Question about "Combining acceleration, braking, and steering"

I reading "Smooth driving techniques" source Drivingfast.net and here is something i dont understand.

## Steering while braking into a corner is known as trail braking and is an advanced technique, however accelerating at the latter stages of the corner is more commonly used. Great care should be taken when performing these actions, as the combined demands of the lateral and longitudinal forces on the tyres is much more likely to exceed the limits of grip ##

I like to know whats this "accelerating at the latter stages of the corner is more commonly used" mean.

Is that latter stages mean after apex ?? If yes then i confuse because we all sure accelerate after apex so why it say more commonly use compare to trail braking ??

Thanks for the concern

 

I think because trail-braking allows you to accelerate earlier it is saying that NOT trail-braking and therefore accelerating later is more common. With trail-braking you're often accelerating before the apex.

 

You mean in real world most racer actually didnt do trail braking and only accelerate after apex ?? if thats the case should the lap time become worst ??

 

I think they mean that you will get back on throttle before the Apex, I do this quite a bit Slow down into the corner holding the brake quite deep and then as soon as you get off the break you will get back on the throttle very lightly more to hold speed into the apex on a long corner then accelerate out of the apex as usual. Doing all this will need pretty good touch on all pedals but is how to take man corners the fastest way possible.

I think the not trail braking way is more common for the average driver but most better drivers will use everything they can to balance the car and get the best lap time possible. Im loving AC as all the advanced techniques work very well as you really need to deal with the balance of the car and many need some trail braking to help turn in otherwise you lose lots of mid corner speed.

 

Interesting pedal cam of the master at work here, you see him brake in fairly deep then well before the apex start tapping the throttle.



Here is another good one at bathurst in the wet

 

So mean we should hold the brake deep (mean no trail braking ??) for better lap time ?? And i see the 2nd video there is a moment 1:15 where that guy actually brake (left foot) & accelerate (right foot) at the same time. I dont understand the logic

Oh sim racing is so god danm difficult

 

It all depends on the situation and corner..

Think about it like this..

Imagine brake, accel, left and right have got 100 points each..

You can apply them altogether but the total must never exceed 100 points.. So for example if your braking at 100points you cant add and left or right otherwise your total will add up to more than 100 and your tyres will start loosing grip..

So in trailbraking you will start by braking at 100 then brakes 90 right 10, brakes 80 right 20 etc until you get low enough that you can start accelerating which then works the other way, accel 20 right 80, accel 50 right 50, accel 95 right 5... Etc etc..

Where to use trail braking or threshold braking depends on how you enter the corner ideally you always want to trail brake, weight transfer is less and its more controlable but your entering the corner much faster so you need to take your brave pills.. If you trail brake usually you decellerate just enough to hit the apex and then start accelerating out of the corner but more importantly it also depends on what corner is next.. Are you entering a selection of corners? Or are you going to be leading onto a straight away.. Which ever it is you have to decide which was is the fastest way out of the corner.. As that is where most time is made up.

 

By holding the brake deep I mean trailbraking as that is what it is, braking deep well into the tun all the way to the apex at times. You do reduce brake pressure all the way in though and as Chris said every corner is different so you need to figure out the best way to deal with each corner and it will be different again in each car. Knowing all the techniques is one thing but then you need to understand when best to use each, with the guy left foot braking at the same time as still being on throttle this is because he wants to shift some weight forward but not lose any rpm especially when that slippery if he got off the gas to brake then went back on he may have got some wheel spin. This is very uncommon though there are some times it may be handy especially with some cars at nurburgring into the Schumacher esses a quick tap of the brake with the left foot can be better then either lifting off or getting completely off throttle and tapping brakes. Your going uphill and want to keep your rpm high but need to get the nose down just a fraction to make the apex and not run wide.

I have been driving that track a bit and in quite a few cars this will gain me .3 to .5 of a sec compared to a quick lift if you cant quite take it flat, lifting fully off the throttle scrubs too much speed and you lose big chunks of time as its a pretty steep uphill section there.

A great car to practice with is the lotus elise at nurburgring as you need to use just about everything for a quick lap around that track with that car there, same with the m3 e92 but thats a bit easier as its a semi auto transmission so you dont need to worry about the shifter and clutch. The best thing with AC is that using realistic advanced techniques helps you lap quicker where many other sims dont deal with weight transfer nearly as well and so you can simply brake shift and steer your way to a good lap without needing to do much more.

 

I think what they mean with that quote is simply that "accelerating while cornering" is more common than "braking while cornering". As in just about everyone gets on the throttle before the wheel is straight.

 

Yeah i guess you right. I thought it's saying "a good accelerate after apex" is more important than "trail braking before apex", thats why i feel confuse when i first read it

 

I like to ask another question about camber :- Is it true more negative camber at front mean oversteer ?? But more negative camber should mean less tyre contact with road surface so should has less grip right ??

Thanks first

 

I have always thought of this like a pie. Same idea just a little more visual rather than with numbers. The amount of traction that a tire has can be represented by a pie/pie chart. If taking the corner so fast uses up 4 slices of a 6 slice pie than you would have 2 slices left to be able to trail brake into the corner or accelerate out of the corner without pushing the tire over its traction limits.

A common practice to teach new riders (Sorry haven't truly raced cars but a lot of the principles are the same) is to pick an on brake point, off brake point, and turn in point. Once a rider is off the brakes they are instructed to maintain steady throttle through corner entry until the apex and then slowly roll on during the corner exit as they straighten out. The steady throttle is to limit the changes made with weight transfer and get the bike nice and stable.

