Is my gear change too late?

[GTR LUST]

Hi,

I know I should be getting my gear changes done before the corner, and I do, but I often find that the last part of letting the clutch out I do in the 1st 1/5th of a corner, which helps knock off a touch more speed.

Is this wrong, should I be compleatly off the clutch before the turn in, or is using the brake / clutch to slow down okay?

(More interested in the best track driving technique more than safe road)....

Cheers for the advise

[ScoobyChris]

For road driving it's probably too late. For track driving it's probably too early.

Possibly

Chris

[kaf]

For best stability the car needs to have the weight as evenly distributed across all wheels as possible.

Only by putting a small amount of power through the the wheels can this be accomplished, zero power means the car is slowing due to road and air friction.

You cannot put power through with the clutch down.

If you decide you need power as a corrective method, then the risk is you will bring the clutch up too quickly in an attempt to do so, the sudden power through the wheels will compromise grip.

IMHO, normally, by the time you steer in you should have completed braking and gear change and have your foot back on the gas.

[Jacobyte]

Letting the clutch out during corner entry can cause imbalance resulting in less control (or worse, a spin). Do all the braking and downchanging before the corner.

If you find yourself having to slow more and/or downchange mid-corner, then you didn't plan your approach properly.

There are instances where a trailbrake is useful, but use the above as a rule of thumb and you'll generally be smoother, safer and faster.

[GTR LUST]

Cheers for the advise, I thought this was likely to be the case, I'll adjust my driving accordingly

[MC Bodge]

Slow down on the straight and down-shift (during the braking or afterwards, depending upon your religious persuasion) before the bend. The brakes should be used to slow the car, you shouldn't really supplement it with engine braking during a corner. Ideally the car should be driven in a balanced way, with smooth transitions between accelerating, braking and steering.

Maintaining a reducing level of braking into the apex of the bend to keep the 'weight' on the front outer tyre is trail braking, and you are doing this, to some extent, with your (possibly abrupt) abrupt corner entry engine-braking, but I'd personally prefer to do it smoothly with brakes!

Edited by MC Bodge on Tuesday 10th January 13:19

[GTR LUST]

That makes a lot of sense Bodge.

So the final bit of slowing during the corner (before the apex), should that be done with gentle braking, or use the natural progressive momentum of the car without power?

[davepoth]

GTR LUST said:

That makes a lot of sense Bodge.

So the final bit of slowing during the corner (before the apex), should that be done with gentle braking, or use the natural progressive momentum of the car without power?

Have you done the "circle of traction" yet?



In truth for most tyres it'll be an ellipse with more grip side to side than forwards and backwards, but it's a good thing to think about. Essentially your tyre only has a certain amount of traction, and if you're using a lot of traction for braking, doing some turning as well will probably move you out of the "circle". So if you want to turn you'll need to brake a bit less. It depends on the corner.

For racing you want to be right at the edge of the circle of traction at all times, that's where the speed is.

[Tartan Pixie]

Interested in this topic as I do the same thing as the OP and scrub off a bit of speed by being late with the clutch. (Original Poster referred to as OP on these forums?).


EG of my novice cornering:

On approach to the corner I'm using 100% of my traction budget to brake.

As I turn in I need to spend a percentage of my traction budget on the corner, the more I turn the wheel the more traction I need to spend on cornering and the less I can spend on braking.

The quantity of my traction budget spent on cornering will gradually increase as I turn in and gradually decrease as I straighten out of the bend.

This means that if I am not decelerating all the way to the point where I wish to accelerate then there will be unspent traction in the budget.

Currently I use the clutch to give a smooth transition between the straight line braking before the corner and the acceleration out of the corner. I'm guessing that there's an advanced heel and toe thing I should be doing to ensure that I can bring the clutch up before the corner but still stay at 99.99% of my traction budget?

Edited by Tartan Pixie on Wednesday 11th January 03:26

[BertBert]

Tartan Pixie said:

Currently I use the clutch to give a smooth transition between the straight line braking before the corner and the acceleration out of the corner. I'm guessing that there's an advanced heel and toe thing I should be doing to ensure that I can bring the clutch up before the corner but still stay at 99.99% of my traction budget?

Not quite sure what you mean by your traction budget, nor whether you are talking on track or road, but as a generalization, the clutch should play no part at all in the dynamic changes you are talking about.

And so as MC bodge says, overlapping or not according to your persuasion, the revs should be matched for the gear change so the engagement of the clutch itself does not affect the dynamics of the car.

