Cornering without a visible limit point?
Discussion
I took a different cross country route home from work today. On three occasions I came across fairly sharp corners (approx 60°-90° ) that could not be taken at NSL speeds. However, due to camber of the road, there was no visible limit point - you could see the entire road surface through the bend and onto the following straight. What sort of technique should be used here? I'm currently considering creating an artificial limit point, that would be fixed at the apex of the corner, might be suitable method?
Cheers,
Phil
Cheers,
Phil
I think I may have found a better solution in another thread on this forum. Using the verge of the road as my limit point. For a RH bend it would be the NS verge and for a LH bend the OS verge would be used. This would at least give a dynamic limit point rather than a static one as I mentioned above.
I'm not sure what you mean by "creating an artificial limit point, that would be fixed at the apex of the corner". The whole theory of limit-point corner assessment is based around the limit point being a mobile point, rather than a fixed point. It's this movement (or apparant movement) of the limit point on your approach to a corner which you use to assess your correct entry speed.
If the limit point is coming towards you, the bend is getting tighter. If it appears stationary, you've found the severity of the bend, and if it's going away from you, the bend is opening up.
As I've mentioned previously, the limit point isn't suitable for all corners, for various reasons, including the reason in this post.
In cases such as this, you should look for other clues as to the severity of the bend. Hedge and tree lines, for instance, or the manner in which other vehicles in front negotiate the bend. If you know the road, then the limit point becomes fairly irrelevent because you'll already know how severe a corner is.
If the limit point is coming towards you, the bend is getting tighter. If it appears stationary, you've found the severity of the bend, and if it's going away from you, the bend is opening up.
As I've mentioned previously, the limit point isn't suitable for all corners, for various reasons, including the reason in this post.
In cases such as this, you should look for other clues as to the severity of the bend. Hedge and tree lines, for instance, or the manner in which other vehicles in front negotiate the bend. If you know the road, then the limit point becomes fairly irrelevent because you'll already know how severe a corner is.
Dear R U local - one of the things about limit points that nearly sent me up the wall (or further up than I already am) was the "matching the limit point" bit.
Everybody always said to me that when the limit point is moving at the same rate as you, neither towards you nor away, then you have "matched the limit point", and your speed is correct.
As far as I can see, this is not the whole story, and is a little bit misleading to beginners like myself. I've done a bit of studying on limit points, and it seems to me that it is matched at the point you enter the bend, and it stays that way throughout the bend, until you leave it.
Assume that there is a traight piece of raod, with a 90 degree bend, then straight. 'A' is the point at which the road itself goes from straight to start turning (where the turn begins), 'B' is the limit point, which may be 10 yards away. As you get nearer to 'A' on the straight the limit point will move towards you. But when you get to 'A' it will move away from you at a constant speed, REGARDLESS OF THE SPEED YOU ARE DOING. So matching the limit point is no guarantee the the speed is correct, if you haven't got it right in the first place.
If anyone thinks that matching the limit point is something that can be affected by speed, they should go out, find a big corner, match the point, then watch what happens if they speed up or slow down. Thats what I did. The distance between you and the limit point remains the same. Speed up - remains the same. Slow to a crawl - the same. So fast you nearly spin off - remains the same. Go in too fast and the limit point is matched at the same position as going in too slowly or going in at the correct speed.
Please excuse the ramblings, but believe me, the idea that matching the limit point somehow means your speed is 'correct' caused me many sleepless nights. I always thought it was wrong, and I had to get out in the car and prove it (as well as sketching it on pages and pages of a scrapbook). Once you have entered the true radius, the limit point moves constantly regardless of your speed.
Having written the above, I fully accept that I may be totally wrong, and I await being corrected.
Regards
Sally
Everybody always said to me that when the limit point is moving at the same rate as you, neither towards you nor away, then you have "matched the limit point", and your speed is correct.
As far as I can see, this is not the whole story, and is a little bit misleading to beginners like myself. I've done a bit of studying on limit points, and it seems to me that it is matched at the point you enter the bend, and it stays that way throughout the bend, until you leave it.
Assume that there is a traight piece of raod, with a 90 degree bend, then straight. 'A' is the point at which the road itself goes from straight to start turning (where the turn begins), 'B' is the limit point, which may be 10 yards away. As you get nearer to 'A' on the straight the limit point will move towards you. But when you get to 'A' it will move away from you at a constant speed, REGARDLESS OF THE SPEED YOU ARE DOING. So matching the limit point is no guarantee the the speed is correct, if you haven't got it right in the first place.