All of my advice should be taken with a grain of salt however. I am not fast by any means (according to RSR at least) an once again I have no car racing experience beyond my couple of dozen hours in this sim, but my old motorcycle techniques have been leading me to run consistent lap times varying by only a couple of tenths each lap.

 

It doesnt effect under and oversteer as directly as you'd think.. But it does effect it, but everything you change effects something someway or another ..

Generally speaking more negative camber means you get more latteral grip up to the point of slipping...

You could have -0.5 degs front camber and get loads of grip at 40mph around a corner but if you tried it at 80mph your tyres would slide. Change to -1.0 deg and now you can take the corner ok at 80 with ease.. But the more negative camber the less stable the car is in a straight line.. Couple that with weight transfer and its starts to get very complicated very quickly.. When weight goes forward under braking camber gets more negative and so does toe.. So sometimes you can get away with a more neutral camber for straight line stability and then when entering a corner under braking the camber increases with weight transfer allowing you to turn in with the grip and then when back on the straights the camber goes more neutral.

 

Oversteer and understeer is just a difference between the balance of grip front to rear. Pretty much any car can be setup to do either and negative camber will give more grip while cornering as it allows the outside loaded tyre to have more rubber contacting the ground. As the car turns in then a car with neautral camber will have the outside wheels try and roll under themselves actually becoming positive camber under load. This would mean only the outer edge of the tyre is contacting the track and most load would be trying to rip the tyre off its rim with less grip and much slower cornering speeds. With the correct negative camber setting under load you will give the tyre the most contact with the road and more load will be going straigh back into the suspension so there will be much more grip. More rubber touching the ground under more load also means more heat is generated, tyre temps difference between front and rear will also have a big effect on car balance. If one side is too cold or too hot then this will have less grip then the other.

A regular street car with street setup will have much less camber as you dont corner anywhere near as hard and spend most of the time driving unloaded and fairly straight, this would cause tyres with too high a negative camber wear the inner edges very quickly and also gives less grip and stability in a straight line due to less rubber contacting the surface when not cornering. In racing you gain more time in corners then you do in a straight line so sacrificing some straight line speed and stability for much higher cornering loads is the better option on most circuits.

With a street car and limited setups you will be quite surprised how much you can change the balance and cornering speed with simple camber, toe and pressure adjustments. This is where its best to start out learning how to setup a car as thats all you can change most of the time. This is critical in all cars but if your in a fully adjustable race car trying to learn how to setup a car for the first time you will likely get lost in all the options, best to start with the basics and then you can learn how all the other adjustments will also effect balance and grip. With more advanced aero cars you can even set them up to behave differently at higher and lower speeds by adjusting the balance differently from mechanical and aero aspects, all adjustments are always a compromise so you need to find the way which it gets the goal your looking for but this may be different between a single lap and a longer race.

 

Very complicated explanation. If i understand it right i like to confirm these:-

1. We actually use just enough (not available max negative camber) negative camber in front tyre so when it cornering we get neutral camber for max grip for the outer front tyre ??
2. How about rear camber ?? Since normally its the outer front tyre do the most cornering work so rear tyre dont need any camber right ?? I only watch Formula One and i notice those car have lot of negative camber in front tyre but like zero camber for rear camber. So i guessing normally rear tyre use very little or none camber value. Am i right ??

From what i see all these car have lot negative camber in front but like none camber for rear ...

 

Less camber is used on the rear because whilst increasing latitudinal grip (cornering) it reduces longitudinal grip (braking/accelerating). They need the neutral camber for traction. If you imagine accelerating out of a corner with lots of negative camber on the rear you're only going to have a small section of the tyre in contact with the road and therefore poor traction. The front tyres are mainly used for cornering so the longitudinal grip is less important.

TL;DR - negative camber gives you less straight line grip. The rear wheels need straight line grip for traction out of corners. The front tyres don't, so you can give them more camber.

 

Ok here is the default setup for BMW Z4 E89, so should i increase alot more negative camber for front wheel & decrease rear camber to zero value ??


Thanks first

 

Depends what your needing to do for the gt cars the default steering is usually good for me personally, but of you want more cornering grip up front then yes you would increase the negative camber of the car is too grippy up front decrease the negative camber, if the cars unstable at high speeds slight toe in at the rear can cure it, if the back end is too loose or you think you can get the power on earlier try more negaitve camber in back, drop the tire psi down a few also if you want more grip add some of you want less grip, heat is a huge issue though also in race cars, hotlapping you might need more extreme setups to heat up the car vs racing where you might need to dial it back to not overheat the tires driving for 5 10 15 laps.

 

Thanks for the tips but i do have one question :-
1. What is the sign if the car is unstable at high speed ??

You know the funny thing is that no matter what min / max i set the camber & toe my best time is still similar. Its like all those different setup work no different for me. Weird.

Thanks again

 

Shaking, wobbly, at speed, noting instability under acceleration and breaking.

Like the 599 in the .3 or .4 patches. thats was a car i would classify as unstable at speed, it was very nervous feeling. at speed under acceleration under breaking.

But unless your doing anything really extreme with the wheels, that is generally not an issue. If you want more turn in to a front more grip more neg camber and increaee the toe. often what i do to make a car turn in sharper if i want the back end to slide while i do that i dial out the negative camber in back, all depends highly on what you want the car to do and your driving style.

Generally you want to maximize grip for the turns while not killing your straight speed is the ultimate goal and its all a balancing act i could make the best turning car ever but i am probably going to lose some straight speed and if i got for straight speed i will not have as much grip in the corners. is a track more turns or more straights? setup for the track as well as the car.