Accelerating before apex
Discussion
I've heard it mentioned before and had it pointed out to me by an instructor on track, that you shouldn't start to accelerate before the apex of a corner as it will induce understeer.
If I understand this correctly, it's because if you're going into the corner at the optimum speed, then up until the apex, the tyre's grip will be fully utilised in turning and any increase in speed will push it over this limit and cause understeer. Once you pass the apex and start winding off the lock, you've got enough grip to start upping the speed.
My question is, if I've understood this correctly, then if you are entering a corner slower than you could potentially go around it (because there was a tighter corner right before it for example) then this is academic and you can get on the gas before the apex, right?
If I understand this correctly, it's because if you're going into the corner at the optimum speed, then up until the apex, the tyre's grip will be fully utilised in turning and any increase in speed will push it over this limit and cause understeer. Once you pass the apex and start winding off the lock, you've got enough grip to start upping the speed.
My question is, if I've understood this correctly, then if you are entering a corner slower than you could potentially go around it (because there was a tighter corner right before it for example) then this is academic and you can get on the gas before the apex, right?
Sure mr Rance will be along with a definitive view, but I though that you should begin using the throttle again as soon as you begin the turn in. You just don't nail it to the floor until you are either at or just beyond the apex. Only variation with this is where you trail brake into the corner and you still get back on a part throttle before the apex in order to settle the back of the car down.
Edited by paulburrell on Friday 27th October 12:45
I think it will depend on the corner. If it is a long sweeper where you spend a long time at the apex, then you should be on constant throttle until after the apex. If it is a tight hairpin with a late apex, then I would have thought that you should be on the power and accelerating before the apex. This is because the point at which you have maximum steering input (ie when all your grip is used in cornering) occurs before the apex, and after you have reached that point you should be winding off steering lock, and hence accelerating.
Mike....
Mike....
Totally depends on the corner. For instance you've got Folly at Castle Coombe which is basically a 'kink' when you're doing 80mph, but becomes a scary bend when doing 120mph - however in both instances you are accelerating fully from the previous corner up to Avon Rise where you are braking, turning, braking.
If you’re talking about front wheel drive, then if you accelerate too early, you will diminish the tyres ability to turn, yes.
If you’ve gone in slower in order to get the car turned ‘early’ then it becomes a question of whether you have enough room to accommodate the understeer on the exit.
If it’s a combination of corners, the whole focus from a lap time point of view is on your exit speed of the final corner; so yes it is academic in your example.
If you’ve gone in slower in order to get the car turned ‘early’ then it becomes a question of whether you have enough room to accommodate the understeer on the exit.
If it’s a combination of corners, the whole focus from a lap time point of view is on your exit speed of the final corner; so yes it is academic in your example.
For a full explanation, you should get a good instruction book such as those by Senna or Piero Taruffi, followed by Mark Hales masterclass in weight transfer, but in principle you are right.
A tyre has only a certain amount of grip available (which is dependent on the vertical load), which has to be split between lateral (cornering) and longtitudinal (braking & acceleration) - use some of it for acceleration, and you have less for cornering.
Basic theory* is that turn-in to apex is all about cornering - get that right and you can smoothly accelerate away from the apex in a parabola.
*This does depend on the layout of the corner and what follows. There are also more advanced techniques involving braking into the corner and/or a stab on the throttle to loosen either end.
So up to the apex, you want to be on a balance throttle - the power this delivers matches the rolling resistance, so all grip from the tyre is devoted to cornering. Apply more power and:
- Some grip is devoted to longtitudinal use, and you have less cornering anility
- Weight is transferred to the rear, reducing the amount of grip available from the front tyres
both of which are likely to induce understeer.
What I suspect your instructor is doing is trying to teach you the correct technique, even though you came in too slow - rather like a ski instructor taking you back to basics of balance. In a race, you might compensate for braking too early (and of course on the next lap brake a bit later), but what's the point on a trackday or training session? Get the basic technique right and it will become intuitive.
A tyre has only a certain amount of grip available (which is dependent on the vertical load), which has to be split between lateral (cornering) and longtitudinal (braking & acceleration) - use some of it for acceleration, and you have less for cornering.
Basic theory* is that turn-in to apex is all about cornering - get that right and you can smoothly accelerate away from the apex in a parabola.
*This does depend on the layout of the corner and what follows. There are also more advanced techniques involving braking into the corner and/or a stab on the throttle to loosen either end.
So up to the apex, you want to be on a balance throttle - the power this delivers matches the rolling resistance, so all grip from the tyre is devoted to cornering. Apply more power and:
- Some grip is devoted to longtitudinal use, and you have less cornering anility
- Weight is transferred to the rear, reducing the amount of grip available from the front tyres
both of which are likely to induce understeer.