If anyone thinks that matching the limit point is something that can be affected by speed, they should go out, find a big corner, match the point, then watch what happens if they speed up or slow down. Thats what I did. The distance between you and the limit point remains the same. Speed up - remains the same. Slow to a crawl - the same. So fast you nearly spin off - remains the same. Go in too fast and the limit point is matched at the same position as going in too slowly or going in at the correct speed.
Please excuse the ramblings, but believe me, the idea that matching the limit point somehow means your speed is 'correct' caused me many sleepless nights. I always thought it was wrong, and I had to get out in the car and prove it (as well as sketching it on pages and pages of a scrapbook). Once you have entered the true radius, the limit point moves constantly regardless of your speed.
Having written the above, I fully accept that I may be totally wrong, and I await being corrected.
Regards
Sally
As I see it, the limit point doesn't directly tell you how fast you should be going. It tells you whether the corner is tightening or opening out ahead of you. You typically will want to slow down as the corner tightens and speed up as it widens, but there's nothing fundamental that says you must. It may be that you can go right through the corner without having to slow down at all, in other circumstances for the same corner you might need to slow down a lot. The movement of the limit point tells you about the shape of the road ahead, which is only one of several factors that you need to work out what line you want to take and how fast you want to go.
You're not wrong in what you say, Sally, I just think you're being a bit narrow minded in relation to the use of the limit point. It's something which is harped on about so much in advanced driving circles that it seems to be some kind of holy grail of driving, when, in reality, that's far from the truth.
The limit point is just a way to assess the severity (sharpness) of a bend. Nothing more, nothing less. It's certainly not a way of planning your speed into or through a corner.
It's one of numerous methods that drivers can use to assess how sharp individual corners are, but your choice of speed is based on numerous other factors. Your vehicles's handling properties, the road surface conditions, traffic conditions, road width, camber, sharpness of the bend, weather conditions, your vehicles braking properties, your own personal level of experience, etc, etc. I've highlighted the only factor there which is determined by the limit point - all the others are seperate assesments made by the driver, based on other information.
So, as a way of assessing the severity of a bend, the limit point method is pretty good, but don't think that it's the only consideration when deciding on your cornering speed.
The limit point is just a way to assess the severity (sharpness) of a bend. Nothing more, nothing less. It's certainly not a way of planning your speed into or through a corner.
It's one of numerous methods that drivers can use to assess how sharp individual corners are, but your choice of speed is based on numerous other factors. Your vehicles's handling properties, the road surface conditions, traffic conditions, road width, camber, sharpness of the bend, weather conditions, your vehicles braking properties, your own personal level of experience, etc, etc. I've highlighted the only factor there which is determined by the limit point - all the others are seperate assesments made by the driver, based on other information.
So, as a way of assessing the severity of a bend, the limit point method is pretty good, but don't think that it's the only consideration when deciding on your cornering speed.
R_U_LOCAL said:
So, as a way of assessing the severity of a bend, the limit point method is pretty good, but don't think that it's the only consideration when deciding on your cornering speed.
In the vast majoriy of cases, it's visibility that limits the speed. So isn't it at least a reasonable generalisation to say that if you could stop on the bit of road you can see, that is, before the limit point, you have slowed down sufficiently. (obviously subject to side turnings etc)Dr Jekyll said:
R_U_LOCAL said:
So, as a way of assessing the severity of a bend, the limit point method is pretty good, but don't think that it's the only consideration when deciding on your cornering speed.
In the vast majoriy of cases, it's visibility that limits the speed. So isn't it at least a reasonable generalisation to say that if you could stop on the bit of road you can see, that is, before the limit point, you have slowed down sufficiently. (obviously subject to side turnings etc)As you're approaching the bend down a long straight, you can easily stop within the distance you can see to be clear. The closer you get the relationship starts to change & the amount of extra space, on top of visible distance required to stop, begins to diminish. What it shouldn't do at any point is result in less vision than that required to stop. The skill is accurately judging the approach correctly, so that with everything considered (surfaces, potential for change etc) you can always stop within the distance you can see to be clear & reasonably expect to remain so, whilst applying the system smoothly on approach (& through), whilst keeping progress to an optimal level.
If all that can't be done, the first thing to sacrifice is speed, the second smoothness, the third system, whilst safety should always be of the utmost importance.