What is your "traction budget" by the way?

Bert

[Tartan Pixie]

BertBert said:

What is your "traction budget" by the way?

A car has a limited amount of traction. Cornering or changing speed will use a percentage of that traction. I think of the maximum traction my car can achieve as my budget, which can be spent on cornering, braking or whatever. It's a similar concept to the circle of traction posted by davepoth, if I spend 25% of my budget on braking then I have 75% left to corner with.

The question I asked was in relation to track driving, it wasn't very clear though as I was posting at the wrong end of 3 in the morning.

I (and I believe the OP too) was asking for the correct technique when entering a corner. If we take this pic as an example then we're talking about the yellow section where the car turns in:

[BertBert]

I had missed the fact that we were mostly talking about track driving.

I'm wondering if you consciously think of it in those terms when on track? I'm much more thinking about the handling characteristics of the car I'm driving rather than percentages of traction budget spent at different parts of the corner.

[Pugsey]

BB is right. If you're racing it needs to be intuitive - no time for lots of thinking - and your primary concern will be the handling characteristics of your car and how you want to manipulate them. Some cars I drive I might be braking and changing down right up to the apex, some will absolutely want everything done in a staight line before the corner. And many will fall between the two! I think your question is almost unanswerable unless the respondent is familiar with you car. The SAFE answer, which won't kill you, is get everything done before turn it - but you may be slow that way depending on your car.

[BertBert]

In the radical ideally you are braking all the way to the apex and then bang the trottle open. Anything in-between generates understeer!
Might be a slight exaggeration, but it's pretty much like that.
BErt

[Pugsey]

BertBert said:

In the radical ideally you are braking all the way to the apex and then bang the trottle open. Anything in-between generates understeer!
Might be a slight exaggeration, but it's pretty much like that.
BErt

Agreed - see my post above. Difficult explaining to people sometimes that the reason they're running out of track is because their entry is too slow. And beyond that something with REAL downforce takes some getting comfortable with. Mind you some 'ordinary' cars can be right pigs and may require deep braking to over ride nasty tendencies. Or not of course! So, as already mentioned, the OP's question can't really be answered without first hand knowledge of his car. IMHO of course!

[davepoth]

But generally, since using the friction plate of the clutch as a brake only acts on two of the 4 wheels (4wd excepted) it has the potential to unbalance the car, much like pulling the handbrake. Best to rev match the shift and use the brakes for slowing on track.

[Tartan Pixie]

Thanks all for the advice.

davepoth said:

But generally, since using the friction plate of the clutch as a brake only acts on two of the 4 wheels (4wd excepted) it has the potential to unbalance the car, much like pulling the handbrake. Best to rev match the shift and use the brakes for slowing on track.

This makes a lot of sense. What is the actual technique I should be using though?

Assuming that I want to change down while braking on the straight do I:
Depress the clutch while braking -> shift gear -> blip the throttle & release clutch while still braking (heel and toe)?

Note, I'm quite an experienced road driver but am totally new to motorsport, hence this is theory crafting till I go on my 1st track day later this year. For what it's worth I'm using a Mk7 celica 140 to learn the ropes.

[BertBert]

Tartan Pixie said:

Depress the clutch while braking -> shift gear -> blip the throttle & release clutch while still braking (heel and toe)?

Absolutely. Also in almost all cases, you'll be getting that lot done before the turn-in.

[Pugsey]

Tartan Pixie said:

Thanks all for the advice.

davepoth said:

Note, I'm quite an experienced road driver but am totally new to motorsport, hence this is theory crafting till I go on my 1st track day later this year. For what it's worth I'm using a Mk7 celica 140 to learn the ropes.

On that basis then, to start with, yes - get it ALL done in straight line and the car nicely settled before turn in. THEN start learning just how late you can actually brake - you'll be amazed. If you think you've braked late on the road you really haven't! Most beginners cook their brakes on track because the use them for too long. Shorter but much harder braking is the way. That's why pro drivers on manufacturers demo days seem to go round all day in standard cars whilst a punter can rubbish the brakes in five laps!

Not saying you won't kill your brakes - or tyres - of course.......

Enjoy!

[MC Bodge]

Yes, 'dragging' the brakes rather than using them decisively, hard and for a shorter duration and allowing them to cool for longer is what leads to overheating.

Even on the road it is noticeable that some drivers use the brakes much more often (and often unnecessarily) than others. It is arguable that better drivers use the brakes less.

Edited by MC Bodge on Thursday 12th January 11:41