What I suspect your instructor is doing is trying to teach you the correct technique, even though you came in too slow - rather like a ski instructor taking you back to basics of balance. In a race, you might compensate for braking too early (and of course on the next lap brake a bit later), but what's the point on a trackday or training session? Get the basic technique right and it will become intuitive.
easy way to practice this is on a wet trackday. Here, you obviously have less ggrip available at each corner, however, the weight transfer of the car will still happen, albeit more gradually. You can experiment what happens with various techniques in relative safety. It's almost equivalent to driving on crap rubber!
mmm-five said:
Totally depends on the corner. For instance you've got Folly at Castle Coombe which is basically a 'kink' when you're doing 80mph, but becomes a scary bend when doing 120mph - however in both instances you are accelerating fully from the previous corner up to Avon Rise where you are braking, turning, braking.
Try this at 150mph
LexSport said:
I've heard it mentioned before and had it pointed out to me by an instructor on track, that you shouldn't start to accelerate before the apex of a corner as it will induce understeer.
If I understand this correctly, it's because if you're going into the corner at the optimum speed, then up until the apex, the tyre's grip will be fully utilised in turning and any increase in speed will push it over this limit and cause understeer. Once you pass the apex and start winding off the lock, you've got enough grip to start upping the speed.
My question is, if I've understood this correctly, then if you are entering a corner slower than you could potentially go around it (because there was a tighter corner right before it for example) then this is academic and you can get on the gas before the apex, right?
If I understand this correctly, it's because if you're going into the corner at the optimum speed, then up until the apex, the tyre's grip will be fully utilised in turning and any increase in speed will push it over this limit and cause understeer. Once you pass the apex and start winding off the lock, you've got enough grip to start upping the speed.
My question is, if I've understood this correctly, then if you are entering a corner slower than you could potentially go around it (because there was a tighter corner right before it for example) then this is academic and you can get on the gas before the apex, right?
This precise driving fault was one that I have been battling the year. I am nearly always too keen to be getting on the power or my idea of a balanced throttle was one with just a little too much gas. I've worked hard at correcting the problem and there is no doubt - I am faster.
AtomicRex said:
mmm-five said:
Totally depends on the corner. For instance you've got Folly at Castle Coombe which is basically a 'kink' when you're doing 80mph, but becomes a scary bend when doing 120mph - however in both instances you are accelerating fully from the previous corner up to Avon Rise where you are braking, turning, braking.
Try this at 150mph
You too!!!!!
Then with your eyes shut?
Dose the Mazda pull 150 there?
I know Keith murray took a Marshal for a blast round the track on the Audi day, 152!!
mmm-five said:
Totally depends on the corner. For instance you've got Folly at Castle Coombe which is basically a 'kink' when you're doing 80mph, but becomes a scary bend when doing 120mph - however in both instances you are accelerating fully from the previous corner
I'm guessing that the OP meant in corners where your entry speed would be too high unless reduced by braking.
mmm-five said:
...up to Avon Rise where you are braking, turning, braking.
Surely a mis-type...er..turning and braking, not sure what the first braking was for!!
Graham
Thanks all for the input. I kind of meant both types of corners in my original post. I think I understand the reason for not accelerating before the apex for a corner that you had to brake for - if you didn't brake to much, any accelerating before winding off lock will result in loss of grip. I was then trying to confirm that if I've understood this premise properly, that you can accelerate before the apex in a corner whose entry speed is actually lower than you could potentially take it at in isolation (e.g. because of a previous, slower corner). I think this has been confirmed, bar the one point that I hadn't taken into account which is weight transfer.
Unfortunately I tend to need to understand something before it fully sinks in rather than just taking it as gospel (part of the reason why I was rather unimpressed with Robb Gravett's UCC course, but that's another story).
Thanks again everyone. I'm slowly getting there.
Unfortunately I tend to need to understand something before it fully sinks in rather than just taking it as gospel (part of the reason why I was rather unimpressed with Robb Gravett's UCC course, but that's another story).
Thanks again everyone. I'm slowly getting there.
gridgway said:
mmm-five said:
Totally depends on the corner. For instance you've got Folly at Castle Coombe which is basically a 'kink' when you're doing 80mph, but becomes a scary bend when doing 120mph - however in both instances you are accelerating fully from the previous corner
I'm guessing that the OP meant in corners where your entry speed would be too high unless reduced by braking.
mmm-five said:
...up to Avon Rise where you are braking, turning, braking.
Surely a mis-type...er..turning and braking, not sure what the first braking was for!!
Graham
Balls the size of melons!
Actually its going to depend on the car isn't it? In my car there is absolutely no way I could lose enough speed after going over the bump at the top of Avon Rise to then actually make Quarry... So I brake going up Avon Rise and get fourth, turn across the track towards the entry for Quarry, go over the bump without braking (it all gets a big loose otherwise), and then brake in a straight line towards the entry whilst getting third.
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