing the road markings allow this.
Before I get to the bend I will access the speed required using a number of factors, not only the limit point but other visual clues such as the cross views, the angle of the center line, tree line or lampposts. Once completed I will balance the car on the throttle, maintaining my speed but not accelerating. I will also “hint” at the steering, that is put on a tiny amount of lock, a split second before I actually enter the bend, why, I hear you ask.
For a tyre to corner, something called a “slip angle” must be set up, this is a very complex subject that I will not attempt to explain fully (feel free to check the internet). In a nutshell, when turning the steering wheel, maximum cornering from the tyres, for the given amount of steering is not immediate, it can actually take up to half a second, dependent on many factors. By turning the wheel very slightly, I 'wake the tyres up' and set up the slip angle. Once set up, any increase in steering will have a more immediate maximum effect, and produce smoother turn in.
Once in the bend, I'll keep an eye on the limit point to ensure it doesn't start to move towards me (ie. a double apex bend). Providing this doesn't happen, at some point it will start to move away from me, signaling the start of the exit of the bend. At this point my vision is increasing and I'll start to accelerate and begin to “shave the bend”, that is actually tighten my line (and therefore increase the cornering forces on the car). As the limit point “sprints” away, I'll bring the car back towards the nearside. I can now begin to straighten the car, and as the steering comes off I can increase my acceleration even harder (dependent of course on the speed limit and if it is safe to do so).
So what have I achieved. By tightening my line I have got the car pointing straight at the earliest possibility and have not driven “all the way around the bend”. This allows my simply to get maximum acceleration sooner, and therefore increase my progress. By using acceleration in the bend (a big gasp I hear ...) I gently press myself, and any passengers back into the seats, giving them more support and preventing them from moving sideways, so I have additionally improved the quality of the ride and passenger comfort'.
Accelerating mid-bend, I better justify this ...
“For the given road conditions, you have an amount of grip available which you can 'spend' on either acceleration (+ve or –ve (braking)) or steering, or a combination of both. However, you have only a certain amount, say £10. So if you spend £5 on steering, you can only spend £5 on accelerating”. Personally I will drive so that I always keep some grip in reserve, in case the unexpected happens. However, especially in the dry, I have plenty of grip for my driving style and can safely use some of this reserve to accelerate mid bend, and then as the steering is straightened (I am now spending less on steering, so have more available for acceleration) I can accelerate harder.
One interesting feature of front wheel drive vehicles is the ability to steer the vehicle on the throttle. If I have a nice flowing bend (eg. 40 - 50-mph) that tightens slightly, by an amount that would require say an 1/8ish increase in turn of the wheel, I can actually leave the wheel completely still and just accelerate. Contrary to what you may think, the car will actually tighten its line, as if you had turned the wheel.
Why is this, back to the slip angle. Within limitations, an increase in the slip angle causes more cornering force. If you apply power to a cornering wheel, the slip angle increases, this provides more cornering force and so the car turns in. Of course there are limits, if the slip angle increases too much, the tyre breaks traction and understeer develops.
Edited by mph999 on Friday 21st March 23:41
mph999 said:
One interesting feature of front wheel drive vehicles is the ability to steer the vehicle on the throttle. If I have a nice flowing bend (eg. 40 - 50-mph) that tightens slightly, by an amount that would require say an 1/8ish increase in turn of the wheel, I can actually leave the wheel completely still and just accelerate. Contrary to what you may think, the car will actually tighten its line, as if you had turned the wheel.
Why is this, back to the slip angle. Within limitations, an increase in the slip angle causes more cornering force. If you apply power to a cornering wheel, the slip angle increases, this provides more cornering force and so the car turns in. Of course there are limits, if the slip angle increases too much, the tyre breaks traction and understeer develops.
That's the answer I was looking for. Thank you Why is this, back to the slip angle. Within limitations, an increase in the slip angle causes more cornering force. If you apply power to a cornering wheel, the slip angle increases, this provides more cornering force and so the car turns in. Of course there are limits, if the slip angle increases too much, the tyre breaks traction and understeer develops.
parapaul said:
What I mean is - for the same corner, in the same conditions, at the same speed, in 3rd gear with plenty of revs the car behaves nicely and sticks to the road, whereas in 4th or 5th gear, with low(er) revs the car feels as though it wants to drift outwards.
If you're off the throttle, then higher revs will give you more engine braking, throwing weight forward which will give you more grip to the front wheels, improving turn in.Gassing Station | Advanced Driving | Top of Page | What's New | My Stuff