In some tight bends where you can see completely through them, there is a danger of getting excited by the exit vision. The nearside & offside kerb lines will intersect at some point though. The limit point isn't just the furthest clear piece of road you can see, it's the furthest piece of uninterrupted surface you can see, which won't be beyond the nearside/offside intersection (even that's a simplification because the limit point isn't actually the point of intersection on left or right hand bends, it's just near as damn it).
Edited by vonhosen on Sunday 2nd September 18:34
Another easily-forgotten aspect of cornering, which can have a huge effect on your assessment of the limit point, is your position on approach to a corner.
Position incorrectly and you'll limit your view, tighten the radius of the corner and generally make life difficult for yourself.
By positioning correctly (as far nearside as is safe for right-handers and as far offside as is safe for left-handers), your improved view will often see the limit point moving very early, sometimes well before you've reached the corner.
Position incorrectly and you'll limit your view, tighten the radius of the corner and generally make life difficult for yourself.
By positioning correctly (as far nearside as is safe for right-handers and as far offside as is safe for left-handers), your improved view will often see the limit point moving very early, sometimes well before you've reached the corner.
Phisp said:
I took a different cross country route home from work today. On three occasions I came across fairly sharp corners (approx 60°-90° ) that could not be taken at NSL speeds. However, due to camber of the road, there was no visible limit point - you could see the entire road surface through the bend and onto the following straight. What sort of technique should be used here? I'm currently considering creating an artificial limit point, that would be fixed at the apex of the corner, might be suitable method?
Cheers,
Phil
Are you concerned about how much to slow down for these bends, or about where and how much to reapply acceleration?Cheers,
Phil
If you are looking for help on how much to slow down, the limit point has no relevance on a corner where you can see the whole road through the bend and beyond. On the majority of bends our speed is limited by vision. Generally, if we can stop in the distance we can see to be clear (and can expect to remain clear) we are well within the limits of cornering grip, so we rarely have to judge the speed which is safe and comfortable in relation to cornering grip. For open bends, we have to judge speed in relation to cornering grip. I think that judgement of acceptable speeds for open bends has to be built up through experience of what is comfortable and what is less so - and of course must take into account factors mentioned above such as road surface, camber, condition of tyres etc.
Now onto the question about where and how much to reapply acceleration. On a corner where speed is limited by available vision, the speed should be at its lowest a little before arriving at the corner. By the time you reach the corner, you are starting to see round it so that the distance you can see is remaining constant, and you should already be applying enough gas to maintain speed. Using limit point technique achieves this. On an open bend, you could apply the same technique, which is safe and comfortable. However, some people would prefer to enter the bend under a trailing throttle, or even under 'trail-braking', in order to transfer the weight of the car forward and onto the front, steering wheels. Most racing drivers would do this, as it maximises cornering speed. However, it is less comfortable and leaves less margin for safety in that if you have not taken off enough speed there is no time or space left in which to do so.
waremark said:
we rarely have to judge the speed which is safe and comfortable in relation to cornering grip.
Surely the cornering grip required to negotiate a corner at a given speed without falling off is hugely important to determine how much grip will be available for braking and hence the distance required to stop. In other words if you take the corner absolutely as fast as possible you will have great trouble stopping. The more grip you have in reserve them more braking you can apply and the sooner you can stop.Apologies, I've been away for a couple of weeks so have not managed to keep up-to-date with this thread.
R_U_LOCAL said:
I'm not sure what you mean by "creating an artificial limit point, that would be fixed at the apex of the corner". The whole theory of limit-point corner assessment is based around the limit point being a mobile point, rather than a fixed point. It's this movement (or apparant movement) of the limit point on your approach to a corner which you use to assess your correct entry speed.
I was think along the lines of that the apex would represent the mid-point of the bend - before it the bend would be tightening and after it opening out. I thought that if I ensured that I could stop at the apex as I entered the bend then my speed for the corner would be correct. Once the apex had been reached the bend would eventually start to open out and so more speed could be added. On reflection (and after reading your post) this idea is rather flawed.waremark said:
Are you concerned about how much to slow down for these bends, or about where and how much to reapply acceleration?
My initial concern is with setting a correct speed for the corner. I always seem to get these types of corner completely wrong and enter too fast - not enough to lose traction but it does feel like I'm getting close. It certainly does not feel comfortable or correct for a public highway. I was hoping to find a technique that would help me to judge these types of corner as the limit point does for blind corners.If you can see the entire corner then you just have to assess how sharp it is and how far it goes and pick your course and speed accordingly. No different really from driving round any other hazard. The power of the limit point approach IMO is that it gives you information about the shape of the road out at the limit of vision, before you can see the whole thing clearly.
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